image: Check hash-nodes when checking configurations

It is currently possible to use a different configuration's signature and
thus bypass the configuration check. Make sure that the configuration node
that was hashed matches the one being checked, to catch this problem.

Also add a proper function comment to fit_config_check_sig() and make it
static.

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

diff --git a/common/image-sig.c b/common/image-sig.c
index 13ccd50bc509a0ef5478aae031ed6e61c8f3010e..03143a40401e90ee4222e8b9011fc2077ec1355b 100644 (file)
--- a/common/image-sig.c
+++ b/common/image-sig.c
@@ -359,20 +359,39 @@ int fit_image_verify_required_sigs(const void *fit, int image_noffset,
        return 0;
 }
 
-int fit_config_check_sig(const void *fit, int noffset, int required_keynode,
-                        char **err_msgp)
+/**
+ * fit_config_check_sig() - Check the signature of a config
+ *
+ * @fit: FIT to check
+ * @noffset: Offset of configuration node (e.g. /configurations/conf-1)
+ * @required_keynode:  Offset in the control FDT of the required key node,
+ *                     if any. If this is given, then the configuration wil not
+ *                     pass verification unless that key is used. If this is
+ *                     -1 then any signature will do.
+ * @conf_noffset: Offset of the configuration subnode being checked (e.g.
+ *      /configurations/conf-1/kernel)
+ * @err_msgp:          In the event of an error, this will be pointed to a
+ *                     help error string to display to the user.
+ * @return 0 if all verified ok, <0 on error
+ */
+static int fit_config_check_sig(const void *fit, int noffset,
+                               int required_keynode, int conf_noffset,
+                               char **err_msgp)
 {
        char * const exc_prop[] = {"data"};
        const char *prop, *end, *name;
        struct image_sign_info info;
        const uint32_t *strings;
+       const char *config_name;
        uint8_t *fit_value;
        int fit_value_len;
+       bool found_config;
        int max_regions;
        int i, prop_len;
        char path[200];
        int count;
 
+       config_name = fit_get_name(fit, conf_noffset, NULL);
        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));
@@ -413,9 +432,20 @@ int fit_config_check_sig(const void *fit, int noffset, int required_keynode,
        char *node_inc[count];
 
        debug("Hash nodes (%d):\n", count);
+       found_config = false;
        for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) {
                debug("   '%s'\n", name);
                node_inc[i] = (char *)name;
+               if (!strncmp(FIT_CONFS_PATH, name, strlen(FIT_CONFS_PATH)) &&
+                   name[sizeof(FIT_CONFS_PATH) - 1] == '/' &&
+                   !strcmp(name + sizeof(FIT_CONFS_PATH), config_name)) {
+                       debug("      (found config node %s)", config_name);
+                       found_config = true;
+               }
+       }
+       if (!found_config) {
+               *err_msgp = "Selected config not in hashed nodes";
+               return -1;
        }
 
        /*
@@ -483,7 +513,7 @@ static int fit_config_verify_sig(const void *fit, int conf_noffset,
                if (!strncmp(name, FIT_SIG_NODENAME,
                             strlen(FIT_SIG_NODENAME))) {
                        ret = fit_config_check_sig(fit, noffset, sig_offset,
-                                                  &err_msg);
+                                                  conf_noffset, &err_msg);
                        if (ret) {
                                puts("- ");
                        } else {