[PATCH 17/23] lib/crypto: Port public_key on MbedTLS

[Raymond Mao]

Integrate function public_key_verify_signature on top of MbedTLS
pk library.

Signed-off-by: Raymond Mao <raymond.mao at linaro.org>
---
 include/crypto/public_key.h  |  6 +++
 lib/crypto/asymmetric_type.c |  2 +-
 lib/crypto/public_key.c      | 75 ++++++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+), 1 deletion(-)

diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index 3ba90fcc34..55cd4c2b01 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h
@@ -12,6 +12,12 @@
 
 #ifdef __UBOOT__
 #include <linux/types.h>
+#if CONFIG_IS_ENABLED(MBEDTLS_LIB_X509)
+#include <external/mbedtls/library/common.h>
+#include <external/mbedtls/include/mbedtls/pk.h>
+#include <external/mbedtls/include/mbedtls/x509_crt.h>
+#include <external/mbedtls/include/mbedtls/md.h>
+#endif
 #else
 #include <linux/keyctl.h>
 #endif
diff --git a/lib/crypto/asymmetric_type.c b/lib/crypto/asymmetric_type.c
index 24c2d15ef9..95b82cd8e8 100644
--- a/lib/crypto/asymmetric_type.c
+++ b/lib/crypto/asymmetric_type.c
@@ -12,7 +12,6 @@
 #include <keys/asymmetric-subtype.h>
 #include <keys/asymmetric-parser.h>
 #endif
-#include <crypto/public_key.h>
 #ifdef __UBOOT__
 #include <linux/bug.h>
 #include <linux/compat.h>
@@ -26,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/ctype.h>
 #endif
+#include <crypto/public_key.h>
 #ifdef __UBOOT__
 #include <keys/asymmetric-type.h>
 #else
diff --git a/lib/crypto/public_key.c b/lib/crypto/public_key.c
index 6efe951c05..29576684f1 100644
--- a/lib/crypto/public_key.c
+++ b/lib/crypto/public_key.c
@@ -94,6 +94,80 @@ EXPORT_SYMBOL_GPL(public_key_signature_free);
  *
  * Return:	0 - verified, non-zero error code - otherwise
  */
+#if CONFIG_IS_ENABLED(MBEDTLS_LIB_X509)
+int public_key_verify_signature(const struct public_key *pkey,
+				const struct public_key_signature *sig)
+{
+	mbedtls_md_type_t mb_hash_algo;
+	mbedtls_pk_context pk_ctx;
+	int ret;
+
+	if (!pkey || !sig || pkey->key_is_private)
+		return -EINVAL;
+
+	/*
+	 * ECRDSA (Elliptic Curve RedDSA) from Red Hat is not supported by
+	 * MbedTLS
+	 */
+	if (strcmp(pkey->pkey_algo, "rsa")) {
+		pr_err("Encryption is not RSA: %s\n", sig->pkey_algo);
+		return -EINVAL;
+	}
+
+	/*
+	 * Can be pkcs1 or raw, but pkcs1 is expected.
+	 * This is just for argument checking, not necessarily passed to MbedTLS,
+	 * For RSA signatures, MbedTLS typically supports the PKCS#1 v1.5
+	 * (aka. pkcs1) encoding by default.
+	 * The library internally handles the details of decoding and verifying
+	 * the signature according to the expected encoding for the specified algorithm.
+	 */
+	if (strcmp(sig->encoding, "pkcs1")) {
+		pr_err("Encoding %s is not supported, only supports pkcs1\n",
+		       sig->encoding);
+		return -EINVAL;
+	}
+
+	if (!strcmp(sig->hash_algo, "sha1"))
+		mb_hash_algo = MBEDTLS_MD_SHA1;
+	else if (!strcmp(sig->hash_algo, "sha224"))
+		mb_hash_algo = MBEDTLS_MD_SHA224;
+	else if (!strcmp(sig->hash_algo, "sha256"))
+		mb_hash_algo = MBEDTLS_MD_SHA256;
+	else if (!strcmp(sig->hash_algo, "sha384"))
+		mb_hash_algo = MBEDTLS_MD_SHA384;
+	else if (!strcmp(sig->hash_algo, "sha512"))
+		mb_hash_algo = MBEDTLS_MD_SHA512;
+	else	/* Unknown or unsupported hash algorithm */
+		return -EINVAL;
+	/* Initialize the mbedtls_pk_context with RSA key type */
+	mbedtls_pk_init(&pk_ctx);
+
+	/* Parse the DER-encoded public key */
+	ret = mbedtls_pk_parse_public_key(&pk_ctx, pkey->key, pkey->keylen);
+	if (ret) {
+		pr_err("Failed to parse public key, ret:-0x%04x\n",
+		       (unsigned int)-ret);
+		ret = -EINVAL;
+		goto err_key;
+	}
+
+	/* Ensure that it is a RSA key */
+	if (mbedtls_pk_get_type(&pk_ctx) != MBEDTLS_PK_RSA) {
+		pr_err("Only RSA keys are supported\n");
+		ret = -EKEYREJECTED;
+		goto err_key;
+	}
+
+	/* Verify the hash */
+	ret = mbedtls_pk_verify(&pk_ctx, mb_hash_algo, sig->digest,
+				sig->digest_size, sig->s, sig->s_size);
+
+err_key:
+	mbedtls_pk_free(&pk_ctx);
+	return ret;
+}
+#else	/* !CONFIG_IS_ENABLED(MBEDTLS_LIB_X509) */
 int public_key_verify_signature(const struct public_key *pkey,
 				const struct public_key_signature *sig)
 {
@@ -142,6 +216,7 @@ int public_key_verify_signature(const struct public_key *pkey,
 	pr_devel("<==%s() = %d\n", __func__, ret);
 	return ret;
 }
+#endif	/* CONFIG_IS_ENABLED(MBEDTLS_LIB_X509) */
 #else
 /*
  * Destroy a public key algorithm key.
-- 
2.25.1