On Fri, Jul 23, 2021 at 01:53:06PM -0600, Shuah Khan wrote:
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?
Sorry for latency, just came from two week leave.
glibc does provide bswap for 16, 32, 64 bit numbers but nothing better.
I have no idea if libssl has such function. Since the test code already uses this function, and it works, and it's not a newly added function in this patch, I would consider keeping it.
thanks, -- Shuah
/Jarkko