gssapictx.c

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/*
 * Copyright (C) 2004-2015  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 2000, 2001  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: gssapictx.c,v 1.29 2011/08/29 06:33:25 marka Exp $ */

#include <config.h>

#include <ctype.h>
#include <stdlib.h>
#include <string.h>

#include <isc/buffer.h>
#include <isc/dir.h>
#include <isc/entropy.h>
#include <isc/file.h>
#include <isc/lex.h>
#include <isc/mem.h>
#include <isc/once.h>
#include <isc/print.h>
#include <isc/platform.h>
#include <isc/random.h>
#include <isc/string.h>
#include <isc/time.h>
#include <isc/util.h>

#include <dns/fixedname.h>
#include <dns/name.h>
#include <dns/rdata.h>
#include <dns/rdataclass.h>
#include <dns/result.h>
#include <dns/types.h>
#include <dns/keyvalues.h>
#include <dns/log.h>

#include <dst/gssapi.h>
#include <dst/result.h>

#include "dst_internal.h"

/*
 * If we're using our own SPNEGO implementation (see configure.in),
 * pull it in now.  Otherwise, we just use whatever GSSAPI supplies.
 */
#if defined(GSSAPI) && defined(USE_ISC_SPNEGO)
#include "spnego.h"
#define gss_accept_sec_context  gss_accept_sec_context_spnego
#define gss_init_sec_context    gss_init_sec_context_spnego
#endif

/*
 * Solaris8 apparently needs an explicit OID set, and Solaris10 needs
 * one for anything but Kerberos.  Supplying an explicit OID set
 * doesn't appear to hurt anything in other implementations, so we
 * always use one.  If we're not using our own SPNEGO implementation,
 * we include SPNEGO's OID.
 */
#ifdef GSSAPI
#ifdef WIN32
#include <krb5/krb5.h>
#else
#include ISC_PLATFORM_KRB5HEADER
#endif

static unsigned char krb5_mech_oid_bytes[] = {
        0x2a, 0x86, 0x48, 0x86, 0xf7, 0x12, 0x01, 0x02, 0x02
};

#ifndef USE_ISC_SPNEGO
static unsigned char spnego_mech_oid_bytes[] = {
        0x2b, 0x06, 0x01, 0x05, 0x05, 0x02
};
#endif

static gss_OID_desc mech_oid_set_array[] = {
        { sizeof(krb5_mech_oid_bytes), krb5_mech_oid_bytes },
#ifndef USE_ISC_SPNEGO
        { sizeof(spnego_mech_oid_bytes), spnego_mech_oid_bytes },
#endif
};

static gss_OID_set_desc mech_oid_set = {
        sizeof(mech_oid_set_array) / sizeof(*mech_oid_set_array),
        mech_oid_set_array
};

#endif

#define REGION_TO_GBUFFER(r, gb) \
        do { \
                (gb).length = (r).length; \
                (gb).value = (r).base; \
        } while (0)

#define GBUFFER_TO_REGION(gb, r) \
        do { \
          (r).length = (unsigned int)(gb).length; \
                (r).base = (gb).value; \
        } while (0)


#define RETERR(x) do { \
        result = (x); \
        if (result != ISC_R_SUCCESS) \
                goto out; \
        } while (0)

#ifdef GSSAPI
static inline void
name_to_gbuffer(dns_name_t *name, isc_buffer_t *buffer,
                gss_buffer_desc *gbuffer)
{
        dns_name_t tname, *namep;
        isc_region_t r;
        isc_result_t result;

        if (!dns_name_isabsolute(name))
                namep = name;
        else
        {
                unsigned int labels;
                dns_name_init(&tname, NULL);
                labels = dns_name_countlabels(name);
                dns_name_getlabelsequence(name, 0, labels - 1, &tname);
                namep = &tname;
        }

        result = dns_name_toprincipal(namep, buffer);
        RUNTIME_CHECK(result == ISC_R_SUCCESS);
        isc_buffer_putuint8(buffer, 0);
        isc_buffer_usedregion(buffer, &r);
        REGION_TO_GBUFFER(r, *gbuffer);
}

static void
log_cred(const gss_cred_id_t cred) {
        OM_uint32 gret, minor, lifetime;
        gss_name_t gname;
        gss_buffer_desc gbuffer;
        gss_cred_usage_t usage;
        const char *usage_text;
        char buf[1024];

        gret = gss_inquire_cred(&minor, cred, &gname, &lifetime, &usage, NULL);
        if (gret != GSS_S_COMPLETE) {
                gss_log(3, "failed gss_inquire_cred: %s",
                        gss_error_tostring(gret, minor, buf, sizeof(buf)));
                return;
        }

        gret = gss_display_name(&minor, gname, &gbuffer, NULL);
        if (gret != GSS_S_COMPLETE)
                gss_log(3, "failed gss_display_name: %s",
                        gss_error_tostring(gret, minor, buf, sizeof(buf)));
        else {
                switch (usage) {
                case GSS_C_BOTH:
                        usage_text = "GSS_C_BOTH";
                        break;
                case GSS_C_INITIATE:
                        usage_text = "GSS_C_INITIATE";
                        break;
                case GSS_C_ACCEPT:
                        usage_text = "GSS_C_ACCEPT";
                        break;
                default:
                        usage_text = "???";
                }
                gss_log(3, "gss cred: \"%s\", %s, %lu", (char *)gbuffer.value,
                        usage_text, (unsigned long)lifetime);
        }

        if (gret == GSS_S_COMPLETE) {
                if (gbuffer.length != 0U) {
                        gret = gss_release_buffer(&minor, &gbuffer);
                        if (gret != GSS_S_COMPLETE)
                                gss_log(3, "failed gss_release_buffer: %s",
                                        gss_error_tostring(gret, minor, buf,
                                                           sizeof(buf)));
                }
        }

        gret = gss_release_name(&minor, &gname);
        if (gret != GSS_S_COMPLETE)
                gss_log(3, "failed gss_release_name: %s",
                        gss_error_tostring(gret, minor, buf, sizeof(buf)));
}
#endif

#ifdef GSSAPI
/*
 * check for the most common configuration errors.
 *
 * The errors checked for are:
 *   - tkey-gssapi-credential doesn't start with DNS/
 *   - the default realm in /etc/krb5.conf and the
 *     tkey-gssapi-credential bind config option don't match
 *
 * Note that if tkey-gssapi-keytab is set then these configure checks
 * are not performed, and runtime errors from gssapi are used instead
 */
static void
check_config(const char *gss_name) {
        const char *p;
        krb5_context krb5_ctx;
        char *krb5_realm_name = NULL;

        if (strncasecmp(gss_name, "DNS/", 4) != 0) {
                gss_log(ISC_LOG_ERROR, "tkey-gssapi-credential (%s) "
                        "should start with 'DNS/'", gss_name);
                return;
        }

        if (krb5_init_context(&krb5_ctx) != 0) {
                gss_log(ISC_LOG_ERROR, "Unable to initialise krb5 context");
                return;
        }
        if (krb5_get_default_realm(krb5_ctx, &krb5_realm_name) != 0) {
                gss_log(ISC_LOG_ERROR, "Unable to get krb5 default realm");
                krb5_free_context(krb5_ctx);
                return;
        }
        p = strchr(gss_name, '@');
        if (p == NULL) {
                gss_log(ISC_LOG_ERROR, "badly formatted "
                        "tkey-gssapi-credentials (%s)", gss_name);
                krb5_free_context(krb5_ctx);
                return;
        }
        if (strcasecmp(p + 1, krb5_realm_name) != 0) {
                gss_log(ISC_LOG_ERROR, "default realm from krb5.conf (%s) "
                        "does not match tkey-gssapi-credential (%s)",
                        krb5_realm_name, gss_name);
                krb5_free_context(krb5_ctx);
                return;
        }
        krb5_free_context(krb5_ctx);
}
#endif

isc_result_t
dst_gssapi_acquirecred(dns_name_t *name, isc_boolean_t initiate,
                       gss_cred_id_t *cred)
{
#ifdef GSSAPI
        isc_result_t result;
        isc_buffer_t namebuf;
        gss_name_t gname;
        gss_buffer_desc gnamebuf;
        unsigned char array[DNS_NAME_MAXTEXT + 1];
        OM_uint32 gret, minor;
        OM_uint32 lifetime;
        gss_cred_usage_t usage;
        char buf[1024];

        REQUIRE(cred != NULL && *cred == NULL);

        /*
         * XXXSRA In theory we could use GSS_C_NT_HOSTBASED_SERVICE
         * here when we're in the acceptor role, which would let us
         * default the hostname and use a compiled in default service
         * name of "DNS", giving one less thing to configure in
         * named.conf.  Unfortunately, this creates a circular
         * dependency due to DNS-based realm lookup in at least one
         * GSSAPI implementation (Heimdal).  Oh well.
         */
        if (name != NULL) {
                isc_buffer_init(&namebuf, array, sizeof(array));
                name_to_gbuffer(name, &namebuf, &gnamebuf);
                gret = gss_import_name(&minor, &gnamebuf,
                                       GSS_C_NO_OID, &gname);
                if (gret != GSS_S_COMPLETE) {
                        check_config((char *)array);

                        gss_log(3, "failed gss_import_name: %s",
                                gss_error_tostring(gret, minor, buf,
                                                   sizeof(buf)));
                        return (ISC_R_FAILURE);
                }
        } else
                gname = NULL;

        /* Get the credentials. */
        if (gname != NULL)
                gss_log(3, "acquiring credentials for %s",
                        (char *)gnamebuf.value);
        else {
                /* XXXDCL does this even make any sense? */
                gss_log(3, "acquiring credentials for ?");
        }

        if (initiate)
                usage = GSS_C_INITIATE;
        else
                usage = GSS_C_ACCEPT;

        gret = gss_acquire_cred(&minor, gname, GSS_C_INDEFINITE,
                                &mech_oid_set, usage, cred, NULL, &lifetime);

        if (gret != GSS_S_COMPLETE) {
                gss_log(3, "failed to acquire %s credentials for %s: %s",
                        initiate ? "initiate" : "accept",
                        (gname != NULL) ? (char *)gnamebuf.value : "?",
                        gss_error_tostring(gret, minor, buf, sizeof(buf)));
                if (gname != NULL)
                        check_config((char *)array);
                result = ISC_R_FAILURE;
                goto cleanup;
        }

        gss_log(4, "acquired %s credentials for %s",
                initiate ? "initiate" : "accept",
                (gname != NULL) ? (char *)gnamebuf.value : "?");

        log_cred(*cred);
        result = ISC_R_SUCCESS;

cleanup:
        if (gname != NULL) {
                gret = gss_release_name(&minor, &gname);
                if (gret != GSS_S_COMPLETE)
                        gss_log(3, "failed gss_release_name: %s",
                                gss_error_tostring(gret, minor, buf,
                                                   sizeof(buf)));
        }

        return (result);
#else
        REQUIRE(cred != NULL && *cred == NULL);

        UNUSED(name);
        UNUSED(initiate);
        UNUSED(cred);

        return (ISC_R_NOTIMPLEMENTED);
#endif
}

isc_boolean_t
dst_gssapi_identitymatchesrealmkrb5(dns_name_t *signer, dns_name_t *name,
                                    dns_name_t *realm)
{
#ifdef GSSAPI
        char sbuf[DNS_NAME_FORMATSIZE];
        char nbuf[DNS_NAME_FORMATSIZE];
        char rbuf[DNS_NAME_FORMATSIZE];
        char *sname;
        char *rname;
        isc_buffer_t buffer;
        isc_result_t result;

        /*
         * It is far, far easier to write the names we are looking at into
         * a string, and do string operations on them.
         */
        isc_buffer_init(&buffer, sbuf, sizeof(sbuf));
        result = dns_name_toprincipal(signer, &buffer);
        RUNTIME_CHECK(result == ISC_R_SUCCESS);
        isc_buffer_putuint8(&buffer, 0);
        if (name != NULL)
                dns_name_format(name, nbuf, sizeof(nbuf));
        dns_name_format(realm, rbuf, sizeof(rbuf));

        /*
         * Find the realm portion.  This is the part after the @.  If it
         * does not exist, we don't have something we like, so we fail our
         * compare.
         */
        rname = strchr(sbuf, '@');
        if (rname == NULL)
                return (isc_boolean_false);
        *rname = '\0';
        rname++;

        /*
         * Find the host portion of the signer's name.  We do this by
         * searching for the first / character.  We then check to make
         * certain the instance name is "host"
         *
         * This will work for
         *    host/example.com@EXAMPLE.COM
         */
        sname = strchr(sbuf, '/');
        if (sname == NULL)
                return (isc_boolean_false);
        *sname = '\0';
        sname++;
        if (strcmp(sbuf, "host") != 0)
                return (isc_boolean_false);

        /*
         * Now, we do a simple comparison between the name and the realm.
         */
        if (name != NULL) {
                if ((strcasecmp(sname, nbuf) == 0)
                    && (strcmp(rname, rbuf) == 0))
                        return (isc_boolean_true);
        } else {
                if (strcmp(rname, rbuf) == 0)
                        return (isc_boolean_true);
        }

        return (isc_boolean_false);
#else
        UNUSED(signer);
        UNUSED(name);
        UNUSED(realm);
        return (isc_boolean_false);
#endif
}

isc_boolean_t
dst_gssapi_identitymatchesrealmms(dns_name_t *signer, dns_name_t *name,
                                  dns_name_t *realm)
{
#ifdef GSSAPI
        char sbuf[DNS_NAME_FORMATSIZE];
        char nbuf[DNS_NAME_FORMATSIZE];
        char rbuf[DNS_NAME_FORMATSIZE];
        char *sname;
        char *nname;
        char *rname;
        isc_buffer_t buffer;
        isc_result_t result;

        /*
         * It is far, far easier to write the names we are looking at into
         * a string, and do string operations on them.
         */
        isc_buffer_init(&buffer, sbuf, sizeof(sbuf));
        result = dns_name_toprincipal(signer, &buffer);
        RUNTIME_CHECK(result == ISC_R_SUCCESS);
        isc_buffer_putuint8(&buffer, 0);
        if (name != NULL)
                dns_name_format(name, nbuf, sizeof(nbuf));
        dns_name_format(realm, rbuf, sizeof(rbuf));

        /*
         * Find the realm portion.  This is the part after the @.  If it
         * does not exist, we don't have something we like, so we fail our
         * compare.
         */
        rname = strchr(sbuf, '@');
        if (rname == NULL)
                return (isc_boolean_false);
        sname = strchr(sbuf, '$');
        if (sname == NULL)
                return (isc_boolean_false);

        /*
         * Verify that the $ and @ follow one another.
         */
        if (rname - sname != 1)
                return (isc_boolean_false);

        /*
         * Find the host portion of the signer's name.  Zero out the $ so
         * it terminates the signer's name, and skip past the @ for
         * the realm.
         *
         * All service principals in Microsoft format seem to be in
         *    machinename$@EXAMPLE.COM
         * format.
         */
        rname++;
        *sname = '\0';
        sname = sbuf;

        /*
         * Find the first . in the target name, and make it the end of
         * the string.   The rest of the name has to match the realm.
         */
        if (name != NULL) {
                nname = strchr(nbuf, '.');
                if (nname == NULL)
                        return (isc_boolean_false);
                *nname++ = '\0';
        }

        /*
         * Now, we do a simple comparison between the name and the realm.
         */
        if (name != NULL) {
                if ((strcasecmp(sname, nbuf) == 0)
                    && (strcmp(rname, rbuf) == 0)
                    && (strcasecmp(nname, rbuf) == 0))
                        return (isc_boolean_true);
        } else {
                if (strcmp(rname, rbuf) == 0)
                        return (isc_boolean_true);
        }


        return (isc_boolean_false);
#else
        UNUSED(signer);
        UNUSED(name);
        UNUSED(realm);
        return (isc_boolean_false);
#endif
}

isc_result_t
dst_gssapi_releasecred(gss_cred_id_t *cred) {
#ifdef GSSAPI
        OM_uint32 gret, minor;
        char buf[1024];

        REQUIRE(cred != NULL && *cred != NULL);

        gret = gss_release_cred(&minor, cred);
        if (gret != GSS_S_COMPLETE) {
                /* Log the error, but still free the credential's memory */
                gss_log(3, "failed releasing credential: %s",
                        gss_error_tostring(gret, minor, buf, sizeof(buf)));
        }
        *cred = NULL;

        return(ISC_R_SUCCESS);
#else
        UNUSED(cred);

        return (ISC_R_NOTIMPLEMENTED);
#endif
}

#ifdef GSSAPI
/*
 * Format a gssapi error message info into a char ** on the given memory
 * context. This is used to return gssapi error messages back up the
 * call chain for reporting to the user.
 */
static void
gss_err_message(isc_mem_t *mctx, isc_uint32_t major, isc_uint32_t minor,
                char **err_message)
{
        char buf[1024];
        char *estr;

        if (err_message == NULL || mctx == NULL) {
                /* the caller doesn't want any error messages */
                return;
        }

        estr = gss_error_tostring(major, minor, buf, sizeof(buf));
        if (estr != NULL)
                (*err_message) = isc_mem_strdup(mctx, estr);
}
#endif

isc_result_t
dst_gssapi_initctx(dns_name_t *name, isc_buffer_t *intoken,
                   isc_buffer_t *outtoken, gss_ctx_id_t *gssctx,
                   isc_mem_t *mctx, char **err_message)
{
#ifdef GSSAPI
        isc_region_t r;
        isc_buffer_t namebuf;
        gss_name_t gname;
        OM_uint32 gret, minor, ret_flags, flags;
        gss_buffer_desc gintoken, *gintokenp, gouttoken = GSS_C_EMPTY_BUFFER;
        isc_result_t result;
        gss_buffer_desc gnamebuf;
        unsigned char array[DNS_NAME_MAXTEXT + 1];

        /* Client must pass us a valid gss_ctx_id_t here */
        REQUIRE(gssctx != NULL);
        REQUIRE(mctx != NULL);

        isc_buffer_init(&namebuf, array, sizeof(array));
        name_to_gbuffer(name, &namebuf, &gnamebuf);

        /* Get the name as a GSS name */
        gret = gss_import_name(&minor, &gnamebuf, GSS_C_NO_OID, &gname);
        if (gret != GSS_S_COMPLETE) {
                gss_err_message(mctx, gret, minor, err_message);
                result = ISC_R_FAILURE;
                goto out;
        }

        if (intoken != NULL) {
                /* Don't call gss_release_buffer for gintoken! */
                REGION_TO_GBUFFER(*intoken, gintoken);
                gintokenp = &gintoken;
        } else {
                gintokenp = NULL;
        }

        /*
         * Note that we don't set GSS_C_SEQUENCE_FLAG as Windows DNS
         * servers don't like it.
         */
        flags = GSS_C_REPLAY_FLAG | GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG;

        gret = gss_init_sec_context(&minor, GSS_C_NO_CREDENTIAL, gssctx,
                                    gname, GSS_SPNEGO_MECHANISM, flags,
                                    0, NULL, gintokenp,
                                    NULL, &gouttoken, &ret_flags, NULL);

        if (gret != GSS_S_COMPLETE && gret != GSS_S_CONTINUE_NEEDED) {
                gss_err_message(mctx, gret, minor, err_message);
                if (err_message != NULL && *err_message != NULL)
                        gss_log(3, "Failure initiating security context: %s",
                                *err_message);
                else
                        gss_log(3, "Failure initiating security context");

                result = ISC_R_FAILURE;
                goto out;
        }

        /*
         * XXXSRA Not handled yet: RFC 3645 3.1.1: check ret_flags
         * MUTUAL and INTEG flags, fail if either not set.
         */

        /*
         * RFC 2744 states the a valid output token has a non-zero length.
         */
        if (gouttoken.length != 0U) {
                GBUFFER_TO_REGION(gouttoken, r);
                RETERR(isc_buffer_copyregion(outtoken, &r));
                (void)gss_release_buffer(&minor, &gouttoken);
        }

        if (gret == GSS_S_COMPLETE)
                result = ISC_R_SUCCESS;
        else
                result = DNS_R_CONTINUE;

 out:
        (void)gss_release_name(&minor, &gname);
        return (result);
#else
        UNUSED(name);
        UNUSED(intoken);
        UNUSED(outtoken);
        UNUSED(gssctx);
        UNUSED(mctx);
        UNUSED(err_message);

        return (ISC_R_NOTIMPLEMENTED);
#endif
}

isc_result_t
dst_gssapi_acceptctx(gss_cred_id_t cred,
                     const char *gssapi_keytab,
                     isc_region_t *intoken, isc_buffer_t **outtoken,
                     gss_ctx_id_t *ctxout, dns_name_t *principal,
                     isc_mem_t *mctx)
{
#ifdef GSSAPI
        isc_region_t r;
        isc_buffer_t namebuf;
        gss_buffer_desc gnamebuf = GSS_C_EMPTY_BUFFER, gintoken,
                        gouttoken = GSS_C_EMPTY_BUFFER;
        OM_uint32 gret, minor;
        gss_ctx_id_t context = GSS_C_NO_CONTEXT;
        gss_name_t gname = NULL;
        isc_result_t result;
        char buf[1024];

        REQUIRE(outtoken != NULL && *outtoken == NULL);

        REGION_TO_GBUFFER(*intoken, gintoken);

        if (*ctxout == NULL)
                context = GSS_C_NO_CONTEXT;
        else
                context = *ctxout;

        if (gssapi_keytab != NULL) {
#if defined(ISC_PLATFORM_GSSAPI_KRB5_HEADER) || defined(WIN32)
                gret = gsskrb5_register_acceptor_identity(gssapi_keytab);
                if (gret != GSS_S_COMPLETE) {
                        gss_log(3, "failed "
                                "gsskrb5_register_acceptor_identity(%s): %s",
                                gssapi_keytab,
                                gss_error_tostring(gret, 0, buf, sizeof(buf)));
                        return (DNS_R_INVALIDTKEY);
                }
#else
                /*
                 * Minimize memory leakage by only setting KRB5_KTNAME
                 * if it needs to change.
                 */
                const char *old = getenv("KRB5_KTNAME");
                if (old == NULL || strcmp(old, gssapi_keytab) != 0) {
                        char *kt = malloc(strlen(gssapi_keytab) + 13);
                        if (kt == NULL)
                                return (ISC_R_NOMEMORY);
                        sprintf(kt, "KRB5_KTNAME=%s", gssapi_keytab);
                        if (putenv(kt) != 0)
                                return (ISC_R_NOMEMORY);
                }
#endif
        }

        log_cred(cred);

        gret = gss_accept_sec_context(&minor, &context, cred, &gintoken,
                                      GSS_C_NO_CHANNEL_BINDINGS, &gname,
                                      NULL, &gouttoken, NULL, NULL, NULL);

        result = ISC_R_FAILURE;

        switch (gret) {
        case GSS_S_COMPLETE:
                result = ISC_R_SUCCESS;
                break;
        case GSS_S_CONTINUE_NEEDED:
                result = DNS_R_CONTINUE;
                break;
        case GSS_S_DEFECTIVE_TOKEN:
        case GSS_S_DEFECTIVE_CREDENTIAL:
        case GSS_S_BAD_SIG:
        case GSS_S_DUPLICATE_TOKEN:
        case GSS_S_OLD_TOKEN:
        case GSS_S_NO_CRED:
        case GSS_S_CREDENTIALS_EXPIRED:
        case GSS_S_BAD_BINDINGS:
        case GSS_S_NO_CONTEXT:
        case GSS_S_BAD_MECH:
        case GSS_S_FAILURE:
                result = DNS_R_INVALIDTKEY;
                /* fall through */
        default:
                gss_log(3, "failed gss_accept_sec_context: %s",
                        gss_error_tostring(gret, minor, buf, sizeof(buf)));
                return (result);
        }

        if (gouttoken.length > 0U) {
                RETERR(isc_buffer_allocate(mctx, outtoken,
                                           (unsigned int)gouttoken.length));
                GBUFFER_TO_REGION(gouttoken, r);
                RETERR(isc_buffer_copyregion(*outtoken, &r));
                (void)gss_release_buffer(&minor, &gouttoken);
        }

        if (gret == GSS_S_COMPLETE) {
                gret = gss_display_name(&minor, gname, &gnamebuf, NULL);
                if (gret != GSS_S_COMPLETE) {
                        gss_log(3, "failed gss_display_name: %s",
                                gss_error_tostring(gret, minor,
                                                   buf, sizeof(buf)));
                        RETERR(ISC_R_FAILURE);
                }

                /*
                 * Compensate for a bug in Solaris8's implementation
                 * of gss_display_name().  Should be harmless in any
                 * case, since principal names really should not
                 * contain null characters.
                 */
                if (gnamebuf.length > 0U &&
                    ((char *)gnamebuf.value)[gnamebuf.length - 1] == '\0')
                        gnamebuf.length--;

                gss_log(3, "gss-api source name (accept) is %.*s",
                        (int)gnamebuf.length, (char *)gnamebuf.value);

                GBUFFER_TO_REGION(gnamebuf, r);
                isc_buffer_init(&namebuf, r.base, r.length);
                isc_buffer_add(&namebuf, r.length);

                RETERR(dns_name_fromtext(principal, &namebuf, dns_rootname,
                                         0, NULL));

                if (gnamebuf.length != 0U) {
                        gret = gss_release_buffer(&minor, &gnamebuf);
                        if (gret != GSS_S_COMPLETE)
                                gss_log(3, "failed gss_release_buffer: %s",
                                        gss_error_tostring(gret, minor, buf,
                                                           sizeof(buf)));
                }
        }

        *ctxout = context;

 out:
        if (gname != NULL) {
                gret = gss_release_name(&minor, &gname);
                if (gret != GSS_S_COMPLETE)
                        gss_log(3, "failed gss_release_name: %s",
                                gss_error_tostring(gret, minor, buf,
                                                   sizeof(buf)));
        }

        return (result);
#else
        UNUSED(cred);
        UNUSED(gssapi_keytab);
        UNUSED(intoken);
        UNUSED(outtoken);
        UNUSED(ctxout);
        UNUSED(principal);
        UNUSED(mctx);

        return (ISC_R_NOTIMPLEMENTED);
#endif
}

isc_result_t
dst_gssapi_deletectx(isc_mem_t *mctx, gss_ctx_id_t *gssctx)
{
#ifdef GSSAPI
        OM_uint32 gret, minor;
        char buf[1024];

        UNUSED(mctx);

        REQUIRE(gssctx != NULL && *gssctx != NULL);

        /* Delete the context from the GSS provider */
        gret = gss_delete_sec_context(&minor, gssctx, GSS_C_NO_BUFFER);
        if (gret != GSS_S_COMPLETE) {
                /* Log the error, but still free the context's memory */
                gss_log(3, "Failure deleting security context %s",
                        gss_error_tostring(gret, minor, buf, sizeof(buf)));
        }
        return(ISC_R_SUCCESS);
#else
        UNUSED(mctx);
        UNUSED(gssctx);
        return (ISC_R_NOTIMPLEMENTED);
#endif
}

char *
gss_error_tostring(isc_uint32_t major, isc_uint32_t minor,
                   char *buf, size_t buflen) {
#ifdef GSSAPI
        gss_buffer_desc msg_minor = GSS_C_EMPTY_BUFFER,
                        msg_major = GSS_C_EMPTY_BUFFER;
        OM_uint32 msg_ctx, minor_stat;

        /* Handle major status */
        msg_ctx = 0;
        (void)gss_display_status(&minor_stat, major, GSS_C_GSS_CODE,
                                 GSS_C_NULL_OID, &msg_ctx, &msg_major);

        /* Handle minor status */
        msg_ctx = 0;
        (void)gss_display_status(&minor_stat, minor, GSS_C_MECH_CODE,
                                 GSS_C_NULL_OID, &msg_ctx, &msg_minor);

        snprintf(buf, buflen, "GSSAPI error: Major = %s, Minor = %s.",
                (char *)msg_major.value, (char *)msg_minor.value);

        if (msg_major.length != 0U)
                (void)gss_release_buffer(&minor_stat, &msg_major);
        if (msg_minor.length != 0U)
                (void)gss_release_buffer(&minor_stat, &msg_minor);
        return(buf);
#else
        snprintf(buf, buflen, "GSSAPI error: Major = %u, Minor = %u.",
                 major, minor);

        return (buf);
#endif
}

void
gss_log(int level, const char *fmt, ...) {
        va_list ap;

        va_start(ap, fmt);
        isc_log_vwrite(dns_lctx, DNS_LOGCATEGORY_GENERAL,
                       DNS_LOGMODULE_TKEY, ISC_LOG_DEBUG(level), fmt, ap);
        va_end(ap);
}

/*! \file */

---