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