Overview
SSLsplit is a tool for man-in-the-middle attacks against SSL/TLS encrypted network connections. Connections are transparently intercepted through a network address translation engine and redirected to SSLsplit. SSLsplit terminates SSL/TLS and initiates a new SSL/TLS connection to the original destination address, while logging all data transmitted. SSLsplit is intended to be useful for network forensics and penetration testing.
SSLsplit supports plain TCP, plain SSL, HTTP and HTTPS connections over both IPv4 and IPv6. For SSL and HTTPS connections, SSLsplit generates and signs forged X509v3 certificates on-the-fly, based on the original server certificate subject DN and subjectAltName extension. SSLsplit fully supports Server Name Indication (SNI) and is able to work with RSA, DSA and ECDSA keys and DHE and ECDHE cipher suites. SSLsplit can also use existing certificates of which the private key is available, instead of generating forged ones. SSLsplit supports NULL-prefix CN certificates and can deny OCSP requests in a generic way. SSLsplit removes HPKP response headers in order to prevent public key pinning.
Usage
% sslsplit -h
Usage: sslsplit [options...] [proxyspecs...]
-c pemfile use CA cert (and key) from pemfile to sign forged certs
-k pemfile use CA key (and cert) from pemfile to sign forged certs
-C pemfile use CA chain from pemfile (intermediate and root CA certs)
-K pemfile use key from pemfile for leaf certs (default: generate)
-t certdir use cert+chain+key PEM files from certdir to target all sites
matching the common names (non-matching: generate if CA)
-O deny all OCSP requests on all proxyspecs
-P passthrough SSL connections if they cannot be split because of
client cert auth or no matching cert and no CA (default: drop)
-g pemfile use DH group params from pemfile (default: keyfiles or auto)
-G curve use ECDH named curve (default: secp160r2 for non-RSA leafkey)
-Z disable SSL/TLS compression on all connections
-s ciphers use the given OpenSSL cipher suite spec (default: ALL:-aNULL)
-e engine specify default NAT engine to use (default: ipfw)
-E list available NAT engines and exit
-u user drop privileges to user (default if run as root: nobody)
-j jaildir chroot() to jaildir (default if run as root: /var/empty)
-p pidfile write pid to pidfile (default: no pid file)
-l logfile connect log: log one line summary per connection to logfile
-L logfile content log: full data to file or named pipe (excludes -S)
-S logdir content log: full data to separate files in dir (excludes -L)
-d daemon mode: run in background, log error messages to syslog
-D debug mode: run in foreground, log debug messages on stderr
-V print version information and exit
-h print usage information and exit
proxyspec = type listenaddr+port [natengine|targetaddr+port|"sni"+port]
e.g. http 0.0.0.0 8080 www.roe.ch 80 # http/4; static hostname dst
https ::1 8443 2001:db8::1 443 # https/6; static address dst
https 127.0.0.1 9443 sni 443 # https/4; SNI DNS lookups
tcp 127.0.0.1 10025 # tcp/4; default NAT engine
ssl 2001:db8::2 9999 pf # ssl/6; NAT engine 'pf'
Example:
sslsplit -k ca.key -c ca.pem -P https 127.0.0.1 8443 https ::1 8443
See the manual page sslsplit(1) for details on using SSLsplit and setting up the various NAT engines.
Requirements
SSLsplit depends on the OpenSSL and libevent 2.x libraries. The build depends on GNU make and a POSIX.2 environment in PATH. The (optional) unit tests depend on the check library.
SSLsplit currently supports the following operating systems and NAT engines:
FreeBSD: pf rdr and divert-to, ipfw fwd, ipfilter rdr
OpenBSD: pf rdr-to and divert-to
Linux: netfilter REDIRECT and TPROXY
Mac OS X: ipfw fwd and pf rdr (experimental)
Installation
SSLsplit is or will be available as a package or port on the following systems:
OpenBSD: security/sslsplit
Arch Linux AUR: sslsplit
Fedora: sslsplit
Kali: sslsplit
Backtrack: sslsplit
To install from source:
make
make test # optional unit tests
make install # optional install
Dependencies are autoconfigured using pkg-config. If dependencies are not picked up and fixing PKG_CONFIG_PATH does not help, you can specify their respective locations manually by setting OPENSSL_BASE, LIBEVENT_BASE and/or CHECK_BASE to the respective prefixes.
You can override the default install prefix (/usr/local) by setting PREFIX.
Development
SSLsplit is being developed on Github. For bug reports, please use the Github issue tracker. For patch submissions, please send me pull requests.
https://github.com/droe/sslsplit
Build Status
You can track releases on freecode (FreshMeat):
http://freecode.com/projects/sslsplit
License
SSLsplit is provided under the simplified BSD license. SSLsplit contains components licensed under the MIT and APSL licenses. See the respective source file headers for details.
Credits
SSLsplit was inspired by mitm-ssl by Claes M. Nyberg and sslsniff by Moxie Marlinspike, but shares no source code with them.
SSLsplit includes khash.h by Attractive Chaos.
Further Reading
Use SSLsplit to transparently sniff TLS/SSL connections – including non-HTTP(S) protocols by Philipp C. Heckel
SSLSplit (sic) unter Kali-Linux einrichten by magnus at cryto dot or