On 7/4/21 11:09 PM, Jarkko Sakkinen wrote:
From: Tianjia Zhang tianjia.zhang@linux.alibaba.com
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
- The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
- 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.
Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests") Link: https://lore.kernel.org/linux-sgx/20210301051836.30738-1-tianjia.zhang@linux... Signed-off-by: Tianjia Zhang tianjia.zhang@linux.alibaba.com Signed-off-by: Jarkko Sakkinen jarkko@kernel.org
The original patch did a bad job explaining the code change but it turned out making sense. I wrote a new description.
v2:
- Added a fixes tag. tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------ 1 file changed, 21 insertions(+), 20 deletions(-)
diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c index dee7a3d6c5a5..92bbc5a15c39 100644 --- a/tools/testing/selftests/sgx/sigstruct.c +++ b/tools/testing/selftests/sgx/sigstruct.c @@ -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--;- }
+}
I was just about apply this one and noticed this reverse_bytes(). Aren't there byteswap functions you could call instead of writing your own?
thanks, -- Shuah