1 /* $OpenBSD: gss-serv.c,v 1.13 2005/10/13 22:24:31 stevesk 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 "bufaux.h" 32 #include "auth.h" 33 #include "log.h" 34 #include "channels.h" 35 #include "session.h" 36 #include "servconf.h" 37 #include "xmalloc.h" 38 #include "getput.h" 39 40 #include "ssh-gss.h" 41 42 static ssh_gssapi_client gssapi_client = 43 { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER, 44 GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}}; 45 46 ssh_gssapi_mech gssapi_null_mech = 47 { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL}; 48 49 #ifdef KRB5 50 extern ssh_gssapi_mech gssapi_kerberos_mech; 51 #endif 52 53 ssh_gssapi_mech* supported_mechs[]= { 54 #ifdef KRB5 55 &gssapi_kerberos_mech, 56 #endif 57 &gssapi_null_mech, 58 }; 59 60 /* Unprivileged */ 61 void 62 ssh_gssapi_supported_oids(gss_OID_set *oidset) 63 { 64 int i = 0; 65 OM_uint32 min_status; 66 int present; 67 gss_OID_set supported; 68 69 gss_create_empty_oid_set(&min_status, oidset); 70 gss_indicate_mechs(&min_status, &supported); 71 72 while (supported_mechs[i]->name != NULL) { 73 if (GSS_ERROR(gss_test_oid_set_member(&min_status, 74 &supported_mechs[i]->oid, supported, &present))) 75 present = 0; 76 if (present) 77 gss_add_oid_set_member(&min_status, 78 &supported_mechs[i]->oid, oidset); 79 i++; 80 } 81 } 82 83 84 /* Wrapper around accept_sec_context 85 * Requires that the context contains: 86 * oid 87 * credentials (from ssh_gssapi_acquire_cred) 88 */ 89 /* Privileged */ 90 OM_uint32 91 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok, 92 gss_buffer_desc *send_tok, OM_uint32 *flags) 93 { 94 OM_uint32 status; 95 gss_OID mech; 96 97 ctx->major = gss_accept_sec_context(&ctx->minor, 98 &ctx->context, ctx->creds, recv_tok, 99 GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech, 100 send_tok, flags, NULL, &ctx->client_creds); 101 102 if (GSS_ERROR(ctx->major)) 103 ssh_gssapi_error(ctx); 104 105 if (ctx->client_creds) 106 debug("Received some client credentials"); 107 else 108 debug("Got no client credentials"); 109 110 status = ctx->major; 111 112 /* Now, if we're complete and we have the right flags, then 113 * we flag the user as also having been authenticated 114 */ 115 116 if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) && 117 (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) { 118 if (ssh_gssapi_getclient(ctx, &gssapi_client)) 119 fatal("Couldn't convert client name"); 120 } 121 122 return (status); 123 } 124 125 /* 126 * This parses an exported name, extracting the mechanism specific portion 127 * to use for ACL checking. It verifies that the name belongs the mechanism 128 * originally selected. 129 */ 130 static OM_uint32 131 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name) 132 { 133 u_char *tok; 134 OM_uint32 offset; 135 OM_uint32 oidl; 136 137 tok = ename->value; 138 139 /* 140 * Check that ename is long enough for all of the fixed length 141 * header, and that the initial ID bytes are correct 142 */ 143 144 if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0) 145 return GSS_S_FAILURE; 146 147 /* 148 * Extract the OID, and check it. Here GSSAPI breaks with tradition 149 * and does use the OID type and length bytes. To confuse things 150 * there are two lengths - the first including these, and the 151 * second without. 152 */ 153 154 oidl = GET_16BIT(tok+2); /* length including next two bytes */ 155 oidl = oidl-2; /* turn it into the _real_ length of the variable OID */ 156 157 /* 158 * Check the BER encoding for correct type and length, that the 159 * string is long enough and that the OID matches that in our context 160 */ 161 if (tok[4] != 0x06 || tok[5] != oidl || 162 ename->length < oidl+6 || 163 !ssh_gssapi_check_oid(ctx, tok+6, oidl)) 164 return GSS_S_FAILURE; 165 166 offset = oidl+6; 167 168 if (ename->length < offset+4) 169 return GSS_S_FAILURE; 170 171 name->length = GET_32BIT(tok+offset); 172 offset += 4; 173 174 if (ename->length < offset+name->length) 175 return GSS_S_FAILURE; 176 177 name->value = xmalloc(name->length+1); 178 memcpy(name->value, tok+offset,name->length); 179 ((char *)name->value)[name->length] = 0; 180 181 return GSS_S_COMPLETE; 182 } 183 184 /* Extract the client details from a given context. This can only reliably 185 * be called once for a context */ 186 187 /* Privileged (called from accept_secure_ctx) */ 188 OM_uint32 189 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client) 190 { 191 int i = 0; 192 193 gss_buffer_desc ename; 194 195 client->mech = NULL; 196 197 while (supported_mechs[i]->name != NULL) { 198 if (supported_mechs[i]->oid.length == ctx->oid->length && 199 (memcmp(supported_mechs[i]->oid.elements, 200 ctx->oid->elements, ctx->oid->length) == 0)) 201 client->mech = supported_mechs[i]; 202 i++; 203 } 204 205 if (client->mech == NULL) 206 return GSS_S_FAILURE; 207 208 if ((ctx->major = gss_display_name(&ctx->minor, ctx->client, 209 &client->displayname, NULL))) { 210 ssh_gssapi_error(ctx); 211 return (ctx->major); 212 } 213 214 if ((ctx->major = gss_export_name(&ctx->minor, ctx->client, 215 &ename))) { 216 ssh_gssapi_error(ctx); 217 return (ctx->major); 218 } 219 220 if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename, 221 &client->exportedname))) { 222 return (ctx->major); 223 } 224 225 /* We can't copy this structure, so we just move the pointer to it */ 226 client->creds = ctx->client_creds; 227 ctx->client_creds = GSS_C_NO_CREDENTIAL; 228 return (ctx->major); 229 } 230 231 /* As user - called on fatal/exit */ 232 void 233 ssh_gssapi_cleanup_creds(void) 234 { 235 if (gssapi_client.store.filename != NULL) { 236 /* Unlink probably isn't sufficient */ 237 debug("removing gssapi cred file\"%s\"", gssapi_client.store.filename); 238 unlink(gssapi_client.store.filename); 239 } 240 } 241 242 /* As user */ 243 void 244 ssh_gssapi_storecreds(void) 245 { 246 if (gssapi_client.mech && gssapi_client.mech->storecreds) { 247 (*gssapi_client.mech->storecreds)(&gssapi_client); 248 } else 249 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism"); 250 } 251 252 /* This allows GSSAPI methods to do things to the childs environment based 253 * on the passed authentication process and credentials. 254 */ 255 /* As user */ 256 void 257 ssh_gssapi_do_child(char ***envp, u_int *envsizep) 258 { 259 260 if (gssapi_client.store.envvar != NULL && 261 gssapi_client.store.envval != NULL) { 262 debug("Setting %s to %s", gssapi_client.store.envvar, 263 gssapi_client.store.envval); 264 child_set_env(envp, envsizep, gssapi_client.store.envvar, 265 gssapi_client.store.envval); 266 } 267 } 268 269 /* Privileged */ 270 int 271 ssh_gssapi_userok(char *user) 272 { 273 OM_uint32 lmin; 274 275 if (gssapi_client.exportedname.length == 0 || 276 gssapi_client.exportedname.value == NULL) { 277 debug("No suitable client data"); 278 return 0; 279 } 280 if (gssapi_client.mech && gssapi_client.mech->userok) 281 if ((*gssapi_client.mech->userok)(&gssapi_client, user)) 282 return 1; 283 else { 284 /* Destroy delegated credentials if userok fails */ 285 gss_release_buffer(&lmin, &gssapi_client.displayname); 286 gss_release_buffer(&lmin, &gssapi_client.exportedname); 287 gss_release_cred(&lmin, &gssapi_client.creds); 288 memset(&gssapi_client, 0, sizeof(ssh_gssapi_client)); 289 return 0; 290 } 291 else 292 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism"); 293 return (0); 294 } 295 296 /* Privileged */ 297 OM_uint32 298 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic) 299 { 300 ctx->major = gss_verify_mic(&ctx->minor, ctx->context, 301 gssbuf, gssmic, NULL); 302 303 return (ctx->major); 304 } 305 306 #endif 307