RTMPE protocol support

This adds two protocols, but one of them is an internal implementation
detail just used as an abstraction layer/generalization in the code. The
RTMPE protocol implementation uses ffrtmpcrypt:// as an alternative to the
tcp:// protocol. This allows moving most of the lower level logic out
from the higher level generic rtmp code.

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

1 files changed, 329 insertions, 0 deletions

diff --git a/libavformat/rtmpdh.c b/libavformat/rtmpdh.c
new file mode 100644
index 0000000000..8ddc5fcee8
--- /dev/null
+++ b/libavformat/rtmpdh.c
@@ -0,0 +1,329 @@
+/*
+ * RTMP Diffie-Hellmann utilities
+ * Copyright (c) 2012 Samuel Pitoiset
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * RTMP Diffie-Hellmann utilities
+ */
+
+#include "config.h"
+#include "rtmpdh.h"
+
+#define P1024                                          \
+    "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1" \
+    "29024E088A67CC74020BBEA63B139B22514A08798E3404DD" \
+    "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245" \
+    "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
+    "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381" \
+    "FFFFFFFFFFFFFFFF"
+
+#define Q1024                                          \
+    "7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68" \
+    "948127044533E63A0105DF531D89CD9128A5043CC71A026E" \
+    "F7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122" \
+    "F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6" \
+    "F71C35FDAD44CFD2D74F9208BE258FF324943328F67329C0" \
+    "FFFFFFFFFFFFFFFF"
+
+#if CONFIG_NETTLE || CONFIG_GCRYPT
+#if CONFIG_NETTLE
+#define bn_new(bn)                      \
+    do {                                \
+        bn = av_malloc(sizeof(*bn));    \
+        if (bn)                         \
+            mpz_init2(bn, 1);           \
+    } while (0)
+#define bn_free(bn)     \
+    do {                \
+        mpz_clear(bn);  \
+        av_free(bn);    \
+    } while (0)
+#define bn_set_word(bn, w)          mpz_set_ui(bn, w)
+#define bn_cmp(a, b)                mpz_cmp(a, b)
+#define bn_copy(to, from)           mpz_set(to, from)
+#define bn_sub_word(bn, w)          mpz_sub_ui(bn, bn, w)
+#define bn_cmp_1(bn)                mpz_cmp_ui(bn, 1)
+#define bn_num_bytes(bn)            (mpz_sizeinbase(bn, 2) + 7) / 8
+#define bn_bn2bin(bn, buf, len)     nettle_mpz_get_str_256(len, buf, bn)
+#define bn_bin2bn(bn, buf, len)                     \
+    do {                                            \
+        bn_new(bn);                                 \
+        if (bn)                                     \
+            nettle_mpz_set_str_256_u(bn, len, buf); \
+    } while (0)
+#define bn_hex2bn(bn, buf, ret)                     \
+    do {                                            \
+        bn_new(bn);                                 \
+        if (bn)                                     \
+            ret = (mpz_set_str(bn, buf, 16) == 0);  \
+    } while (0)
+#define bn_modexp(bn, y, q, p)      mpz_powm(bn, y, q, p)
+#define bn_random(bn, num_bytes)    mpz_random(bn, num_bytes);
+#elif CONFIG_GCRYPT
+#define bn_new(bn)                  bn = gcry_mpi_new(1)
+#define bn_free(bn)                 gcry_mpi_release(bn)
+#define bn_set_word(bn, w)          gcry_mpi_set_ui(bn, w)
+#define bn_cmp(a, b)                gcry_mpi_cmp(a, b)
+#define bn_copy(to, from)           gcry_mpi_set(to, from)
+#define bn_sub_word(bn, w)          gcry_mpi_sub_ui(bn, bn, w)
+#define bn_cmp_1(bn)                gcry_mpi_cmp_ui(bn, 1)
+#define bn_num_bytes(bn)            (gcry_mpi_get_nbits(bn) + 7) / 8
+#define bn_bn2bin(bn, buf, len)     gcry_mpi_print(GCRYMPI_FMT_USG, buf, len, NULL, bn)
+#define bn_bin2bn(bn, buf, len)     gcry_mpi_scan(&bn, GCRYMPI_FMT_USG, buf, len, NULL)
+#define bn_hex2bn(bn, buf, ret)     ret = (gcry_mpi_scan(&bn, GCRYMPI_FMT_HEX, buf, 0, 0) == 0)
+#define bn_modexp(bn, y, q, p)      gcry_mpi_powm(bn, y, q, p)
+#define bn_random(bn, num_bytes)    gcry_mpi_randomize(bn, num_bytes, GCRY_WEAK_RANDOM)
+#endif
+
+#define MAX_BYTES 18000
+
+#define dh_new()                    av_malloc(sizeof(FF_DH))
+
+static FFBigNum dh_generate_key(FF_DH *dh)
+{
+    int num_bytes;
+
+    num_bytes = bn_num_bytes(dh->p) - 1;
+    if (num_bytes <= 0 || num_bytes > MAX_BYTES)
+        return NULL;
+
+    bn_new(dh->priv_key);
+    if (!dh->priv_key)
+        return NULL;
+    bn_random(dh->priv_key, num_bytes);
+
+    bn_new(dh->pub_key);
+    if (!dh->pub_key) {
+        bn_free(dh->priv_key);
+        return NULL;
+    }
+
+    bn_modexp(dh->pub_key, dh->g, dh->priv_key, dh->p);
+
+    return dh->pub_key;
+}
+
+static int dh_compute_key(FF_DH *dh, FFBigNum pub_key_bn,
+                          uint32_t pub_key_len, uint8_t *secret_key)
+{
+    FFBigNum k;
+    int num_bytes;
+
+    num_bytes = bn_num_bytes(dh->p);
+    if (num_bytes <= 0 || num_bytes > MAX_BYTES)
+        return -1;
+
+    bn_new(k);
+    if (!k)
+        return -1;
+
+    bn_modexp(k, pub_key_bn, dh->priv_key, dh->p);
+    bn_bn2bin(k, secret_key, pub_key_len);
+    bn_free(k);
+
+    /* return the length of the shared secret key like DH_compute_key */
+    return pub_key_len;
+}
+
+void ff_dh_free(FF_DH *dh)
+{
+    bn_free(dh->p);
+    bn_free(dh->g);
+    bn_free(dh->pub_key);
+    bn_free(dh->priv_key);
+    av_free(dh);
+}
+#elif CONFIG_OPENSSL
+#define bn_new(bn)                  bn = BN_new()
+#define bn_free(bn)                 BN_free(bn)
+#define bn_set_word(bn, w)          BN_set_word(bn, w)
+#define bn_cmp(a, b)                BN_cmp(a, b)
+#define bn_copy(to, from)           BN_copy(to, from)
+#define bn_sub_word(bn, w)          BN_sub_word(bn, w)
+#define bn_cmp_1(bn)                BN_cmp(bn, BN_value_one())
+#define bn_num_bytes(bn)            BN_num_bytes(bn)
+#define bn_bn2bin(bn, buf, len)     BN_bn2bin(bn, buf)
+#define bn_bin2bn(bn, buf, len)     bn = BN_bin2bn(buf, len, 0)
+#define bn_hex2bn(bn, buf, ret)     ret = BN_hex2bn(&bn, buf)
+#define bn_modexp(bn, y, q, p)               \
+    do {                                     \
+        BN_CTX *ctx = BN_CTX_new();          \
+        if (!ctx)                            \
+            return AVERROR(ENOMEM);          \
+        if (!BN_mod_exp(bn, y, q, p, ctx)) { \
+            BN_CTX_free(ctx);                \
+            return AVERROR(EINVAL);          \
+        }                                    \
+        BN_CTX_free(ctx);                    \
+    } while (0)
+
+#define dh_new()                                DH_new()
+#define dh_generate_key(dh)                     DH_generate_key(dh)
+#define dh_compute_key(dh, pub, len, secret)    DH_compute_key(secret, pub, dh)
+
+void ff_dh_free(FF_DH *dh)
+{
+    DH_free(dh);
+}
+#endif
+
+static int dh_is_valid_public_key(FFBigNum y, FFBigNum p, FFBigNum q)
+{
+    FFBigNum bn = NULL;
+    int ret = AVERROR(EINVAL);
+
+    bn_new(bn);
+    if (!bn)
+        return AVERROR(ENOMEM);
+
+    /* y must lie in [2, p - 1] */
+    bn_set_word(bn, 1);
+    if (!bn_cmp(y, bn))
+        goto fail;
+
+    /* bn = p - 2 */
+    bn_copy(bn, p);
+    bn_sub_word(bn, 1);
+    if (!bn_cmp(y, bn))
+        goto fail;
+
+    /* Verify with Sophie-Germain prime
+     *
+     * This is a nice test to make sure the public key position is calculated
+     * correctly. This test will fail in about 50% of the cases if applied to
+     * random data.
+     */
+    /* y must fulfill y^q mod p = 1 */
+    bn_modexp(bn, y, q, p);
+
+    if (bn_cmp_1(bn))
+        goto fail;
+
+    ret = 0;
+fail:
+    bn_free(bn);
+
+    return ret;
+}
+
+av_cold FF_DH *ff_dh_init(int key_len)
+{
+    FF_DH *dh;
+    int ret;
+
+    if (!(dh = dh_new()))
+        return NULL;
+
+    bn_new(dh->g);
+    if (!dh->g)
+        goto fail;
+
+    bn_hex2bn(dh->p, P1024, ret);
+    if (!ret)
+        goto fail;
+
+    bn_set_word(dh->g, 2);
+    dh->length = key_len;
+
+    return dh;
+
+fail:
+    ff_dh_free(dh);
+
+    return NULL;
+}
+
+int ff_dh_generate_public_key(FF_DH *dh)
+{
+    int ret = 0;
+
+    while (!ret) {
+        FFBigNum q1 = NULL;
+
+        if (!dh_generate_key(dh))
+            return AVERROR(EINVAL);
+
+        bn_hex2bn(q1, Q1024, ret);
+        if (!ret)
+            return AVERROR(ENOMEM);
+
+        ret = dh_is_valid_public_key(dh->pub_key, dh->p, q1);
+        bn_free(q1);
+
+        if (!ret) {
+            /* the public key is valid */
+            break;
+        }
+    }
+
+    return ret;
+}
+
+int ff_dh_write_public_key(FF_DH *dh, uint8_t *pub_key, int pub_key_len)
+{
+    int len;
+
+    /* compute the length of the public key */
+    len = bn_num_bytes(dh->pub_key);
+    if (len <= 0 || len > pub_key_len)
+        return AVERROR(EINVAL);
+
+    /* convert the public key value into big-endian form */
+    memset(pub_key, 0, pub_key_len);
+    bn_bn2bin(dh->pub_key, pub_key + pub_key_len - len, len);
+
+    return 0;
+}
+
+int ff_dh_compute_shared_secret_key(FF_DH *dh, const uint8_t *pub_key,
+                                    int pub_key_len, uint8_t *secret_key)
+{
+    FFBigNum q1 = NULL, pub_key_bn = NULL;
+    int ret;
+
+    /* convert the big-endian form of the public key into a bignum */
+    bn_bin2bn(pub_key_bn, pub_key, pub_key_len);
+    if (!pub_key_bn)
+        return AVERROR(ENOMEM);
+
+    /* convert the string containing a hexadecimal number into a bignum */
+    bn_hex2bn(q1, Q1024, ret);
+    if (!ret) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
+
+    /* when the public key is valid we have to compute the shared secret key */
+    if ((ret = dh_is_valid_public_key(pub_key_bn, dh->p, q1)) < 0) {
+        goto fail;
+    } else if ((ret = dh_compute_key(dh, pub_key_bn, pub_key_len,
+                                     secret_key)) < 0) {
+        ret = AVERROR(EINVAL);
+        goto fail;
+    }
+
+fail:
+    bn_free(pub_key_bn);
+    bn_free(q1);
+
+    return ret;
+}
+