[U-Boot] [PATCH v2 5/6] lib: rsa: add rsa_verify_with_pkey()

[AKASHI Takahiro]

This function, and hence rsa_verify(), will perform RSA verification
with two essential parameters for a RSA public key in contract of
rsa_verify_with_keynode(), which requires additional three parameters
stored in FIT image.

It will be used in implementing UEFI secure boot, i.e. image authentication
and variable authentication.

Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
---
 lib/rsa/rsa-verify.c | 129 +++++++++++++++++++++++++++++++++----------
 1 file changed, 99 insertions(+), 30 deletions(-)

diff --git a/lib/rsa/rsa-verify.c b/lib/rsa/rsa-verify.c
index 1df42f28c64a..43271a10bb84 100644
--- a/lib/rsa/rsa-verify.c
+++ b/lib/rsa/rsa-verify.c
@@ -17,9 +17,14 @@
 #include "mkimage.h"
 #include <fdt_support.h>
 #endif
+#include <linux/kconfig.h>
 #include <u-boot/rsa-mod-exp.h>
 #include <u-boot/rsa.h>
 
+#ifndef __UBOOT__ /* for host tools */
+#undef CONFIG_RSA_VERIFY_WITH_PKEY
+#endif
+
 /* Default public exponent for backward compatibility */
 #define RSA_DEFAULT_PUBEXP	65537
 
@@ -344,6 +349,50 @@ static int rsa_verify_key(struct image_sign_info *info,
 }
 #endif
 
+#ifdef CONFIG_RSA_VERIFY_WITH_PKEY
+/**
+ * rsa_verify_with_pkey() - Verify a signature against some data using
+ * only modulus and exponent as RSA key properties.
+ * @info:	Specifies key information
+ * @hash:	Pointer to the expected hash
+ * @sig:	Signature
+ * @sig_len:	Number of bytes in signature
+ *
+ * Parse a RSA public key blob in DER format pointed to in @info and fill
+ * a key_prop structure with properties of the key. Then verify a RSA PKCS1.5
+ * signature against an expected hash using the calculated properties.
+ *
+ * Return	0 if verified, -ve on error
+ */
+static int rsa_verify_with_pkey(struct image_sign_info *info,
+				const void *hash, uint8_t *sig, uint sig_len)
+{
+	struct key_prop *prop;
+	int ret;
+
+	/* Public key is self-described to fill key_prop */
+	prop = rsa_gen_key_prop(info->key, info->keylen);
+	if (!prop) {
+		debug("Generating necessary parameter for decoding failed\n");
+		return -EACCES;
+	}
+
+	ret = rsa_verify_key(info, prop, sig, sig_len, hash,
+			     info->crypto->key_len);
+
+	rsa_free_key_prop(prop);
+
+	return ret;
+}
+#else
+static int rsa_verify_with_pkey(struct image_sign_info *info,
+				const void *hash, uint8_t *sig, uint sig_len)
+{
+	return -EACCES;
+}
+#endif
+
+#if CONFIG_IS_ENABLED(FIT_SIGNATURE)
 /**
  * rsa_verify_with_keynode() - Verify a signature against some data using
  * information in node with prperties of RSA Key like modulus, exponent etc.
@@ -397,18 +446,22 @@ static int rsa_verify_with_keynode(struct image_sign_info *info,
 
 	return ret;
 }
+#else
+static int rsa_verify_with_keynode(struct image_sign_info *info,
+				   const void *hash, uint8_t *sig,
+				   uint sig_len, int node)
+{
+	return -EACCES;
+}
+#endif
 
 int rsa_verify(struct image_sign_info *info,
 	       const struct image_region region[], int region_count,
 	       uint8_t *sig, uint sig_len)
 {
-	const void *blob = info->fdt_blob;
 	/* Reserve memory for maximum checksum-length */
 	uint8_t hash[info->crypto->key_len];
-	int ndepth, noffset;
-	int sig_node, node;
-	char name[100];
-	int ret;
+	int ret = -EACCES;
 
 	/*
 	 * Verify that the checksum-length does not exceed the
@@ -421,12 +474,6 @@ int rsa_verify(struct image_sign_info *info,
 		return -EINVAL;
 	}
 
-	sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
-	if (sig_node < 0) {
-		debug("%s: No signature node found\n", __func__);
-		return -ENOENT;
-	}
-
 	/* Calculate checksum with checksum-algorithm */
 	ret = info->checksum->calculate(info->checksum->name,
 					region, region_count, hash);
@@ -435,30 +482,52 @@ int rsa_verify(struct image_sign_info *info,
 		return -EINVAL;
 	}
 
-	/* See if we must use a particular key */
-	if (info->required_keynode != -1) {
-		ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
-			info->required_keynode);
-		if (!ret)
-			return ret;
-	}
+	if (IS_ENABLED(CONFIG_RSA_VERIFY_WITH_PKEY) && !info->fdt_blob) {
+		/* don't rely on fdt properties */
+		ret = rsa_verify_with_pkey(info, hash, sig, sig_len);
 
-	/* Look for a key that matches our hint */
-	snprintf(name, sizeof(name), "key-%s", info->keyname);
-	node = fdt_subnode_offset(blob, sig_node, name);
-	ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node);
-	if (!ret)
 		return ret;
+	}
+
+	if (CONFIG_IS_ENABLED(FIT_SIGNATURE)) {
+		const void *blob = info->fdt_blob;
+		int ndepth, noffset;
+		int sig_node, node;
+		char name[100];
+
+		sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
+		if (sig_node < 0) {
+			debug("%s: No signature node found\n", __func__);
+			return -ENOENT;
+		}
 
-	/* No luck, so try each of the keys in turn */
-	for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth);
-			(noffset >= 0) && (ndepth > 0);
-			noffset = fdt_next_node(info->fit, noffset, &ndepth)) {
-		if (ndepth == 1 && noffset != node) {
+		/* See if we must use a particular key */
+		if (info->required_keynode != -1) {
 			ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
-						      noffset);
+						      info->required_keynode);
 			if (!ret)
-				break;
+				return ret;
+		}
+
+		/* Look for a key that matches our hint */
+		snprintf(name, sizeof(name), "key-%s", info->keyname);
+		node = fdt_subnode_offset(blob, sig_node, name);
+		ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node);
+		if (!ret)
+			return ret;
+
+		/* No luck, so try each of the keys in turn */
+		for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node,
+							 &ndepth);
+		     (noffset >= 0) && (ndepth > 0);
+		     noffset = fdt_next_node(info->fit, noffset, &ndepth)) {
+			if (ndepth == 1 && noffset != node) {
+				ret = rsa_verify_with_keynode(info, hash,
+							      sig, sig_len,
+							      noffset);
+				if (!ret)
+					break;
+			}
 		}
 	}
 
-- 
2.21.0