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USAGE.md

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Plugin: keyfind

Summary

The keyfind plugin attempts to locate the point within a replay where TLS master secrets are generated. It does so by watching every memory read and write, and then using this data as a possible key to decrypt some sample data.

The plugin is described in greater detail in PANDA's SSL Tutorial.

The input to the plugin is a configuration file that contains information about the encryption algorithms in use, the sample data to decrypt, and the connection ID. The keyfind_config.txt must contain, at minimum:

  • Client-Random: The random nonce sent by the client.
  • Server-Random: The random nonce sent by the server.
  • Content-Type: The content-type field (used in calculating the HMAC, for verification)
  • Version: The version of the TLS protocol, e.g. 0302
  • Enc-Msg: The encrypted message that we should try to decrypt.
  • Cipher: The cipher used for the session, in the form OpenSSL expects (e.g., AES-128-CBC)
  • MAC: The algorithm used for the TLS MAC (e.g., SHA1).

You can generate a configuration file given a PCAP file with TLS data you want to decrypt using the list_enc.py script (available in PANDA's scripts directory).

You may also, optionally, supply a list of candidate tap points in a file named keytap_candidates.txt. For example, one might exclude all tap points that read or wrote very little data (less than one key's worth -- 48 bytes) or whose content had low entropy (since encryption keys are expected to be random). This can greatly speed up the search.

The key found (if any) will be printed to stderr, and all matching tap points will be saved to the file key_matches.txt for later perusal.

Arguments

None.

Dependencies

keyfind uses the callstack_instr plugin to split memory accesses up into individual tap points.

APIs and Callbacks

None.

Example

An example configuration file:

# ==== 127.0.0.1:443 <-> 127.0.0.1:52103 ====
Client-Random: 508db4fea3925d766805a41f918350b9dc8822253d490d85bfa3d25763bf220a
Server-Random: 508db4fe6d3fa3fa913427f5fd8cbf3213211249acccff598d47fc0a0049143f
Content-Type:  16
Version:       0302
Enc-Msg:       7c90069ae372aba7e91c51a91db7a1d73e282ed44178bb2ec87b7535240a9b394db93219c4227fae48ebcaf40f7a49298ea91849157ed24f83733616ef4bdd68
Cipher:        AES-128-CBC
MAC:           SHA1

Then, run PANDA with keyfind:

$PANDA_PATH/x86_64-softmmu/qemu-system-x86_64 -replay foo \
    -panda callstack_instr -panda keyfind