1 /* $OpenBSD: gss-genr.c,v 1.26 2018/07/10 09:13:30 djm Exp $ */ 2 3 /* 4 * Copyright (c) 2001-2007 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 <limits.h> 34 #include <stdarg.h> 35 #include <string.h> 36 #include <signal.h> 37 #include <unistd.h> 38 39 #include "xmalloc.h" 40 #include "ssherr.h" 41 #include "sshbuf.h" 42 #include "log.h" 43 #include "ssh2.h" 44 45 #include "ssh-gss.h" 46 47 extern u_char *session_id2; 48 extern u_int session_id2_len; 49 50 /* sshbuf_get for gss_buffer_desc */ 51 int 52 ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g) 53 { 54 int r; 55 u_char *p; 56 size_t len; 57 58 if ((r = sshbuf_get_string(b, &p, &len)) != 0) 59 return r; 60 g->value = p; 61 g->length = len; 62 return 0; 63 } 64 65 /* Check that the OID in a data stream matches that in the context */ 66 int 67 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len) 68 { 69 return (ctx != NULL && ctx->oid != GSS_C_NO_OID && 70 ctx->oid->length == len && 71 memcmp(ctx->oid->elements, data, len) == 0); 72 } 73 74 /* Set the contexts OID from a data stream */ 75 void 76 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len) 77 { 78 if (ctx->oid != GSS_C_NO_OID) { 79 free(ctx->oid->elements); 80 free(ctx->oid); 81 } 82 ctx->oid = xcalloc(1, sizeof(gss_OID_desc)); 83 ctx->oid->length = len; 84 ctx->oid->elements = xmalloc(len); 85 memcpy(ctx->oid->elements, data, len); 86 } 87 88 /* Set the contexts OID */ 89 void 90 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid) 91 { 92 ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length); 93 } 94 95 /* All this effort to report an error ... */ 96 void 97 ssh_gssapi_error(Gssctxt *ctxt) 98 { 99 char *s; 100 101 s = ssh_gssapi_last_error(ctxt, NULL, NULL); 102 debug("%s", s); 103 free(s); 104 } 105 106 char * 107 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status, 108 OM_uint32 *minor_status) 109 { 110 OM_uint32 lmin; 111 gss_buffer_desc msg = GSS_C_EMPTY_BUFFER; 112 OM_uint32 ctx; 113 struct sshbuf *b; 114 char *ret; 115 int r; 116 117 if ((b = sshbuf_new()) == NULL) 118 fatal("%s: sshbuf_new failed", __func__); 119 120 if (major_status != NULL) 121 *major_status = ctxt->major; 122 if (minor_status != NULL) 123 *minor_status = ctxt->minor; 124 125 ctx = 0; 126 /* The GSSAPI error */ 127 do { 128 gss_display_status(&lmin, ctxt->major, 129 GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg); 130 131 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 || 132 (r = sshbuf_put_u8(b, '\n')) != 0) 133 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 134 135 gss_release_buffer(&lmin, &msg); 136 } while (ctx != 0); 137 138 /* The mechanism specific error */ 139 do { 140 gss_display_status(&lmin, ctxt->minor, 141 GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg); 142 143 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 || 144 (r = sshbuf_put_u8(b, '\n')) != 0) 145 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 146 147 gss_release_buffer(&lmin, &msg); 148 } while (ctx != 0); 149 150 if ((r = sshbuf_put_u8(b, '\n')) != 0) 151 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 152 ret = xstrdup((const char *)sshbuf_ptr(b)); 153 sshbuf_free(b); 154 return (ret); 155 } 156 157 /* 158 * Initialise our GSSAPI context. We use this opaque structure to contain all 159 * of the data which both the client and server need to persist across 160 * {accept,init}_sec_context calls, so that when we do it from the userauth 161 * stuff life is a little easier 162 */ 163 void 164 ssh_gssapi_build_ctx(Gssctxt **ctx) 165 { 166 *ctx = xcalloc(1, sizeof (Gssctxt)); 167 (*ctx)->context = GSS_C_NO_CONTEXT; 168 (*ctx)->name = GSS_C_NO_NAME; 169 (*ctx)->oid = GSS_C_NO_OID; 170 (*ctx)->creds = GSS_C_NO_CREDENTIAL; 171 (*ctx)->client = GSS_C_NO_NAME; 172 (*ctx)->client_creds = GSS_C_NO_CREDENTIAL; 173 } 174 175 /* Delete our context, providing it has been built correctly */ 176 void 177 ssh_gssapi_delete_ctx(Gssctxt **ctx) 178 { 179 OM_uint32 ms; 180 181 if ((*ctx) == NULL) 182 return; 183 if ((*ctx)->context != GSS_C_NO_CONTEXT) 184 gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER); 185 if ((*ctx)->name != GSS_C_NO_NAME) 186 gss_release_name(&ms, &(*ctx)->name); 187 if ((*ctx)->oid != GSS_C_NO_OID) { 188 free((*ctx)->oid->elements); 189 free((*ctx)->oid); 190 (*ctx)->oid = GSS_C_NO_OID; 191 } 192 if ((*ctx)->creds != GSS_C_NO_CREDENTIAL) 193 gss_release_cred(&ms, &(*ctx)->creds); 194 if ((*ctx)->client != GSS_C_NO_NAME) 195 gss_release_name(&ms, &(*ctx)->client); 196 if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL) 197 gss_release_cred(&ms, &(*ctx)->client_creds); 198 199 free(*ctx); 200 *ctx = NULL; 201 } 202 203 /* 204 * Wrapper to init_sec_context 205 * Requires that the context contains: 206 * oid 207 * server name (from ssh_gssapi_import_name) 208 */ 209 OM_uint32 210 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok, 211 gss_buffer_desc* send_tok, OM_uint32 *flags) 212 { 213 int deleg_flag = 0; 214 215 if (deleg_creds) { 216 deleg_flag = GSS_C_DELEG_FLAG; 217 debug("Delegating credentials"); 218 } 219 220 ctx->major = gss_init_sec_context(&ctx->minor, 221 GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid, 222 GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag, 223 0, NULL, recv_tok, NULL, send_tok, flags, NULL); 224 225 if (GSS_ERROR(ctx->major)) 226 ssh_gssapi_error(ctx); 227 228 return (ctx->major); 229 } 230 231 /* Create a service name for the given host */ 232 OM_uint32 233 ssh_gssapi_import_name(Gssctxt *ctx, const char *host) 234 { 235 gss_buffer_desc gssbuf; 236 char *val; 237 238 xasprintf(&val, "host@%s", host); 239 gssbuf.value = val; 240 gssbuf.length = strlen(gssbuf.value); 241 242 if ((ctx->major = gss_import_name(&ctx->minor, 243 &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name))) 244 ssh_gssapi_error(ctx); 245 246 free(gssbuf.value); 247 return (ctx->major); 248 } 249 250 OM_uint32 251 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash) 252 { 253 if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context, 254 GSS_C_QOP_DEFAULT, buffer, hash))) 255 ssh_gssapi_error(ctx); 256 257 return (ctx->major); 258 } 259 260 void 261 ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service, 262 const char *context) 263 { 264 int r; 265 266 sshbuf_reset(b); 267 if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 || 268 (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 269 (r = sshbuf_put_cstring(b, user)) != 0 || 270 (r = sshbuf_put_cstring(b, service)) != 0 || 271 (r = sshbuf_put_cstring(b, context)) != 0) 272 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 273 } 274 275 int 276 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host) 277 { 278 gss_buffer_desc token = GSS_C_EMPTY_BUFFER; 279 OM_uint32 major, minor; 280 gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"}; 281 282 /* RFC 4462 says we MUST NOT do SPNEGO */ 283 if (oid->length == spnego_oid.length && 284 (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0)) 285 return 0; /* false */ 286 287 ssh_gssapi_build_ctx(ctx); 288 ssh_gssapi_set_oid(*ctx, oid); 289 major = ssh_gssapi_import_name(*ctx, host); 290 if (!GSS_ERROR(major)) { 291 major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, 292 NULL); 293 gss_release_buffer(&minor, &token); 294 if ((*ctx)->context != GSS_C_NO_CONTEXT) 295 gss_delete_sec_context(&minor, &(*ctx)->context, 296 GSS_C_NO_BUFFER); 297 } 298 299 if (GSS_ERROR(major)) 300 ssh_gssapi_delete_ctx(ctx); 301 302 return (!GSS_ERROR(major)); 303 } 304 305 #endif /* GSSAPI */ 306