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+/* $OpenBSD: gss-serv.c,v 1.32 2020/03/13 03:17:07 djm Exp $ */
+
+/*
+ * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "includes.h"
+
+#ifdef GSSAPI
+
+#include <sys/types.h>
+
+#include <stdarg.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "openbsd-compat/sys-queue.h"
+#include "xmalloc.h"
+#include "sshkey.h"
+#include "hostfile.h"
+#include "auth.h"
+#include "log.h"
+#include "channels.h"
+#include "session.h"
+#include "misc.h"
+#include "servconf.h"
+
+#include "ssh-gss.h"
+
+extern ServerOptions options;
+
+static ssh_gssapi_client gssapi_client =
+ { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
+ GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}};
+
+ssh_gssapi_mech gssapi_null_mech =
+ { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
+
+#ifdef KRB5
+extern ssh_gssapi_mech gssapi_kerberos_mech;
+#endif
+
+ssh_gssapi_mech* supported_mechs[]= {
+#ifdef KRB5
+ &gssapi_kerberos_mech,
+#endif
+ &gssapi_null_mech,
+};
+
+/*
+ * ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the
+ * list of supported mechanisms before privsep is set up.
+ */
+static gss_OID_set supported_oids;
+
+void
+ssh_gssapi_prepare_supported_oids(void)
+{
+ ssh_gssapi_supported_oids(&supported_oids);
+}
+
+OM_uint32
+ssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present)
+{
+ if (supported_oids == NULL)
+ ssh_gssapi_prepare_supported_oids();
+ return gss_test_oid_set_member(ms, member, supported_oids, present);
+}
+
+/*
+ * Acquire credentials for a server running on the current host.
+ * Requires that the context structure contains a valid OID
+ */
+
+/* Returns a GSSAPI error code */
+/* Privileged (called from ssh_gssapi_server_ctx) */
+static OM_uint32
+ssh_gssapi_acquire_cred(Gssctxt *ctx)
+{
+ OM_uint32 status;
+ char lname[NI_MAXHOST];
+ gss_OID_set oidset;
+
+ if (options.gss_strict_acceptor) {
+ gss_create_empty_oid_set(&status, &oidset);
+ gss_add_oid_set_member(&status, ctx->oid, &oidset);
+
+ if (gethostname(lname, MAXHOSTNAMELEN)) {
+ gss_release_oid_set(&status, &oidset);
+ return (-1);
+ }
+
+ if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
+ gss_release_oid_set(&status, &oidset);
+ return (ctx->major);
+ }
+
+ if ((ctx->major = gss_acquire_cred(&ctx->minor,
+ ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds,
+ NULL, NULL)))
+ ssh_gssapi_error(ctx);
+
+ gss_release_oid_set(&status, &oidset);
+ return (ctx->major);
+ } else {
+ ctx->name = GSS_C_NO_NAME;
+ ctx->creds = GSS_C_NO_CREDENTIAL;
+ }
+ return GSS_S_COMPLETE;
+}
+
+/* Privileged */
+OM_uint32
+ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
+{
+ if (*ctx)
+ ssh_gssapi_delete_ctx(ctx);
+ ssh_gssapi_build_ctx(ctx);
+ ssh_gssapi_set_oid(*ctx, oid);
+ return (ssh_gssapi_acquire_cred(*ctx));
+}
+
+/* Unprivileged */
+void
+ssh_gssapi_supported_oids(gss_OID_set *oidset)
+{
+ int i = 0;
+ OM_uint32 min_status;
+ int present;
+ gss_OID_set supported;
+
+ gss_create_empty_oid_set(&min_status, oidset);
+ gss_indicate_mechs(&min_status, &supported);
+
+ while (supported_mechs[i]->name != NULL) {
+ if (GSS_ERROR(gss_test_oid_set_member(&min_status,
+ &supported_mechs[i]->oid, supported, &present)))
+ present = 0;
+ if (present)
+ gss_add_oid_set_member(&min_status,
+ &supported_mechs[i]->oid, oidset);
+ i++;
+ }
+
+ gss_release_oid_set(&min_status, &supported);
+}
+
+
+/* Wrapper around accept_sec_context
+ * Requires that the context contains:
+ * oid
+ * credentials (from ssh_gssapi_acquire_cred)
+ */
+/* Privileged */
+OM_uint32
+ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
+ gss_buffer_desc *send_tok, OM_uint32 *flags)
+{
+ OM_uint32 status;
+ gss_OID mech;
+
+ ctx->major = gss_accept_sec_context(&ctx->minor,
+ &ctx->context, ctx->creds, recv_tok,
+ GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
+ send_tok, flags, NULL, &ctx->client_creds);
+
+ if (GSS_ERROR(ctx->major))
+ ssh_gssapi_error(ctx);
+
+ if (ctx->client_creds)
+ debug("Received some client credentials");
+ else
+ debug("Got no client credentials");
+
+ status = ctx->major;
+
+ /* Now, if we're complete and we have the right flags, then
+ * we flag the user as also having been authenticated
+ */
+
+ if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
+ (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
+ if (ssh_gssapi_getclient(ctx, &gssapi_client))
+ fatal("Couldn't convert client name");
+ }
+
+ return (status);
+}
+
+/*
+ * This parses an exported name, extracting the mechanism specific portion
+ * to use for ACL checking. It verifies that the name belongs the mechanism
+ * originally selected.
+ */
+static OM_uint32
+ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
+{
+ u_char *tok;
+ OM_uint32 offset;
+ OM_uint32 oidl;
+
+ tok = ename->value;
+
+ /*
+ * Check that ename is long enough for all of the fixed length
+ * header, and that the initial ID bytes are correct
+ */
+
+ if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
+ return GSS_S_FAILURE;
+
+ /*
+ * Extract the OID, and check it. Here GSSAPI breaks with tradition
+ * and does use the OID type and length bytes. To confuse things
+ * there are two lengths - the first including these, and the
+ * second without.
+ */
+
+ oidl = get_u16(tok+2); /* length including next two bytes */
+ oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
+
+ /*
+ * Check the BER encoding for correct type and length, that the
+ * string is long enough and that the OID matches that in our context
+ */
+ if (tok[4] != 0x06 || tok[5] != oidl ||
+ ename->length < oidl+6 ||
+ !ssh_gssapi_check_oid(ctx, tok+6, oidl))
+ return GSS_S_FAILURE;
+
+ offset = oidl+6;
+
+ if (ename->length < offset+4)
+ return GSS_S_FAILURE;
+
+ name->length = get_u32(tok+offset);
+ offset += 4;
+
+ if (UINT_MAX - offset < name->length)
+ return GSS_S_FAILURE;
+ if (ename->length < offset+name->length)
+ return GSS_S_FAILURE;
+
+ name->value = xmalloc(name->length+1);
+ memcpy(name->value, tok+offset, name->length);
+ ((char *)name->value)[name->length] = 0;
+
+ return GSS_S_COMPLETE;
+}
+
+/* Extract the client details from a given context. This can only reliably
+ * be called once for a context */
+
+/* Privileged (called from accept_secure_ctx) */
+OM_uint32
+ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
+{
+ int i = 0;
+
+ gss_buffer_desc ename;
+
+ client->mech = NULL;
+
+ while (supported_mechs[i]->name != NULL) {
+ if (supported_mechs[i]->oid.length == ctx->oid->length &&
+ (memcmp(supported_mechs[i]->oid.elements,
+ ctx->oid->elements, ctx->oid->length) == 0))
+ client->mech = supported_mechs[i];
+ i++;
+ }
+
+ if (client->mech == NULL)
+ return GSS_S_FAILURE;
+
+ if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
+ &client->displayname, NULL))) {
+ ssh_gssapi_error(ctx);
+ return (ctx->major);
+ }
+
+ if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
+ &ename))) {
+ ssh_gssapi_error(ctx);
+ return (ctx->major);
+ }
+
+ if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
+ &client->exportedname))) {
+ return (ctx->major);
+ }
+
+ /* We can't copy this structure, so we just move the pointer to it */
+ client->creds = ctx->client_creds;
+ ctx->client_creds = GSS_C_NO_CREDENTIAL;
+ return (ctx->major);
+}
+
+/* As user - called on fatal/exit */
+void
+ssh_gssapi_cleanup_creds(void)
+{
+ if (gssapi_client.store.filename != NULL) {
+ /* Unlink probably isn't sufficient */
+ debug("removing gssapi cred file\"%s\"",
+ gssapi_client.store.filename);
+ unlink(gssapi_client.store.filename);
+ }
+}
+
+/* As user */
+void
+ssh_gssapi_storecreds(void)
+{
+ if (gssapi_client.mech && gssapi_client.mech->storecreds) {
+ (*gssapi_client.mech->storecreds)(&gssapi_client);
+ } else
+ debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
+}
+
+/* This allows GSSAPI methods to do things to the child's environment based
+ * on the passed authentication process and credentials.
+ */
+/* As user */
+void
+ssh_gssapi_do_child(char ***envp, u_int *envsizep)
+{
+
+ if (gssapi_client.store.envvar != NULL &&
+ gssapi_client.store.envval != NULL) {
+ debug("Setting %s to %s", gssapi_client.store.envvar,
+ gssapi_client.store.envval);
+ child_set_env(envp, envsizep, gssapi_client.store.envvar,
+ gssapi_client.store.envval);
+ }
+}
+
+/* Privileged */
+int
+ssh_gssapi_userok(char *user)
+{
+ OM_uint32 lmin;
+
+ if (gssapi_client.exportedname.length == 0 ||
+ gssapi_client.exportedname.value == NULL) {
+ debug("No suitable client data");
+ return 0;
+ }
+ if (gssapi_client.mech && gssapi_client.mech->userok)
+ if ((*gssapi_client.mech->userok)(&gssapi_client, user))
+ return 1;
+ else {
+ /* Destroy delegated credentials if userok fails */
+ gss_release_buffer(&lmin, &gssapi_client.displayname);
+ gss_release_buffer(&lmin, &gssapi_client.exportedname);
+ gss_release_cred(&lmin, &gssapi_client.creds);
+ explicit_bzero(&gssapi_client,
+ sizeof(ssh_gssapi_client));
+ return 0;
+ }
+ else
+ debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
+ return (0);
+}
+
+/* Privileged */
+OM_uint32
+ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
+{
+ ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
+ gssbuf, gssmic, NULL);
+
+ return (ctx->major);
+}
+
+/* Privileged */
+const char *ssh_gssapi_displayname(void)
+{
+ if (gssapi_client.displayname.length == 0 ||
+ gssapi_client.displayname.value == NULL)
+ return NULL;
+ return (char *)gssapi_client.displayname.value;
+}
+
+#endif