MODSIGN: Add -s <signature> option to sign-file

This option allows to append an externally computed singature to the
module. This is needed in setups, where the private key is not directly
available, but a service exists that returns signatures for given files.
Signed-off-by: Michal Marek <mmarek@suse.cz>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

scripts/sign-file

@@ -2,31 +2,41 @@
 #
 # Sign a module file using the given key.
 #
-# Format:
-#
-#	./scripts/sign-file [-v] <hash algo> <key> <x509> <module> [<dest>]
-#
-#
+
+my $USAGE =
+"Usage: scripts/sign-file [-v] <hash algo> <key> <x509> <module> [<dest>]\n" .
+"       scripts/sign-file [-v] -s <raw sig> <hash algo> <x509> <module> [<dest>]\n";
+
 use strict;
 use FileHandle;
 use IPC::Open2;
+use Getopt::Std;
 
-my $verbose = 0;
-if ($#ARGV >= 0 && $ARGV[0] eq "-v") {
-    $verbose = 1;
-    shift;
-}
+my %opts;
+getopts('vs:', \%opts) or die $USAGE;
+my $verbose = $opts{'v'};
+my $signature_file = $opts{'s'};
 
-die "Format: ./scripts/sign-file [-v] <hash algo> <key> <x509> <module> [<dest>]\n"
-    if ($#ARGV != 3 && $#ARGV != 4);
+die $USAGE if ($#ARGV > 4);
+die $USAGE if (!$signature_file && $#ARGV < 3 || $signature_file && $#ARGV < 2);
 
-my $dgst = $ARGV[0];
-my $private_key = $ARGV[1];
-my $x509 = $ARGV[2];
-my $module = $ARGV[3];
-my $dest = ($#ARGV == 4) ? $ARGV[4] : $ARGV[3] . "~";
+my $dgst = shift @ARGV;
+my $private_key;
+if (!$signature_file) {
+	$private_key = shift @ARGV;
+}
+my $x509 = shift @ARGV;
+my $module = shift @ARGV;
+my ($dest, $keep_orig);
+if (@ARGV) {
+	$dest = $ARGV[0];
+	$keep_orig = 1;
+} else {
+	$dest = $module . "~";
+}
 
-die "Can't read private key\n" unless (-r $private_key);
+die "Can't read private key\n" if (!$signature_file && !-r $private_key);
+die "Can't read signature file\n" if ($signature_file && !-r $signature_file);
 die "Can't read X.509 certificate\n" unless (-r $x509);
 die "Can't read module\n" unless (-r $module);
 
@@ -340,33 +350,36 @@ if ($dgst eq "sha1") {
     die "Unknown hash algorithm: $dgst\n";
 }
 
-#
-# Generate the digest and read from openssl's stdout
-#
-my $digest;
-$digest = readpipe("openssl dgst -$dgst -binary $module") || die "openssl dgst";
-
-#
-# Generate the binary signature, which will be just the integer that comprises
-# the signature with no metadata attached.
-#
-my $pid;
-$pid = open2(*read_from, *write_to,
-	     "openssl rsautl -sign -inkey $private_key -keyform PEM") ||
-    die "openssl rsautl";
-binmode write_to;
-print write_to $prologue . $digest || die "pipe to openssl rsautl";
-close(write_to) || die "pipe to openssl rsautl";
-
-binmode read_from;
 my $signature;
-read(read_from, $signature, 4096) || die "pipe from openssl rsautl";
-close(read_from) || die "pipe from openssl rsautl";
+if ($signature_file) {
+	$signature = read_file($signature_file);
+} else {
+	#
+	# Generate the digest and read from openssl's stdout
+	#
+	my $digest;
+	$digest = readpipe("openssl dgst -$dgst -binary $module") || die "openssl dgst";
+
+	#
+	# Generate the binary signature, which will be just the integer that
+	# comprises the signature with no metadata attached.
+	#
+	my $pid;
+	$pid = open2(*read_from, *write_to,
+		     "openssl rsautl -sign -inkey $private_key -keyform PEM") ||
+	    die "openssl rsautl";
+	binmode write_to;
+	print write_to $prologue . $digest || die "pipe to openssl rsautl";
+	close(write_to) || die "pipe to openssl rsautl";
+
+	binmode read_from;
+	read(read_from, $signature, 4096) || die "pipe from openssl rsautl";
+	close(read_from) || die "pipe from openssl rsautl";
+	waitpid($pid, 0) || die;
+	die "openssl rsautl died: $?" if ($? >> 8);
+}
 $signature = pack("n", length($signature)) . $signature,
 
-waitpid($pid, 0) || die;
-die "openssl rsautl died: $?" if ($? >> 8);
-
 #
 # Build the signed binary
 #
@@ -403,6 +416,6 @@ print FD
     ;
 close FD || die $dest;
 
-if ($#ARGV != 3) {
+if (!$keep_orig) {
     rename($dest, $module) || die $module;
 }