Merge remote-tracking branch 'origin/topic/jsiwek/gh-1264-ssh-host-key-fingerprints' into master

* origin/topic/jsiwek/gh-1264-ssh-host-key-fingerprints:
  Simply ssh/main.zeek by using "ssh_server_host_key" for fingerprinting
  Deprecate "ssh1_server_host_key" parameters *e* and *p*
  GH-1264: Implement "ssh_server_host_key" event

src/analyzer/protocol/ssh/events.bif

@@ -127,16 +127,54 @@ event ssh2_server_host_key%(c: connection, key: string%);
 ## c: The connection over which the :abbr:`SSH (Secure Shell)`
 ##    connection took place.
 ##
-## p: The prime for the server's public host key.
+## p: The exponent for the server's public host key (note this parameter
+##    is truly the exponent even though named *p* and the *exponent* parameter
+##    will eventually replace it).
 ##
-## e: The exponent for the serer's public host key.
+## e: The prime modulus for the server's public host key (note this parameter
+##    is truly the modulus even though named *e* and the *modulus* parameter
+##    will eventually replace it).
+##
+## modulus: The prime modulus of the server's public host key.
+##
+## exponent: The exponent of the server's public host key.
 ##
 ## .. zeek:see:: ssh_server_version ssh_client_version
 ##    ssh_auth_successful ssh_auth_failed ssh_auth_result
 ##    ssh_auth_attempted ssh_capabilities ssh2_server_host_key
 ##    ssh_server_host_key ssh_encrypted_packet ssh2_dh_server_params
 ##    ssh2_gss_error ssh2_ecc_key
-event ssh1_server_host_key%(c: connection, p: string, e: string%);
+event ssh1_server_host_key%(c: connection, p: string &deprecated="Remove in v4.1", e: string &deprecated="Remove in v4.1", modulus: string, exponent: string%);
+event ssh1_server_host_key%(c: connection, modulus: string, exponent: string%);
+event ssh1_server_host_key%(c: connection, p: string, e: string%) &deprecated="Remove in v4.1.  The 'p' and 'e' parameters are misleadingly named don't use them.";
+
+## During the :abbr:`SSH (Secure Shell)` key exchange, the server
+## supplies its public host key. This event is generated when the
+## appropriate key exchange message is seen for SSH1 or SSH2 and provides
+## a fingerprint of the server's host key.
+##
+## c: The connection over which the :abbr:`SSH (Secure Shell)`
+##    connection took place.
+##
+## hash: an MD5 hash fingerprint associated with the server's host key.
+##       For SSH2, this is the hash of the "server public host key" string as
+##       seen on the wire in the Diffie-Hellman key exchange reply message
+##       (the string itself, excluding the 4-byte length associated with it),
+##       which is also the *key* parameter of :zeek:see:`ssh2_server_host_key`
+##       For SSH1, this is the hash of the combined multiprecision integer
+##       strings representing the RSA1 key's prime modulus and public exponent
+##       (concatenated in that order) as seen on the wire,
+##       which are also the parameters of :zeek:see:`ssh1_server_host_key`.
+##       In either case, the hash is the same "fingerprint" string as presented
+##       by other traditional tools, ``ssh``, ``ssh-keygen``, etc, and is the
+##       hexadecimal representation of all 16 MD5 hash bytes delimited by colons.
+##
+## .. zeek:see:: ssh_server_version ssh_client_version
+##    ssh_auth_successful ssh_auth_failed ssh_auth_result
+##    ssh_auth_attempted ssh_capabilities ssh2_server_host_key
+##    ssh1_server_host_key ssh_encrypted_packet ssh2_dh_server_params
+##    ssh2_gss_error ssh2_ecc_key
+event ssh_server_host_key%(c: connection, hash: string%);
 
 ## This event is generated when an :abbr:`SSH (Secure Shell)`
 ## encrypted packet is seen. This event is not handled by default, but

src/analyzer/protocol/ssh/ssh-analyzer.pac

@@ -2,10 +2,12 @@
 #include <cstdlib>
 #include <vector>
 #include <string>
+#include "zeek/digest.h"
 %}
 
 %header{
 zeek::VectorValPtr name_list_to_vector(const bytestring& nl);
+const char* fingerprint_md5(const unsigned char* d);
 %}
 
 %code{
@@ -45,6 +47,14 @@ zeek::VectorValPtr name_list_to_vector(const bytestring& nl)
 		}
 	return vv;
 	}
+
+const char* fingerprint_md5(const unsigned char* d)
+	{
+	return zeek::util::fmt("%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x:"
+	                       "%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x",
+	                       d[0], d[1], d[2], d[3], d[4], d[5], d[6], d[7],
+	                       d[8], d[9], d[10], d[11], d[12], d[13], d[14], d[15]);
+	}
 %}
 
 refine flow SSH_Flow += {
@@ -147,24 +157,52 @@ refine flow SSH_Flow += {
 
 	function proc_ssh2_server_host_key(key: bytestring): bool
 		%{
+		if ( ssh_server_host_key )
+			{
+			unsigned char digest[MD5_DIGEST_LENGTH];
+			zeek::detail::internal_md5(${key}.data(), ${key}.length(), digest);
+
+			zeek::BifEvent::enqueue_ssh_server_host_key(connection()->zeek_analyzer(),
+				connection()->zeek_analyzer()->Conn(),
+				zeek::make_intrusive<zeek::StringVal>(fingerprint_md5(digest)));
+			}
+
 		if ( ssh2_server_host_key )
 			{
 			zeek::BifEvent::enqueue_ssh2_server_host_key(connection()->zeek_analyzer(),
 				connection()->zeek_analyzer()->Conn(),
 				to_stringval(${key}));
 			}
+
 		return true;
 		%}
 
-	function proc_ssh1_server_host_key(p: bytestring, e: bytestring): bool
+	function proc_ssh1_server_host_key(exp: bytestring, mod: bytestring): bool
 		%{
+		if ( ssh_server_host_key )
+			{
+			unsigned char digest[MD5_DIGEST_LENGTH];
+			auto ctx = zeek::detail::hash_init(zeek::detail::Hash_MD5);
+			// Fingerprint is calculated over concatenation of modulus + exponent.
+			zeek::detail::hash_update(ctx, ${mod}.data(), ${mod}.length());
+			zeek::detail::hash_update(ctx, ${exp}.data(), ${exp}.length());
+			zeek::detail::hash_final(ctx, digest);
+
+			zeek::BifEvent::enqueue_ssh_server_host_key(connection()->zeek_analyzer(),
+				connection()->zeek_analyzer()->Conn(),
+				zeek::make_intrusive<zeek::StringVal>(fingerprint_md5(digest)));
+			}
+
 		if ( ssh1_server_host_key )
 			{
 			zeek::BifEvent::enqueue_ssh1_server_host_key(connection()->zeek_analyzer(),
 				connection()->zeek_analyzer()->Conn(),
-				to_stringval(${p}),
-				to_stringval(${e}));
+				to_stringval(${exp}),
+				to_stringval(${mod}),
+				to_stringval(${mod}),
+				to_stringval(${exp}));
 			}
+
 		return true;
 		%}
 
@@ -229,5 +267,5 @@ refine typeattr SSH2_ECC_INIT += &let {
 };
 
 refine typeattr SSH1_PUBLIC_KEY += &let {
-	proc:  bool = $context.flow.proc_ssh1_server_host_key(host_key_p.val, host_key_e.val);
+	proc:  bool = $context.flow.proc_ssh1_server_host_key(host_key_exp.val, host_key_mod.val);
 };

src/analyzer/protocol/ssh/ssh-protocol.pac

@@ -60,11 +60,11 @@ type SSH1_Message(is_orig: bool, msg_type: uint8, length: uint32) = case msg_typ
 type SSH1_PUBLIC_KEY(length: uint32) = record {
 	cookie            : bytestring &length=8;
 	server_key        : uint32;
-	server_key_p      : ssh1_mp_int;
-	server_key_e      : ssh1_mp_int;
+	server_key_exp    : ssh1_mp_int;
+	server_key_mod    : ssh1_mp_int;
 	host_key          : uint32;
-	host_key_p        : ssh1_mp_int;
-	host_key_e        : ssh1_mp_int;
+	host_key_exp      : ssh1_mp_int;
+	host_key_mod      : ssh1_mp_int;
 	flags             : uint32;
 	supported_ciphers : uint32;
 	supported_auths   : uint32;