Move cookie callbacks implementation to own module

library/ssl_cookie.c

diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
new file mode 100644
index 0000000..5b6a79a
--- /dev/null
+++ b/library/ssl_cookie.c
@@ -0,0 +1,157 @@
+/*
+ *  DTLS cookie callbacks implementation
+ *
+ *  Copyright (C) 2014, Brainspark B.V.
+ *
+ *  This file is part of PolarSSL (http://www.polarssl.org)
+ *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
+ *
+ *  All rights reserved.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+/*
+ * These session callbacks use a simple chained list
+ * to store and retrieve the session information.
+ */
+
+#if !defined(POLARSSL_CONFIG_FILE)
+#include "polarssl/config.h"
+#else
+#include POLARSSL_CONFIG_FILE
+#endif
+
+#if defined(POLARSSL_SSL_DTLS_HELLO_VERIFY)
+
+#include "polarssl/ssl_cookie.h"
+
+#if defined(POLARSSL_PLATFORM_C)
+#include "polarssl/platform.h"
+#else
+#define polarssl_malloc     malloc
+#define polarssl_free       free
+#endif
+
+/* 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;
+}
+
+/*
+ * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
+ * available. Try SHA-256 first, 512 wastes resources since we need to stay
+ * with max 32 bytes of cookie for DTLS 1.0
+ */
+#if defined(POLARSSL_SHA256_C)
+#define HVR_MD      POLARSSL_MD_SHA256
+#define HVR_MD_LEN  32
+#define HVR_MD_USE  32
+#elif defined(POLARSSL_SHA512_C)
+#define HVR_MD      POLARSSL_MD_SHA384
+#define HVR_MD_LEN  48
+#define HVR_MD_USE  32
+#elif defined(POLARSSL_SHA1_C)
+#define HVR_MD      POLARSSL_MD_SHA1
+#define HVR_MD_LEN  20
+#define HVR_MD_USE  20
+#else
+#error "DTLS hello verify needs SHA-1 or SHA-2"
+#endif
+
+void ssl_cookie_init( ssl_cookie_ctx *ctx )
+{
+    md_init( &ctx->hmac_ctx );
+}
+
+void ssl_cookie_free( ssl_cookie_ctx *ctx )
+{
+    md_free( &ctx->hmac_ctx );
+}
+
+int ssl_cookie_setup( ssl_cookie_ctx *ctx,
+                      int (*f_rng)(void *, unsigned char *, size_t),
+                      void *p_rng )
+{
+    int ret;
+    unsigned char key[HVR_MD_LEN];
+
+    if( ( ret = f_rng( p_rng, key, sizeof( key ) ) ) != 0 )
+        return( ret );
+
+    ret = md_init_ctx( &ctx->hmac_ctx, md_info_from_type( HVR_MD ) );
+    if( ret != 0 )
+        return( ret );
+
+    ret = md_hmac_starts( &ctx->hmac_ctx, key, sizeof( key ) );
+    if( ret != 0 )
+        return( ret );
+
+    polarssl_zeroize( key, sizeof( key ) );
+
+    return( 0 );
+}
+
+/*
+ * Generate cookie for DTLS ClientHello verification
+ */
+int ssl_cookie_write( void *ctx,
+                      unsigned char **p, unsigned char *end,
+                      const unsigned char *cli_id, size_t cli_id_len )
+{
+    int ret;
+    unsigned char hmac_out[HVR_MD_LEN];
+    md_context_t *hmac_ctx = (md_context_t *) ctx;
+
+    if( (size_t)( end - *p ) < HVR_MD_USE )
+        return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
+
+    if( ( ret = md_hmac_reset(  hmac_ctx ) ) != 0 ||
+        ( ret = md_hmac_update( hmac_ctx, cli_id, cli_id_len ) ) != 0 ||
+        ( ret = md_hmac_finish( hmac_ctx, hmac_out ) ) != 0 )
+    {
+        return( POLARSSL_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    memcpy( *p, hmac_out, HVR_MD_USE );
+    *p += HVR_MD_USE;
+
+    return( 0 );
+}
+
+/*
+ * Check a cookie
+ */
+int ssl_cookie_check( void *ctx,
+                      const unsigned char *cookie, size_t cookie_len,
+                      const unsigned char *cli_id, size_t cli_id_len )
+{
+    unsigned char ref_cookie[HVR_MD_USE];
+    unsigned char *p = ref_cookie;
+    md_context_t *hmac_ctx = (md_context_t *) ctx;
+
+    if( cookie_len != HVR_MD_USE )
+        return( -1 );
+
+    if( ssl_cookie_write( hmac_ctx,
+                          &p, p + sizeof( ref_cookie ),
+                          cli_id, cli_id_len ) != 0 )
+        return( -1 );
+
+    if( safer_memcmp( cookie, ref_cookie, sizeof( ref_cookie ) ) != 0 )
+        return( -1 );
+
+    return( 0 );
+}
+#endif /* POLARSSL_SSL_COOKIE_C */