1 /* $OpenBSD: gss-serv.c,v 1.20 2006/08/03 03:34:42 deraadt Exp $ */ 2 3 /* 4 * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 29 #ifdef GSSAPI 30 31 #include <sys/types.h> 32 33 #include <stdarg.h> 34 #include <string.h> 35 #include <unistd.h> 36 37 #include "xmalloc.h" 38 #include "buffer.h" 39 #include "key.h" 40 #include "hostfile.h" 41 #include "auth.h" 42 #include "log.h" 43 #include "channels.h" 44 #include "session.h" 45 #include "misc.h" 46 47 #include "ssh-gss.h" 48 49 static ssh_gssapi_client gssapi_client = 50 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, 51 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}}; 52 53 ssh_gssapi_mech gssapi_null_mech = 54 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; 55 56 #ifdef KRB5 57 extern ssh_gssapi_mech gssapi_kerberos_mech; 58 #endif 59 60 ssh_gssapi_mech* supported_mechs[]= { 61 #ifdef KRB5 62 &gssapi_kerberos_mech, 63 #endif 64 &gssapi_null_mech, 65 }; 66 67 /* Unprivileged */ 68 void 69 ssh_gssapi_supported_oids(gss_OID_set *oidset) 70 { 71 int i = 0; 72 OM_uint32 min_status; 73 int present; 74 gss_OID_set supported; 75 76 gss_create_empty_oid_set(&min_status, oidset); 77 gss_indicate_mechs(&min_status, &supported); 78 79 while (supported_mechs[i]->name != NULL) { 80 if (GSS_ERROR(gss_test_oid_set_member(&min_status, 81 &supported_mechs[i]->oid, supported, &present))) 82 present = 0; 83 if (present) 84 gss_add_oid_set_member(&min_status, 85 &supported_mechs[i]->oid, oidset); 86 i++; 87 } 88 89 gss_release_oid_set(&min_status, &supported); 90 } 91 92 93 /* Wrapper around accept_sec_context 94 * Requires that the context contains: 95 * oid 96 * credentials (from ssh_gssapi_acquire_cred) 97 */ 98 /* Privileged */ 99 OM_uint32 100 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, 101 gss_buffer_desc *send_tok, OM_uint32 *flags) 102 { 103 OM_uint32 status; 104 gss_OID mech; 105 106 ctx->major = gss_accept_sec_context(&ctx->minor, 107 &ctx->context, ctx->creds, recv_tok, 108 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, 109 send_tok, flags, NULL, &ctx->client_creds); 110 111 if (GSS_ERROR(ctx->major)) 112 ssh_gssapi_error(ctx); 113 114 if (ctx->client_creds) 115 debug("Received some client credentials"); 116 else 117 debug("Got no client credentials"); 118 119 status = ctx->major; 120 121 /* Now, if we're complete and we have the right flags, then 122 * we flag the user as also having been authenticated 123 */ 124 125 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && 126 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { 127 if (ssh_gssapi_getclient(ctx, &gssapi_client)) 128 fatal("Couldn't convert client name"); 129 } 130 131 return (status); 132 } 133 134 /* 135 * This parses an exported name, extracting the mechanism specific portion 136 * to use for ACL checking. It verifies that the name belongs the mechanism 137 * originally selected. 138 */ 139 static OM_uint32 140 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) 141 { 142 u_char *tok; 143 OM_uint32 offset; 144 OM_uint32 oidl; 145 146 tok = ename->value; 147 148 /* 149 * Check that ename is long enough for all of the fixed length 150 * header, and that the initial ID bytes are correct 151 */ 152 153 if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0) 154 return GSS_S_FAILURE; 155 156 /* 157 * Extract the OID, and check it. Here GSSAPI breaks with tradition 158 * and does use the OID type and length bytes. To confuse things 159 * there are two lengths - the first including these, and the 160 * second without. 161 */ 162 163 oidl = get_u16(tok+2); /* length including next two bytes */ 164 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ 165 166 /* 167 * Check the BER encoding for correct type and length, that the 168 * string is long enough and that the OID matches that in our context 169 */ 170 if (tok[4] != 0x06 || tok[5] != oidl || 171 ename->length < oidl+6 || 172 !ssh_gssapi_check_oid(ctx, tok+6, oidl)) 173 return GSS_S_FAILURE; 174 175 offset = oidl+6; 176 177 if (ename->length < offset+4) 178 return GSS_S_FAILURE; 179 180 name->length = get_u32(tok+offset); 181 offset += 4; 182 183 if (ename->length < offset+name->length) 184 return GSS_S_FAILURE; 185 186 name->value = xmalloc(name->length+1); 187 memcpy(name->value, tok+offset, name->length); 188 ((char *)name->value)[name->length] = 0; 189 190 return GSS_S_COMPLETE; 191 } 192 193 /* Extract the client details from a given context. This can only reliably 194 * be called once for a context */ 195 196 /* Privileged (called from accept_secure_ctx) */ 197 OM_uint32 198 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) 199 { 200 int i = 0; 201 202 gss_buffer_desc ename; 203 204 client->mech = NULL; 205 206 while (supported_mechs[i]->name != NULL) { 207 if (supported_mechs[i]->oid.length == ctx->oid->length && 208 (memcmp(supported_mechs[i]->oid.elements, 209 ctx->oid->elements, ctx->oid->length) == 0)) 210 client->mech = supported_mechs[i]; 211 i++; 212 } 213 214 if (client->mech == NULL) 215 return GSS_S_FAILURE; 216 217 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, 218 &client->displayname, NULL))) { 219 ssh_gssapi_error(ctx); 220 return (ctx->major); 221 } 222 223 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, 224 &ename))) { 225 ssh_gssapi_error(ctx); 226 return (ctx->major); 227 } 228 229 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, 230 &client->exportedname))) { 231 return (ctx->major); 232 } 233 234 /* We can't copy this structure, so we just move the pointer to it */ 235 client->creds = ctx->client_creds; 236 ctx->client_creds = GSS_C_NO_CREDENTIAL; 237 return (ctx->major); 238 } 239 240 /* As user - called on fatal/exit */ 241 void 242 ssh_gssapi_cleanup_creds(void) 243 { 244 if (gssapi_client.store.filename != NULL) { 245 /* Unlink probably isn't sufficient */ 246 debug("removing gssapi cred file\"%s\"", 247 gssapi_client.store.filename); 248 unlink(gssapi_client.store.filename); 249 } 250 } 251 252 /* As user */ 253 void 254 ssh_gssapi_storecreds(void) 255 { 256 if (gssapi_client.mech && gssapi_client.mech->storecreds) { 257 (*gssapi_client.mech->storecreds)(&gssapi_client); 258 } else 259 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); 260 } 261 262 /* This allows GSSAPI methods to do things to the childs environment based 263 * on the passed authentication process and credentials. 264 */ 265 /* As user */ 266 void 267 ssh_gssapi_do_child(char ***envp, u_int *envsizep) 268 { 269 270 if (gssapi_client.store.envvar != NULL && 271 gssapi_client.store.envval != NULL) { 272 debug("Setting %s to %s", gssapi_client.store.envvar, 273 gssapi_client.store.envval); 274 child_set_env(envp, envsizep, gssapi_client.store.envvar, 275 gssapi_client.store.envval); 276 } 277 } 278 279 /* Privileged */ 280 int 281 ssh_gssapi_userok(char *user) 282 { 283 OM_uint32 lmin; 284 285 if (gssapi_client.exportedname.length == 0 || 286 gssapi_client.exportedname.value == NULL) { 287 debug("No suitable client data"); 288 return 0; 289 } 290 if (gssapi_client.mech && gssapi_client.mech->userok) 291 if ((*gssapi_client.mech->userok)(&gssapi_client, user)) 292 return 1; 293 else { 294 /* Destroy delegated credentials if userok fails */ 295 gss_release_buffer(&lmin, &gssapi_client.displayname); 296 gss_release_buffer(&lmin, &gssapi_client.exportedname); 297 gss_release_cred(&lmin, &gssapi_client.creds); 298 memset(&gssapi_client, 0, sizeof(ssh_gssapi_client)); 299 return 0; 300 } 301 else 302 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); 303 return (0); 304 } 305 306 /* Privileged */ 307 OM_uint32 308 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) 309 { 310 ctx->major = gss_verify_mic(&ctx->minor, ctx->context, 311 gssbuf, gssmic, NULL); 312 313 return (ctx->major); 314 } 315 316 #endif 317