commit c71b7eb0e7b9a0ecfe16a418c4c9735af230259f
author Andres AG <andres.amayagarcia@arm.com> Thu Jan 19 11:24:33 2017 +0000
committer Andres AG <andres.amayagarcia@arm.com> Wed Feb 15 10:44:02 2017 +0000
tree cc460bbf23f58b57f0f4e5f4a700a7c47faf1b16
parent df33a6a8056be7fcb8a1784fa026d0308f19dc7b

Fix data loss in unsigned int cast in PK

This patch introduces some additional checks in the PK module for 64-bit
systems only. The problem is that the API functions in the PK
abstraction accept a size_t value for the hashlen, while the RSA module
accepts an unsigned int for the hashlen. Instead of silently casting
size_t to unsigned int, this change checks whether the hashlen overflows
an unsigned int and returns an error.

library/pk_wrap.c

diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index 6068605..ceaaad1 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -31,6 +31,7 @@
 
 /* Even if RSA not activated, for the sake of RSA-alt */
 #include "polarssl/rsa.h"
+#include "polarssl/bignum.h"
 
 #include <string.h>
 
@@ -50,6 +51,8 @@
 #define polarssl_free       free
 #endif
 
+#include <limits.h>
+
 /* Implementation that should never be optimized out by the compiler */
 static void polarssl_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
@@ -73,6 +76,11 @@
 {
     int ret;
 
+#if defined(POLARSSL_HAVE_INT64)
+    if( md_alg == POLARSSL_MD_NONE && UINT_MAX < hash_len )
+        return( POLARSSL_ERR_PK_BAD_INPUT_DATA );
+#endif /* POLARSSL_HAVE_INT64 */
+
     if( sig_len < ((rsa_context *) ctx)->len )
         return( POLARSSL_ERR_RSA_VERIFY_FAILED );
 
@@ -92,6 +100,11 @@
                    unsigned char *sig, size_t *sig_len,
                    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
 {
+#if defined(POLARSSL_HAVE_INT64)
+    if( md_alg == POLARSSL_MD_NONE && UINT_MAX < hash_len )
+        return( POLARSSL_ERR_PK_BAD_INPUT_DATA );
+#endif /* POLARSSL_HAVE_INT64 */
+
     *sig_len = ((rsa_context *) ctx)->len;
 
     return( rsa_pkcs1_sign( (rsa_context *) ctx, f_rng, p_rng, RSA_PRIVATE,
@@ -411,6 +424,11 @@
 {
     rsa_alt_context *rsa_alt = (rsa_alt_context *) ctx;
 
+#if defined(POLARSSL_HAVE_INT64)
+    if( UINT_MAX < hash_len )
+        return( POLARSSL_ERR_PK_BAD_INPUT_DATA );
+#endif /* POLARSSL_HAVE_INT64 */
+
     *sig_len = rsa_alt->key_len_func( rsa_alt->key );
 
     return( rsa_alt->sign_func( rsa_alt->key, f_rng, p_rng, RSA_PRIVATE,