Add documentation about AFL fuzzing and seed SIP messages

tester/afl.md

+# Using the afl-fuzz to look for bugs in the belle-sip parser
+
+This guide expects that you have installed the afl-fuzz package for your distribution, or on Mac using Homebrew or port.
+Windows is not supported right now.
+
+Then follow these steps:
+
+1. Configure belle-sip with the afl instrumentation tools as CC and OBJC, and with static linking:
+
+        # Linux
+        CC=`which afl-gcc` ./configure --disable-shared
+
+        # Mac
+        CC=`which afl-clang` OBJC=`which afl-clang` ./configure --disable-shared
+
+2. Compile and make sure the testers are build. You should have an executable file named testers/belle_sip_parser
+
+        make clean && make
+
+3. You can now run the afl fuzzy tester in the tester/ directory to test the parser for SDP, HTTP or SIP.
+
+        afl-fuzz -i afl/sip -o afl_sip_results -- ./belle_sip_parser --protocol sip @@
+
+With this command:
+
+- It will show you a screen with informations on the current state of the fuzzing steps.  
+
+- The `afl/sip` directory contains valid SIP messages that the fuzzer will use as a base for its investigations. You can add 
+
+- The results of the investigations will be placed in a directory named `afl_sip_results/`. You will have access to the SIP messages that provoked a crash in the `crashes/` directory.
+
+# Notes
+
+The afl directory contains test messages that will be the base for mutation with the afl fuzzer. They are saved using the CRLF line endings. This is important since the parser expects two "\r\n\r\n" at the end of a message.
+
+## TODO:
+
+1. add HTTP and SDP fuzzy tests
+2. add a dictionary of keywords to help the fuzzer generate some valid messages (instead of bitflipping randomly) (see `afl-fuzz -x` option)
\ No newline at end of file

tester/afl/sip/401Unauthorized.txt

+SIP/2.0 401 Unauthorized
+Via: SIP/2.0/TLS 192.168.0.109:49949;alias;branch=z9hG4bK.gWH~ix41h;rport=49949;received=82.216.250.246
+From: <sip:gbi@sip.linphone.org>;tag=5exJTQayL
+To: <sip:gbi@sip.linphone.org>;tag=jv0pZ0cH8ejaF
+Call-ID: PkUb7A2nxg
+CSeq: 20 REGISTER
+Server: Flexisip/1.0.2 (sofia-sip-nta/2.0)
+WWW-Authenticate: Digest realm="sip.linphone.org", nonce="WR5i2QAAAAA9uY8IAADQ03f3p94AAAAA", opaque="+GNywA==", algorithm=MD5, qop="auth"
+Content-Length: 0
+
+

tester/afl/sip/REGISTER.txt

+REGISTER sip:sip.linphone.org SIP/2.0
+Via: SIP/2.0/TLS 192.168.0.109:49949;alias;branch=z9hG4bK.gdQJOpBN5;rport
+From: <sip:gbi@sip.linphone.org>;tag=5exJTQayL
+To: sip:gbi@sip.linphone.org
+CSeq: 21 REGISTER
+Call-ID: PkUb7A2nxg
+Max-Forwards: 70
+Supported: outbound
+Accept: application/sdp, text/plain, application/vnd.gsma.rcs-ft-http+xml
+Contact: <sip:gbi@82.216.250.246:49949;transport=tls>;+sip.instance="<urn:uuid:21cd159b-12cf-4b8b-b653-282bb811da23>"
+Expires: 3600
+User-Agent: Linphone/3.8.5 (belle-sip/1.4.1)
+Content-Length: 0
+Authorization:  Digest realm="sip.linphone.org", nonce="WR5i2QAAAAA9uY8IAADQ03f3p94AAAAA", algorithm=MD5, opaque="+GNywA==", username="gbi",  uri="sip:sip.linphone.org", response="124f0c0ea212786c9f8b5b6f1de92b43", cnonce="faaac8d5", nc=00000001, qop=auth
+
+

tester/afl/sip/SIP200RegSuccess.txt

+SIP/2.0 200 Registration successful
+Via: SIP/2.0/TLS 192.168.0.109:49949;alias;branch=z9hG4bK.gdQJOpBN5;rport=49949;received=82.216.250.246
+From: <sip:gbi@sip.linphone.org>;tag=5exJTQayL
+To: <sip:gbi@sip.linphone.org>;tag=K5SF1UXm5Q8va
+Call-ID: PkUb7A2nxg
+CSeq: 21 REGISTER
+Contact: <sip:gbi@82.216.250.246:49949;transport=tls>;expires=3600;q=0.00
+Contact: <sip:gbi@82.216.250.246:62954;app-id=org.linphone.phone.dev;pn-type=apple;pn-tok=1FDA61D1A73B5C6307699D89DFDB83BD8DC970C481FE4D9D356E80FD19D3240E;pn-msg-str=IM_MSG;pn-call-str=IC_MSG;pn-call-snd=ring.caf;pn-msg-snd=msg.caf;transport=tls>;expires=604442;q=0.00
+Server: Flexisip/1.0.2 (sofia-sip-nta/2.0)
+Content-Length: 0
+
+