Patch proposal - mkimage: fit: Support signed conf 'auto' FITs

[Pegorer Massimo <Massimo.Pegorer@vimar.com>]

Commit 87b0af9317cb4105f3f29cb0a4c28c7cd87ea65f added support for signing auto-generated (mkimage -f auto) FIT. Unfortunately, this signs 'images' subnodes but not 'configurations' ones. Following patch is a proposal to support also 'configurations' signing + 'images' hashing, as an alternative to 'images' signing, with 'auto' FIT. For this purpose, a new optional argument is added to mkimage '-r' option: any other better idea?

=====

From 8c8c8f421d541cc2eccb50490a57e86b81dc8df2 Mon Sep 17 00:00:00 2001
From: Massimo Pegorer <massimo.pegorer@vimar.com>
Date: Sat, 19 Nov 2022 16:25:58 +0100
Subject: [PATCH] mkimage: fit: Support signed conf 'auto' FITs

Extend support for signing in auto-generated FITs. Previously, it was
possible to sign 'images' subnodes in auto FIT, but not 'configurations'
subnodes. Consequently, usage with -K and -r options (i.e. write keys as
'required' in a .dtb file) resulted in adding a signature node with
required = "image" property in the dtb.

This patch allows usage of an optional argument with -r option to select
which subnodes, 'images' ones or 'configurations' ones, have to be signed
(in the second case 'images' subnodes are hashed): with '-r' or '-rimage'
the firsts are signed, while with '-rconf' the seconds; argument values
different than 'image' and 'conf' are invalid.

Example to write a key with required = "conf" attribute into a dtb file:

mkimage -f auto -rconf -d /dev/null -K <dtb-file> -o <algo> \
        -g <key-name-hint> -k <path-to-key-file> <dummy-itb-file>

Signed-off-by: Massimo Pegorer <massimo.pegorer@vimar.com>
---
 tools/fit_image.c | 25 +++++++++++++++++--------
 tools/mkimage.c   | 18 ++++++++++++++----
 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/tools/fit_image.c b/tools/fit_image.c
index 923a9755b7..c78d83d509 100644
--- a/tools/fit_image.c
+++ b/tools/fit_image.c
@@ -199,19 +199,22 @@ static void get_basename(char *str, int size, const char *fname)
 }
 
 /**
- * add_hash_node() - Add a hash or signature node
+ * add_hash_or_sign_node() - Add a hash or signature node
  *
  * @params: Image parameters
  * @fdt: Device tree to add to (in sequential-write mode)
+ * @do_add_hash: true to add hash even if key name hint is provided
  *
- * If there is a key name hint, try to sign the images. Otherwise, just add a
- * CRC.
+ * If do_add_hash is false (default) and there is a key name hint, try to add
+ * a sign node to parent. Otherwise, just add a CRC. Rationale: if conf have
+ * to be signed, image/dt have to be hashed even if there is a key name hint.
  *
  * Return: 0 on success, or -1 on failure
  */
-static int add_hash_node(struct image_tool_params *params, void *fdt)
+static int add_hash_or_sig_node(struct image_tool_params *params, void *fdt,
+				bool do_add_hash)
 {
-	if (params->keyname) {
+	if (!do_add_hash && params->keyname) {
 		if (!params->algo_name) {
 			fprintf(stderr,
 				"%s: Algorithm name must be specified\n",
@@ -269,7 +272,7 @@ static int fit_write_images(struct image_tool_params *params, char *fdt)
 	ret = fdt_property_file(params, fdt, FIT_DATA_PROP, params->datafile);
 	if (ret)
 		return ret;
-	ret = add_hash_node(params, fdt);
+	ret = add_hash_or_sig_node(params, fdt, (params->require_keys == 2));
 	if (ret)
 		return ret;
 	fdt_end_node(fdt);
@@ -294,7 +297,8 @@ static int fit_write_images(struct image_tool_params *params, char *fdt)
 				    genimg_get_arch_short_name(params->arch));
 		fdt_property_string(fdt, FIT_COMP_PROP,
 				    genimg_get_comp_short_name(IH_COMP_NONE));
-		ret = add_hash_node(params, fdt);
+		ret = add_hash_or_sig_node(params, fdt,
+					   (params->require_keys == 2));
 		if (ret)
 			return ret;
 		fdt_end_node(fdt);
@@ -314,7 +318,8 @@ static int fit_write_images(struct image_tool_params *params, char *fdt)
 					params->fit_ramdisk);
 		if (ret)
 			return ret;
-		ret = add_hash_node(params, fdt);
+		ret = add_hash_or_sig_node(params, fdt,
+					   (params->require_keys == 2));
 		if (ret)
 			return ret;
 		fdt_end_node(fdt);
@@ -366,6 +371,8 @@ static void fit_write_configs(struct image_tool_params *params, char *fdt)
 
 		snprintf(str, sizeof(str), FIT_FDT_PROP "-%d", upto);
 		fdt_property_string(fdt, FIT_FDT_PROP, str);
+		if (params->require_keys == 2)
+			add_hash_or_sig_node(params, fdt, false);
 		fdt_end_node(fdt);
 	}
 
@@ -378,6 +385,8 @@ static void fit_write_configs(struct image_tool_params *params, char *fdt)
 		if (params->fit_ramdisk)
 			fdt_property_string(fdt, FIT_RAMDISK_PROP,
 					    FIT_RAMDISK_PROP "-1");
+		if (params->require_keys == 2)
+			add_hash_or_sig_node(params, fdt, false);
 
 		fdt_end_node(fdt);
 	}
diff --git a/tools/mkimage.c b/tools/mkimage.c
index 30c6df7708..4d4f128b54 100644
--- a/tools/mkimage.c
+++ b/tools/mkimage.c
@@ -125,7 +125,7 @@ static void usage(const char *msg)
 		"          -c => add comment in signature node\n"
 		"          -F => re-sign existing FIT image\n"
 		"          -p => place external data at a static position\n"
-		"          -r => mark keys used as 'required' in dtb\n"
+		"          -r => mark keys used as 'required' in dtb (-rconf for 'auto' FIT with signed config)\n"
 		"          -N => openssl engine to use for signing\n"
 		"          -o => algorithm to use for signing\n");
 #else
@@ -159,7 +159,7 @@ static int add_content(int type, const char *fname)
 }
 
 static const char optstring[] =
-	"a:A:b:B:c:C:d:D:e:Ef:Fg:G:i:k:K:ln:N:o:O:p:qrR:stT:vVx";
+	"a:A:b:B:c:C:d:D:e:Ef:Fg:G:i:k:K:ln:N:o:O:p:qr::R:stT:vVx";
 
 static const struct option longopts[] = {
 	{ "load-address", required_argument, NULL, 'a' },
@@ -187,7 +187,7 @@ static const struct option longopts[] = {
 	{ "os", required_argument, NULL, 'O' },
 	{ "position", required_argument, NULL, 'p' },
 	{ "quiet", no_argument, NULL, 'q' },
-	{ "key-required", no_argument, NULL, 'r' },
+	{ "key-required", optional_argument, NULL, 'r' },
 	{ "secondary-config", required_argument, NULL, 'R' },
 	{ "no-copy", no_argument, NULL, 's' },
 	{ "touch", no_argument, NULL, 't' },
@@ -326,7 +326,12 @@ static void process_args(int argc, char **argv)
 			params.quiet = 1;
 			break;
 		case 'r':
-			params.require_keys = 1;
+			if (!optarg || !strcmp(optarg, "image"))
+				params.require_keys = 1;
+			else if (!strcmp(optarg, "conf"))
+				params.require_keys = 2;
+			else
+				usage("Invalid key-required option argument");
 			break;
 		case 'R':
 			/*
@@ -370,6 +375,11 @@ static void process_args(int argc, char **argv)
 	if (optind < argc)
 		params.imagefile = argv[optind];
 
+	if (params.require_keys == 2)
+		if (!params.auto_its || !params.keyname || !params.algo_name)
+			usage("Auto FIT with signed config requires -f auto "
+				"-rconf -g <key name hint> -o <algorithm>");
+
 	/*
 	 * For auto-generated FIT images we need to know the image type to put
 	 * in the FIT, which is separate from the file's image type (which
-- 
2.34.1