Merge pull request #6392 from davidhorstmann-arm/2.28-fix-x509-get-name-cleanup

[Backport 2.28] Fix `mbedtls_x509_get_name()` cleanup

Author: ronald-cron-arm

ChangeLog.d/fix_x509_get_name_mem_leak.txt

@@ -0,0 +1,4 @@
+Bugfix
+    * Fix memory leak in ssl_parse_certificate_request() caused by
+      mbedtls_x509_get_name() not freeing allocated objects in case of error.
+      Change mbedtls_x509_get_name() to clean up allocated objects on error.

library/x509.c

@@ -415,13 +415,20 @@ static int x509_get_attr_type_value( unsigned char **p,
  * For the general case we still use a flat list, but we mark elements of the
  * same set so that they are "merged" together in the functions that consume
  * this list, eg mbedtls_x509_dn_gets().
+ *
+ * On success, this function may allocate a linked list starting at cur->next
+ * that must later be free'd by the caller using mbedtls_free(). In error
+ * cases, this function frees all allocated memory internally and the caller
+ * has no freeing responsibilities.
  */
 int mbedtls_x509_get_name( unsigned char **p, const unsigned char *end,
                    mbedtls_x509_name *cur )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t set_len;
     const unsigned char *end_set;
+    mbedtls_x509_name *head = cur;
+    mbedtls_x509_name *prev, *allocated;
 
     /* don't use recursion, we'd risk stack overflow if not optimized */
     while( 1 )
@@ -431,14 +438,17 @@ int mbedtls_x509_get_name( unsigned char **p, const unsigned char *end,
          */
         if( ( ret = mbedtls_asn1_get_tag( p, end, &set_len,
                 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SET ) ) != 0 )
-            return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_NAME, ret ) );
+        {
+            ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_X509_INVALID_NAME, ret );
+            goto error;
+        }
 
         end_set  = *p + set_len;
 
         while( 1 )
         {
             if( ( ret = x509_get_attr_type_value( p, end_set, cur ) ) != 0 )
-                return( ret );
+                goto error;
 
             if( *p == end_set )
                 break;
@@ -449,7 +459,10 @@ int mbedtls_x509_get_name( unsigned char **p, const unsigned char *end,
             cur->next = mbedtls_calloc( 1, sizeof( mbedtls_x509_name ) );
 
             if( cur->next == NULL )
-                return( MBEDTLS_ERR_X509_ALLOC_FAILED );
+            {
+                ret = MBEDTLS_ERR_X509_ALLOC_FAILED;
+                goto error;
+            }
 
             cur = cur->next;
         }
@@ -463,10 +476,30 @@ int mbedtls_x509_get_name( unsigned char **p, const unsigned char *end,
         cur->next = mbedtls_calloc( 1, sizeof( mbedtls_x509_name ) );
 
         if( cur->next == NULL )
-            return( MBEDTLS_ERR_X509_ALLOC_FAILED );
+        {
+            ret = MBEDTLS_ERR_X509_ALLOC_FAILED;
+            goto error;
+        }
 
         cur = cur->next;
     }
+
+error:
+    /* Skip the first element as we did not allocate it */
+    allocated = head->next;
+
+    while( allocated != NULL )
+    {
+        prev = allocated;
+        allocated = allocated->next;
+
+        mbedtls_platform_zeroize( prev, sizeof( *prev ) );
+        mbedtls_free( prev );
+    }
+
+    mbedtls_platform_zeroize( head, sizeof( *head ) );
+
+    return( ret );
 }
 
 static int x509_parse_int( unsigned char **p, size_t n, int *res )

tests/suites/test_suite_x509parse.data

@@ -427,6 +427,46 @@ X509 Get Modified DN #5 Name exactly 255 bytes, ending with comma requiring esca
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_SHA1_C
 mbedtls_x509_dn_gets_subject_replace:"data_files/server1.crt":"12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234,":"":MBEDTLS_ERR_X509_BUFFER_TOO_SMALL
 
+# Parse the following valid DN:
+#
+# 31 0B <- Set of
+#     30 09 <- Sequence of
+#         06 03 55 04 06 <- OID 2.5.4.6 countryName (C)
+#         13 02 4E 4C <- PrintableString "NL"
+# 31 11 <- Set of
+#     30 0F <- Sequence of
+#         06 03 55 04 0A <- OID 2.5.4.10 organizationName (O)
+#         0C 08 50 6F 6C 61 72 53 53 4C <- UTF8String "PolarSSL"
+# 31 19 <- Set of
+#     30 17 <- Sequence of
+#         06 03 55 04 03 <- OID 2.5.4.3 commonName (CN)
+#         0C 10 50 6F 6C 61 72 53 53 4C 20 54 65 73 74 20 43 41 <- UTF8String "PolarSSL Test CA"
+#
+X509 Get Name Valid DN
+mbedtls_x509_get_name:"310B3009060355040613024E4C3111300F060355040A0C08506F6C617253534C3119301706035504030C10506F6C617253534C2054657374204341":0
+
+# Parse the following corrupted DN:
+#
+# 31 0B <- Set of
+#     30 09 <- Sequence of
+#         06 03 55 04 06 <- OID 2.5.4.6 countryName (C)
+#         13 02 4E 4C <- PrintableString "NL"
+# 31 11 <- Set of
+#     30 0F <- Sequence of
+#         06 03 55 04 0A <- OID 2.5.4.10 organizationName (O)
+#         0C 08 50 6F 6C 61 72 53 53 4C <- UTF8String "PolarSSL"
+# 30 19 <- Sequence of (corrupted)
+#     30 17 <- Sequence of
+#         06 03 55 04 03 <- OID 2.5.4.3 commonName (CN)
+#         0C 10 50 6F 6C 61 72 53 53 4C 20 54 65 73 74 20 43 41 <- UTF8String "PolarSSL Test CA"
+#
+# The third 'Set of' is corrupted to instead be a 'Sequence of', causing an
+# error and forcing mbedtls_x509_get_name() to clean up the names it has
+# already allocated.
+#
+X509 Get Name Corrupted DN Mem Leak
+mbedtls_x509_get_name:"310B3009060355040613024E4C3111300F060355040A0C08506F6C617253534C3019301706035504030C10506F6C617253534C2054657374204341":MBEDTLS_ERR_X509_INVALID_NAME + MBEDTLS_ERR_ASN1_UNEXPECTED_TAG
+
 X509 Time Expired #1
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_RSA_C:MBEDTLS_HAVE_TIME_DATE:MBEDTLS_SHA1_C
 mbedtls_x509_time_is_past:"data_files/server1.crt":"valid_from":1

tests/suites/test_suite_x509parse.function

@@ -799,6 +799,41 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:MBEDTLS_X509_CRT_PARSE_C */
+void mbedtls_x509_get_name( char * rdn_sequence, int exp_ret )
+{
+    unsigned char *name;
+    unsigned char *p;
+    size_t name_len;
+    mbedtls_x509_name head;
+    mbedtls_x509_name *allocated, *prev;
+    int ret;
+
+    memset( &head, 0, sizeof( head ) );
+
+    name = mbedtls_test_unhexify_alloc( rdn_sequence, &name_len );
+    p = name;
+
+    ret = mbedtls_x509_get_name( &p, ( name + name_len ), &head );
+    if( ret == 0 )
+    {
+        allocated = head.next;
+
+        while( allocated != NULL )
+        {
+            prev = allocated;
+            allocated = allocated->next;
+
+            mbedtls_free( prev );
+        }
+    }
+
+    TEST_EQUAL( ret, exp_ret );
+
+    mbedtls_free( name );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_FS_IO:MBEDTLS_X509_CRT_PARSE_C */
 void mbedtls_x509_time_is_past( char * crt_file, char * entity, int result )
 {