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>
diff --git a/common/image-sig.c b/common/image-sig.c
index 9928bfc..5d907cf 100644
--- a/common/image-sig.c
+++ b/common/image-sig.c
@@ -25,10 +25,11 @@
#include <malloc.h>
DECLARE_GLOBAL_DATA_PTR;
#endif /* !USE_HOSTCC*/
-#include <errno.h>
#include <image.h>
#include <rsa.h>
+#define IMAGE_MAX_HASHED_NODES 100
+
struct image_sig_algo image_sig_algos[] = {
{
"sha1,rsa2048",
@@ -50,6 +51,50 @@
return NULL;
}
+/**
+ * fit_region_make_list() - Make a list of image regions
+ *
+ * Given a list of fdt_regions, create a list of image_regions. This is a
+ * simple conversion routine since the FDT and image code use different
+ * structures.
+ *
+ * @fit: FIT image
+ * @fdt_regions: Pointer to FDT regions
+ * @count: Number of FDT regions
+ * @region: Pointer to image regions, which must hold @count records. If
+ * region is NULL, then (except for an SPL build) the array will be
+ * allocated.
+ * @return: Pointer to image regions
+ */
+struct image_region *fit_region_make_list(const void *fit,
+ struct fdt_region *fdt_regions, int count,
+ struct image_region *region)
+{
+ int i;
+
+ debug("Hash regions:\n");
+ debug("%10s %10s\n", "Offset", "Size");
+
+ /*
+ * Use malloc() except in SPL (to save code size). In SPL the caller
+ * must allocate the array.
+ */
+#ifndef CONFIG_SPL_BUILD
+ if (!region)
+ region = calloc(sizeof(*region), count);
+#endif
+ if (!region)
+ return NULL;
+ for (i = 0; i < count; i++) {
+ debug("%10x %10x\n", fdt_regions[i].offset,
+ fdt_regions[i].size);
+ region[i].data = fit + fdt_regions[i].offset;
+ region[i].size = fdt_regions[i].size;
+ }
+
+ return region;
+}
+
static int fit_image_setup_verify(struct image_sign_info *info,
const void *fit, int noffset, int required_keynode,
char **err_msgp)
@@ -191,3 +236,187 @@
return 0;
}
+
+int fit_config_check_sig(const void *fit, int noffset, int required_keynode,
+ char **err_msgp)
+{
+ char * const exc_prop[] = {"data"};
+ const char *prop, *end, *name;
+ struct image_sign_info info;
+ const uint32_t *strings;
+ uint8_t *fit_value;
+ int fit_value_len;
+ int max_regions;
+ int i, prop_len;
+ char path[200];
+ int count;
+
+ debug("%s: fdt=%p, conf='%s', sig='%s'\n", __func__, gd_fdt_blob(),
+ fit_get_name(fit, noffset, NULL),
+ fit_get_name(gd_fdt_blob(), required_keynode, NULL));
+ *err_msgp = NULL;
+ if (fit_image_setup_verify(&info, fit, noffset, required_keynode,
+ err_msgp))
+ return -1;
+
+ if (fit_image_hash_get_value(fit, noffset, &fit_value,
+ &fit_value_len)) {
+ *err_msgp = "Can't get hash value property";
+ return -1;
+ }
+
+ /* Count the number of strings in the property */
+ prop = fdt_getprop(fit, noffset, "hashed-nodes", &prop_len);
+ end = prop ? prop + prop_len : prop;
+ for (name = prop, count = 0; name < end; name++)
+ if (!*name)
+ count++;
+ if (!count) {
+ *err_msgp = "Can't get hashed-nodes property";
+ return -1;
+ }
+
+ /* Add a sanity check here since we are using the stack */
+ if (count > IMAGE_MAX_HASHED_NODES) {
+ *err_msgp = "Number of hashed nodes exceeds maximum";
+ return -1;
+ }
+
+ /* Create a list of node names from those strings */
+ char *node_inc[count];
+
+ debug("Hash nodes (%d):\n", count);
+ for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) {
+ debug(" '%s'\n", name);
+ node_inc[i] = (char *)name;
+ }
+
+ /*
+ * Each node can generate one region for each sub-node. Allow for
+ * 7 sub-nodes (hash@1, signature@1, etc.) and some extra.
+ */
+ max_regions = 20 + count * 7;
+ struct fdt_region fdt_regions[max_regions];
+
+ /* Get a list of regions to hash */
+ count = fdt_find_regions(fit, node_inc, count,
+ exc_prop, ARRAY_SIZE(exc_prop),
+ fdt_regions, max_regions - 1,
+ path, sizeof(path), 0);
+ if (count < 0) {
+ *err_msgp = "Failed to hash configuration";
+ return -1;
+ }
+ if (count == 0) {
+ *err_msgp = "No data to hash";
+ return -1;
+ }
+ if (count >= max_regions - 1) {
+ *err_msgp = "Too many hash regions";
+ return -1;
+ }
+
+ /* Add the strings */
+ strings = fdt_getprop(fit, noffset, "hashed-strings", NULL);
+ if (strings) {
+ fdt_regions[count].offset = fdt_off_dt_strings(fit) +
+ fdt32_to_cpu(strings[0]);
+ fdt_regions[count].size = fdt32_to_cpu(strings[1]);
+ count++;
+ }
+
+ /* Allocate the region list on the stack */
+ struct image_region region[count];
+
+ fit_region_make_list(fit, fdt_regions, count, region);
+ if (info.algo->verify(&info, region, count, fit_value,
+ fit_value_len)) {
+ *err_msgp = "Verification failed";
+ return -1;
+ }
+
+ return 0;
+}
+
+static int fit_config_verify_sig(const void *fit, int conf_noffset,
+ const void *sig_blob, int sig_offset)
+{
+ int noffset;
+ char *err_msg = "";
+ int verified = 0;
+ int ret;
+
+ /* Process all hash subnodes of the component conf node */
+ for (noffset = fdt_first_subnode(fit, conf_noffset);
+ noffset >= 0;
+ noffset = fdt_next_subnode(fit, noffset)) {
+ const char *name = fit_get_name(fit, noffset, NULL);
+
+ if (!strncmp(name, FIT_SIG_NODENAME,
+ strlen(FIT_SIG_NODENAME))) {
+ ret = fit_config_check_sig(fit, noffset, sig_offset,
+ &err_msg);
+ if (ret) {
+ puts("- ");
+ } else {
+ puts("+ ");
+ verified = 1;
+ break;
+ }
+ }
+ }
+
+ if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
+ err_msg = "Corrupted or truncated tree";
+ goto error;
+ }
+
+ return verified ? 0 : -EPERM;
+
+error:
+ printf(" error!\n%s for '%s' hash node in '%s' config node\n",
+ err_msg, fit_get_name(fit, noffset, NULL),
+ fit_get_name(fit, conf_noffset, NULL));
+ return -1;
+}
+
+int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
+ const void *sig_blob)
+{
+ int noffset;
+ int sig_node;
+
+ /* Work out what we need to verify */
+ sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
+ if (sig_node < 0) {
+ debug("%s: No signature node found: %s\n", __func__,
+ fdt_strerror(sig_node));
+ return 0;
+ }
+
+ for (noffset = fdt_first_subnode(sig_blob, sig_node);
+ noffset >= 0;
+ noffset = fdt_next_subnode(sig_blob, noffset)) {
+ const char *required;
+ int ret;
+
+ required = fdt_getprop(sig_blob, noffset, "required", NULL);
+ if (!required || strcmp(required, "conf"))
+ continue;
+ ret = fit_config_verify_sig(fit, conf_noffset, sig_blob,
+ noffset);
+ if (ret) {
+ printf("Failed to verify required signature '%s'\n",
+ fit_get_name(sig_blob, noffset, NULL));
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+int fit_config_verify(const void *fit, int conf_noffset)
+{
+ return !fit_config_verify_required_sigs(fit, conf_noffset,
+ gd_fdt_blob());
+}