[PATCH v2 0/2] Add support for ECDSA-signed kernel modules

[PATCH v2 0/2] Add support for ECDSA-signed kernel modules

[Stefan Berger]

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

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                         | 25 +++++++++++++++++++++++++
 certs/Makefile                        | 14 ++++++++++++++
 crypto/asymmetric_keys/pkcs7_parser.c |  4 ++++
 3 files changed, 43 insertions(+)

-- 
2.29.2

[PATCH v2 1/2] certs: Trigger creation of RSA module signing key if it's not an RSA key

[Stefan Berger]

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 <stefanb@linux.ibm.com>
---
 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

Re: [PATCH v2 1/2] certs: Trigger creation of RSA module signing key if it's not an RSA key

[Mimi Zohar]

On Thu, 2021-04-08 at 11:24 -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 <stefanb@linux.ibm.com>

Thanks, Stefan.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Re: [PATCH v2 1/2] certs: Trigger creation of RSA module signing key if it's not an RSA key

[Stefan Berger]

On 4/8/21 1:15 PM, Mimi Zohar wrote:
> On Thu, 2021-04-08 at 11:24 -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 <stefanb@linux.ibm.com>
> Thanks, Stefan.
>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
>

Via which tree will this go upstream? keyrings?


    Stefan

Re: [PATCH v2 1/2] certs: Trigger creation of RSA module signing key if it's not an RSA key

[Mimi Zohar]

On Thu, 2021-04-08 at 15:19 -0400, Stefan Berger wrote:
> On 4/8/21 1:15 PM, Mimi Zohar wrote:
> > On Thu, 2021-04-08 at 11:24 -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 <stefanb@linux.ibm.com>
> > Thanks, Stefan.
> >
> > Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> >
> 
> Via which tree will this go upstream? keyrings?

This patch set originally had a dependency on Nayna's v1 & v2 "ima:
kernel build support for loading the kernel module signing key" patch
set and on Herbert's "ecc" branch.  With v3, the dependency on Nayna's
patch set is gone.

Jarkko, David, Herbert did you want to pick up this patch set or would
you prefer that I did?  Either way is fine.

thanks,

Mimi

[PATCH v2 2/2] certs: Add support for using elliptic curve keys for signing modules

[Stefan Berger]

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 <stefanb@linux.ibm.com>

---
v2:
  - check for ECDSA key by id-ecPublicKey from output line
    'Public Key Algorithm: id-ecPublicKey'.
---
 certs/Kconfig                         | 25 +++++++++++++++++++++++++
 certs/Makefile                        |  9 +++++++++
 crypto/asymmetric_keys/pkcs7_parser.c |  4 ++++
 3 files changed, 38 insertions(+)

diff --git a/certs/Kconfig b/certs/Kconfig
index 48675ad319db..6f8337874ae0 100644
--- a/certs/Kconfig
+++ b/certs/Kconfig
@@ -15,6 +15,31 @@ 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.
+
+	 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..2546ec6a0505 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.c
+++ b/crypto/asymmetric_keys/pkcs7_parser.c
@@ -269,6 +269,10 @@ 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_sha256:
+		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

Re: [PATCH v2 2/2] certs: Add support for using elliptic curve keys for signing modules

[Mimi Zohar]

On Thu, 2021-04-08 at 11:24 -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 <stefanb@linux.ibm.com>

Thanks, Stefan.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Re: [PATCH v2 2/2] certs: Add support for using elliptic curve keys for signing modules

[Jessica Yu]

+++ Stefan Berger [08/04/21 11:24 -0400]:
>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 <stefanb@linux.ibm.com>
>
>---
>v2:
>  - check for ECDSA key by id-ecPublicKey from output line
>    'Public Key Algorithm: id-ecPublicKey'.
>---
> certs/Kconfig                         | 25 +++++++++++++++++++++++++
> certs/Makefile                        |  9 +++++++++
> crypto/asymmetric_keys/pkcs7_parser.c |  4 ++++
> 3 files changed, 38 insertions(+)
>
>diff --git a/certs/Kconfig b/certs/Kconfig
>index 48675ad319db..6f8337874ae0 100644
>--- a/certs/Kconfig
>+++ b/certs/Kconfig
>@@ -15,6 +15,31 @@ 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.
>+
>+	 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..2546ec6a0505 100644
>--- a/crypto/asymmetric_keys/pkcs7_parser.c
>+++ b/crypto/asymmetric_keys/pkcs7_parser.c
>@@ -269,6 +269,10 @@ 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_sha256:
>+		ctx->sinfo->sig->pkey_algo = "ecdsa";
>+		ctx->sinfo->sig->encoding = "x962";
>+		break;

Hi Stefan,

Does CONFIG_MODULE_SIG_KEY_TYPE_ECDSA have a dependency on MODULE_SIG_SHA256?
By default, MODULE_SIG_SHA1 is selected when CONFIG_MODULE_SIG is enabled.
I was doing some quick testing and found that when I enabled
MODULE_SIG_KEY_TYPE_ECDSA I get a "Unsupported pkey algo: 5" error on
module load, which goes away after fixing my config and selecting
MODULE_SIG_SHA256.

Thanks,

Jessica

Re: [PATCH v2 2/2] certs: Add support for using elliptic curve keys for signing modules

[Stefan Berger]

On 4/20/21 10:03 AM, Jessica Yu wrote:
> +++ Stefan Berger [08/04/21 11:24 -0400]:
>>
>> diff --git a/crypto/asymmetric_keys/pkcs7_parser.c 
>> b/crypto/asymmetric_keys/pkcs7_parser.c
>> index 967329e0a07b..2546ec6a0505 100644
>> --- a/crypto/asymmetric_keys/pkcs7_parser.c
>> +++ b/crypto/asymmetric_keys/pkcs7_parser.c
>> @@ -269,6 +269,10 @@ 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_sha256:
>> +        ctx->sinfo->sig->pkey_algo = "ecdsa";
>> +        ctx->sinfo->sig->encoding = "x962";
>> +        break;
>
> Hi Stefan,
>
> Does CONFIG_MODULE_SIG_KEY_TYPE_ECDSA have a dependency on 
> MODULE_SIG_SHA256?

You are right, per the code above it does have a dependency on SHA256. 
ECDSA is using NIST p384 (secp384r1) for signing and per my tests it can 
be paired with all the sha hashes once the code above is extended. Now 
when it comes to module signing, should we pair it with a particular 
hash? I am not currently aware of a guidance document on this but sha256 
and sha384 seem to be good choices these days, so maybe selecting ECDSA 
module signing should have a 'depends on' on these?

   Stefan

Re: [PATCH v2 2/2] certs: Add support for using elliptic curve keys for signing modules

[Jessica Yu]

+++ Stefan Berger [20/04/21 17:02 -0400]:
>
>On 4/20/21 10:03 AM, Jessica Yu wrote:
>>+++ Stefan Berger [08/04/21 11:24 -0400]:
>>>
>>>diff --git a/crypto/asymmetric_keys/pkcs7_parser.c 
>>>b/crypto/asymmetric_keys/pkcs7_parser.c
>>>index 967329e0a07b..2546ec6a0505 100644
>>>--- a/crypto/asymmetric_keys/pkcs7_parser.c
>>>+++ b/crypto/asymmetric_keys/pkcs7_parser.c
>>>@@ -269,6 +269,10 @@ 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_sha256:
>>>+        ctx->sinfo->sig->pkey_algo = "ecdsa";
>>>+        ctx->sinfo->sig->encoding = "x962";
>>>+        break;
>>
>>Hi Stefan,
>>
>>Does CONFIG_MODULE_SIG_KEY_TYPE_ECDSA have a dependency on 
>>MODULE_SIG_SHA256?
>
>You are right, per the code above it does have a dependency on SHA256. 
>ECDSA is using NIST p384 (secp384r1) for signing and per my tests it 
>can be paired with all the sha hashes once the code above is extended. 
>Now when it comes to module signing, should we pair it with a 
>particular hash? I am not currently aware of a guidance document on 
>this but sha256 and sha384 seem to be good choices these days, so 
>maybe selecting ECDSA module signing should have a 'depends on' on 
>these?

Yeah, I would tack on the 'depends on' until the code above has been
extended to cover more sha hashes - because currently if someone
builds and signs a bunch of modules with an ECDSA key, they will fail
to load if they picked something other than sha256. I am unfortunately
not knowledgeable enough to suggest an official guideline on choice of
hash, but for now it is reasonable to have a 'depends on' for which
hashes the code currently supports, so that users don't run into
module loading rejection issues.

Thanks!

Jessica

Re: [PATCH v2 2/2] certs: Add support for using elliptic curve keys for signing modules

[Stefan Berger]

On 4/21/21 8:52 AM, Jessica Yu wrote:
> +++ Stefan Berger [20/04/21 17:02 -0400]:
>>
>> On 4/20/21 10:03 AM, Jessica Yu wrote:
>>> +++ Stefan Berger [08/04/21 11:24 -0400]:
>>>>
>>>> diff --git a/crypto/asymmetric_keys/pkcs7_parser.c 
>>>> b/crypto/asymmetric_keys/pkcs7_parser.c
>>>> index 967329e0a07b..2546ec6a0505 100644
>>>> --- a/crypto/asymmetric_keys/pkcs7_parser.c
>>>> +++ b/crypto/asymmetric_keys/pkcs7_parser.c
>>>> @@ -269,6 +269,10 @@ 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_sha256:
>>>> +        ctx->sinfo->sig->pkey_algo = "ecdsa";
>>>> +        ctx->sinfo->sig->encoding = "x962";
>>>> +        break;
>>>
>>> Hi Stefan,
>>>
>>> Does CONFIG_MODULE_SIG_KEY_TYPE_ECDSA have a dependency on 
>>> MODULE_SIG_SHA256?
>>
>> You are right, per the code above it does have a dependency on 
>> SHA256. ECDSA is using NIST p384 (secp384r1) for signing and per my 
>> tests it can be paired with all the sha hashes once the code above is 
>> extended. Now when it comes to module signing, should we pair it with 
>> a particular hash? I am not currently aware of a guidance document on 
>> this but sha256 and sha384 seem to be good choices these days, so 
>> maybe selecting ECDSA module signing should have a 'depends on' on 
>> these?
>
> Yeah, I would tack on the 'depends on' until the code above has been
> extended to cover more sha hashes - because currently if someone
> builds and signs a bunch of modules with an ECDSA key, they will fail
> to load if they picked something other than sha256. I am unfortunately
> not knowledgeable enough to suggest an official guideline on choice of
> hash, but for now it is reasonable to have a 'depends on' for which
> hashes the code currently supports, so that users don't run into
> module loading rejection issues.


I was going to repost this series now with the additional OIDs supported 
above and a recommendation to use sha384 in the help text for 
ECDSA-signed modules, but not enforcing this but instead trusting the 
user that they will choose a reasonable hash (probably >= sha256).


    Stefan


>
> Thanks!
>
> Jessica

Re: [PATCH v2 2/2] certs: Add support for using elliptic curve keys for signing modules

[Jessica Yu]

+++ Stefan Berger [21/04/21 08:54 -0400]:
>
>On 4/21/21 8:52 AM, Jessica Yu wrote:
>>+++ Stefan Berger [20/04/21 17:02 -0400]:
>>>
>>>On 4/20/21 10:03 AM, Jessica Yu wrote:
>>>>+++ Stefan Berger [08/04/21 11:24 -0400]:
>>>>>
>>>>>diff --git a/crypto/asymmetric_keys/pkcs7_parser.c 
>>>>>b/crypto/asymmetric_keys/pkcs7_parser.c
>>>>>index 967329e0a07b..2546ec6a0505 100644
>>>>>--- a/crypto/asymmetric_keys/pkcs7_parser.c
>>>>>+++ b/crypto/asymmetric_keys/pkcs7_parser.c
>>>>>@@ -269,6 +269,10 @@ 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_sha256:
>>>>>+        ctx->sinfo->sig->pkey_algo = "ecdsa";
>>>>>+        ctx->sinfo->sig->encoding = "x962";
>>>>>+        break;
>>>>
>>>>Hi Stefan,
>>>>
>>>>Does CONFIG_MODULE_SIG_KEY_TYPE_ECDSA have a dependency on 
>>>>MODULE_SIG_SHA256?
>>>
>>>You are right, per the code above it does have a dependency on 
>>>SHA256. ECDSA is using NIST p384 (secp384r1) for signing and per 
>>>my tests it can be paired with all the sha hashes once the code 
>>>above is extended. Now when it comes to module signing, should we 
>>>pair it with a particular hash? I am not currently aware of a 
>>>guidance document on this but sha256 and sha384 seem to be good 
>>>choices these days, so maybe selecting ECDSA module signing should 
>>>have a 'depends on' on these?
>>
>>Yeah, I would tack on the 'depends on' until the code above has been
>>extended to cover more sha hashes - because currently if someone
>>builds and signs a bunch of modules with an ECDSA key, they will fail
>>to load if they picked something other than sha256. I am unfortunately
>>not knowledgeable enough to suggest an official guideline on choice of
>>hash, but for now it is reasonable to have a 'depends on' for which
>>hashes the code currently supports, so that users don't run into
>>module loading rejection issues.
>
>
>I was going to repost this series now with the additional OIDs 
>supported above and a recommendation to use sha384 in the help text 
>for ECDSA-signed modules, but not enforcing this but instead trusting 
>the user that they will choose a reasonable hash (probably >= sha256).

OK, that sounds good to me.

Thanks Stefan!