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selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c 

commit 567c39047d upstream.

Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the
calculated length of Q1 and Q2 is less than 384 bytes, things will
go wrong.

E.g. if Q2 is 383 bytes, then

1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
2. The entire sigstruct->q2 is reversed, which results it being
   256 * Q2, given that the last byte of sigstruct->q2 is added
   to before the bytes given by calc_q1q2().

Either change in key or measurement can trigger the bug. E.g. an
unmeasured heap could cause a devastating change in Q1 or Q2.

Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning
to the caller.

Intel-SIG: commit 567c39047d selftests/sgx: Fix Q1 and Q2 calculation
in sigstruct.c
Backport for SGX virtualization support on Intel Xeon platform.

Fixes: 2adcba79e6 ("selftests/x86: Add a selftest for SGX")
Link: https://lore.kernel.org/linux-sgx/20210301051836.30738-1-tianjia.zhang@linux.alibaba.com/
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
[ Zhiquan Li: amend commit log ]
Signed-off-by: Zhiquan Li <zhiquan1.li@intel.com>
This commit is contained in:
Tianjia Zhang 2021-07-05 08:09:21 +03:00 committed by Jianping Liu
parent fa92f154dd
commit 440a707701
1 changed files with 21 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
tools/testing/selftests/sgx/sigstruct.c
View File

@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
return true;
}
static void reverse_bytes(void *data, int length)
{
int i = 0;
int j = length - 1;
uint8_t temp;
uint8_t *ptr = data;
while (i < j) {
temp = ptr[i];
ptr[i] = ptr[j];
ptr[j] = temp;
i++;
j--;
}
}
static bool calc_q1q2(const uint8_t *s, const uint8_t *m, uint8_t *q1,
uint8_t *q2)
{
struct q1q2_ctx ctx;
int len;
if (!alloc_q1q2_ctx(s, m, &ctx)) {
fprintf(stderr, "Not enough memory for Q1Q2 calculation\n");
@ -89,8 +106,10 @@ static bool calc_q1q2(const uint8_t *s, const uint8_t *m, uint8_t *q1,
goto out;
}
BN_bn2bin(ctx.q1, q1);
BN_bn2bin(ctx.q2, q2);
len = BN_bn2bin(ctx.q1, q1);
reverse_bytes(q1, len);
len = BN_bn2bin(ctx.q2, q2);
reverse_bytes(q2, len);
free_q1q2_ctx(&ctx);
return true;
@ -152,22 +171,6 @@ static RSA *gen_sign_key(void)
return key;
}
static void reverse_bytes(void *data, int length)
{
int i = 0;
int j = length - 1;
uint8_t temp;
uint8_t *ptr = data;
while (i < j) {
temp = ptr[i];
ptr[i] = ptr[j];
ptr[j] = temp;
i++;
j--;
}
}
enum mrtags {
MRECREATE = 0x0045544145524345,
MREADD = 0x0000000044444145,
@ -367,8 +370,6 @@ bool encl_measure(struct encl *encl)
/* BE -> LE */
reverse_bytes(sigstruct->signature, SGX_MODULUS_SIZE);
reverse_bytes(sigstruct->modulus, SGX_MODULUS_SIZE);
reverse_bytes(sigstruct->q1, SGX_MODULUS_SIZE);
reverse_bytes(sigstruct->q2, SGX_MODULUS_SIZE);
EVP_MD_CTX_destroy(ctx);
RSA_free(key);