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110 lines
3.5 KiB
Text
110 lines
3.5 KiB
Text
##! This script allows for the decryption of certain TLS 1.2 connections, if the user is in possession
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##! of the private key material for the session. Key material can either be provided via a file (useful
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##! for processing trace files) or via sending events via Broker (for live decoding).
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##!
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##! Please note that this feature is experimental and can change without guarantees to our typical
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##! deprecation timeline. Please also note that currently only TLS 1.2 connections that use the
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##! TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 cipher suite are supported.
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@load base/frameworks/input
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@load base/frameworks/notice
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@load base/protocols/conn
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@load base/protocols/ssl
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module SSL;
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# Do not disable analyzers after detection - otherwise we will not receive
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# encrypted packets.
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redef SSL::disable_analyzer_after_detection = F;
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export {
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## This can be set to a file that contains the session secrets for decryption, when parsing a pcap file.
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## Please note that, when using this feature, you probably want to pause processing of data till this
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## file has been read.
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const keylog_file = getenv("ZEEK_TLS_KEYLOG_FILE") &redef;
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## Secrets expire after this time of not being used.
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const secret_expiration = 5 mins &redef;
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## This event can be triggered, e.g., via Broker to add known keys to the TLS key database.
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##
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## client_random: client random for which the key is set
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##
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## keys: key material
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global add_keys: event(client_random: string, keys: string);
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## This event can be triggered, e.g., via Broker to add known secrets to the TLS secret database.
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##
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## client_random: client random for which the secret is set
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##
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## secrets: derived TLS secrets material
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global add_secret: event(client_random: string, secrets: string);
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}
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global secrets: table[string] of string = {} &redef;
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global keys: table[string] of string = {} &redef;
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@if ( keylog_file != "" ) &analyze
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# If a keylog file was given directly (not via an environment variable),
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# set up secret expiration (which doesn't make sense for PCAPs).
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redef secrets &read_expire=secret_expiration;
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redef keys &read_expire=secret_expiration;
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@endif
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redef record SSL::Info += {
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# Decryption uses client_random as identifier
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client_random: string &optional;
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};
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type SecretsIdx: record {
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client_random: string;
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};
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type SecretsVal: record {
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secret: string;
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};
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const tls_decrypt_stream_name = "tls-keylog-file";
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event zeek_init()
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{
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# listen for secrets
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Broker::subscribe("/zeek/tls/decryption");
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if ( keylog_file != "" )
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{
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Input::add_table([$name=tls_decrypt_stream_name, $source=keylog_file, $destination=secrets, $idx=SecretsIdx, $val=SecretsVal, $want_record=F]);
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Input::remove(tls_decrypt_stream_name);
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}
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}
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event SSL::add_keys(client_random: string, val: string)
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{
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SSL::keys[client_random] = val;
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}
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event SSL::add_secret(client_random: string, val: string)
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{
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SSL::secrets[client_random] = val;
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}
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event ssl_client_hello(c: connection, version: count, record_version: count, possible_ts: time, client_random: string, session_id: string, ciphers: index_vec, comp_methods: index_vec)
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{
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c$ssl$client_random = client_random;
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if ( client_random in keys )
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set_keys(c, keys[client_random]);
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else if ( client_random in secrets )
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set_secret(c, secrets[client_random]);
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}
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event ssl_change_cipher_spec(c: connection, is_client: bool)
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{
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if ( c$ssl?$client_random )
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{
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if ( c$ssl$client_random in keys )
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set_keys(c, keys[c$ssl$client_random]);
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else if ( c$ssl$client_random in secrets )
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set_secret(c, secrets[c$ssl$client_random]);
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}
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}
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