tools: Avoid confusion between keys and signatures

We should be consistent in using the term 'signature' to describe a value
added to sign something and 'key' to describe the key that can be used to
verify the signature.

Tidy up the code to stick to this.

Add some comments to fit_config_verify_key() and its callers while we are
here.

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

1 files changed, 72 insertions, 25 deletions

diff --git a/boot/image-fit-sig.c b/boot/image-fit-sig.c
index 495d7768f6..e07bacb77a 100644
--- a/boot/image-fit-sig.c
+++ b/boot/image-fit-sig.c
@@ -135,7 +135,7 @@ int fit_image_check_sig(const void *fit, int noffset, const void *data,
 
 static int fit_image_verify_sig(const void *fit, int image_noffset,
 				const char *data, size_t size,
-				const void *sig_blob, int sig_offset)
+				const void *key_blob, int key_offset)
 {
 	int noffset;
 	char *err_msg = "";
@@ -184,34 +184,34 @@ error:
 
 int fit_image_verify_required_sigs(const void *fit, int image_noffset,
 				   const char *data, size_t size,
-				   const void *sig_blob, int *no_sigsp)
+				   const void *key_blob, int *no_sigsp)
 {
 	int verify_count = 0;
 	int noffset;
-	int sig_node;
+	int key_node;
 
 	/* Work out what we need to verify */
 	*no_sigsp = 1;
-	sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
-	if (sig_node < 0) {
+	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
+	if (key_node < 0) {
 		debug("%s: No signature node found: %s\n", __func__,
-		      fdt_strerror(sig_node));
+		      fdt_strerror(key_node));
 		return 0;
 	}
 
-	fdt_for_each_subnode(noffset, sig_blob, sig_node) {
+	fdt_for_each_subnode(noffset, key_blob, key_node) {
 		const char *required;
 		int ret;
 
-		required = fdt_getprop(sig_blob, noffset, FIT_KEY_REQUIRED,
+		required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
 				       NULL);
 		if (!required || strcmp(required, "image"))
 			continue;
 		ret = fit_image_verify_sig(fit, image_noffset, data, size,
-					   sig_blob, noffset);
+					   key_blob, noffset);
 		if (ret) {
 			printf("Failed to verify required signature '%s'\n",
-			       fit_get_name(sig_blob, noffset, NULL));
+			       fit_get_name(key_blob, noffset, NULL));
 			return ret;
 		}
 		verify_count++;
@@ -368,8 +368,35 @@ static int fit_config_check_sig(const void *fit, int noffset,
 	return 0;
 }
 
-static int fit_config_verify_sig(const void *fit, int conf_noffset,
-				 const void *sig_blob, int sig_offset)
+/**
+ * fit_config_verify_key() - Verify that a configuration is signed with a key
+ *
+ * Here we are looking at a particular configuration that needs verification:
+ *
+ *	configurations {
+ *		default = "conf-1";
+ *		conf-1 {
+ *			kernel = "kernel-1";
+ *			fdt = "fdt-1";
+ *			signature-1 {
+ *				algo = "sha1,rsa2048";
+ *				value = <...conf 1 signature...>;
+ *			};
+ *		};
+ *
+ * We must check each of the signature subnodes of conf-1. Hopefully one of them
+ * will match the key at key_offset.
+ *
+ * @fit: FIT to check
+ * @conf_noffset: Offset of the configuration node to check (e.g.
+ *	/configurations/conf-1)
+ * @key_blob: Blob containing the keys to check against
+ * @key_offset: Offset of the key to check within @key_blob
+ * @return 0 if OK, -EPERM if any signatures did not verify, or the
+ *	configuration node has an invalid name
+ */
+static int fit_config_verify_key(const void *fit, int conf_noffset,
+				 const void *key_blob, int key_offset)
 {
 	int noffset;
 	char *err_msg = "No 'signature' subnode found";
@@ -382,7 +409,7 @@ 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,
+			ret = fit_config_check_sig(fit, noffset, key_offset,
 						   conf_noffset, &err_msg);
 			if (ret) {
 				puts("- ");
@@ -409,12 +436,25 @@ error:
 	return -EPERM;
 }
 
-static int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
-					   const void *sig_blob)
+/**
+ * fit_config_verify_required_keys() - verify any required signatures for config
+ *
+ * This looks through all the signatures we expect and verifies that at least
+ * all the required ones are valid signatures for the configuration
+ *
+ * @fit: FIT to check
+ * @conf_noffset: Offset of the configuration node to check (e.g.
+ *	/configurations/conf-1)
+ * @key_blob: Blob containing the keys to check against
+ * @return 0 if OK, -EPERM if any signatures did not verify, or the
+ *	configuration node has an invalid name
+ */
+static int fit_config_verify_required_keys(const void *fit, int conf_noffset,
+					   const void *key_blob)
 {
 	const char *name = fit_get_name(fit, conf_noffset, NULL);
 	int noffset;
-	int sig_node;
+	int key_node;
 	int verified = 0;
 	int reqd_sigs = 0;
 	bool reqd_policy_all = true;
@@ -430,38 +470,45 @@ static int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
 	}
 
 	/* Work out what we need to verify */
-	sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
-	if (sig_node < 0) {
+	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
+	if (key_node < 0) {
 		debug("%s: No signature node found: %s\n", __func__,
-		      fdt_strerror(sig_node));
+		      fdt_strerror(key_node));
 		return 0;
 	}
 
 	/* Get required-mode policy property from DTB */
-	reqd_mode = fdt_getprop(sig_blob, sig_node, "required-mode", NULL);
+	reqd_mode = fdt_getprop(key_blob, key_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) {
+	/*
+	 * The algorithm here is a little convoluted due to how we want it to
+	 * work. Here we work through each of the signature nodes in the
+	 * public-key area. These are in the U-Boot control devicetree. Each
+	 * node was created by signing a configuration, so we check if it is
+	 * 'required' and if so, request that it be verified.
+	 */
+	fdt_for_each_subnode(noffset, key_blob, key_node) {
 		const char *required;
 		int ret;
 
-		required = fdt_getprop(sig_blob, noffset, FIT_KEY_REQUIRED,
+		required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
 				       NULL);
 		if (!required || strcmp(required, "conf"))
 			continue;
 
 		reqd_sigs++;
 
-		ret = fit_config_verify_sig(fit, conf_noffset, sig_blob,
+		ret = fit_config_verify_key(fit, conf_noffset, key_blob,
 					    noffset);
 		if (ret) {
 			if (reqd_policy_all) {
 				printf("Failed to verify required signature '%s'\n",
-				       fit_get_name(sig_blob, noffset, NULL));
+				       fit_get_name(key_blob, noffset, NULL));
 				return ret;
 			}
 		} else {
@@ -481,6 +528,6 @@ static int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
 
 int fit_config_verify(const void *fit, int conf_noffset)
 {
-	return fit_config_verify_required_sigs(fit, conf_noffset,
+	return fit_config_verify_required_keys(fit, conf_noffset,
 					       gd_fdt_blob());
 }