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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>
master
Stefan Berger 4 months ago
committed by Jarkko Sakkinen
parent
commit
a4aed36ed5
  1. 26
      certs/Kconfig
  2. 13
      certs/Makefile
  3. 8
      crypto/asymmetric_keys/pkcs7_parser.c

26
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

13
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."

8
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;

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