git: 564b6aa7fccd - main - aesni: Avoid a potential out-of-bounds load in aes_encrypt_icm()

[Mark Johnston]

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=564b6aa7fccd98654207447f870b82659b895e7b

commit 564b6aa7fccd98654207447f870b82659b895e7b
Author:     Mark Johnston <markj at FreeBSD.org>
AuthorDate: 2021-08-30 18:22:20 +0000
Commit:     Mark Johnston <markj at FreeBSD.org>
CommitDate: 2021-08-30 18:22:20 +0000

    aesni: Avoid a potential out-of-bounds load in aes_encrypt_icm()
    
    Given a partial block at the end of a payload, aes_encrypt_icm() would
    perform a 16-byte load of the residual into a temporary variable.  This
    is unsafe in principle since the full block may cross a page boundary.
    Fix the problem by copying the residual into a stack buffer first.
    
    Reported by:    syzbot+b7e44cde9e2e89f0f6c9 at syzkaller.appspotmail.com
    Reported by:    syzbot+4b5eaf123a99456b5160 at syzkaller.appspotmail.com
    Reported by:    syzbot+70c74c1aa232633355ca at syzkaller.appspotmail.com
    Reported by:    syzbot+2c663776a52828373d41 at syzkaller.appspotmail.com
    Reviewed by:    cem, jhb
    MFC after:      1 week
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D31730
---
 sys/crypto/aesni/aesni_wrap.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/sys/crypto/aesni/aesni_wrap.c b/sys/crypto/aesni/aesni_wrap.c
index 95f7e191d00d..4d2a45b7e4c4 100644
--- a/sys/crypto/aesni/aesni_wrap.c
+++ b/sys/crypto/aesni/aesni_wrap.c
@@ -213,9 +213,10 @@ aesni_encrypt_icm(int rounds, const void *key_schedule, size_t len,
 	__m128i ctr5, ctr6, ctr7, ctr8;
 	__m128i BSWAP_EPI64;
 	__m128i tout[8];
+	__m128i block;
 	struct blocks8 *top;
 	const struct blocks8 *blks;
-	size_t i, cnt;
+	size_t i, cnt, resid;
 
 	BSWAP_EPI64 = _mm_set_epi8(8,9,10,11,12,13,14,15,0,1,2,3,4,5,6,7);
 
@@ -273,12 +274,19 @@ aesni_encrypt_icm(int rounds, const void *key_schedule, size_t len,
 		to += AES_BLOCK_LEN;
 	}
 
-	/* handle remaining partial round */
-	if (len % AES_BLOCK_LEN != 0) {
+	/*
+	 * Handle remaining partial round.  Copy the remaining payload onto the
+	 * stack to ensure that the full block can be loaded safely.
+	 */
+	resid = len % AES_BLOCK_LEN;
+	if (resid != 0) {
 		tmp1 = _mm_shuffle_epi8(ctr1, BSWAP_EPI64);
 		tot = aesni_enc(rounds - 1, key_schedule, tmp1);
-		tot = tot ^ _mm_loadu_si128((const __m128i *)from);
-		memcpy(to, &tot, len % AES_BLOCK_LEN);
+		block = _mm_setzero_si128();
+		memcpy(&block, from, resid);
+		tot = tot ^ _mm_loadu_si128(&block);
+		memcpy(to, &tot, resid);
+		explicit_bzero(&block, sizeof(block));
 	}
 }