SSLsplit - transparent and scalable SSL/TLS interception
Copyright 2009–2014 Daniel Roethlisberger and contributors. All rights reserved.
Licensed under a two-clause BSD license.
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. Depending on the version of OpenSSL, SSLsplit supports SSL 3.0, TLS 1.0, TLS 1.1 and TLS 1.2, and optionally SSL 2.0 as well. 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. For HTTP and HTTPS connections, SSLsplit removes response headers for HPKP in order to prevent public key pinning, for HSTS to allow the user to accept untrusted certificates, and Alternate Protocols to prevent switching to QUIC/SPDY.
% 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 -r proto only support one of ssl3 tls10 tls11 tls12 (default: all) -R proto disable one of ssl3 tls10 tls11 tls12 (default: none) -s ciphers use the given OpenSSL cipher suite spec (default: ALL:-aNULL) -e engine specify default NAT engine to use (default: pf) -E list available NAT engines and exit -u user drop privileges to user (default if run as root: nobody) -m group when using -u, override group (default: primary group of user) -j jaildir chroot() to jaildir (impacts -S/-F and sni, see manual page) -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/-F) -S logdir content log: full data to separate files in dir (excludes -L/-F) -F pathspec content log: full data to sep files with % subst (excl. -L/-S): %T - initial connection time as an ISO 8601 UTC timestamp %d - dest address:port %s - source address:port %x - base name of local process (requires -i) %X - full path to local process (requires -i) %u - user name or id of local process (requires -i) %g - group name or id of local process (requires -i) %% - literal '%' e.g. "/var/log/sslsplit/%X/%u-%s-%d-%T.log" -i look up local process owning each connection for logging -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.
SSLsplit depends on the OpenSSL and libevent 2.x libraries.
The build depends on GNU make and a POSIX.2 environment in
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
Support for local process information (
-i) is currently available on Mac OS X and FreeBSD.
SSL/TLS features and compatibility greatly depend on the version of OpenSSL linked against; for optimal results, use the latest 1.0.1 series release.
SSLsplit is or will be available as a package or port on the following systems:
- FreeBSD: security/sslsplit
- OpenBSD: security/sslsplit
- Arch Linux AUR: sslsplit
- ALT Linux autoimports: sslsplit
- Debian: sslsplit
- Fedora/RHEL/CentOS: sslsplit
- ArchAssault: sslsplit
- BlackArch Linux: sslsplit
- Kali Linux: sslsplit
- Backtrack: sslsplit
- WiFi Pineapple Infusion: 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
CHECK_BASE to the respective prefixes.
You can override the default install prefix (
/usr/local) by setting
SSLsplit is being developed on Github. For bug reports, please use the Github issue tracker. For patch submissions, please send me pull requests.
Freecode has ceased to exist; I currently announce new releases on my Twitter feed @droethlisberger and by pushing release tags to Github.
Further Reading and Success Stories
These links are provided in the hope that they may be useful, but without implying endorsement of any kind.
- Use SSLsplit to transparently sniff TLS/SSL connections – including non-HTTP(S) protocols by Philipp C. Heckel
- ARP spoofing, MITM attack over SSL-splitted connections, and fake CA certificate forging. All together. Against an iPhone by Claudio Di Nardo
- Yik Hak: Smashing the Yak by Sanford Moskowitz
- Fun with honeypots by Eric Severance
- Threema security assessment by Hristo Dimitrov, Jan Laan and Guido Pineda
- SSLSplit (sic) unter Kali-Linux einrichten by magnus at cryto dot org
- SSL-Traffic mit SSLsplit und Wireshark untersuchen by Andreas Hainke
- SSL中间人证书攻击测试演练 by xia0k
- 用SSLsplit分析SSL连接-包括非https协议 by Zhiwei Li
SSLsplit is also mentioned in «Bulletproof SSL and TLS» by Ivan Ristić; unfortunately at first under the category “SSL Stripping” instead of “MITM Certificate”, which was later fixed in the digital version of the book.