Add @load-sigs directive for loading signature files (addresses #551).

doc/signatures.rst

@@ -51,13 +51,18 @@ This script contains a default event handler that raises
 :bro:enum:`Signatures::Sensitive_Signature` :doc:`Notices <notice>`
 (as well as others; see the beginning of the script).
 
-As signatures are independent of Bro's policy scripts, they are put
-into their own file(s). There are two ways to specify which files
-contain signatures: By using the ``-s`` flag when you invoke Bro, or
-by extending the Bro variable :bro:id:`signature_files` using the ``+=``
-operator. If a signature file is given without a path, it is searched
-along the normal ``BROPATH``. The default extension of the file name
-is ``.sig``, and Bro appends that automatically when necessary.
+As signatures are independent of Bro's policy scripts, they are put into
+their own file(s). There are three ways to specify which files contain
+signatures: By using the ``-s`` flag when you invoke Bro, or by
+extending the Bro variable :bro:id:`signature_files` using the ``+=``
+operator, or by using the ``@load-sigs`` directive inside a Bro script.
+If a signature file is given without a full path, it is searched for
+along the normal ``BROPATH``.  Additionally, the ``@load-sigs``
+directive can be used to load signature files in a path relative to the
+Bro script in which it's placed, e.g. ``@load-sigs ./mysigs.sig`` will
+expect that signature file in the same directory as the Bro script. The
+default extension of the file name is ``.sig``, and Bro appends that
+automatically when necessary.
 
 Signature language
 ==================

scripts/base/frameworks/dpd/main.bro

@@ -3,8 +3,7 @@
 
 module DPD;
 
-## Add the DPD signatures to the signature framework.
-redef signature_files += "base/frameworks/dpd/dpd.sig";
+@load-sigs ./dpd.sig
 
 export {
 	## Add the DPD logging stream identifier.

scripts/base/init-bare.bro

@@ -615,7 +615,9 @@ function add_signature_file(sold: string, snew: string): string
 	}
 
 ## Signature files to read. Use ``redef signature_files  += "foo.sig"`` to
-## extend. Signature files will be searched relative to ``BROPATH``.
+## extend. Signature files added this way will be searched relative to
+## ``BROPATH``.  Using the ``@load-sigs`` directive instead is preferred
+## since that can search paths relative to the current script.
 global signature_files = "" &add_func = add_signature_file;
 
 ## ``p0f`` fingerprint file to use. Will be searched relative to ``BROPATH``.

scripts/base/protocols/http/file-ident.bro

@@ -6,7 +6,8 @@
 @load ./utils
 
 # Add the magic number signatures to the core signature set.
-redef signature_files += "base/protocols/http/file-ident.sig";
+@load-sigs ./file-ident.sig
+
 # Ignore the signatures used to match files
 redef Signatures::ignored_ids += /^matchfile-/;
 

scripts/policy/protocols/http/detect-webapps.bro

@@ -4,9 +4,10 @@
 @load base/frameworks/software
 @load base/protocols/http
 
+@load-sigs ./detect-webapps.sig
+
 module HTTP;
 
-redef signature_files += "protocols/http/detect-webapps.sig";
 # Ignore the signatures used to match webapps
 redef Signatures::ignored_ids += /^webapp-/;
 

scripts/site/local.bro

@@ -25,7 +25,7 @@ redef Software::vulnerable_versions += {
 @load frameworks/software/version-changes
 
 # This adds signatures to detect cleartext forward and reverse windows shells.
-redef signature_files += "frameworks/signatures/detect-windows-shells.sig";
+@load-sigs frameworks/signatures/detect-windows-shells
 
 # Uncomment the following line to begin receiving (by default hourly) emails
 # containing all of your notices.

src/Net.cc

@@ -69,6 +69,7 @@ PktSrc* current_pktsrc = 0;
 IOSource* current_iosrc;
 
 std::list<ScannedFile> files_scanned;
+std::vector<string> sig_files;
 
 RETSIGTYPE watchdog(int /* signo */)
 	{

src/Net.h

@@ -111,5 +111,6 @@ struct ScannedFile {
 };
 
 extern std::list<ScannedFile> files_scanned;
+extern std::vector<string> sig_files;
 
 #endif

src/main.cc

@@ -838,6 +838,10 @@ int main(int argc, char** argv)
 		if ( *s )
 			rule_files.append(s);
 
+	// Append signature files defined in @load-sigs
+	for ( size_t i = 0; i < sig_files.size(); ++i )
+		rule_files.append(copy_string(sig_files[i].c_str()));
+
 	if ( rule_files.length() > 0 )
 		{
 		rule_matcher = new RuleMatcher(RE_level);

src/scan.l

@@ -358,6 +358,22 @@ when	return TOK_WHEN;
 	(void) load_files(new_file);
 	}
 
+@load-sigs{WS}{FILE} {
+	const char* new_sig_file = skip_whitespace(yytext + 10);
+	const char* full_filename = 0;
+	FILE* f = search_for_file(new_sig_file, "sig", &full_filename, false, 0);
+
+	if ( f )
+		{
+		sig_files.push_back(full_filename);
+		fclose(f);
+		delete [] full_filename;
+		}
+	else
+		reporter->Error("failed to find file associated with @load-sigs %s",
+		                new_sig_file);
+	}
+
 @unload{WS}{FILE}	{
 	// Skip "@unload".
 	const char* new_file = skip_whitespace(yytext + 7);

testing/btest/Baseline/core.load-sigs/output

@@ -0,0 +1,3 @@
+[orig_h=141.142.220.118, orig_p=35642/tcp, resp_h=208.80.152.2, resp_p=80/tcp]
+works
+GET /images/wikimedia-button.png HTTP/1.1^M^JHost: meta.wikimedia.org^M^JUser-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Geck...

testing/btest/core/load-sigs.bro

@@ -0,0 +1,21 @@
+# A test of signature loading using @load-sigs.
+
+# @TEST-EXEC: bro -C -r $TRACES/wikipedia.trace %INPUT >output
+# @TEST-EXEC: btest-diff output
+
+@load-sigs ./subdir/mysigs.sig
+
+event signature_match(state: signature_state, msg: string, data: string)
+	{
+	print state$conn$id;
+	print msg;
+	print data;
+	}
+
+@TEST-START-FILE subdir/mysigs.sig
+signature my-sig {
+ip-proto == tcp
+payload /GET \/images/
+event "works"
+}
+@TEST-END-FILE