futility: Make rwsig sign command produce EC_RW image

This change makes futility write out a EC_RW image to the filesystem.
It also allows the command to run without '--prikey' option. When a
private key isn't provided, the command copies the previous signature.
This can be used to extract EC_RW without changing the key or the
signature. Since data only mode doesn't have a previous signature,
the command returns error if '--prikey' isn't specified (as done
before).

BUG=b:65027647
BRANCH=none
TEST=Run futility as follows
futility sign --type rwsig ec.RW.flat ec.RW.sig (Missing key error, expected)
futility sign --type rwsig ec.bin (EC_RW.bin is produced)
futility sign --type rwsig EC_RW.bin
futility sign --type rwsig --prikey key.vbprik2 ec.RW.flat ec.RW.sig
futility sign --type rwsig --prikey key.vbprik2 ec.bin (EC_RW.bin is produced)
futility sign --type rwsig --prikey key.vbprik2 EC_RW.bin
make runfutiltests

Change-Id: I8c1e0cef147967cfd6d28aa7272b88c03e109e0d
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/647804
Reviewed-by: Randall Spangler <rspangler@chromium.org>

futility/cmd_sign.c

@@ -495,12 +495,16 @@ static void print_help_rwsig(int argc, char *argv[])
 	       "If INFILE contains an FMAP, RW and signatures offsets are read from\n"
 	       "FMAP. These regions must be named EC_RW and SIG_RW respectively.\n"
 	       "If a public key is found in the region named KEY_RO, it will be replaced\n"
-	       "in the RO image.\n"
+	       "in the RO image. This mode also produces EC_RW.bin which is a EC_RW\n"
+	       "region image (same as the input file for 'Data + Signature mode').\n"
 	       "\n"
 	       "Options:\n"
 	       "\n"
-	       "  --prikey      FILE.vbprik2      Private key in vb2 format (required)\n"
-	       "  --version     NUM               Public key version if we are replacing"
+	       "  --prikey      FILE.vbprik2      Private key in vb2 format. Required\n"
+	       "                                  if INFILE is a binary blob. If not\n"
+	       "                                  provided, previous signature is copied\n"
+	       "                                  and a public key won't be replaced.\n"
+	       "  --version     NUM               Public key version if we are replacing\n"
 	       "                                  the key in INFILE (default: 1)\n"
 	       "  --sig_size    NUM               Offset from the end of INFILE where the\n"
 	       "                                    signature blob should be located, if\n"
@@ -972,7 +976,9 @@ static int do_sign(int argc, char *argv[])
 				      "hash_alg");
 		break;
 	case FILE_TYPE_RWSIG:
-		errorcnt += no_opt_if(!sign_option.prikey, "prikey");
+		if (sign_option.inout_file_count > 1)
+			/* Signing raw data. No signature pre-exists. */
+			errorcnt += no_opt_if(!sign_option.prikey, "prikey");
 		break;
 	default:
 		/* Anything else we don't care */

futility/file_type_rwsig.c

@@ -28,10 +28,12 @@
 #include "vb21_common.h"
 #include "host_common.h"
 #include "host_key2.h"
+#include "host_misc.h"
 #include "host_signature2.h"
 #include "util_misc.h"
 
 #define SIGNATURE_RSVD_SIZE 1024
+#define EC_RW_FILENAME "EC_RW.bin"
 
 static inline void vb2_print_bytes(const void *ptr, uint32_t len)
 {
@@ -215,14 +217,13 @@ int ft_sign_rwsig(const char *name, uint8_t *buf, uint32_t len, void *nuthin)
 	int retval = 1;
 	FmapHeader *fmap = NULL;
 	FmapAreaHeader *fmaparea;
+	const struct vb21_signature *old_sig = 0;
 
 	Debug("%s(): name %s\n", __func__, name);
 	Debug("%s(): len  0x%08x (%d)\n", __func__, len, len);
 
 	/* If we don't have a distinct OUTFILE, look for an existing sig */
 	if (sign_option.inout_file_count < 2) {
-		const struct vb21_signature *old_sig;
-
 		fmap = fmap_find(buf, len);
 
 		if (fmap) {
@@ -284,12 +285,26 @@ int ft_sign_rwsig(const char *name, uint8_t *buf, uint32_t len, void *nuthin)
 		data_size = sign_option.data_size;
 
 	/* Sign the blob */
-	r = vb21_sign_data(&tmp_sig, data, data_size, sign_option.prikey, 0);
-	if (r) {
-		fprintf(stderr,
-			"Unable to sign data (error 0x%08x, if that helps)\n",
-			r);
-		goto done;
+	if (sign_option.prikey) {
+		r = vb21_sign_data(&tmp_sig,
+				   data, data_size, sign_option.prikey, 0);
+		if (r) {
+			fprintf(stderr,
+				"Unable to sign data (error 0x%08x)\n", r);
+			goto done;
+		}
+	} else {
+		Debug("Private key not provided. Copying previous signature\n");
+		if (!old_sig) {
+			/* This isn't necessary because no prikey mode runs only
+			 * for fmap input or RW input */
+			fprintf(stderr, "Previous signature not found.\n");
+			goto done;
+		}
+		tmp_sig = calloc(1, old_sig->c.total_size);
+		if (!tmp_sig)
+			goto done;
+		memcpy(tmp_sig, old_sig, old_sig->c.total_size);
 	}
 
 	if (sign_option.inout_file_count < 2) {
@@ -301,6 +316,13 @@ int ft_sign_rwsig(const char *name, uint8_t *buf, uint32_t len, void *nuthin)
 		}
 		memset(buf + len - sig_size, 0xff, sig_size);
 		memcpy(buf + len - sig_size, tmp_sig, tmp_sig->c.total_size);
+		if (fmap) {
+			Debug("Writing %s (size=%d)\n",
+			      EC_RW_FILENAME, fmaparea->area_size);
+			if (vb2_write_file(EC_RW_FILENAME,
+					   data, fmaparea->area_size))
+				goto done;
+		}
 	} else {
 		/* Write the signature to a new file */
 		r = vb21_write_object(sign_option.outfile, tmp_sig);
@@ -311,8 +333,9 @@ int ft_sign_rwsig(const char *name, uint8_t *buf, uint32_t len, void *nuthin)
 		}
 	}
 
-	/* For full images, let's replace the public key in RO. */
-	if (fmap) {
+	/* For full images, let's replace the public key in RO. If prikey is
+	 * not provided, skip it. */
+	if (fmap && sign_option.prikey) {
 		uint8_t *new_pubkey;
 		uint8_t *pubkey_buf = 0;
 

tests/futility/test_rwsig.sh

@@ -14,16 +14,20 @@ TESTKEYS=${SRCDIR}/tests/testkeys
 
 SIGS="1024 2048 2048_exp3 3072_exp3 4096 8192"
 HASHES="SHA1 SHA256 SHA512"
+EC_RW="EC_RW.bin"
 
 set -o pipefail
 
+infile=${DATADIR}/hammer_dev.bin
+# Signing without private key should extract EC_RW.bin
+${FUTILITY} sign --type rwsig --version 2 ${infile}
+cmp ${EC_RW} ${DATADIR}/${EC_RW}
+
 for s in $SIGS; do
     echo -n "$s " 1>&3
 
     for h in $HASHES; do
         pemfile=${TESTKEYS}/key_rsa${s}.pem
-        outfile=${TMP}.${s}_${h}.new
-        infile=${DATADIR}/hammer_dev.bin
         outkeys=${TMP}.${s}_${h}
         outfile=${TMP}.${s}_${h}.bin
 
@@ -41,8 +45,11 @@ for s in $SIGS; do
 
         cp ${infile} ${outfile}
 
+	# Sign ec.bin with a new private key
         ${FUTILITY} sign --type rwsig --prikey ${outkeys}.vbprik2 \
                 --version 2 ${outfile}
+        # Check EC_RW.bin is produced
+        [[ -e ${EC_RW} ]]
 
         ${FUTILITY} show --type rwsig --pubkey ${outkeys}.vbpubk2 ${outfile}
         ${FUTILITY} show --type rwsig ${outfile}