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Diffstat (limited to 'gss-serv.c')
| -rw-r--r-- | gss-serv.c | 404 |
1 files changed, 404 insertions, 0 deletions
diff --git a/gss-serv.c b/gss-serv.c new file mode 100644 index 0000000..00e3d11 --- /dev/null +++ b/gss-serv.c @@ -0,0 +1,404 @@ +/* $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, HOST_NAME_MAX)) { + 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 |