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From: Stefan Berger <stefanb@linux.vnet.ibm.com>
To: jeyu@kernel.org, keyrings@vger.kernel.org, dhowells@redhat.com,
	dwmw2@infradead.org, zohar@linux.ibm.com, jarkko@kernel.org
Cc: nayna@linux.ibm.com, linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
	Stefan Berger <stefanb@linux.ibm.com>
Subject: [PATCH v8 2/2] certs: Add support for using elliptic curve keys for signing modules
Date: Tue, 29 Jun 2021 17:34:21 -0400	[thread overview]
Message-ID: <20210629213421.60320-3-stefanb@linux.vnet.ibm.com> (raw)
In-Reply-To: <20210629213421.60320-1-stefanb@linux.vnet.ibm.com>

From: Stefan Berger <stefanb@linux.ibm.com>

Add support for using elliptic curve keys for signing modules. It uses
a NIST P384 (secp384r1) key if the user chooses an elliptic curve key
and will have ECDSA support built into the kernel.

Note: A developer choosing an ECDSA key for signing modules should still
delete the signing key (rm certs/signing_key.*) when building an older
version of a kernel that only supports RSA keys. Unless kbuild automati-
cally detects and generates a new kernel module key, ECDSA-signed kernel
modules will fail signature verification.

Cc: David Howells <dhowells@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
---
 certs/Kconfig                         | 26 ++++++++++++++++++++++++++
 certs/Makefile                        | 13 +++++++++++++
 crypto/asymmetric_keys/pkcs7_parser.c |  8 ++++++++
 3 files changed, 47 insertions(+)

diff --git a/certs/Kconfig b/certs/Kconfig
index f4e61116f94e..7d38d65e2128 100644
--- a/certs/Kconfig
+++ b/certs/Kconfig
@@ -15,6 +15,32 @@ config MODULE_SIG_KEY
          then the kernel will automatically generate the private key and
          certificate as described in Documentation/admin-guide/module-signing.rst
 
+choice
+	prompt "Type of module signing key to be generated"
+	default MODULE_SIG_KEY_TYPE_RSA
+	help
+	 The type of module signing key type to generate. This option
+	 does not apply if a #PKCS11 URI is used.
+
+config MODULE_SIG_KEY_TYPE_RSA
+	bool "RSA"
+	depends on MODULE_SIG || (IMA_APPRAISE_MODSIG && MODULES)
+	help
+	 Use an RSA key for module signing.
+
+config MODULE_SIG_KEY_TYPE_ECDSA
+	bool "ECDSA"
+	select CRYPTO_ECDSA
+	depends on MODULE_SIG || (IMA_APPRAISE_MODSIG && MODULES)
+	help
+	 Use an elliptic curve key (NIST P384) for module signing. Consider
+	 using a strong hash like sha256 or sha384 for hashing modules.
+
+	 Note: Remove all ECDSA signing keys, e.g. certs/signing_key.pem,
+	 when falling back to building Linux 5.13 and older kernels.
+
+endchoice
+
 config SYSTEM_TRUSTED_KEYRING
 	bool "Provide system-wide ring of trusted keys"
 	depends on KEYS
diff --git a/certs/Makefile b/certs/Makefile
index f9344e52ecda..279433783b10 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -66,9 +66,21 @@ ifeq ($(CONFIG_MODULE_SIG_KEY),"certs/signing_key.pem")
 
 ifeq ($(openssl_available),yes)
 X509TEXT=$(shell openssl x509 -in "certs/signing_key.pem" -text 2>/dev/null)
+endif
 
+# Support user changing key type
+ifdef CONFIG_MODULE_SIG_KEY_TYPE_ECDSA
+keytype_openssl = -newkey ec -pkeyopt ec_paramgen_curve:secp384r1
+ifeq ($(openssl_available),yes)
+$(if $(findstring id-ecPublicKey,$(X509TEXT)),,$(shell rm -f "certs/signing_key.pem"))
+endif
+endif # CONFIG_MODULE_SIG_KEY_TYPE_ECDSA
+
+ifdef CONFIG_MODULE_SIG_KEY_TYPE_RSA
+ifeq ($(openssl_available),yes)
 $(if $(findstring rsaEncryption,$(X509TEXT)),,$(shell rm -f "certs/signing_key.pem"))
 endif
+endif # CONFIG_MODULE_SIG_KEY_TYPE_RSA
 
 $(obj)/signing_key.pem: $(obj)/x509.genkey
 	@$(kecho) "###"
@@ -83,6 +95,7 @@ $(obj)/signing_key.pem: $(obj)/x509.genkey
 		-batch -x509 -config $(obj)/x509.genkey \
 		-outform PEM -out $(obj)/signing_key.pem \
 		-keyout $(obj)/signing_key.pem \
+		$(keytype_openssl) \
 		$($(quiet)redirect_openssl)
 	@$(kecho) "###"
 	@$(kecho) "### Key pair generated."
diff --git a/crypto/asymmetric_keys/pkcs7_parser.c b/crypto/asymmetric_keys/pkcs7_parser.c
index 967329e0a07b..6592279d839a 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.c
+++ b/crypto/asymmetric_keys/pkcs7_parser.c
@@ -269,6 +269,14 @@ int pkcs7_sig_note_pkey_algo(void *context, size_t hdrlen,
 		ctx->sinfo->sig->pkey_algo = "rsa";
 		ctx->sinfo->sig->encoding = "pkcs1";
 		break;
+	case OID_id_ecdsa_with_sha1:
+	case OID_id_ecdsa_with_sha224:
+	case OID_id_ecdsa_with_sha256:
+	case OID_id_ecdsa_with_sha384:
+	case OID_id_ecdsa_with_sha512:
+		ctx->sinfo->sig->pkey_algo = "ecdsa";
+		ctx->sinfo->sig->encoding = "x962";
+		break;
 	default:
 		printk("Unsupported pkey algo: %u\n", ctx->last_oid);
 		return -ENOPKG;
-- 
2.31.1


  parent reply	other threads:[~2021-06-29 21:34 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-29 21:34 [PATCH v8 0/2] Add support for ECDSA-signed kernel modules Stefan Berger
2021-06-29 21:34 ` [PATCH v8 1/2] certs: Trigger creation of RSA module signing key if it's not an RSA key Stefan Berger
2021-06-30 19:17   ` Linus Torvalds
2021-07-02  6:49     ` Jarkko Sakkinen
2021-06-29 21:34 ` Stefan Berger [this message]
2021-07-02  6:50 ` [PATCH v8 0/2] Add support for ECDSA-signed kernel modules Jarkko Sakkinen

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