akcipher: Move the RSA DER encoding check to the crypto layer

Move the RSA EMSA-PKCS1-v1_5 encoding from the asymmetric-key public_key
subtype to the rsa crypto module's pkcs1pad template.  This means that the
public_key subtype no longer has any dependencies on public key type.

To make this work, the following changes have been made:

 (1) The rsa pkcs1pad template is now used for RSA keys.  This strips off the
     padding and returns just the message hash.

 (2) In a previous patch, the pkcs1pad template gained an optional second
     parameter that, if given, specifies the hash used.  We now give this,
     and pkcs1pad checks the encoded message E(M) for the EMSA-PKCS1-v1_5
     encoding and verifies that the correct digest OID is present.

 (3) The crypto driver in crypto/asymmetric_keys/rsa.c is now reduced to
     something that doesn't care about what the encryption actually does
     and and has been merged into public_key.c.

 (4) CONFIG_PUBLIC_KEY_ALGO_RSA is gone.  Module signing must set
     CONFIG_CRYPTO_RSA=y instead.

Thoughts:

 (*) Should the encoding style (eg. raw, EMSA-PKCS1-v1_5) also be passed to
     the padding template?  Should there be multiple padding templates
     registered that share most of the code?

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 1 insertions, 1 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 22320804fbaf..af4de4f1b02c 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1757,9 +1757,9 @@ config SYSTEM_DATA_VERIFICATION
         select SYSTEM_TRUSTED_KEYRING
         select KEYS
         select CRYPTO
+        select CRYPTO_RSA
         select ASYMMETRIC_KEY_TYPE
         select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
-        select PUBLIC_KEY_ALGO_RSA
         select ASN1
         select OID_REGISTRY
         select X509_CERTIFICATE_PARSER