Approaches to automatically extract TLS keys from memory have been described in the TeLeScope, TLSkex and DroidKex publications. Unfortunately, their source code has never been released. This is a proof-of-concept implementation of a TLS 1.2 key extractor based on ptrace. It is not very sophisticated and does not implement many possible optimizations. TLS 1.3 is not supported.
Compilation requires CMake. First clone the repository, cd into it, then run:
cmake . && make
TLSDump will output the key in SSLKEYLOGFILE Format.
The following will output the key material for the curl command:
tlsdump -- curl --tlsv1.2 --tls-max 1.2 --http1.1 https://example.org
Alternatively, the -w option can be used to specify a file which to write the key material to:
tlsdump -w /tmp/sslkeylogfile.txt -- curl --tlsv1.2 --tls-max 1.2 --http1.1 https://example.org
TLSDump performs syscall hooking using ptrace. Upon a call to connect, it will remember the returned file
descriptor. TLSDump will then monitor this file descriptor for TLS handshakes by hooking
the write, sendto, and sendmsg syscalls, as well as their read, recvfrom, and recvmsg counterparts. Once the
completion of a handshake is detected, TLSDump will pause the target program, extract its memory and perform an
exhaustive search over the memory by testing whether the current search position is the start of a TLS master secret. To
this end, decryption functions copied from the Wireshark project are used.
Sometimes you might want to inspect the TLS traffic of closed-source applications without having to tediously reverse engineer them.
TLS 1.3 is currently not supported. However, adding support for TLS 1.3 should be possible as follows: First, identify the CLIENT_HANDSHAKE_TRAFFIC_SECRET by trying to decrypt the Handshake Protocol: Finished message through an exhaustive search in memory for the key. Having identified this secret, an exhaustive search for the CLIENT_TRAFFIC_SECRET_0 should be possible.
- A target program can easily evade this approach by obfuscating the keys stored in memory. A simple XOR would suffice.
- The current implementation does not support processes that perform fork operations.