[RFC PATCH 0/8] crypto: Add generic Kerberos library with crypto as AEAD algorithms

David Howells
2025-01-10T01:03:28Z

Hi Herbert, Chuck,

Here's my next 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. The crypto bits are inside AEAD
algorithms as Herbert required, but there's also a library of supplementary
functions to aid in managing message layout.

You can use:

const struct krb5_enctype *crypto_krb5_find_enctype(u32 enctype);

to go and get an information table and this will also let you get at the
name of the AEAD algorithm associated with that encoding type number.

Each AEAD algorithm is defined for a particular Kerberos 5 type by name
(not by enctype number) and supports both encryption and checksumming
(MIC) through the AEAD encrypt/decrypt request API.

Note that the plain text may be a different size to the cipher text and
this causes the testmgr some issues as it thinks the extra data is an auth
tag (but this doesn't want auth tags).

A kerberos AEAD object is configured through its setkey method and this
takes a compound structure that indicates the mode of operation (encrypt or
checksum), the usage type and either the transport key or the subkeys. The
setkey method allocates and keys the constituent ciphers and hashes - but
that's a detail hidden inside the object.

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.

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 (8):
crypto/krb5: Add some constants out of sunrpc headers
crypto/krb5: Provide Kerberos 5 crypto through AEAD API
crypto/krb5: Test manager data
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

crypto/Kconfig | 1 +
crypto/Makefile | 2 +
crypto/aead.c | 2 +
crypto/krb5/Kconfig | 24 +
crypto/krb5/Makefile | 17 +
crypto/krb5/internal.h | 162 ++++
crypto/krb5/kdf.c | 334 ++++++++
crypto/krb5/krb5_aead.c | 462 +++++++++++
crypto/krb5/rfc3961_simplified.c | 815 +++++++++++++++++++
crypto/krb5/rfc6803_camellia.c | 190 +++++
crypto/krb5/rfc8009_aes2.c | 394 ++++++++++
crypto/krb5/selftest.c | 533 +++++++++++++
crypto/krb5/selftest_data.c | 370 +++++++++
crypto/testmgr.c | 24 +
crypto/testmgr.h | 456 +++++++++++
fs/afs/misc.c | 13 +
include/crypto/aead.h | 2 +
include/crypto/krb5.h | 147 ++++
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 | 1244 ++++++++++++++++++++++++++++++
net/rxrpc/rxgk_app.c | 318 ++++++++
net/rxrpc/rxgk_common.h | 58 ++
net/rxrpc/rxgk_kdf.c | 260 +++++++
net/rxrpc/rxkad.c | 6 +-
net/rxrpc/security.c | 3 +
35 files changed, 6147 insertions(+), 5 deletions(-)
create mode 100644 crypto/krb5/Kconfig
create mode 100644 crypto/krb5/Makefile
create mode 100644 crypto/krb5/internal.h
create mode 100644 crypto/krb5/kdf.c
create mode 100644 crypto/krb5/krb5_aead.c
create mode 100644 crypto/krb5/rfc3961_simplified.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 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