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KEYS: Convert KEYCTL_DH_COMPUTE to use the crypto KPP API 

The initial Diffie-Hellman computation made direct use of the MPI
library because the crypto module did not support DH at the time. Now
that KPP is implemented, KEYCTL_DH_COMPUTE should use it to get rid of
duplicate code and leverage possible hardware acceleration.

This fixes an issue whereby the input to the KDF computation would
include additional uninitialized memory when the result of the
Diffie-Hellman computation was shorter than the input prime number.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
This commit is contained in:
Mat Martineau 2017-06-08 14:50:11 +01:00 committed by James Morris
parent da7798a7b6
commit 7cbe0932c2
2 changed files with 177 additions and 109 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
security/keys/Kconfig
View File

@ -93,9 +93,9 @@ config ENCRYPTED_KEYS
config KEY_DH_OPERATIONS
bool "Diffie-Hellman operations on retained keys"
depends on KEYS
select MPILIB
select CRYPTO
select CRYPTO_HASH
select CRYPTO_DH
help
This option provides support for calculating Diffie-Hellman
public keys and shared secrets using values stored as keys

282
security/keys/dh.c
View File

@ -8,34 +8,17 @@
* 2 of the License, or (at your option) any later version.
*/
#include <linux/mpi.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/scatterlist.h>
#include <linux/crypto.h>
#include <crypto/hash.h>
#include <crypto/kpp.h>
#include <crypto/dh.h>
#include <keys/user-type.h>
#include "internal.h"
/*
* Public key or shared secret generation function [RFC2631 sec 2.1.1]
*
* ya = g^xa mod p;
* or
* ZZ = yb^xa mod p;
*
* where xa is the local private key, ya is the local public key, g is
* the generator, p is the prime, yb is the remote public key, and ZZ
* is the shared secret.
*
* Both are the same calculation, so g or yb are the "base" and ya or
* ZZ are the "result".
*/
static int do_dh(MPI result, MPI base, MPI xa, MPI p)
{
return mpi_powm(result, base, xa, p);
}
static ssize_t mpi_from_key(key_serial_t keyid, size_t maxlen, MPI *mpi)
static ssize_t dh_data_from_key(key_serial_t keyid, void **data)
{
struct key *key;
key_ref_t key_ref;
@ -56,19 +39,17 @@ static ssize_t mpi_from_key(key_serial_t keyid, size_t maxlen, MPI *mpi)
status = key_validate(key);
if (status == 0) {
const struct user_key_payload *payload;
uint8_t *duplicate;
payload = user_key_payload_locked(key);
if (maxlen == 0) {
*mpi = NULL;
ret = payload->datalen;
} else if (payload->datalen <= maxlen) {
*mpi = mpi_read_raw_data(payload->data,
payload->datalen);
if (*mpi)
duplicate = kmemdup(payload->data, payload->datalen,
GFP_KERNEL);
if (duplicate) {
*data = duplicate;
ret = payload->datalen;
} else {
ret = -EINVAL;
ret = -ENOMEM;
}
}
up_read(&key->sem);
@ -79,6 +60,29 @@ error:
return ret;
}
static void dh_free_data(struct dh *dh)
{
kzfree(dh->key);
kzfree(dh->p);
kzfree(dh->g);
}
struct dh_completion {
struct completion completion;
int err;
};
static void dh_crypto_done(struct crypto_async_request *req, int err)
{
struct dh_completion *compl = req->data;
if (err == -EINPROGRESS)
return;
compl->err = err;
complete(&compl->completion);
}
struct kdf_sdesc {
struct shash_desc shash;
char ctx[];
@ -140,7 +144,7 @@ static void kdf_dealloc(struct kdf_sdesc *sdesc)
* 5.8.1.2).
*/
static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
u8 *dst, unsigned int dlen)
u8 *dst, unsigned int dlen, unsigned int zlen)
{
struct shash_desc *desc = &sdesc->shash;
unsigned int h = crypto_shash_digestsize(desc->tfm);
@ -157,6 +161,22 @@ static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
if (err)
goto err;
if (zlen && h) {
u8 tmpbuffer[h];
size_t chunk = min_t(size_t, zlen, h);
memset(tmpbuffer, 0, chunk);
do {
err = crypto_shash_update(desc, tmpbuffer,
chunk);
if (err)
goto err;
zlen -= chunk;
chunk = min_t(size_t, zlen, h);
} while (zlen);
}
if (src && slen) {
err = crypto_shash_update(desc, src, slen);
if (err)
@ -192,7 +212,7 @@ err:
static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
char __user *buffer, size_t buflen,
uint8_t *kbuf, size_t kbuflen)
uint8_t *kbuf, size_t kbuflen, size_t lzero)
{
uint8_t *outbuf = NULL;
int ret;
@ -203,7 +223,7 @@ static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
goto err;
}
ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, buflen);
ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, buflen, lzero);
if (ret)
goto err;
@ -221,21 +241,26 @@ long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
struct keyctl_kdf_params *kdfcopy)
{
long ret;
MPI base, private, prime, result;
unsigned nbytes;
ssize_t dlen;
int secretlen;
int outlen;
struct keyctl_dh_params pcopy;
uint8_t *kbuf;
ssize_t keylen;
size_t resultlen;
struct dh dh_inputs;
struct scatterlist outsg;
struct dh_completion compl;
struct crypto_kpp *tfm;
struct kpp_request *req;
uint8_t *secret;
uint8_t *outbuf;
struct kdf_sdesc *sdesc = NULL;
if (!params || (!buffer && buflen)) {
ret = -EINVAL;
goto out;
goto out1;
}
if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
ret = -EFAULT;
goto out;
goto out1;
}
if (kdfcopy) {
@ -244,104 +269,147 @@ long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
ret = -EMSGSIZE;
goto out;
goto out1;
}
/* get KDF name string */
hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
if (IS_ERR(hashname)) {
ret = PTR_ERR(hashname);
goto out;
goto out1;
}
/* allocate KDF from the kernel crypto API */
ret = kdf_alloc(&sdesc, hashname);
kfree(hashname);
if (ret)
goto out;
goto out1;
}
memset(&dh_inputs, 0, sizeof(dh_inputs));
dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p);
if (dlen < 0) {
ret = dlen;
goto out1;
}
dh_inputs.p_size = dlen;
dlen = dh_data_from_key(pcopy.base, &dh_inputs.g);
if (dlen < 0) {
ret = dlen;
goto out2;
}
dh_inputs.g_size = dlen;
dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
if (dlen < 0) {
ret = dlen;
goto out2;
}
dh_inputs.key_size = dlen;
secretlen = crypto_dh_key_len(&dh_inputs);
secret = kmalloc(secretlen, GFP_KERNEL);
if (!secret) {
ret = -ENOMEM;
goto out2;
}
ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs);
if (ret)
goto out3;
tfm = crypto_alloc_kpp("dh", CRYPTO_ALG_TYPE_KPP, 0);
if (IS_ERR(tfm)) {
ret = PTR_ERR(tfm);
goto out3;
}
ret = crypto_kpp_set_secret(tfm, secret, secretlen);
if (ret)
goto out4;
outlen = crypto_kpp_maxsize(tfm);
if (!kdfcopy) {
/*
* When not using a KDF, buflen 0 is used to read the
* required buffer length
*/
if (buflen == 0) {
ret = outlen;
goto out4;
} else if (outlen > buflen) {
ret = -EOVERFLOW;
goto out4;
}
}
outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen,
GFP_KERNEL);
if (!outbuf) {
ret = -ENOMEM;
goto out4;
}
sg_init_one(&outsg, outbuf, outlen);
req = kpp_request_alloc(tfm, GFP_KERNEL);
if (!req) {
ret = -ENOMEM;
goto out5;
}
kpp_request_set_input(req, NULL, 0);
kpp_request_set_output(req, &outsg, outlen);
init_completion(&compl.completion);
kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
dh_crypto_done, &compl);
/*
* If the caller requests postprocessing with a KDF, allow an
* arbitrary output buffer size since the KDF ensures proper truncation.
* For DH, generate_public_key and generate_shared_secret are
* the same calculation
*/
keylen = mpi_from_key(pcopy.prime, kdfcopy ? SIZE_MAX : buflen, &prime);
if (keylen < 0 || !prime) {
/* buflen == 0 may be used to query the required buffer size,
* which is the prime key length.
*/
ret = keylen;
goto out;
}
/* The result is never longer than the prime */
resultlen = keylen;
keylen = mpi_from_key(pcopy.base, SIZE_MAX, &base);
if (keylen < 0 || !base) {
ret = keylen;
goto error1;
}
keylen = mpi_from_key(pcopy.private, SIZE_MAX, &private);
if (keylen < 0 || !private) {
ret = keylen;
goto error2;
}
result = mpi_alloc(0);
if (!result) {
ret = -ENOMEM;
goto error3;
}
/* allocate space for DH shared secret and SP800-56A otherinfo */
kbuf = kmalloc(kdfcopy ? (resultlen + kdfcopy->otherinfolen) : resultlen,
GFP_KERNEL);
if (!kbuf) {
ret = -ENOMEM;
goto error4;
ret = crypto_kpp_generate_public_key(req);
if (ret == -EINPROGRESS) {
wait_for_completion(&compl.completion);
ret = compl.err;
if (ret)
goto out6;
}
if (kdfcopy) {
/*
* Concatenate SP800-56A otherinfo past DH shared secret -- the
* input to the KDF is (DH shared secret || otherinfo)
*/
if (kdfcopy &&
copy_from_user(kbuf + resultlen, kdfcopy->otherinfo,
if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo,
kdfcopy->otherinfolen) != 0) {
ret = -EFAULT;
goto error5;
goto out6;
}
ret = do_dh(result, base, private, prime);
if (ret)
goto error5;
ret = mpi_read_buffer(result, kbuf, resultlen, &nbytes, NULL);
if (ret != 0)
goto error5;
if (kdfcopy) {
ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, kbuf,
resultlen + kdfcopy->otherinfolen);
ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf,
req->dst_len + kdfcopy->otherinfolen,
outlen - req->dst_len);
} else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) {
ret = req->dst_len;
} else {
ret = nbytes;
if (copy_to_user(buffer, kbuf, nbytes) != 0)
ret = -EFAULT;
}
error5:
kzfree(kbuf);
error4:
mpi_free(result);
error3:
mpi_free(private);
error2:
mpi_free(base);
error1:
mpi_free(prime);
out:
out6:
kpp_request_free(req);
out5:
kzfree(outbuf);
out4:
crypto_free_kpp(tfm);
out3:
kzfree(secret);
out2:
dh_free_data(&dh_inputs);
out1:
kdf_dealloc(sdesc);
return ret;
}