[PATCH] cmd: fdt: keep control FDT during checksign

[James Hilliard]

The fdt checksign command accepts an optional address for an FDT
containing public keys. It currently installs that blob as gd->fdt_blob
before verifying the FIT configuration.

This breaks verification with DM-backed crypto drivers which have not
probed yet, since the later probe path expects gd->fdt_blob to remain
U-Boot's control FDT. For example, an ECDSA verifier can be bound from
the control FDT but fail to probe after fdt checksign points
gd->fdt_blob at the key-only DTB.

Add a FIT config verification helper that takes the key blob explicitly
and use it from fdt checksign. This keeps gd->fdt_blob unchanged while
still allowing the command to verify against an external key DTB.

Signed-off-by: James Hilliard <james.hilliard1 at gmail.com>
---
 boot/image-fit-sig.c |  8 +++++++-
 cmd/fdt.c            | 14 ++++++--------
 include/image.h      |  9 +++++++++
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/boot/image-fit-sig.c b/boot/image-fit-sig.c
index 9b5ab754561..fe7ca6e4ab5 100644
--- a/boot/image-fit-sig.c
+++ b/boot/image-fit-sig.c
@@ -708,8 +708,14 @@ static int fit_config_verify_required_keys(const void *fit, int conf_noffset,
 	return 0;
 }
 
+int fit_config_verify_with_key_blob(const void *fit, int conf_noffset,
+				    const void *key_blob)
+{
+	return fit_config_verify_required_keys(fit, conf_noffset, key_blob);
+}
+
 int fit_config_verify(const void *fit, int conf_noffset)
 {
-	return fit_config_verify_required_keys(fit, conf_noffset,
+	return fit_config_verify_with_key_blob(fit, conf_noffset,
 					       gd_fdt_blob());
 }
diff --git a/cmd/fdt.c b/cmd/fdt.c
index d6d5b9fdfd2..7e2abf96103 100644
--- a/cmd/fdt.c
+++ b/cmd/fdt.c
@@ -719,22 +719,19 @@ static int do_fdt(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	} else if (strncmp(argv[1], "che", 3) == 0) {
 		int cfg_noffset;
 		int ret;
-		unsigned long addr;
-		struct fdt_header *blob;
+		struct fdt_header *key_blob;
 
 		if (!working_fdt)
 			return CMD_RET_FAILURE;
 
 		if (argc > 2) {
-			addr = hextoul(argv[2], NULL);
-			blob = map_sysmem(addr, 0);
+			key_blob = map_sysmem(hextoul(argv[2], NULL), 0);
 		} else {
-			blob = (struct fdt_header *)gd->fdt_blob;
+			key_blob = (struct fdt_header *)gd->fdt_blob;
 		}
-		if (!fdt_valid(&blob))
+		if (!fdt_valid(&key_blob))
 			return 1;
 
-		gd->fdt_blob = blob;
 		cfg_noffset = fit_conf_get_node(working_fdt, NULL);
 		if (cfg_noffset < 0) {
 			printf("Could not find configuration node: %s\n",
@@ -742,7 +739,8 @@ static int do_fdt(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 			return CMD_RET_FAILURE;
 		}
 
-		ret = fit_config_verify(working_fdt, cfg_noffset);
+		ret = fit_config_verify_with_key_blob(working_fdt, cfg_noffset,
+						      key_blob);
 		if (ret == 0)
 			return CMD_RET_SUCCESS;
 		else
diff --git a/include/image.h b/include/image.h
index 9c8a746d576..4b3c9c87bf5 100644
--- a/include/image.h
+++ b/include/image.h
@@ -1461,11 +1461,20 @@ int fit_image_verify_with_data(const void *fit, int image_noffset,
 int fit_image_verify(const void *fit, int noffset);
 #if CONFIG_IS_ENABLED(FIT_SIGNATURE)
 int fit_config_verify(const void *fit, int conf_noffset);
+int fit_config_verify_with_key_blob(const void *fit, int conf_noffset,
+				    const void *key_blob);
 #else
 static inline int fit_config_verify(const void *fit, int conf_noffset)
 {
 	return 0;
 }
+
+static inline int fit_config_verify_with_key_blob(const void *fit,
+						  int conf_noffset,
+						  const void *key_blob)
+{
+	return 0;
+}
 #endif
 int fit_all_image_verify(const void *fit);
 int fit_config_decrypt(const void *fit, int conf_noffset);
-- 
2.53.0