vboot: add DTB policy for supporting multiple required conf keys
Currently FIT image must be signed by all required conf keys. This means
Verified Boot fails if there is a signature verification failure
using any required key in U-Boot DTB.
This patch introduces a new policy in DTB that can be set to any required
conf key. This means if verified boot passes with one of the required
keys, U-Boot will continue the OS hand off.
There were prior attempts to address this:
https://lists.denx.de/pipermail/u-boot/2019-April/366047.html
The above patch was failing "make tests".
https://lists.denx.de/pipermail/u-boot/2020-January/396629.html
Signed-off-by: Thirupathaiah Annapureddy <thiruan@linux.microsoft.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/common/image-fit-sig.c b/common/image-fit-sig.c
index cc19671..5401d94 100644
--- a/common/image-fit-sig.c
+++ b/common/image-fit-sig.c
@@ -416,6 +416,10 @@
{
int noffset;
int sig_node;
+ int verified = 0;
+ int reqd_sigs = 0;
+ bool reqd_policy_all = true;
+ const char *reqd_mode;
/* Work out what we need to verify */
sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
@@ -425,6 +429,14 @@
return 0;
}
+ /* Get required-mode policy property from DTB */
+ reqd_mode = fdt_getprop(sig_blob, sig_node, "required-mode", NULL);
+ if (reqd_mode && !strcmp(reqd_mode, "any"))
+ reqd_policy_all = false;
+
+ debug("%s: required-mode policy set to '%s'\n", __func__,
+ reqd_policy_all ? "all" : "any");
+
fdt_for_each_subnode(noffset, sig_blob, sig_node) {
const char *required;
int ret;
@@ -433,15 +445,29 @@
NULL);
if (!required || strcmp(required, "conf"))
continue;
+
+ reqd_sigs++;
+
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;
+ if (reqd_policy_all) {
+ printf("Failed to verify required signature '%s'\n",
+ fit_get_name(sig_blob, noffset, NULL));
+ return ret;
+ }
+ } else {
+ verified++;
+ if (!reqd_policy_all)
+ break;
}
}
+ if (reqd_sigs && !verified) {
+ printf("Failed to verify 'any' of the required signature(s)\n");
+ return -EPERM;
+ }
+
return 0;
}