Add guards for MBEDTLS_X509_CRL_PARSE_C in sample

Add checks in `ssl_server2` that `MBEDTLS_X509_CRL_PARSE_C` is defined
to fix compilation issue. Fixes Mbed-TLS#560.

ChangeLog

@@ -83,6 +83,8 @@ Bugfix
      extensions in CSRs and CRTs that caused these bitstrings to not be encoded
      correctly as trailing zeroes were not accounted for as unused bits in the
      leading content octet. Fixes #1610.
+   * Add a check for MBEDTLS_X509_CRL_PARSE_C in ssl_server2, guarding the crl
+     sni entry parameter. Reported by inestlerode in #560.
 
 Changes
    * Reduce RAM consumption during session renegotiation by not storing

programs/ssl/ssl_server2.c

@@ -282,8 +282,14 @@ int main( void )
 #endif /* MBEDTLS_SSL_CACHE_C */
 
 #if defined(SNI_OPTION)
+#if defined(MBEDTLS_X509_CRL_PARSE_C)
+#define SNI_CRL              ",crl"
+#else
+#define SNI_CRL              ""
+#endif
+
 #define USAGE_SNI                                                           \
-    "    sni=%%s              name1,cert1,key1,ca1,crl1,auth1[,...]\n"  \
+    "    sni=%%s              name1,cert1,key1,ca1"SNI_CRL",auth1[,...]\n"  \
     "                        default: disabled\n"
 #else
 #define USAGE_SNI ""
@@ -654,10 +660,10 @@ void sni_free( sni_entry *head )
 
         mbedtls_x509_crt_free( cur->ca );
         mbedtls_free( cur->ca );
-
+#if defined(MBEDTLS_X509_CRL_PARSE_C)
         mbedtls_x509_crl_free( cur->crl );
         mbedtls_free( cur->crl );
-
+#endif
         next = cur->next;
         mbedtls_free( cur );
         cur = next;
@@ -676,7 +682,10 @@ sni_entry *sni_parse( char *sni_string )
     sni_entry *cur = NULL, *new = NULL;
     char *p = sni_string;
     char *end = p;
-    char *crt_file, *key_file, *ca_file, *crl_file, *auth_str;
+    char *crt_file, *key_file, *ca_file, *auth_str;
+#if defined(MBEDTLS_X509_CRL_PARSE_C)
+    char *crl_file;
+#endif
 
     while( *end != '\0' )
         ++end;
@@ -694,7 +703,9 @@ sni_entry *sni_parse( char *sni_string )
         GET_ITEM( crt_file );
         GET_ITEM( key_file );
         GET_ITEM( ca_file );
+#if defined(MBEDTLS_X509_CRL_PARSE_C)
         GET_ITEM( crl_file );
+#endif
         GET_ITEM( auth_str );
 
         if( ( new->cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) ) ) == NULL ||
@@ -719,6 +730,7 @@ sni_entry *sni_parse( char *sni_string )
                 goto error;
         }
 
+#if defined(MBEDTLS_X509_CRL_PARSE_C)
         if( strcmp( crl_file, "-" ) != 0 )
         {
             if( ( new->crl = mbedtls_calloc( 1, sizeof( mbedtls_x509_crl ) ) ) == NULL )
@@ -729,6 +741,7 @@ sni_entry *sni_parse( char *sni_string )
             if( mbedtls_x509_crl_parse_file( new->crl, crl_file ) != 0 )
                 goto error;
         }
+#endif
 
         if( strcmp( auth_str, "-" ) != 0 )
         {