lavu: Add an API for calculating HMAC (RFC 2104)

This supports HMAC-MD5 and HMAC-SHA1 for now, other hashes are
simple to add.

Signed-off-by: Martin Storsjö <martin@martin.st>

1 files changed, 138 insertions, 0 deletions

diff --git a/libavutil/hmac.c b/libavutil/hmac.c
new file mode 100644
index 0000000000..3308f1bb58
--- /dev/null
+++ b/libavutil/hmac.c
@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2012 Martin Storsjo
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <string.h>
+
+#include "hmac.h"
+#include "md5.h"
+#include "sha.h"
+#include "mem.h"
+
+#define MAX_HASHLEN 20
+#define MAX_BLOCKLEN 64
+
+struct AVHMAC {
+    void *hash;
+    int blocklen, hashlen;
+    void (*final)(void*, uint8_t*);
+    void (*update)(void*, const uint8_t*, int len);
+    void (*init)(void*);
+    uint8_t key[MAX_BLOCKLEN];
+    int keylen;
+};
+
+static void sha1_init(void *ctx)
+{
+    av_sha_init(ctx, 160);
+}
+
+AVHMAC *av_hmac_alloc(enum AVHMACType type)
+{
+    AVHMAC *c = av_mallocz(sizeof(*c));
+    if (!c)
+        return NULL;
+    switch (type) {
+    case AV_HMAC_MD5:
+        c->blocklen = 64;
+        c->hashlen  = 16;
+        c->init     = av_md5_init;
+        c->update   = av_md5_update;
+        c->final    = av_md5_final;
+        c->hash     = av_md5_alloc();
+        break;
+    case AV_HMAC_SHA1:
+        c->blocklen = 64;
+        c->hashlen  = 20;
+        c->init     = sha1_init;
+        c->update   = av_sha_update;
+        c->final    = av_sha_final;
+        c->hash     = av_sha_alloc();
+        break;
+    default:
+        av_free(c);
+        return NULL;
+    }
+    if (!c->hash) {
+        av_free(c);
+        return NULL;
+    }
+    return c;
+}
+
+void av_hmac_free(AVHMAC *c)
+{
+    if (!c)
+        return;
+    av_free(c->hash);
+    av_free(c);
+}
+
+void av_hmac_init(AVHMAC *c, const uint8_t *key, unsigned int keylen)
+{
+    int i;
+    uint8_t block[MAX_BLOCKLEN];
+    if (keylen > c->blocklen) {
+        c->init(c->hash);
+        c->update(c->hash, key, keylen);
+        c->final(c->hash, c->key);
+        c->keylen = c->hashlen;
+    } else {
+        memcpy(c->key, key, keylen);
+        c->keylen = keylen;
+    }
+    c->init(c->hash);
+    for (i = 0; i < c->keylen; i++)
+        block[i] = c->key[i] ^ 0x36;
+    for (i = c->keylen; i < c->blocklen; i++)
+        block[i] = 0x36;
+    c->update(c->hash, block, c->blocklen);
+}
+
+void av_hmac_update(AVHMAC *c, const uint8_t *data, unsigned int len)
+{
+    c->update(c->hash, data, len);
+}
+
+int av_hmac_final(AVHMAC *c, uint8_t *out, unsigned int outlen)
+{
+    uint8_t block[MAX_BLOCKLEN];
+    int i;
+    if (outlen < c->hashlen)
+        return AVERROR(EINVAL);
+    c->final(c->hash, out);
+    c->init(c->hash);
+    for (i = 0; i < c->keylen; i++)
+        block[i] = c->key[i] ^ 0x5C;
+    for (i = c->keylen; i < c->blocklen; i++)
+        block[i] = 0x5C;
+    c->update(c->hash, block, c->blocklen);
+    c->update(c->hash, out, c->hashlen);
+    c->final(c->hash, out);
+    return c->hashlen;
+}
+
+int av_hmac_calc(AVHMAC *c, const uint8_t *data, unsigned int len,
+                 const uint8_t *key, unsigned int keylen,
+                 uint8_t *out, unsigned int outlen)
+{
+    av_hmac_init(c, key, keylen);
+    av_hmac_update(c, data, len);
+    return av_hmac_final(c, out, outlen);
+}