Refactor code structure for improved readability and maintainability

libsrtp/crypto/hash/hmac.c

@@ -0,0 +1,248 @@
+/*
+ * hmac.c
+ *
+ * implementation of hmac srtp_auth_type_t
+ *
+ * David A. McGrew
+ * Cisco Systems, Inc.
+ */
+/*
+ *
+ * Copyright(c) 2001-2017 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 "hmac.h"
+#include "alloc.h"
+#include "cipher_types.h"
+#include "auth_test_cases.h"
+
+/* the debug module for authentiation */
+
+srtp_debug_module_t srtp_mod_hmac = {
+    false,       /* debugging is off by default */
+    "hmac sha-1" /* printable name for module   */
+};
+
+static srtp_err_status_t srtp_hmac_alloc(srtp_auth_t **a,
+                                         size_t key_len,
+                                         size_t out_len)
+{
+    extern const srtp_auth_type_t srtp_hmac;
+    uint8_t *pointer;
+
+    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 key length - note that we don't support keys larger
+     * than 20 bytes yet
+     */
+    if (key_len > 20) {
+        return srtp_err_status_bad_param;
+    }
+
+    /* check output length - should be less than 20 bytes */
+    if (out_len > 20) {
+        return srtp_err_status_bad_param;
+    }
+
+    /* allocate memory for auth and srtp_hmac_ctx_t structures */
+    pointer = (uint8_t *)srtp_crypto_alloc(sizeof(srtp_hmac_ctx_t) +
+                                           sizeof(srtp_auth_t));
+    if (pointer == NULL) {
+        return srtp_err_status_alloc_fail;
+    }
+
+    /* set pointers */
+    *a = (srtp_auth_t *)pointer;
+    (*a)->type = &srtp_hmac;
+    (*a)->state = pointer + sizeof(srtp_auth_t);
+    (*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_dealloc(srtp_auth_t *a)
+{
+    /* zeroize entire state*/
+    octet_string_set_to_zero(a, sizeof(srtp_hmac_ctx_t) + sizeof(srtp_auth_t));
+
+    /* free memory */
+    srtp_crypto_free(a);
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_init(void *statev,
+                                        const uint8_t *key,
+                                        size_t key_len)
+{
+    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
+    uint8_t ipad[64];
+
+    /*
+     * check key length - note that we don't support keys larger
+     * than 20 bytes yet
+     */
+    if (key_len > 20) {
+        return srtp_err_status_bad_param;
+    }
+
+    /*
+     * set values of ipad and opad by exoring the key into the
+     * appropriate constant values
+     */
+    for (size_t i = 0; i < key_len; i++) {
+        ipad[i] = key[i] ^ 0x36;
+        state->opad[i] = key[i] ^ 0x5c;
+    }
+    /* set the rest of ipad, opad to constant values */
+    for (size_t i = key_len; i < 64; i++) {
+        ipad[i] = 0x36;
+        ((uint8_t *)state->opad)[i] = 0x5c;
+    }
+
+    debug_print(srtp_mod_hmac, "ipad: %s",
+                srtp_octet_string_hex_string(ipad, 64));
+
+    /* initialize sha1 context */
+    srtp_sha1_init(&state->init_ctx);
+
+    /* hash ipad ^ key */
+    srtp_sha1_update(&state->init_ctx, ipad, 64);
+    memcpy(&state->ctx, &state->init_ctx, sizeof(srtp_sha1_ctx_t));
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_start(void *statev)
+{
+    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
+
+    memcpy(&state->ctx, &state->init_ctx, sizeof(srtp_sha1_ctx_t));
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_update(void *statev,
+                                          const uint8_t *message,
+                                          size_t msg_octets)
+{
+    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
+
+    debug_print(srtp_mod_hmac, "input: %s",
+                srtp_octet_string_hex_string(message, msg_octets));
+
+    /* hash message into sha1 context */
+    srtp_sha1_update(&state->ctx, message, msg_octets);
+
+    return srtp_err_status_ok;
+}
+
+static srtp_err_status_t srtp_hmac_compute(void *statev,
+                                           const uint8_t *message,
+                                           size_t msg_octets,
+                                           size_t tag_len,
+                                           uint8_t *result)
+{
+    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
+    uint32_t hash_value[5];
+    uint32_t H[5];
+    size_t i;
+
+    /* check tag length, return error if we can't provide the value expected */
+    if (tag_len > 20) {
+        return srtp_err_status_bad_param;
+    }
+
+    /* hash message, copy output into H */
+    srtp_hmac_update(state, message, msg_octets);
+    srtp_sha1_final(&state->ctx, H);
+
+    /*
+     * note that we don't need to debug_print() the input, since the
+     * function hmac_update() already did that for us
+     */
+    debug_print(srtp_mod_hmac, "intermediate state: %s",
+                srtp_octet_string_hex_string((uint8_t *)H, 20));
+
+    /* re-initialize hash context */
+    srtp_sha1_init(&state->ctx);
+
+    /* hash opad ^ key  */
+    srtp_sha1_update(&state->ctx, (uint8_t *)state->opad, 64);
+
+    /* hash the result of the inner hash */
+    srtp_sha1_update(&state->ctx, (uint8_t *)H, 20);
+
+    /* the result is returned in the array hash_value[] */
+    srtp_sha1_final(&state->ctx, hash_value);
+
+    /* copy hash_value to *result */
+    for (i = 0; i < tag_len; i++) {
+        result[i] = ((uint8_t *)hash_value)[i];
+    }
+
+    debug_print(srtp_mod_hmac, "output: %s",
+                srtp_octet_string_hex_string((uint8_t *)hash_value, tag_len));
+
+    return srtp_err_status_ok;
+}
+
+static const char srtp_hmac_description[] =
+    "hmac sha-1 authentication function";
+
+/*
+ * srtp_auth_type_t hmac is the hmac metaobject
+ */
+
+const srtp_auth_type_t srtp_hmac = {
+    srtp_hmac_alloc,        /* */
+    srtp_hmac_dealloc,      /* */
+    srtp_hmac_init,         /* */
+    srtp_hmac_compute,      /* */
+    srtp_hmac_update,       /* */
+    srtp_hmac_start,        /* */
+    srtp_hmac_description,  /* */
+    &srtp_hmac_test_case_0, /* */
+    SRTP_HMAC_SHA1          /* */
+};