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RFC 8009 enctypes use different crypt formulae than previous
Kerberos 5 encryption types. Section 1 of RFC 8009 explains the
reason for this change:
> The new types conform to the framework specified in [RFC3961],
> but do not use the simplified profile, as the simplified profile
> is not compliant with modern cryptographic best practices such as
> calculating Message Authentication Codes (MACs) over ciphertext
> rather than plaintext.
Add new .encrypt and .decrypt functions to handle this variation.
The new approach described above is referred to as Encrypt-then-MAC
(or EtM). Hence the names of the new functions added here are
prefixed with "krb5_etm_".
A critical second difference with previous crypt formulae is that
the cipher state is included in the computed HMAC. Note however that
for RPCSEC, the initial cipher state is easy to compute on both
initiator and acceptor because it is always all zeroes.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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The RFC 8009 encryption types use a different key derivation
function than the RFC 3962 encryption types. The new key derivation
function is defined in Section 3 of RFC 8009.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Fill in entries in the supported_gss_krb5_enctypes array for the
encryption types defined in RFC 8009. These new enctypes use the
SHA-256 and SHA-384 message digest algorithms (as defined in
FIPS-180) instead of the deprecated SHA-1 algorithm, and are thus
more secure.
Note that NIST has scheduled SHA-1 for deprecation:
https://www.nist.gov/news-events/news/2022/12/nist-retires-sha-1-cryptographic-algorithm
Thus these new encryption types are placed under a separate CONFIG
option to enable distributors to separately introduce support for
the AES-SHA2 enctypes and deprecate support for the current set of
AES-SHA1 encryption types as their user space allows.
As this implementation is still a "beta", the default is to not
build it automatically.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Cryptosystem profile enctypes all use cipher block chaining
with ciphertext steal (CBC-with-CTS). However enctypes that are
currently supported in the Linux kernel SunRPC implementation
use only the encrypt-&-MAC approach. The RFC 8009 enctypes use
encrypt-then-MAC, which performs encryption and checksumming in
a different order.
Refactor to make it possible to share the CBC with CTS encryption
and decryption mechanisms between e&M and etM enctypes.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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The aes256-cts-hmac-sha384-192 enctype specifies the length of its
checksum and integrity subkeys as 192 bits, but the length of its
encryption subkey (Ke) as 256 bits. Add new fields to struct
gss_krb5_enctype that specify the key lengths individually, and
where needed, use the correct new field instead of ->keylength.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Although the Kerberos specs have always listed separate subkey
lengths, the Linux kernel's SunRPC GSS Kerberos enctype profiles
assume the base key and the derived keys have identical lengths.
The aes256-cts-hmac-sha384-192 enctype specifies the length of its
checksum and integrity subkeys as 192 bits, but the length of its
encryption subkey (Ke) as 256 bits.
To support that enctype, parametrize context_v2_alloc_cipher() so
that each of its call sites can pass in its desired key length. For
now it will be the same length as before (gk5e->keylength), but a
subsequent patch will change this.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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De-duplicate some common code.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Each Kerberos enctype can have a different KDF. Refactor the key
derivation path to support different KDFs for the enctypes
introduced in subsequent patches.
In particular, expose the key derivation function in struct
gss_krb5_enctype instead of the enctype's preferred random-to-key
function. The latter is usually the identity function and is only
ever called during key derivation, so have each KDF call it
directly.
A couple of extra clean-ups:
- Deduplicate the set_cdata() helper
- Have ->derive_key return negative errnos, in accordance with usual
kernel coding conventions
This patch is a little bigger than I'd like, but these are all
mechanical changes and they are all to the same areas of code. No
behavior change is intended.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Clean up: there is now only one encrypt and only one decrypt method,
thus there is no longer a need for the v2-suffixed method names.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Clean up: ->encrypt is set to only one value. Replace the two
remaining call sites with direct calls to krb5_encrypt().
There have never been any call sites for the ->decrypt() method.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Because the DES block cipher has been deprecated by Internet
standard, highly secure configurations might require that DES
support be blacklisted or not installed. NFS Kerberos should still
be able to work correctly with only the AES-based enctypes in that
situation.
Also note that MIT Kerberos has begun a deprecation process for DES
encryption types. Their README for 1.19.3 states:
> Beginning with the krb5-1.19 release, a warning will be issued
> if initial credentials are acquired using the des3-cbc-sha1
> encryption type. In future releases, this encryption type will
> be disabled by default and eventually removed.
>
> Beginning with the krb5-1.18 release, single-DES encryption
> types have been removed.
Aside from the CONFIG option name change, there are two important
policy changes:
1. The 'insecure enctype' group is now disabled by default.
Distributors have to take action to enable support for deprecated
enctypes. Implementation of these enctypes will be removed in a
future kernel release.
2. des3-cbc-sha1 is now considered part of the 'insecure enctype'
group, having been deprecated by RFC 8429, and is thus disabled
by default
After this patch is applied, SunRPC support can be built with
Kerberos 5 support but without CRYPTO_DES enabled in the kernel.
And, when these enctypes are disabled, the Linux kernel's SunRPC
RPCSEC GSS implementation fully complies with BCP 179 / RFC 6649
and BCP 218 / RFC 8429.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Now that all consumers of the KRB5_SUPPORTED_ENCTYPES macro are
within the SunRPC layer, the macro can be replaced with something
private and more flexible.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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I would like to replace the KRB5_SUPPORTED_ENCTYPES macro so that
there is finer granularity about what enctype support is built in
to the kernel and then advertised by it.
The /proc/fs/nfsd/supported_krb5_enctypes file is a legacy API
that advertises supported enctypes to rpc.svcgssd (I think?). It
simply prints the value of the KRB5_SUPPORTED_ENCTYPES macro, so it
will need to be replaced with something that can instead display
exactly which enctypes are configured and built into the SunRPC
layer.
Completely decommissioning such APIs is hard. Instead, add a file
that is managed by SunRPC's GSS Kerberos mechanism, which is
authoritative about enctype support status. A subsequent patch will
replace /proc/fs/nfsd/supported_krb5_enctypes with a symlink to this
new file.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Replace another switch on encryption type so that it does not have
to be modified when adding or removing support for an enctype.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Replace a number of switches on encryption type so that all of them don't
have to be modified when adding or removing support for an enctype.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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There's no need to keep the integrity keys around if we instead
allocate and key a pair of ahashes and keep those. This not only
enables the subkeys to be destroyed immediately after deriving
them, but it makes the Kerberos integrity code path more efficient.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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There's no need to keep the signing keys around if we instead allocate
and key an ahash and keep that. This not only enables the subkeys to
be destroyed immediately after deriving them, but it makes the
Kerberos signing code path more efficient.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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The encryption subkeys are not used after the cipher transforms have
been allocated and keyed. There is no need to retain them in struct
krb5_ctx.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Hoist the name of the aux_cipher into struct gss_krb5_enctype to
prepare for obscuring the encryption keys just after they are
derived.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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ctx->Ksess is never used after import has completed. Obscure it
immediately so it cannot be re-used or copied.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Other common Kerberos implementations use a fully random confounder
for encryption. The reason for this is explained in the new comment
added by this patch. The current get_random_bytes() implementation
does not exhaust system entropy.
Since confounder generation is part of Kerberos itself rather than
the GSS-API Kerberos mechanism, the function is renamed and moved.
Note that light top-down analysis shows that the SHA-1 transform
is by far the most CPU-intensive part of encryption. Thus we do not
expect this change to result in a significant performance impact.
However, eventually it might be necessary to generate an independent
stream of confounders for each Kerberos context to help improve I/O
parallelism.
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Now that arcfour-hmac is gone, the confounder length is again the
same as the cipher blocksize for every implemented enctype. The
gss_krb5_enctype::conflen field is no longer necessary.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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It is not clear from documenting comments, specifications, or code
usage what value the gss_krb5_enctype.blocksize field is supposed
to store. The "encryption blocksize" depends only on the cipher
being used, so that value can be derived where it's needed instead
of stored as a constant.
RFC 3961 Section 5.2 says:
> cipher block size, c
> This is the block size of the block cipher underlying the
> encryption and decryption functions indicated above, used for key
> derivation and for the size of the message confounder and initial
> vector. (If a block cipher is not in use, some comparable
> parameter should be determined.) It must be at least 5 octets.
>
> This is not actually an independent parameter; rather, it is a
> property of the functions E and D. It is listed here to clarify
> the distinction between it and the message block size, m.
In the Linux kernel's implemenation of the SunRPC RPCSEC GSS
Kerberos 5 mechanism, the cipher block size, which is dependent on
the encryption and decryption transforms, is used only in
krb5_derive_key(), so it is straightforward to replace it.
Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Now that svcauth_gss_prepare_to_wrap() no longer computes the
location of RPC header fields in the response buffer,
svcauth_gss_accept() can save the location of the databody
rather than the location of the verifier.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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To navigate around the space that svcauth_gss_accept() reserves
for the RPC payload body length and sequence number fields,
svcauth_gss_release() does a little dance with the reply's
accept_stat, moving the accept_stat value in the response buffer
down by two words.
Instead, let's have the ->accept() methods each set the proper
final location of the accept_stat to avoid having to move
things.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Now that each ->accept method has been converted, the
svcxdr_init_encode() calls can be hoisted back up into the generic
RPC server code.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Done as part of hardening the server-side RPC header encoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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This code constructs replies to the decorated NULL procedure calls
that establish GSS contexts. Convert this code path to use struct
xdr_stream to encode such responses.
Done as part of hardening the server-side RPC header encoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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We're now moving svcxdr_init_encode() to /before/ the flavor's
->accept method has set rq_auth_slack. Add a helper that can
set rq_auth_slack /after/ svcxdr_init_encode() has been called.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Refactor: So that the overhaul of each ->accept method can be done
in separate smaller patches, temporarily move the
svcxdr_init_encode() call into those methods.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Commit 5b304bc5bfcc ("[PATCH] knfsd: svcrpc: gss: fix failure on
SVC_DENIED in integrity case") added a check to prevent wrapping an
RPC response if reply_stat == MSG_DENIED, assuming that the only way
to get to svcauth_gss_release() with that reply_stat value was if
the reject_stat was AUTH_ERROR (reject_stat == MISMATCH is handled
earlier in svc_process_common()).
The code there is somewhat confusing. For one thing, rpc_success is
an accept_stat value, not a reply_stat value. The correct reply_stat
value to look for is RPC_MSG_DENIED. It happens to be the same value
as rpc_success, so it all works out, but it's not terribly readable.
Since commit 438623a06bac ("SUNRPC: Add svc_rqst::rq_auth_stat"),
the actual auth_stat value is stored in the svc_rqst, so that value
is now available to svcauth_gss_prepare_to_wrap() to make its
decision to wrap, based on direct information about the
authentication status of the RPC caller.
No behavior change is intended, this simply replaces some old code
with something that should be more self-documenting.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Actually xdr_stream does not add value here because of how
gss_wrap() works. This is just a clean-up patch.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Simplify the references to the head and tail iovecs for readability.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Match the error reporting in the other unwrap and wrap functions.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Clean up variable names to match the other unwrap and wrap
functions.
Additionally, the explicit type cast on @gsd in unnecessary; and
@resbuf is renamed to match the variable naming in the unwrap
functions.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Done as part of hardening the server-side RPC header decoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Replace finicky logic: Instead of trying to find scratch space in
the response buffer, use the scratch buffer from struct
gss_svc_data.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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An error computing the checksum here is an exceptional event.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Clean up: To help orient readers, name the stack variables to match
the XDR field names.
Additionally, the explicit type cast on @gsd is unnecessary; and
@resbuf is renamed to match the variable naming in the unwrap
functions.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Now that upper layers use an xdr_stream to track the construction
of each RPC Reply message, resbuf->len is kept up-to-date
automatically. There's no need to recompute it in svc_gss_release().
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Now that each ->accept method has been converted to use xdr_stream,
the svcxdr_init_decode() calls can be hoisted back up into the
generic RPC server code.
The dprintk in svc_authenticate() is removed, since
trace_svc_authenticate() reports the same information.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Done as part of hardening the server-side RPC header decoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Micro-optimizations:
1. The value of rqstp->rq_auth_stat is replaced no matter which
arm of the switch is taken, so the initial assignment can be
safely removed.
2. Avoid checking the value of gc->gc_proc twice in the I/O
(RPC_GSS_PROC_DATA) path.
The cost is a little extra code redundancy.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Done as part of hardening the server-side RPC header decoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Done as part of hardening the server-side RPC header decoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Clean up: To help orient readers, name the stack variables to match
the XDR field names.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Done as part of hardening the server-side RPC header decoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Clean up: To help orient readers, name the stack variables to match
the XDR field names.
For readability, I'm also going to rename the unwrap and wrap
functions in a consistent manner, starting with unwrap_integ_data().
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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Clean up / code de-duplication - this functionality is already
available in the generic XDR layer.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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The entire RPC_GSS_PROC_INIT path is converted over to xdr_stream
for decoding the Call credential and verifier.
Done as part of hardening the server-side RPC header decoding path.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
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