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IABSD.fr/src/usr.bin/ssh/gss-serv.c
dtucker
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/* $OpenBSD: gss-serv.c,v 1.37 2026/02/11 16:57:38 dtucker 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. */ #ifdef GSSAPI #include <sys/types.h> #include <sys/param.h> #include <sys/queue.h> #include <netdb.h> #include <stdarg.h> #include <string.h> #include <unistd.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, sizeof(lname))) { 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 (options.gss_deleg_creds == 0) { debug_f("delegate credential is disabled, doing nothing"); return; } 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