[U-Boot] [RFC 3/3] 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/Kconfig      |  7 +++++
 lib/rsa/Makefile     |  3 ++-
 lib/rsa/rsa-verify.c | 63 ++++++++++++++++++++++++++++++++++++++------
 3 files changed, 64 insertions(+), 9 deletions(-)

diff --git a/lib/rsa/Kconfig b/lib/rsa/Kconfig
index 338c8124da59..3c1986a26f8c 100644
--- a/lib/rsa/Kconfig
+++ b/lib/rsa/Kconfig
@@ -25,6 +25,13 @@ config RSA_VERIFY
 	help
 	  Add RSA signature verification support.
 
+config RSA_VERIFY_WITH_PKEY
+	bool "Execute RSA verification without key parameters from FDT"
+	depends on RSA
+	help
+	  This options enables RSA signature verification without
+	  using public key parameters which is embedded control FDT.
+
 config RSA_SOFTWARE_EXP
 	bool "Enable driver for RSA Modular Exponentiation in software"
 	depends on DM
diff --git a/lib/rsa/Makefile b/lib/rsa/Makefile
index d66eef74c514..fd4592fd6a8a 100644
--- a/lib/rsa/Makefile
+++ b/lib/rsa/Makefile
@@ -5,5 +5,6 @@
 # (C) Copyright 2000-2007
 # Wolfgang Denk, DENX Software Engineering, wd at denx.de.
 
-obj-$(CONFIG_RSA_VERIFY) += rsa-verify.o rsa-checksum.o rsa-keyprop.o
+obj-$(CONFIG_RSA_VERIFY) += rsa-verify.o rsa-checksum.o
+obj-$(CONFIG_RSA_VERIFY_WITH_PKEY) += rsa-keyprop.o
 obj-$(CONFIG_RSA_SOFTWARE_EXP) += rsa-mod-exp.o
diff --git a/lib/rsa/rsa-verify.c b/lib/rsa/rsa-verify.c
index 287fcc4d234d..80eabff3e940 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
 
@@ -342,6 +347,34 @@ static int rsa_verify_key(struct image_sign_info *info,
 	return 0;
 }
 
+#ifdef CONFIG_RSA_VERIFY_WITH_PKEY
+/**
+ * rsa_verify_with_pkey()
+ *
+ */
+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;
+}
+#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.
@@ -395,18 +428,21 @@ static int rsa_verify_with_keynode(struct image_sign_info *info,
 
 	return ret;
 }
+#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 ret = -EACCES;
+#if CONFIG_IS_ENABLED(FIT_SIGNATURE)
+	const void *blob = info->fdt_blob;
 	int ndepth, noffset;
 	int sig_node, node;
 	char name[100];
-	int ret;
+#endif
 
 	/*
 	 * Verify that the checksum-length does not exceed the
@@ -419,12 +455,6 @@ 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);
@@ -433,6 +463,22 @@ int rsa_verify(struct image_sign_info *info,
 		return -EINVAL;
 	}
 
+#ifdef CONFIG_RSA_VERIFY_WITH_PKEY
+	if (!info->fdt_blob) {
+		/* don't rely on fdt properties */
+		ret = rsa_verify_with_pkey(info, hash, sig, sig_len);
+
+		return ret;
+	}
+#endif
+
+#if CONFIG_IS_ENABLED(FIT_SIGNATURE)
+	sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
+	if (sig_node < 0) {
+		debug("%s: No signature node found\n", __func__);
+		return -ENOENT;
+	}
+
 	/* See if we must use a particular key */
 	if (info->required_keynode != -1) {
 		ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
@@ -459,6 +505,7 @@ int rsa_verify(struct image_sign_info *info,
 				break;
 		}
 	}
+#endif
 
 	return ret;
 }
-- 
2.21.0