This series adds support for ECDSA-signed kernel modules. It also
attempts to address a kbuild issue where a developer created an ECDSA
key for signing kernel modules and then builds an older version of the
kernel, when bisecting the kernel for example, that does not support
ECDSA keys.
The first patch addresses the kbuild issue of needing to delete that
ECDSA key if it is in certs/signing_key.pem and trigger the creation
of an RSA key. However, for this to work this patch would have to be
backported to previous versions of the kernel but would also only work
for the developer if he/she used a stable version of the kernel to which
this patch was applied. So whether this patch actually achieves the
wanted effect is not always guaranteed.
The 2nd patch adds the support for the ECSDA-signed kernel modules.
This patch depends on the ECDSA support series currently queued here:
https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/log/?h=ecc
Stefan
v3:
- added missing OIDs for ECDSA signed hashes to pkcs7_sig_note_pkey_algo
- added recommendation to use string hash to Kconfig help text
v2:
- Adjustment to ECDSA key detector string in 2/2
- Rephrased cover letter and patch descriptions with Mimi
Stefan Berger (2):
certs: Trigger creation of RSA module signing key if it's not an RSA
key
certs: Add support for using elliptic curve keys for signing modules
certs/Kconfig | 26 ++++++++++++++++++++++++++
certs/Makefile | 14 ++++++++++++++
crypto/asymmetric_keys/pkcs7_parser.c | 8 ++++++++
3 files changed, 48 insertions(+)
--
2.29.2
Address a kbuild issue where a developer created an ECDSA key for signing
kernel modules and then builds an older version of the kernel, when bi-
secting the kernel for example, that does not support ECDSA keys.
Trigger the creation of an RSA module signing key if it is not an RSA key.
Fixes: cfc411e7fff3 ("Move certificate handling to its own directory")
Signed-off-by: Stefan Berger <[email protected]>
---
certs/Makefile | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/certs/Makefile b/certs/Makefile
index e3185c57fbd8..f64bc89ccbf1 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -59,6 +59,11 @@ silent_redirect_openssl = 2>/dev/null
# external private key, because 'make randconfig' might enable such a
# boolean option and we unfortunately can't make it depend on !RANDCONFIG.
ifeq ($(CONFIG_MODULE_SIG_KEY),"certs/signing_key.pem")
+
+X509TEXT=$(shell openssl x509 -in $(CONFIG_MODULE_SIG_KEY) -text)
+
+$(if $(findstring rsaEncryption,$(X509TEXT)),,$(shell rm -f $(CONFIG_MODULE_SIG_KEY)))
+
$(obj)/signing_key.pem: $(obj)/x509.genkey
@$(kecho) "###"
@$(kecho) "### Now generating an X.509 key pair to be used for signing modules."
--
2.29.2
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.
Signed-off-by: Stefan Berger <[email protected]>
---
v3:
- added missing OIDs for ECDSA signed hashes to pkcs7_sig_note_pkey_algo
- added recommendation to use string hash to Kconfig help text
v2:
- check for ECDSA key by id-ecPublicKey from output line
'Public Key Algorithm: id-ecPublicKey'.
---
certs/Kconfig | 26 ++++++++++++++++++++++++++
certs/Makefile | 9 +++++++++
crypto/asymmetric_keys/pkcs7_parser.c | 8 ++++++++
3 files changed, 43 insertions(+)
diff --git a/certs/Kconfig b/certs/Kconfig
index 48675ad319db..d58f16c9f2d9 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
+ 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
+ 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 5.11 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 f64bc89ccbf1..c2fabc288550 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -62,7 +62,15 @@ ifeq ($(CONFIG_MODULE_SIG_KEY),"certs/signing_key.pem")
X509TEXT=$(shell openssl x509 -in $(CONFIG_MODULE_SIG_KEY) -text)
+# Support user changing key type
+ifdef CONFIG_MODULE_SIG_KEY_TYPE_ECDSA
+keytype_openssl = -newkey ec -pkeyopt ec_paramgen_curve:secp384r1
+$(if $(findstring id-ecPublicKey,$(X509TEXT)),,$(shell rm -f $(CONFIG_MODULE_SIG_KEY)))
+endif
+
+ifdef CONFIG_MODULE_SIG_KEY_TYPE_RSA
$(if $(findstring rsaEncryption,$(X509TEXT)),,$(shell rm -f $(CONFIG_MODULE_SIG_KEY)))
+endif
$(obj)/signing_key.pem: $(obj)/x509.genkey
@$(kecho) "###"
@@ -77,6 +85,7 @@ $(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;
--
2.29.2
On Wed, Apr 21, 2021 at 03:43:19PM -0400, Stefan Berger wrote:
> 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.
>
> Signed-off-by: Stefan Berger <[email protected]>
Looks good to me.
Acked-by: Jarkko Sakkinen <[email protected]>
/Jarkko
>
> ---
> v3:
> - added missing OIDs for ECDSA signed hashes to pkcs7_sig_note_pkey_algo
> - added recommendation to use string hash to Kconfig help text
>
> v2:
> - check for ECDSA key by id-ecPublicKey from output line
> 'Public Key Algorithm: id-ecPublicKey'.
> ---
> certs/Kconfig | 26 ++++++++++++++++++++++++++
> certs/Makefile | 9 +++++++++
> crypto/asymmetric_keys/pkcs7_parser.c | 8 ++++++++
> 3 files changed, 43 insertions(+)
>
> diff --git a/certs/Kconfig b/certs/Kconfig
> index 48675ad319db..d58f16c9f2d9 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
> + 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
> + 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 5.11 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 f64bc89ccbf1..c2fabc288550 100644
> --- a/certs/Makefile
> +++ b/certs/Makefile
> @@ -62,7 +62,15 @@ ifeq ($(CONFIG_MODULE_SIG_KEY),"certs/signing_key.pem")
>
> X509TEXT=$(shell openssl x509 -in $(CONFIG_MODULE_SIG_KEY) -text)
>
> +# Support user changing key type
> +ifdef CONFIG_MODULE_SIG_KEY_TYPE_ECDSA
> +keytype_openssl = -newkey ec -pkeyopt ec_paramgen_curve:secp384r1
> +$(if $(findstring id-ecPublicKey,$(X509TEXT)),,$(shell rm -f $(CONFIG_MODULE_SIG_KEY)))
> +endif
> +
> +ifdef CONFIG_MODULE_SIG_KEY_TYPE_RSA
> $(if $(findstring rsaEncryption,$(X509TEXT)),,$(shell rm -f $(CONFIG_MODULE_SIG_KEY)))
> +endif
>
> $(obj)/signing_key.pem: $(obj)/x509.genkey
> @$(kecho) "###"
> @@ -77,6 +85,7 @@ $(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;
> --
> 2.29.2
>
>
On Wed, Apr 21, 2021 at 03:43:18PM -0400, Stefan Berger wrote:
> Address a kbuild issue where a developer created an ECDSA key for signing
> kernel modules and then builds an older version of the kernel, when bi-
> secting the kernel for example, that does not support ECDSA keys.
>
> Trigger the creation of an RSA module signing key if it is not an RSA key.
>
> Fixes: cfc411e7fff3 ("Move certificate handling to its own directory")
> Signed-off-by: Stefan Berger <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
> ---
> certs/Makefile | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/certs/Makefile b/certs/Makefile
> index e3185c57fbd8..f64bc89ccbf1 100644
> --- a/certs/Makefile
> +++ b/certs/Makefile
> @@ -59,6 +59,11 @@ silent_redirect_openssl = 2>/dev/null
> # external private key, because 'make randconfig' might enable such a
> # boolean option and we unfortunately can't make it depend on !RANDCONFIG.
> ifeq ($(CONFIG_MODULE_SIG_KEY),"certs/signing_key.pem")
> +
> +X509TEXT=$(shell openssl x509 -in $(CONFIG_MODULE_SIG_KEY) -text)
> +
> +$(if $(findstring rsaEncryption,$(X509TEXT)),,$(shell rm -f $(CONFIG_MODULE_SIG_KEY)))
> +
> $(obj)/signing_key.pem: $(obj)/x509.genkey
> @$(kecho) "###"
> @$(kecho) "### Now generating an X.509 key pair to be used for signing modules."
> --
> 2.29.2
>
>
/Jarkko