image: Add support for signing of FIT configurations

While signing images is useful, it does not provide complete protection
against several types of attack. For example, it it possible to create a
FIT with the same signed images, but with the configuration changed such
that a different one is selected (mix and match attack). It is also possible
to substitute a signed image from an older FIT version into a newer FIT
(roll-back attack).

Add support for signing of FIT configurations using the libfdt's region
support.

Please see doc/uImage.FIT/signature.txt for more information.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 340 insertions, 1 deletions

diff --git a/tools/image-host.c b/tools/image-host.c
index 7aebc29..932384b 100644
--- a/tools/image-host.c
+++ b/tools/image-host.c
@@ -341,10 +341,326 @@ int fit_image_add_verification_data(const char *keydir, void *keydest,
 	return 0;
 }
 
+struct strlist {
+	int count;
+	char **strings;
+};
+
+static void strlist_init(struct strlist *list)
+{
+	memset(list, '\0', sizeof(*list));
+}
+
+static void strlist_free(struct strlist *list)
+{
+	int i;
+
+	for (i = 0; i < list->count; i++)
+		free(list->strings[i]);
+	free(list->strings);
+}
+
+static int strlist_add(struct strlist *list, const char *str)
+{
+	char *dup;
+
+	dup = strdup(str);
+	list->strings = realloc(list->strings,
+				(list->count + 1) * sizeof(char *));
+	if (!list || !str)
+		return -1;
+	list->strings[list->count++] = dup;
+
+	return 0;
+}
+
+static const char *fit_config_get_image_list(void *fit, int noffset,
+		int *lenp, int *allow_missingp)
+{
+	static const char default_list[] = FIT_KERNEL_PROP "\0"
+			FIT_FDT_PROP;
+	const char *prop;
+
+	/* If there is an "image" property, use that */
+	prop = fdt_getprop(fit, noffset, "sign-images", lenp);
+	if (prop) {
+		*allow_missingp = 0;
+		return *lenp ? prop : NULL;
+	}
+
+	/* Default image list */
+	*allow_missingp = 1;
+	*lenp = sizeof(default_list);
+
+	return default_list;
+}
+
+static int fit_config_get_hash_list(void *fit, int conf_noffset,
+				    int sig_offset, struct strlist *node_inc)
+{
+	int allow_missing;
+	const char *prop, *iname, *end;
+	const char *conf_name, *sig_name;
+	char name[200], path[200];
+	int image_count;
+	int ret, len;
+
+	conf_name = fit_get_name(fit, conf_noffset, NULL);
+	sig_name = fit_get_name(fit, sig_offset, NULL);
+
+	/*
+	 * Build a list of nodes we need to hash. We always need the root
+	 * node and the configuration.
+	 */
+	strlist_init(node_inc);
+	snprintf(name, sizeof(name), "%s/%s", FIT_CONFS_PATH, conf_name);
+	if (strlist_add(node_inc, "/") ||
+	    strlist_add(node_inc, name))
+		goto err_mem;
+
+	/* Get a list of images that we intend to sign */
+	prop = fit_config_get_image_list(fit, conf_noffset, &len,
+					&allow_missing);
+	if (!prop)
+		return 0;
+
+	/* Locate the images */
+	end = prop + len;
+	image_count = 0;
+	for (iname = prop; iname < end; iname += strlen(iname) + 1) {
+		int noffset;
+		int image_noffset;
+		int hash_count;
+
+		image_noffset = fit_conf_get_prop_node(fit, conf_noffset,
+						       iname);
+		if (image_noffset < 0) {
+			printf("Failed to find image '%s' in  configuration '%s/%s'\n",
+			       iname, conf_name, sig_name);
+			if (allow_missing)
+				continue;
+
+			return -ENOENT;
+		}
+
+		ret = fdt_get_path(fit, image_noffset, path, sizeof(path));
+		if (ret < 0)
+			goto err_path;
+		if (strlist_add(node_inc, path))
+			goto err_mem;
+
+		snprintf(name, sizeof(name), "%s/%s", FIT_CONFS_PATH,
+			 conf_name);
+
+		/* Add all this image's hashes */
+		hash_count = 0;
+		for (noffset = fdt_first_subnode(fit, image_noffset);
+		     noffset >= 0;
+		     noffset = fdt_next_subnode(fit, noffset)) {
+			const char *name = fit_get_name(fit, noffset, NULL);
+
+			if (strncmp(name, FIT_HASH_NODENAME,
+				    strlen(FIT_HASH_NODENAME)))
+				continue;
+			ret = fdt_get_path(fit, noffset, path, sizeof(path));
+			if (ret < 0)
+				goto err_path;
+			if (strlist_add(node_inc, path))
+				goto err_mem;
+			hash_count++;
+		}
+
+		if (!hash_count) {
+			printf("Failed to find any hash nodes in configuration '%s/%s' image '%s' - without these it is not possible to verify this image\n",
+			       conf_name, sig_name, iname);
+			return -ENOMSG;
+		}
+
+		image_count++;
+	}
+
+	if (!image_count) {
+		printf("Failed to find any images for configuration '%s/%s'\n",
+		       conf_name, sig_name);
+		return -ENOMSG;
+	}
+
+	return 0;
+
+err_mem:
+	printf("Out of memory processing configuration '%s/%s'\n", conf_name,
+	       sig_name);
+	return -ENOMEM;
+
+err_path:
+	printf("Failed to get path for image '%s' in configuration '%s/%s': %s\n",
+	       iname, conf_name, sig_name, fdt_strerror(ret));
+	return -ENOENT;
+}
+
+static int fit_config_get_data(void *fit, int conf_noffset, int noffset,
+		struct image_region **regionp, int *region_countp,
+		char **region_propp, int *region_proplen)
+{
+	char * const exc_prop[] = {"data"};
+	struct strlist node_inc;
+	struct image_region *region;
+	struct fdt_region fdt_regions[100];
+	const char *conf_name, *sig_name;
+	char path[200];
+	int count, i;
+	char *region_prop;
+	int ret, len;
+
+	conf_name = fit_get_name(fit, conf_noffset, NULL);
+	sig_name = fit_get_name(fit, conf_noffset, NULL);
+	debug("%s: conf='%s', sig='%s'\n", __func__, conf_name, sig_name);
+
+	/* Get a list of nodes we want to hash */
+	ret = fit_config_get_hash_list(fit, conf_noffset, noffset, &node_inc);
+	if (ret)
+		return ret;
+
+	/* Get a list of regions to hash */
+	count = fdt_find_regions(fit, node_inc.strings, node_inc.count,
+			exc_prop, ARRAY_SIZE(exc_prop),
+			fdt_regions, ARRAY_SIZE(fdt_regions),
+			path, sizeof(path), 1);
+	if (count < 0) {
+		printf("Failed to hash configuration '%s/%s': %s\n", conf_name,
+		       sig_name, fdt_strerror(ret));
+		return -EIO;
+	}
+	if (count == 0) {
+		printf("No data to hash for configuration '%s/%s': %s\n",
+		       conf_name, sig_name, fdt_strerror(ret));
+		return -EINVAL;
+	}
+
+	/* Build our list of data blocks */
+	region = fit_region_make_list(fit, fdt_regions, count, NULL);
+	if (!region) {
+		printf("Out of memory hashing configuration '%s/%s'\n",
+		       conf_name, sig_name);
+		return -ENOMEM;
+	}
+
+	/* Create a list of all hashed properties */
+	debug("Hash nodes:\n");
+	for (i = len = 0; i < node_inc.count; i++) {
+		debug("   %s\n", node_inc.strings[i]);
+		len += strlen(node_inc.strings[i]) + 1;
+	}
+	region_prop = malloc(len);
+	if (!region_prop) {
+		printf("Out of memory setting up regions for configuration '%s/%s'\n",
+		       conf_name, sig_name);
+		return -ENOMEM;
+	}
+	for (i = len = 0; i < node_inc.count;
+	     len += strlen(node_inc.strings[i]) + 1, i++)
+		strcpy(region_prop + len, node_inc.strings[i]);
+	strlist_free(&node_inc);
+
+	*region_countp = count;
+	*regionp = region;
+	*region_propp = region_prop;
+	*region_proplen = len;
+
+	return 0;
+}
+
+static int fit_config_process_sig(const char *keydir, void *keydest,
+		void *fit, const char *conf_name, int conf_noffset,
+		int noffset, const char *comment, int require_keys)
+{
+	struct image_sign_info info;
+	const char *node_name;
+	struct image_region *region;
+	char *region_prop;
+	int region_proplen;
+	int region_count;
+	uint8_t *value;
+	uint value_len;
+	int ret;
+
+	node_name = fit_get_name(fit, noffset, NULL);
+	if (fit_config_get_data(fit, conf_noffset, noffset, &region,
+				&region_count, &region_prop, &region_proplen))
+		return -1;
+
+	if (fit_image_setup_sig(&info, keydir, fit, conf_name, noffset,
+				require_keys ? "conf" : NULL))
+		return -1;
+
+	ret = info.algo->sign(&info, region, region_count, &value, &value_len);
+	free(region);
+	if (ret) {
+		printf("Failed to sign '%s' signature node in '%s' conf node\n",
+		       node_name, conf_name);
+
+		/* We allow keys to be missing */
+		if (ret == -ENOENT)
+			return 0;
+		return -1;
+	}
+
+	if (fit_image_write_sig(fit, noffset, value, value_len, comment,
+				region_prop, region_proplen)) {
+		printf("Can't write signature for '%s' signature node in '%s' conf node\n",
+		       node_name, conf_name);
+		return -1;
+	}
+	free(value);
+	free(region_prop);
+
+	/* Get keyname again, as FDT has changed and invalidated our pointer */
+	info.keyname = fdt_getprop(fit, noffset, "key-name-hint", NULL);
+
+	/* Write the public key into the supplied FDT file */
+	if (keydest && info.algo->add_verify_data(&info, keydest)) {
+		printf("Failed to add verification data for '%s' signature node in '%s' image node\n",
+		       node_name, conf_name);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int fit_config_add_verification_data(const char *keydir, void *keydest,
+		void *fit, int conf_noffset, const char *comment,
+		int require_keys)
+{
+	const char *conf_name;
+	int noffset;
+
+	conf_name = fit_get_name(fit, conf_noffset, NULL);
+
+	/* Process all hash subnodes of the configuration node */
+	for (noffset = fdt_first_subnode(fit, conf_noffset);
+	     noffset >= 0;
+	     noffset = fdt_next_subnode(fit, noffset)) {
+		const char *node_name;
+		int ret = 0;
+
+		node_name = fit_get_name(fit, noffset, NULL);
+		if (!strncmp(node_name, FIT_SIG_NODENAME,
+			     strlen(FIT_SIG_NODENAME))) {
+			ret = fit_config_process_sig(keydir, keydest,
+				fit, conf_name, conf_noffset, noffset, comment,
+				require_keys);
+		}
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 int fit_add_verification_data(const char *keydir, void *keydest, void *fit,
 			      const char *comment, int require_keys)
 {
-	int images_noffset;
+	int images_noffset, confs_noffset;
 	int noffset;
 	int ret;
 
@@ -370,5 +686,28 @@ int fit_add_verification_data(const char *keydir, void *keydest, void *fit,
 			return ret;
 	}
 
+	/* If there are no keys, we can't sign configurations */
+	if (!IMAGE_ENABLE_SIGN || !keydir)
+		return 0;
+
+	/* Find configurations parent node offset */
+	confs_noffset = fdt_path_offset(fit, FIT_CONFS_PATH);
+	if (confs_noffset < 0) {
+		printf("Can't find images parent node '%s' (%s)\n",
+		       FIT_IMAGES_PATH, fdt_strerror(confs_noffset));
+		return -ENOENT;
+	}
+
+	/* Process its subnodes, print out component images details */
+	for (noffset = fdt_first_subnode(fit, confs_noffset);
+	     noffset >= 0;
+	     noffset = fdt_next_subnode(fit, noffset)) {
+		ret = fit_config_add_verification_data(keydir, keydest,
+						       fit, noffset, comment,
+						       require_keys);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }