1513 lines
45 KiB
C
1513 lines
45 KiB
C
/*
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* random.c -- A strong random number generator
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*
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* Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
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*
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* Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
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* rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, and the entire permission notice in its entirety,
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* including the disclaimer of warranties.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* ALTERNATIVELY, this product may be distributed under the terms of
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* the GNU General Public License, in which case the provisions of the GPL are
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* required INSTEAD OF the above restrictions. (This clause is
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* necessary due to a potential bad interaction between the GPL and
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* the restrictions contained in a BSD-style copyright.)
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
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* WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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* USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*/
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/*
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* (now, with legal B.S. out of the way.....)
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*
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* This routine gathers environmental noise from device drivers, etc.,
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* and returns good random numbers, suitable for cryptographic use.
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* Besides the obvious cryptographic uses, these numbers are also good
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* for seeding TCP sequence numbers, and other places where it is
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* desirable to have numbers which are not only random, but hard to
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* predict by an attacker.
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*
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* Theory of operation
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* ===================
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*
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* Computers are very predictable devices. Hence it is extremely hard
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* to produce truly random numbers on a computer --- as opposed to
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* pseudo-random numbers, which can easily generated by using a
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* algorithm. Unfortunately, it is very easy for attackers to guess
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* the sequence of pseudo-random number generators, and for some
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* applications this is not acceptable. So instead, we must try to
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* gather "environmental noise" from the computer's environment, which
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* must be hard for outside attackers to observe, and use that to
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* generate random numbers. In a Unix environment, this is best done
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* from inside the kernel.
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*
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* Sources of randomness from the environment include inter-keyboard
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* timings, inter-interrupt timings from some interrupts, and other
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* events which are both (a) non-deterministic and (b) hard for an
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* outside observer to measure. Randomness from these sources are
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* added to an "entropy pool", which is mixed using a CRC-like function.
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* This is not cryptographically strong, but it is adequate assuming
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* the randomness is not chosen maliciously, and it is fast enough that
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* the overhead of doing it on every interrupt is very reasonable.
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* As random bytes are mixed into the entropy pool, the routines keep
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* an *estimate* of how many bits of randomness have been stored into
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* the random number generator's internal state.
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*
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* When random bytes are desired, they are obtained by taking the SHA
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* hash of the contents of the "entropy pool". The SHA hash avoids
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* exposing the internal state of the entropy pool. It is believed to
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* be computationally infeasible to derive any useful information
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* about the input of SHA from its output. Even if it is possible to
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* analyze SHA in some clever way, as long as the amount of data
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* returned from the generator is less than the inherent entropy in
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* the pool, the output data is totally unpredictable. For this
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* reason, the routine decreases its internal estimate of how many
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* bits of "true randomness" are contained in the entropy pool as it
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* outputs random numbers.
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*
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* If this estimate goes to zero, the routine can still generate
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* random numbers; however, an attacker may (at least in theory) be
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* able to infer the future output of the generator from prior
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* outputs. This requires successful cryptanalysis of SHA, which is
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* not believed to be feasible, but there is a remote possibility.
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* Nonetheless, these numbers should be useful for the vast majority
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* of purposes.
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*
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* Exported interfaces ---- output
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* ===============================
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*
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* There are three exported interfaces; the first is one designed to
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* be used from within the kernel:
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*
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* void get_random_bytes(void *buf, int nbytes);
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*
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* This interface will return the requested number of random bytes,
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* and place it in the requested buffer.
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*
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* The two other interfaces are two character devices /dev/random and
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* /dev/urandom. /dev/random is suitable for use when very high
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* quality randomness is desired (for example, for key generation or
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* one-time pads), as it will only return a maximum of the number of
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* bits of randomness (as estimated by the random number generator)
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* contained in the entropy pool.
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*
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* The /dev/urandom device does not have this limit, and will return
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* as many bytes as are requested. As more and more random bytes are
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* requested without giving time for the entropy pool to recharge,
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* this will result in random numbers that are merely cryptographically
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* strong. For many applications, however, this is acceptable.
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*
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* Exported interfaces ---- input
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* ==============================
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*
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* The current exported interfaces for gathering environmental noise
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* from the devices are:
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*
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* void add_device_randomness(const void *buf, unsigned int size);
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* void add_input_randomness(unsigned int type, unsigned int code,
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* unsigned int value);
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* void add_interrupt_randomness(int irq, int irq_flags);
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* void add_disk_randomness(struct gendisk *disk);
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*
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* add_device_randomness() is for adding data to the random pool that
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* is likely to differ between two devices (or possibly even per boot).
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* This would be things like MAC addresses or serial numbers, or the
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* read-out of the RTC. This does *not* add any actual entropy to the
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* pool, but it initializes the pool to different values for devices
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* that might otherwise be identical and have very little entropy
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* available to them (particularly common in the embedded world).
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*
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* add_input_randomness() uses the input layer interrupt timing, as well as
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* the event type information from the hardware.
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*
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* add_interrupt_randomness() uses the interrupt timing as random
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* inputs to the entropy pool. Using the cycle counters and the irq source
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* as inputs, it feeds the randomness roughly once a second.
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*
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* add_disk_randomness() uses what amounts to the seek time of block
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* layer request events, on a per-disk_devt basis, as input to the
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* entropy pool. Note that high-speed solid state drives with very low
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* seek times do not make for good sources of entropy, as their seek
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* times are usually fairly consistent.
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*
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* All of these routines try to estimate how many bits of randomness a
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* particular randomness source. They do this by keeping track of the
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* first and second order deltas of the event timings.
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*
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* Ensuring unpredictability at system startup
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* ============================================
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*
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* When any operating system starts up, it will go through a sequence
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* of actions that are fairly predictable by an adversary, especially
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* if the start-up does not involve interaction with a human operator.
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* This reduces the actual number of bits of unpredictability in the
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* entropy pool below the value in entropy_count. In order to
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* counteract this effect, it helps to carry information in the
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* entropy pool across shut-downs and start-ups. To do this, put the
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* following lines an appropriate script which is run during the boot
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* sequence:
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*
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* echo "Initializing random number generator..."
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* random_seed=/var/run/random-seed
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* # Carry a random seed from start-up to start-up
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* # Load and then save the whole entropy pool
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* if [ -f $random_seed ]; then
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* cat $random_seed >/dev/urandom
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* else
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* touch $random_seed
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* fi
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* chmod 600 $random_seed
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* dd if=/dev/urandom of=$random_seed count=1 bs=512
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*
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* and the following lines in an appropriate script which is run as
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* the system is shutdown:
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*
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* # Carry a random seed from shut-down to start-up
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* # Save the whole entropy pool
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* echo "Saving random seed..."
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* random_seed=/var/run/random-seed
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* touch $random_seed
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* chmod 600 $random_seed
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* dd if=/dev/urandom of=$random_seed count=1 bs=512
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*
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* For example, on most modern systems using the System V init
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* scripts, such code fragments would be found in
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* /etc/rc.d/init.d/random. On older Linux systems, the correct script
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* location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
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*
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* Effectively, these commands cause the contents of the entropy pool
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* to be saved at shut-down time and reloaded into the entropy pool at
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* start-up. (The 'dd' in the addition to the bootup script is to
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* make sure that /etc/random-seed is different for every start-up,
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* even if the system crashes without executing rc.0.) Even with
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* complete knowledge of the start-up activities, predicting the state
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* of the entropy pool requires knowledge of the previous history of
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* the system.
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*
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* Configuring the /dev/random driver under Linux
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* ==============================================
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*
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* The /dev/random driver under Linux uses minor numbers 8 and 9 of
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* the /dev/mem major number (#1). So if your system does not have
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* /dev/random and /dev/urandom created already, they can be created
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* by using the commands:
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*
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* mknod /dev/random c 1 8
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* mknod /dev/urandom c 1 9
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*
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* Acknowledgements:
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* =================
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*
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* Ideas for constructing this random number generator were derived
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* from Pretty Good Privacy's random number generator, and from private
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* discussions with Phil Karn. Colin Plumb provided a faster random
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* number generator, which speed up the mixing function of the entropy
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* pool, taken from PGPfone. Dale Worley has also contributed many
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* useful ideas and suggestions to improve this driver.
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*
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* Any flaws in the design are solely my responsibility, and should
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* not be attributed to the Phil, Colin, or any of authors of PGP.
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*
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* Further background information on this topic may be obtained from
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* RFC 1750, "Randomness Recommendations for Security", by Donald
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* Eastlake, Steve Crocker, and Jeff Schiller.
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*/
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#include <linux/utsname.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/major.h>
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#include <linux/string.h>
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#include <linux/fcntl.h>
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#include <linux/slab.h>
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#include <linux/random.h>
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#include <linux/poll.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/genhd.h>
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#include <linux/interrupt.h>
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#include <linux/mm.h>
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#include <linux/spinlock.h>
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#include <linux/percpu.h>
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#include <linux/cryptohash.h>
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#include <linux/fips.h>
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#include <linux/ptrace.h>
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#include <linux/kmemcheck.h>
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#include <linux/irq.h>
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#include <asm/processor.h>
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#include <asm/uaccess.h>
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#include <asm/irq.h>
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#include <asm/irq_regs.h>
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#include <asm/io.h>
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#define CREATE_TRACE_POINTS
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#include <trace/events/random.h>
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/*
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* Configuration information
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*/
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#define INPUT_POOL_WORDS 128
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#define OUTPUT_POOL_WORDS 32
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#define SEC_XFER_SIZE 512
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#define EXTRACT_SIZE 10
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#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
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/*
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* The minimum number of bits of entropy before we wake up a read on
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* /dev/random. Should be enough to do a significant reseed.
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*/
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static int random_read_wakeup_thresh = 64;
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/*
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* If the entropy count falls under this number of bits, then we
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* should wake up processes which are selecting or polling on write
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* access to /dev/random.
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*/
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static int random_write_wakeup_thresh = 128;
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/*
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* When the input pool goes over trickle_thresh, start dropping most
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* samples to avoid wasting CPU time and reduce lock contention.
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*/
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static int trickle_thresh __read_mostly = INPUT_POOL_WORDS * 28;
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static DEFINE_PER_CPU(int, trickle_count);
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/*
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* A pool of size .poolwords is stirred with a primitive polynomial
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* of degree .poolwords over GF(2). The taps for various sizes are
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* defined below. They are chosen to be evenly spaced (minimum RMS
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* distance from evenly spaced; the numbers in the comments are a
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* scaled squared error sum) except for the last tap, which is 1 to
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* get the twisting happening as fast as possible.
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*/
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static struct poolinfo {
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int poolwords;
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int tap1, tap2, tap3, tap4, tap5;
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} poolinfo_table[] = {
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/* x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 -- 105 */
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{ 128, 103, 76, 51, 25, 1 },
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/* x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 -- 15 */
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{ 32, 26, 20, 14, 7, 1 },
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#if 0
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/* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
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{ 2048, 1638, 1231, 819, 411, 1 },
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/* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
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{ 1024, 817, 615, 412, 204, 1 },
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/* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
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{ 1024, 819, 616, 410, 207, 2 },
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/* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
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{ 512, 411, 308, 208, 104, 1 },
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/* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
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{ 512, 409, 307, 206, 102, 2 },
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/* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
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{ 512, 409, 309, 205, 103, 2 },
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/* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
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{ 256, 205, 155, 101, 52, 1 },
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/* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
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{ 128, 103, 78, 51, 27, 2 },
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/* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
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{ 64, 52, 39, 26, 14, 1 },
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#endif
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};
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#define POOLBITS poolwords*32
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#define POOLBYTES poolwords*4
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/*
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* For the purposes of better mixing, we use the CRC-32 polynomial as
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* well to make a twisted Generalized Feedback Shift Reigster
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*
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* (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM
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* Transactions on Modeling and Computer Simulation 2(3):179-194.
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* Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators
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* II. ACM Transactions on Mdeling and Computer Simulation 4:254-266)
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*
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* Thanks to Colin Plumb for suggesting this.
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*
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* We have not analyzed the resultant polynomial to prove it primitive;
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* in fact it almost certainly isn't. Nonetheless, the irreducible factors
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* of a random large-degree polynomial over GF(2) are more than large enough
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* that periodicity is not a concern.
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*
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* The input hash is much less sensitive than the output hash. All
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* that we want of it is that it be a good non-cryptographic hash;
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* i.e. it not produce collisions when fed "random" data of the sort
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* we expect to see. As long as the pool state differs for different
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* inputs, we have preserved the input entropy and done a good job.
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* The fact that an intelligent attacker can construct inputs that
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* will produce controlled alterations to the pool's state is not
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* important because we don't consider such inputs to contribute any
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* randomness. The only property we need with respect to them is that
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* the attacker can't increase his/her knowledge of the pool's state.
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* Since all additions are reversible (knowing the final state and the
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* input, you can reconstruct the initial state), if an attacker has
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* any uncertainty about the initial state, he/she can only shuffle
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* that uncertainty about, but never cause any collisions (which would
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* decrease the uncertainty).
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*
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* The chosen system lets the state of the pool be (essentially) the input
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* modulo the generator polymnomial. Now, for random primitive polynomials,
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* this is a universal class of hash functions, meaning that the chance
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* of a collision is limited by the attacker's knowledge of the generator
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* polynomail, so if it is chosen at random, an attacker can never force
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* a collision. Here, we use a fixed polynomial, but we *can* assume that
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* ###--> it is unknown to the processes generating the input entropy. <-###
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* Because of this important property, this is a good, collision-resistant
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* hash; hash collisions will occur no more often than chance.
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*/
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/*
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* Static global variables
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*/
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static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
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static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
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static struct fasync_struct *fasync;
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static bool debug;
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module_param(debug, bool, 0644);
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#define DEBUG_ENT(fmt, arg...) do { \
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if (debug) \
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printk(KERN_DEBUG "random %04d %04d %04d: " \
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fmt,\
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input_pool.entropy_count,\
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blocking_pool.entropy_count,\
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nonblocking_pool.entropy_count,\
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## arg); } while (0)
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/**********************************************************************
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*
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* OS independent entropy store. Here are the functions which handle
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* storing entropy in an entropy pool.
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*
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**********************************************************************/
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struct entropy_store;
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struct entropy_store {
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/* read-only data: */
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struct poolinfo *poolinfo;
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__u32 *pool;
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const char *name;
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struct entropy_store *pull;
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int limit;
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/* read-write data: */
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spinlock_t lock;
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unsigned add_ptr;
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unsigned input_rotate;
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int entropy_count;
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int entropy_total;
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unsigned int initialized:1;
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bool last_data_init;
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__u8 last_data[EXTRACT_SIZE];
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};
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static __u32 input_pool_data[INPUT_POOL_WORDS];
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static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
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static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
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static struct entropy_store input_pool = {
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.poolinfo = &poolinfo_table[0],
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.name = "input",
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.limit = 1,
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.lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
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.pool = input_pool_data
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};
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static struct entropy_store blocking_pool = {
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.poolinfo = &poolinfo_table[1],
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.name = "blocking",
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.limit = 1,
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.pull = &input_pool,
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.lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
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.pool = blocking_pool_data
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};
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static struct entropy_store nonblocking_pool = {
|
|
.poolinfo = &poolinfo_table[1],
|
|
.name = "nonblocking",
|
|
.pull = &input_pool,
|
|
.lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
|
|
.pool = nonblocking_pool_data
|
|
};
|
|
|
|
static __u32 const twist_table[8] = {
|
|
0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
|
|
0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
|
|
|
|
/*
|
|
* This function adds bytes into the entropy "pool". It does not
|
|
* update the entropy estimate. The caller should call
|
|
* credit_entropy_bits if this is appropriate.
|
|
*
|
|
* The pool is stirred with a primitive polynomial of the appropriate
|
|
* degree, and then twisted. We twist by three bits at a time because
|
|
* it's cheap to do so and helps slightly in the expected case where
|
|
* the entropy is concentrated in the low-order bits.
|
|
*/
|
|
static void _mix_pool_bytes(struct entropy_store *r, const void *in,
|
|
int nbytes, __u8 out[64])
|
|
{
|
|
unsigned long i, j, tap1, tap2, tap3, tap4, tap5;
|
|
int input_rotate;
|
|
int wordmask = r->poolinfo->poolwords - 1;
|
|
const char *bytes = in;
|
|
__u32 w;
|
|
|
|
tap1 = r->poolinfo->tap1;
|
|
tap2 = r->poolinfo->tap2;
|
|
tap3 = r->poolinfo->tap3;
|
|
tap4 = r->poolinfo->tap4;
|
|
tap5 = r->poolinfo->tap5;
|
|
|
|
smp_rmb();
|
|
input_rotate = ACCESS_ONCE(r->input_rotate);
|
|
i = ACCESS_ONCE(r->add_ptr);
|
|
|
|
/* mix one byte at a time to simplify size handling and churn faster */
|
|
while (nbytes--) {
|
|
w = rol32(*bytes++, input_rotate & 31);
|
|
i = (i - 1) & wordmask;
|
|
|
|
/* XOR in the various taps */
|
|
w ^= r->pool[i];
|
|
w ^= r->pool[(i + tap1) & wordmask];
|
|
w ^= r->pool[(i + tap2) & wordmask];
|
|
w ^= r->pool[(i + tap3) & wordmask];
|
|
w ^= r->pool[(i + tap4) & wordmask];
|
|
w ^= r->pool[(i + tap5) & wordmask];
|
|
|
|
/* Mix the result back in with a twist */
|
|
r->pool[i] = (w >> 3) ^ twist_table[w & 7];
|
|
|
|
/*
|
|
* Normally, we add 7 bits of rotation to the pool.
|
|
* At the beginning of the pool, add an extra 7 bits
|
|
* rotation, so that successive passes spread the
|
|
* input bits across the pool evenly.
|
|
*/
|
|
input_rotate += i ? 7 : 14;
|
|
}
|
|
|
|
ACCESS_ONCE(r->input_rotate) = input_rotate;
|
|
ACCESS_ONCE(r->add_ptr) = i;
|
|
smp_wmb();
|
|
|
|
if (out)
|
|
for (j = 0; j < 16; j++)
|
|
((__u32 *)out)[j] = r->pool[(i - j) & wordmask];
|
|
}
|
|
|
|
static void __mix_pool_bytes(struct entropy_store *r, const void *in,
|
|
int nbytes, __u8 out[64])
|
|
{
|
|
trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
|
|
_mix_pool_bytes(r, in, nbytes, out);
|
|
}
|
|
|
|
static void mix_pool_bytes(struct entropy_store *r, const void *in,
|
|
int nbytes, __u8 out[64])
|
|
{
|
|
unsigned long flags;
|
|
|
|
trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
|
|
spin_lock_irqsave(&r->lock, flags);
|
|
_mix_pool_bytes(r, in, nbytes, out);
|
|
spin_unlock_irqrestore(&r->lock, flags);
|
|
}
|
|
|
|
struct fast_pool {
|
|
__u32 pool[4];
|
|
unsigned long last;
|
|
unsigned short count;
|
|
unsigned char rotate;
|
|
unsigned char last_timer_intr;
|
|
};
|
|
|
|
/*
|
|
* This is a fast mixing routine used by the interrupt randomness
|
|
* collector. It's hardcoded for an 128 bit pool and assumes that any
|
|
* locks that might be needed are taken by the caller.
|
|
*/
|
|
static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
|
|
{
|
|
const char *bytes = in;
|
|
__u32 w;
|
|
unsigned i = f->count;
|
|
unsigned input_rotate = f->rotate;
|
|
|
|
while (nbytes--) {
|
|
w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
|
|
f->pool[(i + 1) & 3];
|
|
f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
|
|
input_rotate += (i++ & 3) ? 7 : 14;
|
|
}
|
|
f->count = i;
|
|
f->rotate = input_rotate;
|
|
}
|
|
|
|
/*
|
|
* Credit (or debit) the entropy store with n bits of entropy
|
|
*/
|
|
static void credit_entropy_bits(struct entropy_store *r, int nbits)
|
|
{
|
|
int entropy_count, orig;
|
|
|
|
if (!nbits)
|
|
return;
|
|
|
|
DEBUG_ENT("added %d entropy credits to %s\n", nbits, r->name);
|
|
retry:
|
|
entropy_count = orig = ACCESS_ONCE(r->entropy_count);
|
|
entropy_count += nbits;
|
|
|
|
if (entropy_count < 0) {
|
|
DEBUG_ENT("negative entropy/overflow\n");
|
|
entropy_count = 0;
|
|
} else if (entropy_count > r->poolinfo->POOLBITS)
|
|
entropy_count = r->poolinfo->POOLBITS;
|
|
if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
|
|
goto retry;
|
|
|
|
if (!r->initialized && nbits > 0) {
|
|
r->entropy_total += nbits;
|
|
if (r->entropy_total > 128)
|
|
r->initialized = 1;
|
|
}
|
|
|
|
trace_credit_entropy_bits(r->name, nbits, entropy_count,
|
|
r->entropy_total, _RET_IP_);
|
|
|
|
/* should we wake readers? */
|
|
if (r == &input_pool && entropy_count >= random_read_wakeup_thresh) {
|
|
wake_up_interruptible(&random_read_wait);
|
|
kill_fasync(&fasync, SIGIO, POLL_IN);
|
|
}
|
|
}
|
|
|
|
/*********************************************************************
|
|
*
|
|
* Entropy input management
|
|
*
|
|
*********************************************************************/
|
|
|
|
/* There is one of these per entropy source */
|
|
struct timer_rand_state {
|
|
cycles_t last_time;
|
|
long last_delta, last_delta2;
|
|
unsigned dont_count_entropy:1;
|
|
};
|
|
|
|
/*
|
|
* Add device- or boot-specific data to the input and nonblocking
|
|
* pools to help initialize them to unique values.
|
|
*
|
|
* None of this adds any entropy, it is meant to avoid the
|
|
* problem of the nonblocking pool having similar initial state
|
|
* across largely identical devices.
|
|
*/
|
|
void add_device_randomness(const void *buf, unsigned int size)
|
|
{
|
|
unsigned long time = get_cycles() ^ jiffies;
|
|
|
|
mix_pool_bytes(&input_pool, buf, size, NULL);
|
|
mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);
|
|
mix_pool_bytes(&nonblocking_pool, buf, size, NULL);
|
|
mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);
|
|
}
|
|
EXPORT_SYMBOL(add_device_randomness);
|
|
|
|
static struct timer_rand_state input_timer_state;
|
|
|
|
/*
|
|
* This function adds entropy to the entropy "pool" by using timing
|
|
* delays. It uses the timer_rand_state structure to make an estimate
|
|
* of how many bits of entropy this call has added to the pool.
|
|
*
|
|
* The number "num" is also added to the pool - it should somehow describe
|
|
* the type of event which just happened. This is currently 0-255 for
|
|
* keyboard scan codes, and 256 upwards for interrupts.
|
|
*
|
|
*/
|
|
static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
|
|
{
|
|
struct {
|
|
long jiffies;
|
|
unsigned cycles;
|
|
unsigned num;
|
|
} sample;
|
|
long delta, delta2, delta3;
|
|
|
|
preempt_disable();
|
|
/* if over the trickle threshold, use only 1 in 4096 samples */
|
|
if (input_pool.entropy_count > trickle_thresh &&
|
|
((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
|
|
goto out;
|
|
|
|
sample.jiffies = jiffies;
|
|
sample.cycles = get_cycles();
|
|
sample.num = num;
|
|
mix_pool_bytes(&input_pool, &sample, sizeof(sample), NULL);
|
|
|
|
/*
|
|
* Calculate number of bits of randomness we probably added.
|
|
* We take into account the first, second and third-order deltas
|
|
* in order to make our estimate.
|
|
*/
|
|
|
|
if (!state->dont_count_entropy) {
|
|
delta = sample.jiffies - state->last_time;
|
|
state->last_time = sample.jiffies;
|
|
|
|
delta2 = delta - state->last_delta;
|
|
state->last_delta = delta;
|
|
|
|
delta3 = delta2 - state->last_delta2;
|
|
state->last_delta2 = delta2;
|
|
|
|
if (delta < 0)
|
|
delta = -delta;
|
|
if (delta2 < 0)
|
|
delta2 = -delta2;
|
|
if (delta3 < 0)
|
|
delta3 = -delta3;
|
|
if (delta > delta2)
|
|
delta = delta2;
|
|
if (delta > delta3)
|
|
delta = delta3;
|
|
|
|
/*
|
|
* delta is now minimum absolute delta.
|
|
* Round down by 1 bit on general principles,
|
|
* and limit entropy entimate to 12 bits.
|
|
*/
|
|
credit_entropy_bits(&input_pool,
|
|
min_t(int, fls(delta>>1), 11));
|
|
}
|
|
out:
|
|
preempt_enable();
|
|
}
|
|
|
|
void add_input_randomness(unsigned int type, unsigned int code,
|
|
unsigned int value)
|
|
{
|
|
static unsigned char last_value;
|
|
|
|
/* ignore autorepeat and the like */
|
|
if (value == last_value)
|
|
return;
|
|
|
|
DEBUG_ENT("input event\n");
|
|
last_value = value;
|
|
add_timer_randomness(&input_timer_state,
|
|
(type << 4) ^ code ^ (code >> 4) ^ value);
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_input_randomness);
|
|
|
|
static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
|
|
|
|
void add_interrupt_randomness(int irq, int irq_flags)
|
|
{
|
|
struct entropy_store *r;
|
|
struct fast_pool *fast_pool = &__get_cpu_var(irq_randomness);
|
|
struct pt_regs *regs = get_irq_regs();
|
|
unsigned long now = jiffies;
|
|
__u32 input[4], cycles = get_cycles();
|
|
|
|
input[0] = cycles ^ jiffies;
|
|
input[1] = irq;
|
|
if (regs) {
|
|
__u64 ip = instruction_pointer(regs);
|
|
input[2] = ip;
|
|
input[3] = ip >> 32;
|
|
}
|
|
|
|
fast_mix(fast_pool, input, sizeof(input));
|
|
|
|
if ((fast_pool->count & 1023) &&
|
|
!time_after(now, fast_pool->last + HZ))
|
|
return;
|
|
|
|
fast_pool->last = now;
|
|
|
|
r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
|
|
__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool), NULL);
|
|
/*
|
|
* If we don't have a valid cycle counter, and we see
|
|
* back-to-back timer interrupts, then skip giving credit for
|
|
* any entropy.
|
|
*/
|
|
if (cycles == 0) {
|
|
if (irq_flags & __IRQF_TIMER) {
|
|
if (fast_pool->last_timer_intr)
|
|
return;
|
|
fast_pool->last_timer_intr = 1;
|
|
} else
|
|
fast_pool->last_timer_intr = 0;
|
|
}
|
|
credit_entropy_bits(r, 1);
|
|
}
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
void add_disk_randomness(struct gendisk *disk)
|
|
{
|
|
if (!disk || !disk->random)
|
|
return;
|
|
/* first major is 1, so we get >= 0x200 here */
|
|
DEBUG_ENT("disk event %d:%d\n",
|
|
MAJOR(disk_devt(disk)), MINOR(disk_devt(disk)));
|
|
|
|
add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
|
|
}
|
|
#endif
|
|
|
|
/*********************************************************************
|
|
*
|
|
* Entropy extraction routines
|
|
*
|
|
*********************************************************************/
|
|
|
|
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
|
|
size_t nbytes, int min, int rsvd);
|
|
|
|
/*
|
|
* This utility inline function is responsible for transferring entropy
|
|
* from the primary pool to the secondary extraction pool. We make
|
|
* sure we pull enough for a 'catastrophic reseed'.
|
|
*/
|
|
static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
|
|
{
|
|
__u32 tmp[OUTPUT_POOL_WORDS];
|
|
|
|
if (r->pull && r->entropy_count < nbytes * 8 &&
|
|
r->entropy_count < r->poolinfo->POOLBITS) {
|
|
/* If we're limited, always leave two wakeup worth's BITS */
|
|
int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
|
|
int bytes = nbytes;
|
|
|
|
/* pull at least as many as BYTES as wakeup BITS */
|
|
bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
|
|
/* but never more than the buffer size */
|
|
bytes = min_t(int, bytes, sizeof(tmp));
|
|
|
|
DEBUG_ENT("going to reseed %s with %d bits "
|
|
"(%zu of %d requested)\n",
|
|
r->name, bytes * 8, nbytes * 8, r->entropy_count);
|
|
|
|
bytes = extract_entropy(r->pull, tmp, bytes,
|
|
random_read_wakeup_thresh / 8, rsvd);
|
|
mix_pool_bytes(r, tmp, bytes, NULL);
|
|
credit_entropy_bits(r, bytes*8);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* These functions extracts randomness from the "entropy pool", and
|
|
* returns it in a buffer.
|
|
*
|
|
* The min parameter specifies the minimum amount we can pull before
|
|
* failing to avoid races that defeat catastrophic reseeding while the
|
|
* reserved parameter indicates how much entropy we must leave in the
|
|
* pool after each pull to avoid starving other readers.
|
|
*
|
|
* Note: extract_entropy() assumes that .poolwords is a multiple of 16 words.
|
|
*/
|
|
|
|
static size_t account(struct entropy_store *r, size_t nbytes, int min,
|
|
int reserved)
|
|
{
|
|
unsigned long flags;
|
|
int wakeup_write = 0;
|
|
|
|
/* Hold lock while accounting */
|
|
spin_lock_irqsave(&r->lock, flags);
|
|
|
|
BUG_ON(r->entropy_count > r->poolinfo->POOLBITS);
|
|
DEBUG_ENT("trying to extract %zu bits from %s\n",
|
|
nbytes * 8, r->name);
|
|
|
|
/* Can we pull enough? */
|
|
if (r->entropy_count / 8 < min + reserved) {
|
|
nbytes = 0;
|
|
} else {
|
|
int entropy_count, orig;
|
|
retry:
|
|
entropy_count = orig = ACCESS_ONCE(r->entropy_count);
|
|
/* If limited, never pull more than available */
|
|
if (r->limit && nbytes + reserved >= entropy_count / 8)
|
|
nbytes = entropy_count/8 - reserved;
|
|
|
|
if (entropy_count / 8 >= nbytes + reserved) {
|
|
entropy_count -= nbytes*8;
|
|
if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
|
|
goto retry;
|
|
} else {
|
|
entropy_count = reserved;
|
|
if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
|
|
goto retry;
|
|
}
|
|
|
|
if (entropy_count < random_write_wakeup_thresh)
|
|
wakeup_write = 1;
|
|
}
|
|
|
|
DEBUG_ENT("debiting %zu entropy credits from %s%s\n",
|
|
nbytes * 8, r->name, r->limit ? "" : " (unlimited)");
|
|
|
|
spin_unlock_irqrestore(&r->lock, flags);
|
|
|
|
if (wakeup_write) {
|
|
wake_up_interruptible(&random_write_wait);
|
|
kill_fasync(&fasync, SIGIO, POLL_OUT);
|
|
}
|
|
|
|
return nbytes;
|
|
}
|
|
|
|
static void extract_buf(struct entropy_store *r, __u8 *out)
|
|
{
|
|
int i;
|
|
union {
|
|
__u32 w[5];
|
|
unsigned long l[LONGS(EXTRACT_SIZE)];
|
|
} hash;
|
|
__u32 workspace[SHA_WORKSPACE_WORDS];
|
|
__u8 extract[64];
|
|
unsigned long flags;
|
|
|
|
/* Generate a hash across the pool, 16 words (512 bits) at a time */
|
|
sha_init(hash.w);
|
|
spin_lock_irqsave(&r->lock, flags);
|
|
for (i = 0; i < r->poolinfo->poolwords; i += 16)
|
|
sha_transform(hash.w, (__u8 *)(r->pool + i), workspace);
|
|
|
|
/*
|
|
* We mix the hash back into the pool to prevent backtracking
|
|
* attacks (where the attacker knows the state of the pool
|
|
* plus the current outputs, and attempts to find previous
|
|
* ouputs), unless the hash function can be inverted. By
|
|
* mixing at least a SHA1 worth of hash data back, we make
|
|
* brute-forcing the feedback as hard as brute-forcing the
|
|
* hash.
|
|
*/
|
|
__mix_pool_bytes(r, hash.w, sizeof(hash.w), extract);
|
|
spin_unlock_irqrestore(&r->lock, flags);
|
|
|
|
/*
|
|
* To avoid duplicates, we atomically extract a portion of the
|
|
* pool while mixing, and hash one final time.
|
|
*/
|
|
sha_transform(hash.w, extract, workspace);
|
|
memset(extract, 0, sizeof(extract));
|
|
memset(workspace, 0, sizeof(workspace));
|
|
|
|
/*
|
|
* In case the hash function has some recognizable output
|
|
* pattern, we fold it in half. Thus, we always feed back
|
|
* twice as much data as we output.
|
|
*/
|
|
hash.w[0] ^= hash.w[3];
|
|
hash.w[1] ^= hash.w[4];
|
|
hash.w[2] ^= rol32(hash.w[2], 16);
|
|
|
|
/*
|
|
* If we have a architectural hardware random number
|
|
* generator, mix that in, too.
|
|
*/
|
|
for (i = 0; i < LONGS(EXTRACT_SIZE); i++) {
|
|
unsigned long v;
|
|
if (!arch_get_random_long(&v))
|
|
break;
|
|
hash.l[i] ^= v;
|
|
}
|
|
|
|
memcpy(out, &hash, EXTRACT_SIZE);
|
|
memset(&hash, 0, sizeof(hash));
|
|
}
|
|
|
|
static ssize_t extract_entropy(struct entropy_store *r, void *buf,
|
|
size_t nbytes, int min, int reserved)
|
|
{
|
|
ssize_t ret = 0, i;
|
|
__u8 tmp[EXTRACT_SIZE];
|
|
unsigned long flags;
|
|
|
|
/* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
|
|
if (fips_enabled) {
|
|
spin_lock_irqsave(&r->lock, flags);
|
|
if (!r->last_data_init) {
|
|
r->last_data_init = true;
|
|
spin_unlock_irqrestore(&r->lock, flags);
|
|
trace_extract_entropy(r->name, EXTRACT_SIZE,
|
|
r->entropy_count, _RET_IP_);
|
|
xfer_secondary_pool(r, EXTRACT_SIZE);
|
|
extract_buf(r, tmp);
|
|
spin_lock_irqsave(&r->lock, flags);
|
|
memcpy(r->last_data, tmp, EXTRACT_SIZE);
|
|
}
|
|
spin_unlock_irqrestore(&r->lock, flags);
|
|
}
|
|
|
|
trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
|
|
xfer_secondary_pool(r, nbytes);
|
|
nbytes = account(r, nbytes, min, reserved);
|
|
|
|
while (nbytes) {
|
|
extract_buf(r, tmp);
|
|
|
|
if (fips_enabled) {
|
|
spin_lock_irqsave(&r->lock, flags);
|
|
if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
|
|
panic("Hardware RNG duplicated output!\n");
|
|
memcpy(r->last_data, tmp, EXTRACT_SIZE);
|
|
spin_unlock_irqrestore(&r->lock, flags);
|
|
}
|
|
i = min_t(int, nbytes, EXTRACT_SIZE);
|
|
memcpy(buf, tmp, i);
|
|
nbytes -= i;
|
|
buf += i;
|
|
ret += i;
|
|
}
|
|
|
|
/* Wipe data just returned from memory */
|
|
memset(tmp, 0, sizeof(tmp));
|
|
|
|
return ret;
|
|
}
|
|
|
|
static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
|
|
size_t nbytes)
|
|
{
|
|
ssize_t ret = 0, i;
|
|
__u8 tmp[EXTRACT_SIZE];
|
|
|
|
trace_extract_entropy_user(r->name, nbytes, r->entropy_count, _RET_IP_);
|
|
xfer_secondary_pool(r, nbytes);
|
|
nbytes = account(r, nbytes, 0, 0);
|
|
|
|
while (nbytes) {
|
|
if (need_resched()) {
|
|
if (signal_pending(current)) {
|
|
if (ret == 0)
|
|
ret = -ERESTARTSYS;
|
|
break;
|
|
}
|
|
schedule();
|
|
}
|
|
|
|
extract_buf(r, tmp);
|
|
i = min_t(int, nbytes, EXTRACT_SIZE);
|
|
if (copy_to_user(buf, tmp, i)) {
|
|
ret = -EFAULT;
|
|
break;
|
|
}
|
|
|
|
nbytes -= i;
|
|
buf += i;
|
|
ret += i;
|
|
}
|
|
|
|
/* Wipe data just returned from memory */
|
|
memset(tmp, 0, sizeof(tmp));
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* This function is the exported kernel interface. It returns some
|
|
* number of good random numbers, suitable for key generation, seeding
|
|
* TCP sequence numbers, etc. It does not use the hw random number
|
|
* generator, if available; use get_random_bytes_arch() for that.
|
|
*/
|
|
void get_random_bytes(void *buf, int nbytes)
|
|
{
|
|
extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
|
|
}
|
|
EXPORT_SYMBOL(get_random_bytes);
|
|
|
|
/*
|
|
* This function will use the architecture-specific hardware random
|
|
* number generator if it is available. The arch-specific hw RNG will
|
|
* almost certainly be faster than what we can do in software, but it
|
|
* is impossible to verify that it is implemented securely (as
|
|
* opposed, to, say, the AES encryption of a sequence number using a
|
|
* key known by the NSA). So it's useful if we need the speed, but
|
|
* only if we're willing to trust the hardware manufacturer not to
|
|
* have put in a back door.
|
|
*/
|
|
void get_random_bytes_arch(void *buf, int nbytes)
|
|
{
|
|
char *p = buf;
|
|
|
|
trace_get_random_bytes(nbytes, _RET_IP_);
|
|
while (nbytes) {
|
|
unsigned long v;
|
|
int chunk = min(nbytes, (int)sizeof(unsigned long));
|
|
|
|
if (!arch_get_random_long(&v))
|
|
break;
|
|
|
|
memcpy(p, &v, chunk);
|
|
p += chunk;
|
|
nbytes -= chunk;
|
|
}
|
|
|
|
if (nbytes)
|
|
extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
|
|
}
|
|
EXPORT_SYMBOL(get_random_bytes_arch);
|
|
|
|
|
|
/*
|
|
* init_std_data - initialize pool with system data
|
|
*
|
|
* @r: pool to initialize
|
|
*
|
|
* This function clears the pool's entropy count and mixes some system
|
|
* data into the pool to prepare it for use. The pool is not cleared
|
|
* as that can only decrease the entropy in the pool.
|
|
*/
|
|
static void init_std_data(struct entropy_store *r)
|
|
{
|
|
int i;
|
|
ktime_t now = ktime_get_real();
|
|
unsigned long rv;
|
|
|
|
r->entropy_count = 0;
|
|
r->entropy_total = 0;
|
|
r->last_data_init = false;
|
|
mix_pool_bytes(r, &now, sizeof(now), NULL);
|
|
for (i = r->poolinfo->POOLBYTES; i > 0; i -= sizeof(rv)) {
|
|
if (!arch_get_random_long(&rv))
|
|
break;
|
|
mix_pool_bytes(r, &rv, sizeof(rv), NULL);
|
|
}
|
|
mix_pool_bytes(r, utsname(), sizeof(*(utsname())), NULL);
|
|
}
|
|
|
|
/*
|
|
* Note that setup_arch() may call add_device_randomness()
|
|
* long before we get here. This allows seeding of the pools
|
|
* with some platform dependent data very early in the boot
|
|
* process. But it limits our options here. We must use
|
|
* statically allocated structures that already have all
|
|
* initializations complete at compile time. We should also
|
|
* take care not to overwrite the precious per platform data
|
|
* we were given.
|
|
*/
|
|
static int rand_initialize(void)
|
|
{
|
|
init_std_data(&input_pool);
|
|
init_std_data(&blocking_pool);
|
|
init_std_data(&nonblocking_pool);
|
|
return 0;
|
|
}
|
|
module_init(rand_initialize);
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
void rand_initialize_disk(struct gendisk *disk)
|
|
{
|
|
struct timer_rand_state *state;
|
|
|
|
/*
|
|
* If kzalloc returns null, we just won't use that entropy
|
|
* source.
|
|
*/
|
|
state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
|
|
if (state)
|
|
disk->random = state;
|
|
}
|
|
#endif
|
|
|
|
static ssize_t
|
|
random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
|
|
{
|
|
ssize_t n, retval = 0, count = 0;
|
|
|
|
if (nbytes == 0)
|
|
return 0;
|
|
|
|
while (nbytes > 0) {
|
|
n = nbytes;
|
|
if (n > SEC_XFER_SIZE)
|
|
n = SEC_XFER_SIZE;
|
|
|
|
DEBUG_ENT("reading %zu bits\n", n*8);
|
|
|
|
n = extract_entropy_user(&blocking_pool, buf, n);
|
|
|
|
if (n < 0) {
|
|
retval = n;
|
|
break;
|
|
}
|
|
|
|
DEBUG_ENT("read got %zd bits (%zd still needed)\n",
|
|
n*8, (nbytes-n)*8);
|
|
|
|
if (n == 0) {
|
|
if (file->f_flags & O_NONBLOCK) {
|
|
retval = -EAGAIN;
|
|
break;
|
|
}
|
|
|
|
DEBUG_ENT("sleeping?\n");
|
|
|
|
wait_event_interruptible(random_read_wait,
|
|
input_pool.entropy_count >=
|
|
random_read_wakeup_thresh);
|
|
|
|
DEBUG_ENT("awake\n");
|
|
|
|
if (signal_pending(current)) {
|
|
retval = -ERESTARTSYS;
|
|
break;
|
|
}
|
|
|
|
continue;
|
|
}
|
|
|
|
count += n;
|
|
buf += n;
|
|
nbytes -= n;
|
|
break; /* This break makes the device work */
|
|
/* like a named pipe */
|
|
}
|
|
|
|
return (count ? count : retval);
|
|
}
|
|
|
|
static ssize_t
|
|
urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
|
|
{
|
|
return extract_entropy_user(&nonblocking_pool, buf, nbytes);
|
|
}
|
|
|
|
static unsigned int
|
|
random_poll(struct file *file, poll_table * wait)
|
|
{
|
|
unsigned int mask;
|
|
|
|
poll_wait(file, &random_read_wait, wait);
|
|
poll_wait(file, &random_write_wait, wait);
|
|
mask = 0;
|
|
if (input_pool.entropy_count >= random_read_wakeup_thresh)
|
|
mask |= POLLIN | POLLRDNORM;
|
|
if (input_pool.entropy_count < random_write_wakeup_thresh)
|
|
mask |= POLLOUT | POLLWRNORM;
|
|
return mask;
|
|
}
|
|
|
|
static int
|
|
write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
|
|
{
|
|
size_t bytes;
|
|
__u32 buf[16];
|
|
const char __user *p = buffer;
|
|
|
|
while (count > 0) {
|
|
bytes = min(count, sizeof(buf));
|
|
if (copy_from_user(&buf, p, bytes))
|
|
return -EFAULT;
|
|
|
|
count -= bytes;
|
|
p += bytes;
|
|
|
|
mix_pool_bytes(r, buf, bytes, NULL);
|
|
cond_resched();
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static ssize_t random_write(struct file *file, const char __user *buffer,
|
|
size_t count, loff_t *ppos)
|
|
{
|
|
size_t ret;
|
|
|
|
ret = write_pool(&blocking_pool, buffer, count);
|
|
if (ret)
|
|
return ret;
|
|
ret = write_pool(&nonblocking_pool, buffer, count);
|
|
if (ret)
|
|
return ret;
|
|
|
|
return (ssize_t)count;
|
|
}
|
|
|
|
static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
|
|
{
|
|
int size, ent_count;
|
|
int __user *p = (int __user *)arg;
|
|
int retval;
|
|
|
|
switch (cmd) {
|
|
case RNDGETENTCNT:
|
|
/* inherently racy, no point locking */
|
|
if (put_user(input_pool.entropy_count, p))
|
|
return -EFAULT;
|
|
return 0;
|
|
case RNDADDTOENTCNT:
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
if (get_user(ent_count, p))
|
|
return -EFAULT;
|
|
credit_entropy_bits(&input_pool, ent_count);
|
|
return 0;
|
|
case RNDADDENTROPY:
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
if (get_user(ent_count, p++))
|
|
return -EFAULT;
|
|
if (ent_count < 0)
|
|
return -EINVAL;
|
|
if (get_user(size, p++))
|
|
return -EFAULT;
|
|
retval = write_pool(&input_pool, (const char __user *)p,
|
|
size);
|
|
if (retval < 0)
|
|
return retval;
|
|
credit_entropy_bits(&input_pool, ent_count);
|
|
return 0;
|
|
case RNDZAPENTCNT:
|
|
case RNDCLEARPOOL:
|
|
/* Clear the entropy pool counters. */
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
rand_initialize();
|
|
return 0;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
static int random_fasync(int fd, struct file *filp, int on)
|
|
{
|
|
return fasync_helper(fd, filp, on, &fasync);
|
|
}
|
|
|
|
const struct file_operations random_fops = {
|
|
.read = random_read,
|
|
.write = random_write,
|
|
.poll = random_poll,
|
|
.unlocked_ioctl = random_ioctl,
|
|
.fasync = random_fasync,
|
|
.llseek = noop_llseek,
|
|
};
|
|
|
|
const struct file_operations urandom_fops = {
|
|
.read = urandom_read,
|
|
.write = random_write,
|
|
.unlocked_ioctl = random_ioctl,
|
|
.fasync = random_fasync,
|
|
.llseek = noop_llseek,
|
|
};
|
|
|
|
/***************************************************************
|
|
* Random UUID interface
|
|
*
|
|
* Used here for a Boot ID, but can be useful for other kernel
|
|
* drivers.
|
|
***************************************************************/
|
|
|
|
/*
|
|
* Generate random UUID
|
|
*/
|
|
void generate_random_uuid(unsigned char uuid_out[16])
|
|
{
|
|
get_random_bytes(uuid_out, 16);
|
|
/* Set UUID version to 4 --- truly random generation */
|
|
uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
|
|
/* Set the UUID variant to DCE */
|
|
uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
|
|
}
|
|
EXPORT_SYMBOL(generate_random_uuid);
|
|
|
|
/********************************************************************
|
|
*
|
|
* Sysctl interface
|
|
*
|
|
********************************************************************/
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
|
|
#include <linux/sysctl.h>
|
|
|
|
static int min_read_thresh = 8, min_write_thresh;
|
|
static int max_read_thresh = INPUT_POOL_WORDS * 32;
|
|
static int max_write_thresh = INPUT_POOL_WORDS * 32;
|
|
static char sysctl_bootid[16];
|
|
|
|
/*
|
|
* These functions is used to return both the bootid UUID, and random
|
|
* UUID. The difference is in whether table->data is NULL; if it is,
|
|
* then a new UUID is generated and returned to the user.
|
|
*
|
|
* If the user accesses this via the proc interface, it will be returned
|
|
* as an ASCII string in the standard UUID format. If accesses via the
|
|
* sysctl system call, it is returned as 16 bytes of binary data.
|
|
*/
|
|
static int proc_do_uuid(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
struct ctl_table fake_table;
|
|
unsigned char buf[64], tmp_uuid[16], *uuid;
|
|
|
|
uuid = table->data;
|
|
if (!uuid) {
|
|
uuid = tmp_uuid;
|
|
generate_random_uuid(uuid);
|
|
} else {
|
|
static DEFINE_SPINLOCK(bootid_spinlock);
|
|
|
|
spin_lock(&bootid_spinlock);
|
|
if (!uuid[8])
|
|
generate_random_uuid(uuid);
|
|
spin_unlock(&bootid_spinlock);
|
|
}
|
|
|
|
sprintf(buf, "%pU", uuid);
|
|
|
|
fake_table.data = buf;
|
|
fake_table.maxlen = sizeof(buf);
|
|
|
|
return proc_dostring(&fake_table, write, buffer, lenp, ppos);
|
|
}
|
|
|
|
static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
|
|
extern struct ctl_table random_table[];
|
|
struct ctl_table random_table[] = {
|
|
{
|
|
.procname = "poolsize",
|
|
.data = &sysctl_poolsize,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0444,
|
|
.proc_handler = proc_dointvec,
|
|
},
|
|
{
|
|
.procname = "entropy_avail",
|
|
.maxlen = sizeof(int),
|
|
.mode = 0444,
|
|
.proc_handler = proc_dointvec,
|
|
.data = &input_pool.entropy_count,
|
|
},
|
|
{
|
|
.procname = "read_wakeup_threshold",
|
|
.data = &random_read_wakeup_thresh,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec_minmax,
|
|
.extra1 = &min_read_thresh,
|
|
.extra2 = &max_read_thresh,
|
|
},
|
|
{
|
|
.procname = "write_wakeup_threshold",
|
|
.data = &random_write_wakeup_thresh,
|
|
.maxlen = sizeof(int),
|
|
.mode = 0644,
|
|
.proc_handler = proc_dointvec_minmax,
|
|
.extra1 = &min_write_thresh,
|
|
.extra2 = &max_write_thresh,
|
|
},
|
|
{
|
|
.procname = "boot_id",
|
|
.data = &sysctl_bootid,
|
|
.maxlen = 16,
|
|
.mode = 0444,
|
|
.proc_handler = proc_do_uuid,
|
|
},
|
|
{
|
|
.procname = "uuid",
|
|
.maxlen = 16,
|
|
.mode = 0444,
|
|
.proc_handler = proc_do_uuid,
|
|
},
|
|
{ }
|
|
};
|
|
#endif /* CONFIG_SYSCTL */
|
|
|
|
static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
|
|
|
|
static int __init random_int_secret_init(void)
|
|
{
|
|
get_random_bytes(random_int_secret, sizeof(random_int_secret));
|
|
return 0;
|
|
}
|
|
late_initcall(random_int_secret_init);
|
|
|
|
/*
|
|
* Get a random word for internal kernel use only. Similar to urandom but
|
|
* with the goal of minimal entropy pool depletion. As a result, the random
|
|
* value is not cryptographically secure but for several uses the cost of
|
|
* depleting entropy is too high
|
|
*/
|
|
static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
|
|
unsigned int get_random_int(void)
|
|
{
|
|
__u32 *hash;
|
|
unsigned int ret;
|
|
|
|
if (arch_get_random_int(&ret))
|
|
return ret;
|
|
|
|
hash = get_cpu_var(get_random_int_hash);
|
|
|
|
hash[0] += current->pid + jiffies + get_cycles();
|
|
md5_transform(hash, random_int_secret);
|
|
ret = hash[0];
|
|
put_cpu_var(get_random_int_hash);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(get_random_int);
|
|
|
|
/*
|
|
* randomize_range() returns a start address such that
|
|
*
|
|
* [...... <range> .....]
|
|
* start end
|
|
*
|
|
* a <range> with size "len" starting at the return value is inside in the
|
|
* area defined by [start, end], but is otherwise randomized.
|
|
*/
|
|
unsigned long
|
|
randomize_range(unsigned long start, unsigned long end, unsigned long len)
|
|
{
|
|
unsigned long range = end - len - start;
|
|
|
|
if (end <= start + len)
|
|
return 0;
|
|
return PAGE_ALIGN(get_random_int() % range + start);
|
|
}
|