Transparent and scalable SSL/TLS interception
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.
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)
SSLsplit is or will be available as a package or port on the following systems:
% 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