commit 02c9d3b9c2098ecd5a5affe1c229c8400f1fcd6e
author Werner Lewis <Werner.Lewis@arm.com> Fri May 20 12:48:46 2022 +0100
committer Werner Lewis <Werner.Lewis@arm.com> Wed Jun 08 14:38:38 2022 +0100
tree b23410c5751e5e8b4726d5f7ee101c27344f25b1
parent bdd6905a5cb44fce66af373b3faa80f23002afc4

Fix parsing of special chars in X509 DN values

Use escape mechanism defined in RFC 1779 when parsing commas and other
special characters in X509 DN values. Resolves failures when generating
a certificate with a CSR containing a comma in subject value.
Fixes #769.

Signed-off-by: Werner Lewis <werner.lewis@arm.com>

library/x509.c

diff --git a/library/x509.c b/library/x509.c
index f21e9e6..c55d038 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -741,7 +741,7 @@
 int mbedtls_x509_dn_gets( char *buf, size_t size, const mbedtls_x509_name *dn )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
-    size_t i, n;
+    size_t i, j, n;
     unsigned char c, merge = 0;
     const mbedtls_x509_name *name;
     const char *short_name = NULL;
@@ -775,17 +775,24 @@
             ret = mbedtls_snprintf( p, n, "\?\?=" );
         MBEDTLS_X509_SAFE_SNPRINTF;
 
-        for( i = 0; i < name->val.len; i++ )
+        for( i = 0, j = 0; i < name->val.len; i++, j++ )
         {
-            if( i >= sizeof( s ) - 1 )
-                break;
+            if( j >= sizeof( s ) - 1 )
+                return( MBEDTLS_ERR_X509_BUFFER_TOO_SMALL );
 
             c = name->val.p[i];
+            // Special characters requiring escaping, RFC 1779
+            if( c && strchr( ",=+<>#;\"\\", c ) )
+            {
+                if( j + 1 >= sizeof( s ) - 1 )
+                    continue;
+                s[j++] = '\\';
+            }
             if( c < 32 || c >= 127 )
-                 s[i] = '?';
-            else s[i] = c;
+                 s[j] = '?';
+            else s[j] = c;
         }
-        s[i] = '\0';
+        s[j] = '\0';
         ret = mbedtls_snprintf( p, n, "%s", s );
         MBEDTLS_X509_SAFE_SNPRINTF;