Initial support for Secure Real-Time Protocol (RFC3711) - refs #321

Uses libgcrypt, as we have it in our deps/contrib already for GnuTLS.

This could be used in both "UDP"[1] access and access output plugins,
though they should really be called "RTP" instead nowadays.

Done:
 - AES(-128) Counter Mode key derivation and RTP en-/decryption
 - test vectors for AES-CM
 - NULL cipher (with the *_UNENCRYPTED flags) - untested

To do (missing mandatory features):
 - RTCP en-/decryption
 - HMAC-SHA1 authentication
 - replay attack protection

Also to probably do:
 - integrate with udp access and access output plugins
 - integrate with RTSP server (err, I won't do that myself)
 - support for Transform Carrying ROC for SRTP (RFC4771)
   so we can use it easily for multicast streaming

configure.ac

@@ -5235,6 +5235,9 @@ AS_IF([test "${enable_gnutls}" != "no"], [
   ])
 ])
 
+AM_PATH_LIBGCRYPT([1:1.1.94], [have_libgcrypt="yes"], [have_libgcrypt="no"])
+AM_CONDITIONAL([HAVE_LIBGCRYPT], [test "${have_libgcrypt}" = "yes"])
+
 
 dnl
 dnl  Endianness check, AC_C_BIGENDIAN doesn't work if we are cross-compiling
@@ -5773,6 +5776,7 @@ AC_CONFIG_FILES([
   ipkg/Makefile
   libs/Makefile
   libs/loader/Makefile
+  libs/srtp/Makefile
   modules/Makefile
   mozilla/Makefile
   m4/Makefile

libs/Makefile.am

-SUBDIRS = loader
-
+SUBDIRS = loader srtp

libs/srtp/Makefile.am

+# Secure RTP with libgcrypt
+# Copyright (C) 2007  Rémi Denis-Courmont <rdenis # simphalempin , com>
+#
+# This library 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.
+#
+# This library 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 this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+
+AM_CPPFLAGS = @LIBGCRYPT_CFLAGS@
+AM_LDFLAGS = @LIBGCRYPT_LIBS@
+
+if !HAVE_WIN32
+AM_LDFLAGS += -lpthread
+endif
+
+noinst_HEADERS = srtp.h
+
+EXTRA_PROGRAMS = srtp
+if HAVE_LIBGCRYPT
+noinst_LTLIBRARIES = libvlc_srtp.la
+check_PROGRAMS = test-aes
+TESTS = test-aes
+endif
+
+libvlc_srtp_la_SOURCES = srtp.c
+test_aes_SOURCES = test-aes.c
+srtp_SOURCES = recv.c
+srtp_LDADD = libvlc_srtp.la
+

libs/srtp/recv.c

+/*
+ * Secure RTP with libgcrypt
+ * Copyright (C) 2007  Rémi Denis-Courmont <rdenis # simphalempin , com>
+ *
+ * This library 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.
+ *
+ * This library 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 this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stdint.h>
+#include <stddef.h>
+#include "srtp.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#include <unistd.h>
+#include <netinet/in.h>
+
+int main (void)
+{
+    int fd = socket (AF_INET, SOCK_DGRAM, 0);
+    struct sockaddr_in addr;
+    memset (&addr, 0, sizeof (addr));
+    addr.sin_family = AF_INET;
+#ifdef HAVE_SA_LEN
+    addr.sin_len = sizeof (addr);
+#endif
+    addr.sin_port = htons (10000);
+    addr.sin_addr.s_addr = htonl (0x7f000001);
+    if (bind (fd, (struct sockaddr *)&addr, sizeof (addr)))
+        return 1;
+
+    static const uint8_t key[16] =
+        "\x12\x34\x56\x78\x9A\xBC\xDE\xF0"
+        "\x12\x34\x56\x78\x9A\xBC\xDE\xF0";
+    static const uint8_t salt[14] =
+        "\x12\x34\x56\x78\x90" "\x12\x34\x56\x78\x90" "\x12\x34\x56\x78";
+
+    srtp_session_t *s = srtp_create ("AES_CM_128_HMAC_SHA1_80", 0, 0, 0);
+    if (s == NULL)
+        return 1;
+    if (srtp_setkey (s, key, 16, salt, 14))
+        goto error;
+
+    uint8_t buf[1500];
+    size_t len;
+#if 0
+    memset (buf, 0, sizeof (buf));
+    buf[0] = 2 << 6;
+    buf[1] = 1;
+    memcpy (buf + 2, &(uint16_t){ htons (9527) }, 2);
+    memcpy (buf + 8, "\xde\xad\xbe\xef", 4);
+    memcpy (buf + 4, &(uint32_t){ htonl (1) }, 4);
+    strcpy ((char *)buf + 12, "a\n");
+    len = 12 + strlen ((char *)buf + 12) + 1;
+#endif
+    for (;;)
+    {
+        len = read (fd, buf, sizeof (buf));
+        if (srtp_recv (s, buf, &len))
+            fputs ("Cannot decrypt!\n", stderr);
+        puts ((char *)buf + 12);
+        if (srtp_send (s, buf, &len, sizeof (buf)) || srtp_recv (s, buf, &len))
+            break;
+        puts ((char *)buf + 12);
+    }
+
+error:
+    srtp_destroy (s);
+    close (fd);
+    return 0;
+}

libs/srtp/srtp.h

+/*
+ * Secure RTP with libgcrypt
+ * Copyright (C) 2007  Rémi Denis-Courmont <rdenis # simphalempin , com>
+ *
+ * This library 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.
+ *
+ * This library 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 this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef LIBVLC_SRTP_H
+# define LIBVLC_SRTP_H 1
+
+typedef struct srtp_session_t srtp_session_t;
+
+enum
+{
+	SRTP_UNENCRYPTED=0x1, // do not encrypt SRTP packets
+	SRTCP_UNENCRYPTED=0x2, // do not encrypt SRTCP packets
+	SRTP_NULL_CIPHER=0x3, // use NULL cipher (encrypt nothing)
+	SRTP_UNAUTHENTICATED=0x4, // do not authenticated SRTP packets
+	SRTP_FLAGS_MASK=0x7
+};
+
+
+# ifdef __cplusplus
+extern "C" {
+# endif
+
+srtp_session_t *srtp_create (const char *name, unsigned flags, unsigned kdr,
+                             uint16_t winsize);
+void srtp_destroy (srtp_session_t *s);
+int srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t maxsize);
+int srtp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp);
+
+int srtp_setkey (srtp_session_t *s, const void *key, size_t keylen,
+                 const void *salt, size_t saltlen);
+# ifdef __cplusplus
+}
+# endif
+#endif
+

libs/srtp/test-aes.c

+/*
+ * Secure RTP with libgcrypt
+ * Copyright (C) 2007  Rémi Denis-Courmont <rdenis # simphalempin , com>
+ *
+ * This library 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.
+ *
+ * This library 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 this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <stdio.h>
+#include "srtp.c"
+
+static void printhex (const void *buf, size_t len)
+{
+    for (size_t i = 0; i < len; i++)
+        printf ("%02X", ((uint8_t *)buf)[i]);
+    fputc ('\n', stdout);
+}
+
+static void fatal (const char *msg)
+{
+    puts (msg);
+    exit (1);
+}
+
+/** AES-CM key derivation test vectors */
+static void test_derivation (void)
+{
+    static const uint8_t key[16] =
+        "\xE1\xF9\x7A\x0D\x3E\x01\x8B\xE0\xD6\x4F\xA3\x2C\x06\xDE\x41\x39";
+    static const uint8_t salt[14] =
+        "\x0E\xC6\x75\xAD\x49\x8A\xFE\xEB\xB6\x96\x0B\x3A\xAB\xE6";
+
+    static const uint8_t good_cipher[16] =
+        "\xC6\x1E\x7A\x93\x74\x4F\x39\xEE\x10\x73\x4A\xFE\x3F\xF7\xA0\x87";
+    static const uint8_t good_salt[14] =
+        "\x30\xCB\xBC\x08\x86\x3D\x8C\x85\xD4\x9D\xB3\x4A\x9A\xE1";
+    static const uint8_t good_auth[94] =
+        "\xCE\xBE\x32\x1F\x6F\xF7\x71\x6B\x6F\xD4\xAB\x49\xAF\x25\x6A\x15"
+        "\x6D\x38\xBA\xA4\x8F\x0A\x0A\xCF\x3C\x34\xE2\x35\x9E\x6C\xDB\xCE"
+        "\xE0\x49\x64\x6C\x43\xD9\x32\x7A\xD1\x75\x57\x8E\xF7\x22\x70\x98"
+        "\x63\x71\xC1\x0C\x9A\x36\x9A\xC2\xF9\x4A\x8C\x5F\xBC\xDD\xDC\x25"
+        "\x6D\x6E\x91\x9A\x48\xB6\x10\xEF\x17\xC2\x04\x1E\x47\x40\x35\x76"
+        "\x6B\x68\x64\x2C\x59\xBB\xFC\x2F\x34\xDB\x60\xDB\xDF\xB2";
+
+    static const uint8_t r[6] = { 0, 0, 0, 0, 0, 0 };
+    gcry_cipher_hd_t prf;
+    uint8_t out[94];
+
+    puts ("AES-CM key derivation test...");
+    printf (" master key:  ");
+    printhex (key, sizeof (key));
+    printf (" master salt: ");
+    printhex (salt, sizeof (salt));
+
+    if (gcry_cipher_open (&prf, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_ECB, 0)
+     || gcry_cipher_setkey (prf, key, sizeof (key)))
+        fatal ("Internal PRF error");
+
+    if (derive (prf, salt, r, sizeof (r), SRTP_CRYPT, out, 16))
+        fatal ("Internal cipher derivation error");
+    printf (" cipher key:  ");
+    printhex (out, 16);
+    if (memcmp (out, good_cipher, 16))
+        fatal ("Test failed");
+
+    if (derive (prf, salt, r, sizeof (r), SRTP_SALT, out, 14))
+        fatal ("Internal salt derivation error");
+    printf (" cipher salt: ");
+    printhex (out, 14);
+    if (memcmp (out, good_salt, 14))
+        fatal ("Test failed");
+
+    if (derive (prf, salt, r, sizeof (r), SRTP_AUTH, out, 94))
+        fatal ("Internal auth key derivation error");
+    printf (" auth key:    ");
+    printhex (out, 94);
+    if (memcmp (out, good_auth, 94))
+        fatal ("Test failed");
+
+    gcry_cipher_close (prf);
+}
+
+/** AES-CM key derivation test vectors */
+static void test_keystream (void)
+{
+    static const uint8_t key[16] =
+        "\x2B\x7E\x15\x16\x28\xAE\xD2\xA6\xAB\xF7\x15\x88\x09\xCF\x4F\x3C";
+    const uint32_t salt[4]=
+        { htonl (0xf0f1f2f3), htonl (0xf4f5f6f7),
+          htonl (0xf8f9fafb), htonl (0xfcfd0000) };
+
+    puts ("AES-CM key stream test...");
+    uint8_t *buf = calloc (0xff02, 16);
+    if (buf == NULL)
+    {
+        fputs ("Not enough memory for test\n", stderr);
+        return;
+    }
+
+    printf (" session key: ");
+    printhex (key, sizeof (key));
+
+    gcry_cipher_hd_t hd;
+    if (gcry_cipher_open (&hd, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR, 0))
+        fatal ("Cipher initialization error");
+    if (gcry_cipher_setkey (hd, key, sizeof (key)))
+        fatal ("Cipher key error");
+
+    if (rtp_encrypt (hd, 0, 0, 0, salt, buf, 0xff020))
+        fatal ("Encryption failure");
+    gcry_cipher_close (hd);
+
+    static const uint8_t good_start[48] =
+        "\xE0\x3E\xAD\x09\x35\xC9\x5E\x80\xE1\x66\xB1\x6D\xD9\x2B\x4E\xB4"
+        "\xD2\x35\x13\x16\x2B\x02\xD0\xF7\x2A\x43\xA2\xFE\x4A\x5F\x97\xAB"
+        "\x41\xE9\x5B\x3B\xB0\xA2\xE8\xDD\x47\x79\x01\xE4\xFC\xA8\x94\xC0";
+    static const uint8_t good_end[48] =
+        "\xEC\x8C\xDF\x73\x98\x60\x7C\xB0\xF2\xD2\x16\x75\xEA\x9E\xA1\xE4"
+        "\x36\x2B\x7C\x3C\x67\x73\x51\x63\x18\xA0\x77\xD7\xFC\x50\x73\xAE"
+        "\x6A\x2C\xC3\x78\x78\x89\x37\x4F\xBE\xB4\xC8\x1B\x17\xBA\x6C\x44";
+
+    printf (" key stream:  ");
+    printhex (buf, sizeof (good_start));
+    printf (" ... cont'd : ");
+    printhex (buf + 0xff020 - sizeof (good_end), sizeof (good_end));
+    if (memcmp (buf, good_start, sizeof (good_start))
+     || memcmp (buf + 0xff020 - sizeof (good_end), good_end,
+                sizeof (good_end)))
+        fatal ("Key stream test failed");
+    free (buf);
+}
+
+static void srtp_test (void)
+{
+    if (init_libgcrypt ())
+        fatal ("Libgcrypt initialization error");
+    test_derivation ();
+    test_keystream ();
+}
+
+int main (void)
+{
+    srtp_test ();
+    return 0;
+}