Refactor code structure for improved readability and maintainability

libsrtp/crypto/hash/hmac_mbedtls.c

@@ -0,0 +1,224 @@
+/*
+ * hmac_mbedtls.c
+ *
+ * Implementation of hmac srtp_auth_type_t that leverages Mbedtls
+ *
+ * YongCheng Yang
+ */
+/*
+ *
+ * Copyright(c) 2013-2017, Cisco Systems, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ *   Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ *   Neither the name of the Cisco Systems, Inc. nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "auth.h"
+#include "alloc.h"
+#include "err.h" /* for srtp_debug */
+#include "auth_test_cases.h"
+#include <mbedtls/md.h>
+
+#define SHA1_DIGEST_SIZE 20
+
+/* the debug module for authentiation */
+
+srtp_debug_module_t srtp_mod_hmac = {
+    false,               /* debugging is off by default */
+    "hmac sha-1 mbedtls" /* printable name for module   */
+};
+
+static srtp_err_status_t srtp_hmac_mbedtls_alloc(srtp_auth_t **a,
+                                                 size_t key_len,
+                                                 size_t out_len)
+{
+    extern const srtp_auth_type_t srtp_hmac;
+
+    debug_print(srtp_mod_hmac, "allocating auth func with key length %zu",
+                key_len);
+    debug_print(srtp_mod_hmac, "                          tag length %zu",
+                out_len);
+
+    /* check output length - should be less than 20 bytes */
+    if (out_len > SHA1_DIGEST_SIZE) {
+        return srtp_err_status_bad_param;
+    }
+
+    *a = (srtp_auth_t *)srtp_crypto_alloc(sizeof(srtp_auth_t));
+    if (*a == NULL) {
+        return srtp_err_status_alloc_fail;
+    }
+    // allocate the buffer of mbedtls context.
+    (*a)->state = srtp_crypto_alloc(sizeof(mbedtls_md_context_t));
+    if ((*a)->state == NULL) {
+        srtp_crypto_free(*a);
+        *a = NULL;
+        return srtp_err_status_alloc_fail;
+    }
+    mbedtls_md_init((mbedtls_md_context_t *)(*a)->state);
+
+    /* set pointers */
+    (*a)->type = &srtp_hmac;
+    (*a)->out_len = out_len;
+    (*a)->key_len = key_len;
+    (*a)->prefix_len = 0;
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_mbedtls_dealloc(srtp_auth_t *a)
+{
+    mbedtls_md_context_t *hmac_ctx;
+    hmac_ctx = (mbedtls_md_context_t *)a->state;
+    mbedtls_md_free(hmac_ctx);
+    srtp_crypto_free(hmac_ctx);
+    /* zeroize entire state*/
+    octet_string_set_to_zero(a, sizeof(srtp_auth_t));
+
+    /* free memory */
+    srtp_crypto_free(a);
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_mbedtls_start(void *statev)
+{
+    mbedtls_md_context_t *state = (mbedtls_md_context_t *)statev;
+    if (mbedtls_md_hmac_reset(state) != 0) {
+        return srtp_err_status_auth_fail;
+    }
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_mbedtls_init(void *statev,
+                                                const uint8_t *key,
+                                                size_t key_len)
+{
+    mbedtls_md_context_t *state = (mbedtls_md_context_t *)statev;
+    const mbedtls_md_info_t *info = NULL;
+
+    info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA1);
+    if (info == NULL) {
+        return srtp_err_status_auth_fail;
+    }
+
+    if (mbedtls_md_setup(state, info, 1) != 0) {
+        return srtp_err_status_auth_fail;
+    }
+
+    debug_print(srtp_mod_hmac, "mbedtls setup, name: %s",
+                mbedtls_md_get_name(info));
+    debug_print(srtp_mod_hmac, "mbedtls setup, size: %d",
+                mbedtls_md_get_size(info));
+
+    if (mbedtls_md_hmac_starts(state, key, key_len) != 0) {
+        return srtp_err_status_auth_fail;
+    }
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_mbedtls_update(void *statev,
+                                                  const uint8_t *message,
+                                                  size_t msg_octets)
+{
+    mbedtls_md_context_t *state = (mbedtls_md_context_t *)statev;
+
+    debug_print(srtp_mod_hmac, "input: %s",
+                srtp_octet_string_hex_string(message, msg_octets));
+
+    if (mbedtls_md_hmac_update(state, message, msg_octets) != 0) {
+        return srtp_err_status_auth_fail;
+    }
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_mbedtls_compute(void *statev,
+                                                   const uint8_t *message,
+                                                   size_t msg_octets,
+                                                   size_t tag_len,
+                                                   uint8_t *result)
+{
+    mbedtls_md_context_t *state = (mbedtls_md_context_t *)statev;
+    uint8_t hash_value[SHA1_DIGEST_SIZE];
+    size_t i;
+
+    /* check tag length, return error if we can't provide the value expected */
+    if (tag_len > SHA1_DIGEST_SIZE) {
+        return srtp_err_status_bad_param;
+    }
+
+    /* hash message, copy output into H */
+    if (mbedtls_md_hmac_update(statev, message, msg_octets) != 0) {
+        return srtp_err_status_auth_fail;
+    }
+
+    if (mbedtls_md_hmac_finish(state, hash_value) != 0) {
+        return srtp_err_status_auth_fail;
+    }
+
+    /* copy hash_value to *result */
+    for (i = 0; i < tag_len; i++) {
+        result[i] = hash_value[i];
+    }
+
+    debug_print(srtp_mod_hmac, "output: %s",
+                srtp_octet_string_hex_string(hash_value, tag_len));
+
+    return srtp_err_status_ok;
+}
+
+/* end test case 0 */
+
+static const char srtp_hmac_mbedtls_description[] =
+    "hmac sha-1 authentication function using mbedtls";
+
+/*
+ * srtp_auth_type_t hmac is the hmac metaobject
+ */
+
+const srtp_auth_type_t srtp_hmac = {
+    srtp_hmac_mbedtls_alloc,       /* */
+    srtp_hmac_mbedtls_dealloc,     /* */
+    srtp_hmac_mbedtls_init,        /* */
+    srtp_hmac_mbedtls_compute,     /* */
+    srtp_hmac_mbedtls_update,      /* */
+    srtp_hmac_mbedtls_start,       /* */
+    srtp_hmac_mbedtls_description, /* */
+    &srtp_hmac_test_case_0,        /* */
+    SRTP_HMAC_SHA1                 /* */
+};