3a6229f64a
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.
520 lines
18 KiB
C
520 lines
18 KiB
C
/*-
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* Copyright (c) 2005 Doug Rabson
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD: src/lib/libgssapi/gss_accept_sec_context.c,v 1.1 2005/12/29 14:40:20 dfr Exp $
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*/
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#include "mech_locl.h"
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/*
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* accumulate_token() tries to assemble a complete GSS token which may
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* be fed to it in pieces. Microsoft does this when tokens are too large
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* in CIFS, e.g. It may occur in other places as well. It is specified in:
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*
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* [MS-SPNG]: Simple and Protected GSS-API Negotiation
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* Mechanism (SPNEGO) Extension
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*
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* https://winprotocoldoc.blob.core.windows.net/
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* productionwindowsarchives/MS-SPNG/%5bMS-SPNG%5d.pdf
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*
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* Sections 3.1.5.4 to 3.1.5.9.
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*
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* We only accumulate if we see the appropriate application tag in the
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* first byte of 0x60 because in the absence of this, we cannot interpret
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* the following bytes as a DER length.
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*
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* We only allocate an accumulating buffer if we detect that the token
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* is split between multiple packets as this is the uncommon case and
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* we want to optimise for the common case. If we aren't accumulating,
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* we simply return success.
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*
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* Our return value is GSS_S_CONTINUE_NEEDED if we need more input.
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* We return GSS_S_COMPLETE if we are either finished accumulating or
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* if we decide that we do not understand this token. We only return
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* an error if we think that we should understand the token and still
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* fail to understand it.
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*/
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static OM_uint32
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accumulate_token(struct _gss_context *ctx, gss_buffer_t input_token)
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{
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unsigned char *p = input_token->value;
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size_t len = input_token->length;
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gss_buffer_t gci;
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size_t l;
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/*
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* Token must start with [APPLICATION 0] SEQUENCE.
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* But if it doesn't assume it is DCE-STYLE Kerberos!
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*/
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if (!ctx->gc_target_len) {
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free(ctx->gc_free_this);
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ctx->gc_free_this = NULL;
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_mg_buffer_zero(&ctx->gc_input);
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/*
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* Let's prepare gc_input for the case where
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* we aren't accumulating.
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*/
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ctx->gc_input.length = len;
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ctx->gc_input.value = p;
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if (len == 0)
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return GSS_S_COMPLETE;
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/* Not our DER w/ a length */
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if (*p != 0x60)
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return GSS_S_COMPLETE;
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if (der_get_length(p+1, len-1, &ctx->gc_target_len, &l) != 0)
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return GSS_S_DEFECTIVE_TOKEN;
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_gss_mg_log(10, "gss-asc: DER length: %zu",
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ctx->gc_target_len);
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ctx->gc_oid_offset = l + 1;
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ctx->gc_target_len += ctx->gc_oid_offset;
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_gss_mg_log(10, "gss-asc: total length: %zu",
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ctx->gc_target_len);
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if (ctx->gc_target_len == ASN1_INDEFINITE ||
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ctx->gc_target_len < len)
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return GSS_S_DEFECTIVE_TOKEN;
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/* We've got it all, short-circuit the accumulating */
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if (ctx->gc_target_len == len)
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goto done;
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_gss_mg_log(10, "gss-asc: accumulating partial token");
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ctx->gc_input.length = 0;
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ctx->gc_input.value = calloc(ctx->gc_target_len, 1);
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if (!ctx->gc_input.value)
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return GSS_S_FAILURE;
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ctx->gc_free_this = ctx->gc_input.value;
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}
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if (len == 0)
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return GSS_S_DEFECTIVE_TOKEN;
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gci = &ctx->gc_input;
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if (ctx->gc_target_len > gci->length) {
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if (gci->length + len > ctx->gc_target_len) {
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_gss_mg_log(10, "gss-asc: accumulation exceeded "
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"target length: bailing");
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return GSS_S_DEFECTIVE_TOKEN;
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}
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memcpy((char *)gci->value + gci->length, p, len);
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gci->length += len;
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}
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if (gci->length != ctx->gc_target_len) {
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_gss_mg_log(10, "gss-asc: collected %zu/%zu bytes",
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gci->length, ctx->gc_target_len);
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return GSS_S_CONTINUE_NEEDED;
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}
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done:
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_gss_mg_log(10, "gss-asc: received complete %zu byte token",
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ctx->gc_target_len);
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ctx->gc_target_len = 0;
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return GSS_S_COMPLETE;
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}
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static void
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log_oid(const char *str, gss_OID mech)
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{
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OM_uint32 maj, min;
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gss_buffer_desc buf;
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maj = gss_oid_to_str(&min, mech, &buf);
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if (maj == GSS_S_COMPLETE) {
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_gss_mg_log(10, "%s: %.*s", str, (int)buf.length,
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(char *)buf.value);
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gss_release_buffer(&min, &buf);
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}
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}
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static OM_uint32
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choose_mech(struct _gss_context *ctx)
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{
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gss_OID_desc mech;
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gss_OID mech_oid;
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unsigned char *p = ctx->gc_input.value;
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size_t len = ctx->gc_input.length;
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if (len == 0) {
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/*
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* There is the a wierd mode of SPNEGO (in CIFS and
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* SASL GSS-SPENGO where the first token is zero
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* length and the acceptor returns a mech_list, lets
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* hope that is what is happening now.
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*
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* http://msdn.microsoft.com/en-us/library/cc213114.aspx
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* "NegTokenInit2 Variation for Server-Initiation"
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*/
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mech_oid = &__gss_spnego_mechanism_oid_desc;
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goto gss_get_mechanism;
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}
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p += ctx->gc_oid_offset;
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len -= ctx->gc_oid_offset;
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/*
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* Decode the OID for the mechanism. Simplify life by
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* assuming that the OID length is less than 128 bytes.
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*/
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if (len < 2 || *p != 0x06)
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goto bail;
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if ((p[1] & 0x80) || p[1] > (len - 2))
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goto bail;
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mech.length = p[1];
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p += 2;
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len -= 2;
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mech.elements = p;
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mech_oid = _gss_mg_support_mechanism(&mech);
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if (mech_oid == GSS_C_NO_OID)
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return GSS_S_COMPLETE;
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gss_get_mechanism:
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/*
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* If mech_oid == GSS_C_NO_OID then the mech is non-standard
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* and we have to try all mechs (that we have a cred element
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* for, if we have a cred).
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*/
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if (mech_oid != GSS_C_NO_OID) {
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log_oid("mech oid", mech_oid);
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ctx->gc_mech = __gss_get_mechanism(mech_oid);
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if (!ctx->gc_mech) {
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_gss_mg_log(10, "mechanism client used is unknown");
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return (GSS_S_BAD_MECH);
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}
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_gss_mg_log(10, "using mech \"%s\"", ctx->gc_mech->gm_name);
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return GSS_S_COMPLETE;
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}
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bail:
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_gss_mg_log(10, "no mech oid found");
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return GSS_S_COMPLETE;
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}
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GSSAPI_LIB_FUNCTION OM_uint32 GSSAPI_LIB_CALL
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gss_accept_sec_context(OM_uint32 *minor_status,
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gss_ctx_id_t *context_handle,
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gss_const_cred_id_t acceptor_cred_handle,
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const gss_buffer_t input_token,
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const gss_channel_bindings_t input_chan_bindings,
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gss_name_t *src_name,
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gss_OID *mech_type,
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gss_buffer_t output_token,
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OM_uint32 *ret_flags,
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OM_uint32 *time_rec,
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gss_cred_id_t *delegated_cred_handle)
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{
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OM_uint32 major_status, mech_ret_flags, junk;
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gssapi_mech_interface m = NULL;
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struct _gss_context *ctx = (struct _gss_context *) *context_handle;
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struct _gss_cred *cred = (struct _gss_cred *) acceptor_cred_handle;
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struct _gss_mechanism_cred *mc;
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gss_buffer_desc defective_token_error;
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gss_const_cred_id_t acceptor_mc;
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gss_cred_id_t delegated_mc = GSS_C_NO_CREDENTIAL;
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gss_name_t src_mn = GSS_C_NO_NAME;
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gss_OID mech_ret_type = GSS_C_NO_OID;
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int initial;
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defective_token_error.length = 0;
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defective_token_error.value = NULL;
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*minor_status = 0;
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if (src_name)
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*src_name = GSS_C_NO_NAME;
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if (mech_type)
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*mech_type = GSS_C_NO_OID;
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if (ret_flags)
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*ret_flags = 0;
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if (time_rec)
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*time_rec = 0;
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if (delegated_cred_handle)
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*delegated_cred_handle = GSS_C_NO_CREDENTIAL;
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_mg_buffer_zero(output_token);
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if (!*context_handle) {
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ctx = calloc(sizeof(*ctx), 1);
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if (!ctx) {
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*minor_status = ENOMEM;
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return (GSS_S_DEFECTIVE_TOKEN);
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}
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*context_handle = (gss_ctx_id_t)ctx;
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ctx->gc_initial = 1;
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}
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major_status = accumulate_token(ctx, input_token);
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if (major_status != GSS_S_COMPLETE)
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return major_status;
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/*
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* If we get here, then we have a complete token. Please note
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* that we may have a major_status of GSS_S_DEFECTIVE_TOKEN. This
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*
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*/
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initial = ctx->gc_initial;
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ctx->gc_initial = 0;
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if (major_status == GSS_S_COMPLETE && initial) {
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major_status = choose_mech(ctx);
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if (major_status != GSS_S_COMPLETE)
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return major_status;
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}
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m = ctx->gc_mech;
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if (initial && !m && acceptor_cred_handle == GSS_C_NO_CREDENTIAL) {
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/*
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* No header, not a standard mechanism. Try all the mechanisms
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* (because default credential).
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*/
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struct _gss_mech_switch *ms;
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_gss_load_mech();
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acceptor_mc = GSS_C_NO_CREDENTIAL;
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HEIM_TAILQ_FOREACH(ms, &_gss_mechs, gm_link) {
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m = &ms->gm_mech;
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mech_ret_flags = 0;
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major_status = m->gm_accept_sec_context(minor_status,
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&ctx->gc_ctx,
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acceptor_mc,
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&ctx->gc_input,
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input_chan_bindings,
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&src_mn,
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&mech_ret_type,
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output_token,
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&mech_ret_flags,
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time_rec,
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&delegated_mc);
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if (major_status == GSS_S_DEFECTIVE_TOKEN) {
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/*
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* Try to retain and output one error token for
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* GSS_S_DEFECTIVE_TOKEN. The first one.
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*/
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if (output_token->length &&
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defective_token_error.length == 0) {
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defective_token_error = *output_token;
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output_token->length = 0;
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output_token->value = NULL;
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}
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gss_release_buffer(&junk, output_token);
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continue;
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}
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gss_release_buffer(&junk, &defective_token_error);
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ctx->gc_mech = m;
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goto got_one;
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}
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m = NULL;
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acceptor_mc = GSS_C_NO_CREDENTIAL;
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} else if (initial && !m) {
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/*
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* No header, not a standard mechanism. Try all the mechanisms
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* that we have a credential element for if we have a
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* non-default credential.
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*/
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HEIM_TAILQ_FOREACH(mc, &cred->gc_mc, gmc_link) {
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m = mc->gmc_mech;
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acceptor_mc = (m->gm_flags & GM_USE_MG_CRED) ?
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acceptor_cred_handle : mc->gmc_cred;
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mech_ret_flags = 0;
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major_status = m->gm_accept_sec_context(minor_status,
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&ctx->gc_ctx,
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acceptor_mc,
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&ctx->gc_input,
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input_chan_bindings,
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&src_mn,
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&mech_ret_type,
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output_token,
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&mech_ret_flags,
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time_rec,
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&delegated_mc);
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if (major_status == GSS_S_DEFECTIVE_TOKEN) {
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if (output_token->length &&
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defective_token_error.length == 0) {
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defective_token_error = *output_token;
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output_token->length = 0;
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output_token->value = NULL;
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}
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gss_release_buffer(&junk, output_token);
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continue;
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}
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gss_release_buffer(&junk, &defective_token_error);
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ctx->gc_mech = m;
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goto got_one;
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}
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m = NULL;
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acceptor_mc = GSS_C_NO_CREDENTIAL;
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}
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if (m == NULL) {
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gss_delete_sec_context(&junk, context_handle, NULL);
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_gss_mg_log(10, "No mechanism accepted the non-standard initial security context token");
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*output_token = defective_token_error;
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return GSS_S_BAD_MECH;
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}
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if (m->gm_flags & GM_USE_MG_CRED) {
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acceptor_mc = acceptor_cred_handle;
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} else if (cred) {
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HEIM_TAILQ_FOREACH(mc, &cred->gc_mc, gmc_link)
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if (mc->gmc_mech == m)
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break;
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if (!mc) {
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gss_delete_sec_context(&junk, context_handle, NULL);
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_gss_mg_log(10, "gss-asc: client sent mech %s "
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"but no credential was matching",
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m->gm_name);
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HEIM_TAILQ_FOREACH(mc, &cred->gc_mc, gmc_link)
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_gss_mg_log(10, "gss-asc: available creds were %s", mc->gmc_mech->gm_name);
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return (GSS_S_BAD_MECH);
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}
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acceptor_mc = mc->gmc_cred;
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} else {
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acceptor_mc = GSS_C_NO_CREDENTIAL;
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}
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mech_ret_flags = 0;
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major_status = m->gm_accept_sec_context(minor_status,
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&ctx->gc_ctx,
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acceptor_mc,
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&ctx->gc_input,
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input_chan_bindings,
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&src_mn,
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&mech_ret_type,
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output_token,
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&mech_ret_flags,
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time_rec,
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&delegated_mc);
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got_one:
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if (major_status != GSS_S_COMPLETE &&
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major_status != GSS_S_CONTINUE_NEEDED)
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{
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_gss_mg_error(m, *minor_status);
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gss_delete_sec_context(&junk, context_handle, NULL);
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return (major_status);
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}
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if (mech_type)
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*mech_type = mech_ret_type;
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if (src_name && src_mn) {
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if (ctx->gc_mech->gm_flags & GM_USE_MG_NAME) {
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/* Negotiation mechanisms use mechglue names as names */
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*src_name = src_mn;
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src_mn = GSS_C_NO_NAME;
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} else {
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/*
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* Make a new name and mark it as an MN.
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*
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* Note that _gss_create_name() consumes `src_mn' but doesn't
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* take a pointer, so it can't set it to GSS_C_NO_NAME.
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*/
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struct _gss_name *name = _gss_create_name(src_mn, m);
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if (!name) {
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m->gm_release_name(minor_status, &src_mn);
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gss_delete_sec_context(&junk, context_handle, NULL);
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return (GSS_S_FAILURE);
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}
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*src_name = (gss_name_t) name;
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src_mn = GSS_C_NO_NAME;
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}
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} else if (src_mn) {
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if (ctx->gc_mech->gm_flags & GM_USE_MG_NAME) {
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_gss_mg_release_name((struct _gss_name *)src_mn);
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src_mn = GSS_C_NO_NAME;
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} else {
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m->gm_release_name(minor_status, &src_mn);
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}
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}
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|
|
|
if (mech_ret_flags & GSS_C_DELEG_FLAG) {
|
|
if (!delegated_cred_handle) {
|
|
if (m->gm_flags & GM_USE_MG_CRED)
|
|
gss_release_cred(minor_status, &delegated_mc);
|
|
else
|
|
m->gm_release_cred(minor_status, &delegated_mc);
|
|
mech_ret_flags &=
|
|
~(GSS_C_DELEG_FLAG|GSS_C_DELEG_POLICY_FLAG);
|
|
} else if ((m->gm_flags & GM_USE_MG_CRED) != 0) {
|
|
/*
|
|
* If credential is uses mechglue cred, assume it
|
|
* returns one too.
|
|
*/
|
|
*delegated_cred_handle = delegated_mc;
|
|
} else if (gss_oid_equal(mech_ret_type, &m->gm_mech_oid) == 0) {
|
|
/*
|
|
* If the returned mech_type is not the same
|
|
* as the mech, assume its pseudo mech type
|
|
* and the returned type is already a
|
|
* mech-glue object
|
|
*/
|
|
*delegated_cred_handle = delegated_mc;
|
|
|
|
} else if (delegated_mc) {
|
|
struct _gss_cred *dcred;
|
|
struct _gss_mechanism_cred *dmc;
|
|
|
|
dcred = _gss_mg_alloc_cred();
|
|
if (!dcred) {
|
|
*minor_status = ENOMEM;
|
|
gss_delete_sec_context(&junk, context_handle, NULL);
|
|
return (GSS_S_FAILURE);
|
|
}
|
|
dmc = malloc(sizeof(struct _gss_mechanism_cred));
|
|
if (!dmc) {
|
|
free(dcred);
|
|
*minor_status = ENOMEM;
|
|
gss_delete_sec_context(&junk, context_handle, NULL);
|
|
return (GSS_S_FAILURE);
|
|
}
|
|
dmc->gmc_mech = m;
|
|
dmc->gmc_mech_oid = &m->gm_mech_oid;
|
|
dmc->gmc_cred = delegated_mc;
|
|
HEIM_TAILQ_INSERT_TAIL(&dcred->gc_mc, dmc, gmc_link);
|
|
|
|
*delegated_cred_handle = (gss_cred_id_t) dcred;
|
|
}
|
|
}
|
|
|
|
_gss_mg_log(10, "gss-asc: return %d/%d", (int)major_status, (int)*minor_status);
|
|
|
|
if (ret_flags)
|
|
*ret_flags = mech_ret_flags;
|
|
return (major_status);
|
|
}
|