On 1/17/25 1:35 PM, David Howells wrote:
Hi Herbert, Chuck, Here's yet another go at a generic Kerberos crypto library in the kernel so that I can share code between rxrpc and sunrpc (and cifs?). I derived some of the parts from the sunrpc gss library and added more advanced AES and Camellia crypto. I added an addition AEAD template type, derived from authenc, that does hash-then-crypt rather than crypt-then-hash as authenc does. I called it "krb5enc" for want of a better name. Possibly I should call it "hashenc" or something like that. I went back to my previous more library-based approach, but for encrypt mode, I replaced the separate skcipher and shash objects with a single templated AEAD object - either krb5enc (AES+SHA1 and Camellia) or authenc (AES+SHA2).
I'm philosophically in favor of sharing this code. One of the biggest benefits will be making review/audit easier. Another will be the opportunities for more hardware acceleration. But I can't tell if the library API as laid out here will be a good fit for SunRPC and our kernel XDR implementation until I actually try to use the API, which I don't have time for right now. The set of enctypes indeed seems sufficient to support GSS-API Kerberos, and that is a fundamental requirement for us. The Linux in-kernel SMB community might be interested in sharing some of this too, though they seem to have grown their own enctypes. The Cc list on the thread is already substantial, but they should be included. I think it would be fine to merge this, as long as the crypto folks are happy with it, with its current single consumer (RxRPC), and then we can explore broader sharing.
Apart from that, things are much as they were previously from the point of view of someone using the API. There's a new pair of functions that, given an encoding type, a key and a usage value, will derive the necessary keys and return an AEAD or hash handle. These handles can then be passed to operation functions that will do the actual work of performing an encryption, a decryption, MIC generation or MIC verification. Querying functions are also available to look up an encoding type table by kerberos protocol number and to help manage message layout. This library has its own self-testing framework that checks more things than is possible with the testmgr, including subkey derivation. It also checks things about the output of encrypt + decrypt that testmgr doesn't. That said, testmgr is also provisioned with some encryption and checksumming tests for Camilla and AES2, though these have to be provisioned with the intermediate subkeys rather than the transport key. Note that, for purposes of illustration, I've included some rxrpc patches that use this interface to implement the rxgk Rx security class. The branch also is based on net-next that carries some rxrpc patches that are a prerequisite for this, but the crypto patches don't need it. --- The patches can be found here also: http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=crypto-krb5 David David Howells (24): crypto/krb5: Add API Documentation crypto/krb5: Add some constants out of sunrpc headers crypto: Add 'krb5enc' hash and cipher AEAD algorithm crypto/krb5: Test manager data crypto/krb5: Implement Kerberos crypto core crypto/krb5: Add an API to query the layout of the crypto section crypto/krb5: Add an API to alloc and prepare a crypto object crypto/krb5: Add an API to perform requests crypto/krb5: Provide infrastructure and key derivation crypto/krb5: Implement the Kerberos5 rfc3961 key derivation crypto/krb5: Provide RFC3961 setkey packaging functions crypto/krb5: Implement the Kerberos5 rfc3961 encrypt and decrypt functions crypto/krb5: Implement the Kerberos5 rfc3961 get_mic and verify_mic crypto/krb5: Implement the AES enctypes from rfc3962 crypto/krb5: Implement the AES enctypes from rfc8009 crypto/krb5: Implement the AES encrypt/decrypt from rfc8009 crypto/krb5: Implement crypto self-testing crypto/krb5: Add the AES self-testing data from rfc8009 crypto/krb5: Implement the Camellia enctypes from rfc6803 rxrpc: Add the security index for yfs-rxgk rxrpc: Add YFS RxGK (GSSAPI) security class rxrpc: rxgk: Provide infrastructure and key derivation rxrpc: rxgk: Implement the yfs-rxgk security class (GSSAPI) rxrpc: rxgk: Implement connection rekeying Documentation/crypto/index.rst | 1 + Documentation/crypto/krb5.rst | 262 +++++++ crypto/Kconfig | 13 + crypto/Makefile | 3 + crypto/krb5/Kconfig | 26 + crypto/krb5/Makefile | 18 + crypto/krb5/internal.h | 257 +++++++ crypto/krb5/krb5_api.c | 452 ++++++++++++ crypto/krb5/krb5_kdf.c | 145 ++++ crypto/krb5/rfc3961_simplified.c | 791 ++++++++++++++++++++ crypto/krb5/rfc3962_aes.c | 115 +++ crypto/krb5/rfc6803_camellia.c | 237 ++++++ crypto/krb5/rfc8009_aes2.c | 431 +++++++++++ crypto/krb5/selftest.c | 544 ++++++++++++++ crypto/krb5/selftest_data.c | 291 ++++++++ crypto/krb5enc.c | 491 +++++++++++++ crypto/testmgr.c | 16 + crypto/testmgr.h | 401 ++++++++++ fs/afs/misc.c | 13 + include/crypto/krb5.h | 167 +++++ include/keys/rxrpc-type.h | 17 + include/trace/events/rxrpc.h | 36 + include/uapi/linux/rxrpc.h | 17 + net/rxrpc/Kconfig | 10 + net/rxrpc/Makefile | 5 +- net/rxrpc/ar-internal.h | 22 + net/rxrpc/conn_event.c | 2 +- net/rxrpc/conn_object.c | 1 + net/rxrpc/key.c | 183 +++++ net/rxrpc/output.c | 2 +- net/rxrpc/protocol.h | 20 + net/rxrpc/rxgk.c | 1170 ++++++++++++++++++++++++++++++ net/rxrpc/rxgk_app.c | 284 ++++++++ net/rxrpc/rxgk_common.h | 140 ++++ net/rxrpc/rxgk_kdf.c | 287 ++++++++ net/rxrpc/rxkad.c | 6 +- net/rxrpc/security.c | 3 + 37 files changed, 6874 insertions(+), 5 deletions(-) create mode 100644 Documentation/crypto/krb5.rst create mode 100644 crypto/krb5/Kconfig create mode 100644 crypto/krb5/Makefile create mode 100644 crypto/krb5/internal.h create mode 100644 crypto/krb5/krb5_api.c create mode 100644 crypto/krb5/krb5_kdf.c create mode 100644 crypto/krb5/rfc3961_simplified.c create mode 100644 crypto/krb5/rfc3962_aes.c create mode 100644 crypto/krb5/rfc6803_camellia.c create mode 100644 crypto/krb5/rfc8009_aes2.c create mode 100644 crypto/krb5/selftest.c create mode 100644 crypto/krb5/selftest_data.c create mode 100644 crypto/krb5enc.c create mode 100644 include/crypto/krb5.h create mode 100644 net/rxrpc/rxgk.c create mode 100644 net/rxrpc/rxgk_app.c create mode 100644 net/rxrpc/rxgk_common.h create mode 100644 net/rxrpc/rxgk_kdf.c
-- Chuck Lever
