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    SubjectRe: [RFC][PATCH 00/18] crypto: Add generic Kerberos library
    On Thu, Nov 12, 2020 at 12:57:45PM +0000, David Howells wrote:
    >
    > Hi Herbert, Bruce,
    >
    > Here's my first cut 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 haven't ported across the DES-based
    > crypto yet - I figure that can wait a bit till the interface is sorted.
    >
    > Whilst I have put it into a directory under crypto/, I haven't made an
    > interface that goes and loads it (analogous to crypto_alloc_skcipher,
    > say). Instead, you call:
    >
    > const struct krb5_enctype *crypto_krb5_find_enctype(u32 enctype);
    >
    > to go and get a handler table and then use a bunch of accessor functions to
    > jump through the hoops. This is basically the way the sunrpc gsslib does
    > things. It might be worth making it so you do something like:
    >
    > struct crypto_mech *ctx = crypto_mech_alloc("krb5(18)");
    >
    > to get enctype 18, but I'm not sure if it's worth the effort. Also, I'm
    > not sure if there are any alternatives to kerberos we will need to support.

    We did have code for a non-krb5 mechanism at some point, but it was torn
    out. So I don't think that's a priority.

    (Chuck, will RPC-over-SSL need a new non-krb5 mechanism?)

    > There are three main interfaces to it:
    >
    > (*) I/O crypto: encrypt, decrypt, get_mic and verify_mic.
    >
    > These all do in-place crypto, using an sglist to define the buffer
    > with the data in it. Is it necessary to make it able to take separate
    > input and output buffers?

    I don't know. My memory is that the buffer management in the existing
    rpcsec_gss code is complex and fragile. See e.g. the long comment in
    gss_krb5_remove_padding.

    --b.

    > (*) PRF+ calculation for key derivation.
    > (*) Kc, Ke, Ki derivation.
    >
    > These use krb5_buffer structs to pass objects around. This is akin to
    > the xdr_netobj, but has a void* instead of a u8* data pointer.
    >
    > In terms of rxrpc's rxgk, there's another step in key derivation that isn't
    > part of the kerberos standard, but uses the PRF+ function to generate a key
    > that is then used to generate Kc, Ke and Ki. Is it worth putting this into
    > the directory or maybe having a callout to insert an intermediate step in
    > key derivation?
    >
    > 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 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 (18):
    > crypto/krb5: Implement Kerberos crypto core
    > crypto/krb5: Add some constants out of sunrpc headers
    > crypto/krb5: Provide infrastructure and key derivation
    > crypto/krb5: Implement the Kerberos5 rfc3961 key derivation
    > 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 crypto self-testing
    > crypto/krb5: Implement the AES enctypes from rfc8009
    > crypto/krb5: Implement the AES encrypt/decrypt from rfc8009
    > 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
    > rxgk: Support OpenAFS's rxgk implementation
    >
    >
    > crypto/krb5/Kconfig | 9 +
    > crypto/krb5/Makefile | 11 +-
    > crypto/krb5/internal.h | 101 +++
    > crypto/krb5/kdf.c | 223 ++++++
    > crypto/krb5/main.c | 190 +++++
    > crypto/krb5/rfc3961_simplified.c | 732 ++++++++++++++++++
    > crypto/krb5/rfc3962_aes.c | 140 ++++
    > crypto/krb5/rfc6803_camellia.c | 249 ++++++
    > crypto/krb5/rfc8009_aes2.c | 440 +++++++++++
    > crypto/krb5/selftest.c | 543 +++++++++++++
    > crypto/krb5/selftest_data.c | 289 +++++++
    > fs/afs/misc.c | 13 +
    > include/crypto/krb5.h | 100 +++
    > include/keys/rxrpc-type.h | 17 +
    > include/trace/events/rxrpc.h | 4 +
    > include/uapi/linux/rxrpc.h | 17 +
    > net/rxrpc/Kconfig | 10 +
    > net/rxrpc/Makefile | 5 +
    > net/rxrpc/ar-internal.h | 20 +
    > net/rxrpc/conn_object.c | 2 +
    > net/rxrpc/key.c | 319 ++++++++
    > net/rxrpc/rxgk.c | 1232 ++++++++++++++++++++++++++++++
    > net/rxrpc/rxgk_app.c | 424 ++++++++++
    > net/rxrpc/rxgk_common.h | 164 ++++
    > net/rxrpc/rxgk_kdf.c | 271 +++++++
    > net/rxrpc/security.c | 6 +
    > 26 files changed, 5530 insertions(+), 1 deletion(-)
    > create mode 100644 crypto/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 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
    >

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