From: Jouni Malinen <j@w1.fi>
Date: Sun, 9 Feb 2025 16:12:40 +0000 (+0200)
Subject: SHA-PRF: Make code easier for static analyzers
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=50330cb919dc5a94dc0b0bb018b59bf5655f5a5e;p=thirdparty%2Fhostap.git

SHA-PRF: Make code easier for static analyzers

pos cannot be 0 when buf_len_bits != 0 and as such, buf[pos - 1] here
cannot point to invalid index. However, this is apparently too complex
for static analyzers, so make this more obvious to avoid false
positives.

Signed-off-by: Jouni Malinen <j@w1.fi>
---

diff --git a/src/crypto/sha256-prf.c b/src/crypto/sha256-prf.c
index d665a9983..de7394a32 100644
--- a/src/crypto/sha256-prf.c
+++ b/src/crypto/sha256-prf.c
@@ -97,7 +97,7 @@ int sha256_prf_bits(const u8 *key, size_t key_len, const char *label,
 	 * Mask out unused bits in the last octet if it does not use all the
 	 * bits.
 	 */
-	if (buf_len_bits % 8) {
+	if (pos > 0 && (buf_len_bits % 8)) {
 		u8 mask = 0xff << (8 - buf_len_bits % 8);
 		buf[pos - 1] &= mask;
 	}
diff --git a/src/crypto/sha384-prf.c b/src/crypto/sha384-prf.c
index 420e78c38..fdf331655 100644
--- a/src/crypto/sha384-prf.c
+++ b/src/crypto/sha384-prf.c
@@ -97,7 +97,7 @@ int sha384_prf_bits(const u8 *key, size_t key_len, const char *label,
 	 * Mask out unused bits in the last octet if it does not use all the
 	 * bits.
 	 */
-	if (buf_len_bits % 8) {
+	if (pos > 0 && (buf_len_bits % 8)) {
 		u8 mask = 0xff << (8 - buf_len_bits % 8);
 		buf[pos - 1] &= mask;
 	}
diff --git a/src/crypto/sha512-prf.c b/src/crypto/sha512-prf.c
index e48cf5f05..be458141d 100644
--- a/src/crypto/sha512-prf.c
+++ b/src/crypto/sha512-prf.c
@@ -97,7 +97,7 @@ int sha512_prf_bits(const u8 *key, size_t key_len, const char *label,
 	 * Mask out unused bits in the last octet if it does not use all the
 	 * bits.
 	 */
-	if (buf_len_bits % 8) {
+	if (pos > 0 && (buf_len_bits % 8)) {
 		u8 mask = 0xff << (8 - buf_len_bits % 8);
 		buf[pos - 1] &= mask;
 	}