From: Matt Caswell
Date: Thu, 12 Mar 2015 15:59:07 +0000 (+0000)
Subject: Fix unintended sign extension
X-Git-Tag: OpenSSL_1_1_0-pre1~1521
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=3475c7a1854977e290ab44deb16551f6d55ad9a7
Fix unintended sign extension
The function CRYPTO_128_unwrap_pad uses an 8 byte AIV (Alternative Initial
Value). The least significant 4 bytes of this is placed into the local
variable |ptext_len|. This is done as follows:
ptext_len = (aiv[4] << 24) | (aiv[5] << 16) | (aiv[6] << 8) | aiv[7];
aiv[4] is an unsigned char, but (aiv[4] << 24) is promoted to a *signed*
int - therefore we could end up shifting into the sign bit and end up with
a negative value. |ptext_len| is a size_t (typically 64-bits). If the
result of the shifts is negative then the upper bits of |ptext_len| will
all be 1.
This commit fixes the issue by explicitly casting to an unsigned int.
Reviewed-by: Richard Levitte
---
diff --git a/crypto/modes/wrap128.c b/crypto/modes/wrap128.c
index ccb58c5a0b..73718ae59f 100644
--- a/crypto/modes/wrap128.c
+++ b/crypto/modes/wrap128.c
@@ -350,7 +350,10 @@ size_t CRYPTO_128_unwrap_pad(void *key, const unsigned char *icv,
* LSB(32,AIV).
*/
- ptext_len = (aiv[4] << 24) | (aiv[5] << 16) | (aiv[6] << 8) | aiv[7];
+ ptext_len = ((unsigned int)aiv[4] << 24)
+ | ((unsigned int)aiv[5] << 16)
+ | ((unsigned int)aiv[6] << 8)
+ | (unsigned int)aiv[7];
if (8 * (n - 1) >= ptext_len || ptext_len > 8 * n) {
OPENSSL_cleanse(out, inlen);
return 0;