From 4d0985295bbb50a952f4312c0a818cd89b8ee7aa Mon Sep 17 00:00:00 2001 From: Simon Glass Date: Thu, 13 Jun 2013 15:10:09 -0700 Subject: 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 --- tools/image-host.c | 341 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 340 insertions(+), 1 deletion(-) (limited to 'tools/image-host.c') diff --git a/tools/image-host.c b/tools/image-host.c index 7aebc2903b..932384beab 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, ®ion, + ®ion_count, ®ion_prop, ®ion_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; } -- cgit v1.2.1