certs: Add support for using elliptic curve keys for signing modules

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>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

diff --git a/certs/Kconfig b/certs/Kconfig
index f4e61116f94ed9bf9394645e04ad90c9c10a565c..ae7f2e876a31b584ad43172c226a6be19704fd9a 100644 (file)
--- 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 5.14 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 f9344e52ecdaef90e927a1a0e796db07a0a64ca5..279433783b10af16ead0e84e2cf6fd4be65193e2 100644 (file)
--- 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 967329e0a07b7958a60b334d24d89273868cb5ba..6592279d839aff6d267cd225e5e51f0e6bbe0ea2 100644 (file)
--- 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;