libavutil: add aes-ctr support

for supporting mp4 cenc encoding/decoding

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavutil/Makefile

@@ -4,6 +4,7 @@ NAME = avutil
 
 HEADERS = adler32.h                                                     \
           aes.h                                                         \
+          aes_ctr.h                                                     \
           attributes.h                                                  \
           audio_fifo.h                                                  \
           avassert.h                                                    \
@@ -80,6 +81,7 @@ BUILT_HEADERS = avconfig.h                                              \
 
 OBJS = adler32.o                                                        \
        aes.o                                                            \
+       aes_ctr.o                                                        \
        audio_fifo.o                                                     \
        avstring.o                                                       \
        base64.o                                                         \

libavutil/aes_ctr.c

@@ -0,0 +1,129 @@
+/*
+ * AES-CTR cipher
+ * Copyright (c) 2015 Eran Kornblau <erankor at gmail dot com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "common.h"
+#include "aes_ctr.h"
+#include "aes.h"
+#include "random_seed.h"
+
+#define AES_BLOCK_SIZE (16)
+
+typedef struct AVAESCTR {
+    struct AVAES* aes;
+    uint8_t counter[AES_BLOCK_SIZE];
+    uint8_t encrypted_counter[AES_BLOCK_SIZE];
+    int block_offset;
+} AVAESCTR;
+
+struct AVAESCTR *av_aes_ctr_alloc(void)
+{
+    return av_mallocz(sizeof(struct AVAESCTR));
+}
+
+void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv)
+{
+    memcpy(a->counter, iv, AES_CTR_IV_SIZE);
+    memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
+    a->block_offset = 0;
+}
+
+const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a)
+{
+    return a->counter;
+}
+
+void av_aes_ctr_set_random_iv(struct AVAESCTR *a)
+{
+    uint32_t iv[2];
+
+    iv[0] = av_get_random_seed();
+    iv[1] = av_get_random_seed();
+
+    av_aes_ctr_set_iv(a, (uint8_t*)iv);
+}
+
+int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key)
+{
+    a->aes = av_aes_alloc();
+    if (!a->aes) {
+        return AVERROR(ENOMEM);
+    }
+
+    av_aes_init(a->aes, key, 128, 0);
+
+    memset(a->counter, 0, sizeof(a->counter));
+    a->block_offset = 0;
+
+    return 0;
+}
+
+void av_aes_ctr_free(struct AVAESCTR *a)
+{
+    if (a) {
+        av_freep(&a->aes);
+        av_freep(a);
+    }
+}
+
+static void av_aes_ctr_increment_be64(uint8_t* counter)
+{
+    uint8_t* cur_pos;
+
+    for (cur_pos = counter + 7; cur_pos >= counter; cur_pos--) {
+        (*cur_pos)++;
+        if (*cur_pos != 0) {
+            break;
+        }
+    }
+}
+
+void av_aes_ctr_increment_iv(struct AVAESCTR *a)
+{
+    av_aes_ctr_increment_be64(a->counter);
+    memset(a->counter + AES_CTR_IV_SIZE, 0, sizeof(a->counter) - AES_CTR_IV_SIZE);
+    a->block_offset = 0;
+}
+
+void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int count)
+{
+    const uint8_t* src_end = src + count;
+    const uint8_t* cur_end_pos;
+    uint8_t* encrypted_counter_pos;
+
+    while (src < src_end) {
+        if (a->block_offset == 0) {
+            av_aes_crypt(a->aes, a->encrypted_counter, a->counter, 1, NULL, 0);
+
+            av_aes_ctr_increment_be64(a->counter + 8);
+        }
+
+        encrypted_counter_pos = a->encrypted_counter + a->block_offset;
+        cur_end_pos = src + AES_BLOCK_SIZE - a->block_offset;
+        cur_end_pos = FFMIN(cur_end_pos, src_end);
+
+        a->block_offset += cur_end_pos - src;
+        a->block_offset &= (AES_BLOCK_SIZE - 1);
+
+        while (src < cur_end_pos) {
+            *dst++ = *src++ ^ *encrypted_counter_pos++;
+        }
+    }
+}

libavutil/aes_ctr.h

@@ -0,0 +1,83 @@
+/*
+ * AES-CTR cipher
+ * Copyright (c) 2015 Eran Kornblau <erankor at gmail dot com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_AES_CTR_H
+#define AVUTIL_AES_CTR_H
+
+#include <stdint.h>
+
+#include "attributes.h"
+#include "version.h"
+
+#define AES_CTR_KEY_SIZE (16)
+#define AES_CTR_IV_SIZE (8)
+
+struct AVAESCTR;
+
+/**
+ * Allocate an AVAESCTR context.
+ */
+struct AVAESCTR *av_aes_ctr_alloc(void);
+
+/**
+ * Initialize an AVAESCTR context.
+ * @param key encryption key, must have a length of AES_CTR_KEY_SIZE
+ */
+int av_aes_ctr_init(struct AVAESCTR *a, const uint8_t *key);
+
+/**
+ * Release an AVAESCTR context.
+ */
+void av_aes_ctr_free(struct AVAESCTR *a);
+
+/**
+ * Process a buffer using a previously initialized context.
+ * @param dst destination array, can be equal to src
+ * @param src source array, can be equal to dst
+ * @param size the size of src and dst
+ */
+void av_aes_ctr_crypt(struct AVAESCTR *a, uint8_t *dst, const uint8_t *src, int size);
+
+/**
+ * Get the current iv
+ */
+const uint8_t* av_aes_ctr_get_iv(struct AVAESCTR *a);
+
+/**
+ * Generate a random iv
+ */
+void av_aes_ctr_set_random_iv(struct AVAESCTR *a);
+
+/**
+ * Forcefully change the iv
+ */
+void av_aes_ctr_set_iv(struct AVAESCTR *a, const uint8_t* iv);
+
+/**
+ * Increment the top 64 bit of the iv (performed after each frame)
+ */
+void av_aes_ctr_increment_iv(struct AVAESCTR *a);
+
+/**
+ * @}
+ */
+
+#endif /* AVUTIL_AES_CTR_H */

libavutil/version.h

@@ -64,7 +64,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  55
-#define LIBAVUTIL_VERSION_MINOR  10
+#define LIBAVUTIL_VERSION_MINOR  11
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \