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diff --git a/srtp/README b/srtp/README new file mode 100644 index 0000000..08fafae --- /dev/null +++ b/srtp/README @@ -0,0 +1,174 @@ +Secure RTP (SRTP) Reference Implementation +David A. McGrew +Cisco Systems, Inc. +mcgrew@cisco.com + + +This package provides an implementation of the Secure Real-time +Transport Protocol (SRTP), the Universal Security Transform (UST), and +a supporting cryptographic kernel. These mechanisms are documented in +the Internet Drafts in the doc/ subdirectory. The SRTP API is +documented in include/srtp.h, and the library is in libsrtp.a (after +compilation). An overview and reference manual is available in +doc/libsrtp.pdf. The PDF documentation is more up to date than this +file. + + +Installation: + +./configure [ options ] # GNU autoconf script +make # or gmake if needed; use GNU make + +The configure script accepts the following options: + + --help provides a usage summary + --disable-debug compile without the runtime debugging system + --enable-syslog use syslog for error reporting + --disable-stdout use stdout for error reporting + --enable-console use /dev/console for error reporting + --gdoi use GDOI key management (disabled at present) + +By default, debbuging is enabled and stdout is used for debugging. +You can use the above configure options to have the debugging output +sent to syslog or the system console. Alternatively, you can define +ERR_REPORTING_FILE in include/conf.h to be any other file that can be +opened by libSRTP, and debug messages will be sent to it. + +This package has been tested on Mac OS X (powerpc-apple-darwin1.4), +Cygwin (i686-pc-cygwin), and Sparc (sparc-sun-solaris2.6). Previous +versions have been tested on Linux and OpenBSD on both x86 and sparc +platforms. + +A quick tour of this package: + +Makefile targets: all, clean, ... +README this file +CHANGES change log +VERSION version number of this package +LICENSE legal details (it's a BSD-like license) +crypto/ciphers/ ciphers (null, aes_icm, ...) +crypto/math/ crypto math routines +crypto/hash/ crypto hashing (hmac, tmmhv2, ...) +crypto/replay/ replay protection +doc/ documentation: rfcs, apis, and suchlike +include/ include files for all code in distribution +srtp/ secure real-time transport protocol implementation +tables/ apps for generating tables (useful in porting) +test/ test drivers + + +Applications + + Several test drivers and a simple and portable srtp application + are included in the test/ subdirectory. + + test driver function tested + ------------------------------------------------------------- + kernel_driver crypto kernel (ciphers, auth funcs, rng) + srtp_driver srtp in-memory tests (does not use the network) + rdbx_driver rdbx (extended replay database) + roc_driver extended sequence number functions + replay_driver replay database (n.b. not used in libsrtp) + cipher_driver ciphers + auth_driver hash functions + + The app rtpw is a simple rtp application which reads words from + /usr/dict/words and then sends them out one at a time using [s]rtp. + Manual srtp keying uses the -k option; automated key management + using gdoi will be added later. + +usage: rtpw [-d <debug>]* [-k <key> [-a][-e]] [-s | -r] dest_ip dest_port +or rtpw -l + + Either the -s (sender) or -r (receiver) option must be chosen. + + The values dest_ip, dest_port are the ip address and udp port to + which the dictionary will be sent, respectively. + + options: + + -s (s)rtp sender - causes app to send words + + -r (s)rtp receive - causes app to receve words + + -k <key> use srtp master key <key>, where the + key is a hexadecimal value (without the + leading "0x") + + -e encrypt/decrypt (for data confidentiality) + (requires use of -k option as well) + + -a message authentication + (requires use of -k option as well) + + -l list debug modules + + -d <debug> turn on debugging for module <debug> + + +In order to get random 30-byte values for use as key/salt pairs , you +can use the following bash function to format the output of +/dev/random (where that device is available). + +function randhex() { + cat /dev/random | od --read-bytes=32 --width=32 -x | awk '{ print $2 $3 $4 $5 $6 $7 $8 $9 $10 $11 $12 $13 $14 $15 $16 }' +} + + +An example of an SRTP session using two rtpw programs follows: + +set k=c1eec3717da76195bb878578790af71c4ee9f859e197a414a78d5abc7451 + +[sh1]$ test/rtpw -s -k $k -ea 0.0.0.0 9999 +Security services: confidentiality message authentication +set master key/salt to C1EEC3717DA76195BB878578790AF71C/4EE9F859E197A414A78D5ABC7451 +setting SSRC to 2078917053 +sending word: A +sending word: a +sending word: aa +sending word: aal +... + +[sh2]$ test/rtpw -r -k $k -ea 0.0.0.0 9999 +security services: confidentiality message authentication +set master key/salt to C1EEC3717DA76195BB878578790AF71C/4EE9F859E197A414A78D5ABC7451 +19 octets received from SSRC 2078917053 word: A +19 octets received from SSRC 2078917053 word: a +20 octets received from SSRC 2078917053 word: aa +21 octets received from SSRC 2078917053 word: aal +... + +Implementation Notes + + * The srtp_protect() function assumes that the buffer holding the + rtp packet has enough storage allocated that the authentication + tag can be written to the end of that packet. If this assumption + is not valid, memory corruption will ensue. + + * Automated tests for the crypto functions are provided through + the cipher_type_self_test() and auth_type_self_test() functions. + These functions should be used to test each port of this code + to a new platform. + + * Replay protection is contained in the crypto engine, and + tests for it are provided. + + * This implementation provides calls to initialize, protect, and + unprotect RTP packets, and makes as few as possible assumptions + about how these functions will be called. For example, the + caller is not expected to provide packets in order (though if + they're called more than 65k out of sequence, synchronization + will be lost). + + * The sequence number in the rtp packet is used as the low 16 bits + of the sender's local packet index. Note that RTP will start its + sequence number in a random place, and the SRTP layer just jumps + forward to that number at its first invocation. An earlier + version of this library used initial sequence numbers that are + less than 32,768; this trick is no longer required as the + rdbx_estimate_index(...) function has been made smarter. + + * The replay window is 128 bits in length, and is hard-coded to this + value for now. + + |