Fix _gss_spnego_set_sec_context_option() to return GSS_S_UNAVAILABLE if no
context handle is provided, so that mechglue will skip to the next mechanism.
There are no globally settable options on SPNEGO itself.
Fixes: #803
Correctly implement gss_krb5_ccache_name() in terms of
gss_set_sec_context_option(GSS_KRB5_CCACHE_NAME_X). The previous implementation
was a NOOP.
Note: global ccache name should really be thread-specific rather than global.
Closes#803.
We do not need to zero out the local variable output_token
if we do not later call gss_release_buffer() on it.
This aovids a -Werror=address compile failure under the
strict compiler options Samba uses when compiled on Ubuntu
20.04 with gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04)
In file included from ../../source4/heimdal/lib/gssapi/preauth/pa_client.c:34:
../../source4/heimdal/lib/gssapi/preauth/pa_client.c:148:21: error: the address of ‘output_token’ will always evaluate as ‘true’ [-Werror=address]
148 | _mg_buffer_zero(&output_token);
| ^
../../source4/heimdal/lib/gssapi/mech/mech_locl.h:72:7: note: in definition of macro ‘_mg_buffer_zero’
72 | if (buffer) { \
| ^~~~~~
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
When importing a Kerberos name for GSS pre-auth, first try to import the name
as GSS_KRB5_NT_PRINCIPAL_NAME. If that fails, fall back to GSS_C_NT_USER_NAME.
The target (acceptor) name for GSS-API pre-authentication should be the name of
the TGS, not the server name in the AS-REQ, as it is the KDC which is being
mutually authenticated. If the client is not requesting a TGT, they may differ.
Add support for GSS-API pre-authentication to the KDC, using a simplified
variation of draft-perez-krb-wg-gss-preauth-02 that encodes GSS-API context
tokens directly in PADATA, and uses FX-COOKIE for state management.
More information on the protocol and implementation may be found in
lib/gssapi/preauth/README.md.
The functions for storing and retrieving GSS OIDs and buffers from
krb5_storage, added in 6554dc69, are generally useful. Move those into private
_gss_mg_XXX() API and update gss_{export,import}_{cred,sec_context} to use them
where appropriate.
Code style/consistency: store_negoex_auth_mech() should free the exported
context buffer after use. There is no leak as the buffer was freed at the end
of the function.
This function became used outside the protection of
HAVE_DLOPEN (which Samba sets) with:
commit 5966c00701
Author: Luke Howard <lukeh@padl.com>
Date: Sun Aug 8 10:34:28 2021 +1000
gss: add gss_mg_name_to_oid internal API
Add a new function for future internal use, gss_mg_name_to_oid(), which takes
either a dot-separated OID or a "short" mechanism name (such as
"sanon-x25519"), and returns a mechanism OID.
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
gss_{import,export}_sec_context did not work with partially accumulating
contexts, where the initial context token had not been completely accumulated,
Further, in gss_import_sec_context(), ctx->gc_input.value was not allocated to
a buffer sufficiently large to accumulate the target length.
The recently introduced gss_mg_name_to_oid() function supported looking up
dynamically loaded mechanisms by name, but did not support partial matches or
the legacy "Kerberos 5" name as supported by gss_name_to_oid().
Consolidate these into a single function, and also add support for dynamically
loaded mechanisms to gss_oid_to_name().
API behavior difference: the Kerberos mechanism is now referred to by "krb5"
rather tha "Kerberos 5", although for legacy compatibility gss_name_to_oid()
will recognize the old name. However, gss_oid_to_name() will return "krb5". The
anticipated impact is minimal as these are not standard GSS-APIs and do not
appear to have any public usage outside Heimdal.
Add a new function for future internal use, gss_mg_name_to_oid(), which takes
either a dot-separated OID or a "short" mechanism name (such as
"sanon-x25519"), and returns a mechanism OID.
Support for exporting partially established acceptor context tokens. With this,
an acceptor can send the initiator an encrypted state cookie containing the
exported context token.
(The concrete mechanism, of course, must either require a single round trip or
support partial context export itself. Kerberos and GSS EAP would work, but
Kerberos with GSS_C_DCE_STYLE would not, as currently implemented.)
Partial context export is not permitted for initiators.
Microsoft will sometimes split GSS tokens when they exceed a certain
size in some protocols. This is specified in
[MS-SPNG]: Simple and Protected GSS-API Negotiation
Mechanism (SPNEGO) Extension
https://winprotocoldoc.blob.core.windows.net/productionwindowsarchives/MS-SPNG/%5bMS-SPNG%5d.pdf
sections 3.1.5.4 to 3.1.5.9.
We extend gss_accept_sec_context() to recognise partial tokens and
to accumulate the fragments until an entire token is available to
be processed. If the entire token is not yet available,
GSS_S_CONTINUE_NEEDED is returned with a zero length output token.
This is specified in RFC2744 page 25-26 to indicate that no reply
need be sent.
We include updates to the test framework to test split tokens when
using SPNEGO.
When using these functions with gss_init_sec_context(), we noticed
that some things were missing and some needed to be made optional.
ctx->order may be NULL, ctx->ac->authenticator needs to be filled
out, and ctx->state needs be stored.
Note: SPNEGO still needs a little more work.
SAnon includes channel bindings as part of the key derivation function, so they
cannot be ignored. Always set GSS_C_CHANNEL_BOUND_FLAG in the SAnon acceptor.
In acquire_mech_cred(), treat a credential store with no elements as equivalent
to GSS_C_NO_CRED_STORE, allowing a mechanism's gss_acquire_cred()
implementation to be called.
GM_USE_MG_NAME was not honored in the case where the mechanism emitted a name,
but the caller of gss_accept_sec_context() did not request it be returned. This
would result in m->gm_release_name() being called on the mechglue name, which
would crash either because that function pointer was NULL or because it would
have expected a mechanism name.
To avoid future regressions such as the one corrected in 0dd19003, make
IS_DCE_STYLE() an inline function (rather than a macro) so that its
argument is typed.
4b543b7 introduced a regression in the krb5 mechanism's gss_unwrap for
DCE applications, owing to IS_DCE_STYLE() being called with a krb5
instead of mechanism context handle.
Samba compiles Heimdal internally without HAVE_DLOPEN to keep
to internally supplied mechanisms and plugins.
Samba compiles with strict warning flags and on Ubuntu 20.04
with gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04) we see:
../../source4/heimdal/lib/gssapi/mech/gss_mech_switch.c: In function ‘_gss_load_mech’:
../../source4/heimdal/lib/gssapi/mech/gss_mech_switch.c:462:1: error: label ‘out’ defined but not used [-Werror=unused-label]
462 | out:
| ^~~
cc1: all warnings being treated as errors
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Some compilers with -Wstring-concatenation enabled warned about a suspicious
concatenation of string literals in the initialization of the GSS-API error
message array.
At the expense of a long line, avoid this warning but explicitly concatenating
the offending string literal.
Fixes: #775
