mkimage: Add -K to write public keys to an FDT blob

FIT image verification requires public keys. Add a convenient option to
mkimage to write the public keys to an FDT blob when it uses then for
signing an image. This allows us to use:

   mkimage -f test.its -K dest.dtb -k keys test.fit

and have the signatures written to test.fit and the corresponding public
keys written to dest.dtb. Then dest.dtb can be used as the control FDT
for U-Boot (CONFIG_OF_CONTROL), thus providing U-Boot with access to the
public keys it needs.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Vasut <marex@denx.de>

doc/mkimage.1

@@ -109,6 +109,14 @@ Specifies the directory containing keys to use for signing. This directory
 should contain a private key file <name>.key for use with signing and a
 certificate <name>.crt (containing the public key) for use with verification.
 
+.TP
+.BI "\-K [" "key_destination" "]"
+Specifies a compiled device tree binary file (typically .dtb) to write
+public key information into. When a private key is used to sign an image,
+the corresponding public key is written into this file for for run-time
+verification. Typically the file here is the device tree binary used by
+CONFIG_OF_CONTROL in U-Boot.
+
 .SH EXAMPLES
 
 List image information:
@@ -127,6 +135,14 @@ Create FIT image with compressed PowerPC Linux kernel:
 .nf
 .B mkimage -f kernel.its kernel.itb
 .fi
+.P
+Create FIT image with compressed kernel and sign it with keys in the
+/public/signing-keys directory. Add corresponding public keys into u-boot.dtb,
+skipping those for which keys cannot be found. Also add a comment.
+.nf
+.B mkimage -f kernel.its -k /public/signing-keys -K u-boot.dtb \\\\
+-c "Kernel 3.8 image for production devices" kernel.itb
+.fi
 
 .SH HOMEPAGE
 http://www.denx.de/wiki/U-Boot/WebHome

tools/fit_image.c

@@ -105,9 +105,11 @@ static int fit_handle_file (struct mkimage_params *params)
 {
 	char tmpfile[MKIMAGE_MAX_TMPFILE_LEN];
 	char cmd[MKIMAGE_MAX_DTC_CMDLINE_LEN];
-	int tfd;
+	int tfd, destfd = 0;
+	void *dest_blob = NULL;
 	struct stat sbuf;
 	void *ptr;
+	off_t destfd_size = 0;
 
 	/* Flattened Image Tree (FIT) format  handling */
 	debug ("FIT format handling\n");
@@ -132,12 +134,20 @@ static int fit_handle_file (struct mkimage_params *params)
 		goto err_system;
 	}
 
+	if (params->keydest) {
+		destfd = mmap_fdt(params, params->keydest, &dest_blob, &sbuf);
+		if (destfd < 0)
+			goto err_keydest;
+		destfd_size = sbuf.st_size;
+	}
+
 	tfd = mmap_fdt(params, tmpfile, &ptr, &sbuf);
 	if (tfd < 0)
 		goto err_mmap;
 
 	/* set hashes for images in the blob */
-	if (fit_add_verification_data(params->keydir, NULL, ptr, NULL, 0)) {
+	if (fit_add_verification_data(params->keydir, dest_blob, ptr,
+				      NULL, 0)) {
 		fprintf (stderr, "%s Can't add hashes to FIT blob",
 				params->cmdname);
 		goto err_add_hashes;
@@ -153,6 +163,10 @@ static int fit_handle_file (struct mkimage_params *params)
 
 	munmap ((void *)ptr, sbuf.st_size);
 	close (tfd);
+	if (dest_blob) {
+		munmap(dest_blob, destfd_size);
+		close(destfd);
+	}
 
 	if (rename (tmpfile, params->imagefile) == -1) {
 		fprintf (stderr, "%s: Can't rename %s to %s: %s\n",
@@ -168,6 +182,9 @@ err_add_timestamp:
 err_add_hashes:
 	munmap(ptr, sbuf.st_size);
 err_mmap:
+	if (dest_blob)
+		munmap(dest_blob, destfd_size);
+err_keydest:
 err_system:
 	unlink(tmpfile);
 	return -1;

tools/mkimage.c

@@ -253,6 +253,11 @@ main (int argc, char **argv)
 					usage();
 				params.keydir = *++argv;
 				goto NXTARG;
+			case 'K':
+				if (--argc <= 0)
+					usage();
+				params.keydest = *++argv;
+				goto NXTARG;
 			case 'n':
 				if (--argc <= 0)
 					usage ();
@@ -633,8 +638,9 @@ usage ()
 	fprintf(stderr, "          -D => set options for device tree compiler\n"
 			"          -f => input filename for FIT source\n");
 #ifdef CONFIG_FIT_SIGNATURE
-	fprintf(stderr, "Signing / verified boot options: [-k keydir]\n"
-			"          -k => set directory containing private keys\n");
+	fprintf(stderr, "Signing / verified boot options: [-k keydir] [-K dtb]\n"
+			"          -k => set directory containing private keys\n"
+			"          -K => write public keys to this .dtb file\n");
 #else
 	fprintf(stderr, "Signing / verified boot not supported (CONFIG_FIT_SIGNATURE undefined)\n");
 #endif

tools/mkimage.h

@@ -88,6 +88,7 @@ struct mkimage_params {
 	char *imagefile;
 	char *cmdname;
 	const char *keydir;	/* Directory holding private keys */
+	const char *keydest;	/* Destination .dtb for public key */
 };
 
 /*