Patch "selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c" has been added to the 5.13-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     selftests-sgx-fix-q1-and-q2-calculation-in-sigstruct.patch
and it can be found in the queue-5.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit af6336a636dc4103d27dd6baed3a98445accbc05
Author: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
Date:   Mon Jul 5 08:09:21 2021 +0300

    selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c
    
    [ Upstream commit 567c39047dbee341244fe3bf79fea24ee0897ff9 ]
    
    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.
    
    Fixes: 2adcba79e69d ("selftests/x86: Add a selftest for SGX")
    Link: https://lore.kernel.org/linux-sgx/20210301051836.30738-1-tianjia.zhang@xxxxxxxxxxxxxxxxx/
    Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
    Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
    Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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--;
+	}
+}
+
 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);