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

2021-04-20 Thread 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

2021-04-20 Thread 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 

---
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

2021-04-08 Thread 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 

Thanks, Stefan.

Reviewed-by: Mimi Zohar