kek_unwrap_key(): Fix incorrect check of unwrapped key size

Fixes CVE-2025-9230

The check is off by 8 bytes so it is possible to overread by
up to 8 bytes and overwrite up to 4 bytes.

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(cherry picked from commit 9c462be2cea54ebfc62953224220b56f8ba22a0c)

diff --git a/crypto/cms/cms_pwri.c b/crypto/cms/cms_pwri.c
index a7d609f83791a21ed5b3fe3ff1c87659e78bbdef..ee1b8aa6ed61d8a8b4075c975dd407e52db0a31a 100644 (file)
--- a/crypto/cms/cms_pwri.c
+++ b/crypto/cms/cms_pwri.c
@@ -242,7 +242,7 @@ static int kek_unwrap_key(unsigned char *out, size_t *outlen,
         /* Check byte failure */
         goto err;
     }
-    if (inlen < (size_t)(tmp[0] - 4)) {
+    if (inlen < 4 + (size_t)tmp[0]) {
         /* Invalid length value */
         goto err;
     }