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 #ifdef GSSAPI 28 29 30 #include <stdarg.h> 31 #include <string.h> 32 #include <limits.h> 33 34 #include "xmalloc.h" 35 #include "ssherr.h" 36 #include "sshbuf.h" 37 #include "log.h" 38 #include "ssh2.h" 39 40 #include "ssh-gss.h" 41 42 extern u_char *session_id2; 43 extern u_int session_id2_len; 44 45 /* sshbuf_get for gss_buffer_desc */ 46 int 47 ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g) 48 { 49 int r; 50 u_char *p; 51 size_t len; 52 53 if ((r = sshbuf_get_string(b, &p, &len)) != 0) 54 return r; 55 g->value = p; 56 g->length = len; 57 return 0; 58 } 59 60 /* Check that the OID in a data stream matches that in the context */ 61 int 62 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len) 63 { 64 return (ctx != NULL && ctx->oid != GSS_C_NO_OID && 65 ctx->oid->length == len && 66 memcmp(ctx->oid->elements, data, len) == 0); 67 } 68 69 /* Set the contexts OID from a data stream */ 70 void 71 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len) 72 { 73 if (ctx->oid != GSS_C_NO_OID) { 74 free(ctx->oid->elements); 75 free(ctx->oid); 76 } 77 ctx->oid = xcalloc(1, sizeof(gss_OID_desc)); 78 ctx->oid->length = len; 79 ctx->oid->elements = xmalloc(len); 80 memcpy(ctx->oid->elements, data, len); 81 } 82 83 /* Set the contexts OID */ 84 void 85 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid) 86 { 87 ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length); 88 } 89 90 /* All this effort to report an error ... */ 91 void 92 ssh_gssapi_error(Gssctxt *ctxt) 93 { 94 char *s; 95 96 s = ssh_gssapi_last_error(ctxt, NULL, NULL); 97 debug("%s", s); 98 free(s); 99 } 100 101 char * 102 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status, 103 OM_uint32 *minor_status) 104 { 105 OM_uint32 lmin; 106 gss_buffer_desc msg = GSS_C_EMPTY_BUFFER; 107 OM_uint32 ctx; 108 struct sshbuf *b; 109 char *ret; 110 int r; 111 112 if ((b = sshbuf_new()) == NULL) 113 fatal("%s: sshbuf_new failed", __func__); 114 115 if (major_status != NULL) 116 *major_status = ctxt->major; 117 if (minor_status != NULL) 118 *minor_status = ctxt->minor; 119 120 ctx = 0; 121 /* The GSSAPI error */ 122 do { 123 gss_display_status(&lmin, ctxt->major, 124 GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg); 125 126 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 || 127 (r = sshbuf_put_u8(b, '\n')) != 0) 128 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 129 130 gss_release_buffer(&lmin, &msg); 131 } while (ctx != 0); 132 133 /* The mechanism specific error */ 134 do { 135 gss_display_status(&lmin, ctxt->minor, 136 GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg); 137 138 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 || 139 (r = sshbuf_put_u8(b, '\n')) != 0) 140 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 141 142 gss_release_buffer(&lmin, &msg); 143 } while (ctx != 0); 144 145 if ((r = sshbuf_put_u8(b, '\n')) != 0) 146 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 147 ret = xstrdup((const char *)sshbuf_ptr(b)); 148 sshbuf_free(b); 149 return (ret); 150 } 151 152 /* 153 * Initialise our GSSAPI context. We use this opaque structure to contain all 154 * of the data which both the client and server need to persist across 155 * {accept,init}_sec_context calls, so that when we do it from the userauth 156 * stuff life is a little easier 157 */ 158 void 159 ssh_gssapi_build_ctx(Gssctxt **ctx) 160 { 161 *ctx = xcalloc(1, sizeof (Gssctxt)); 162 (*ctx)->context = GSS_C_NO_CONTEXT; 163 (*ctx)->name = GSS_C_NO_NAME; 164 (*ctx)->oid = GSS_C_NO_OID; 165 (*ctx)->creds = GSS_C_NO_CREDENTIAL; 166 (*ctx)->client = GSS_C_NO_NAME; 167 (*ctx)->client_creds = GSS_C_NO_CREDENTIAL; 168 } 169 170 /* Delete our context, providing it has been built correctly */ 171 void 172 ssh_gssapi_delete_ctx(Gssctxt **ctx) 173 { 174 OM_uint32 ms; 175 176 if ((*ctx) == NULL) 177 return; 178 if ((*ctx)->context != GSS_C_NO_CONTEXT) 179 gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER); 180 if ((*ctx)->name != GSS_C_NO_NAME) 181 gss_release_name(&ms, &(*ctx)->name); 182 if ((*ctx)->oid != GSS_C_NO_OID) { 183 free((*ctx)->oid->elements); 184 free((*ctx)->oid); 185 (*ctx)->oid = GSS_C_NO_OID; 186 } 187 if ((*ctx)->creds != GSS_C_NO_CREDENTIAL) 188 gss_release_cred(&ms, &(*ctx)->creds); 189 if ((*ctx)->client != GSS_C_NO_NAME) 190 gss_release_name(&ms, &(*ctx)->client); 191 if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL) 192 gss_release_cred(&ms, &(*ctx)->client_creds); 193 194 free(*ctx); 195 *ctx = NULL; 196 } 197 198 /* 199 * Wrapper to init_sec_context 200 * Requires that the context contains: 201 * oid 202 * server name (from ssh_gssapi_import_name) 203 */ 204 OM_uint32 205 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok, 206 gss_buffer_desc* send_tok, OM_uint32 *flags) 207 { 208 int deleg_flag = 0; 209 210 if (deleg_creds) { 211 deleg_flag = GSS_C_DELEG_FLAG; 212 debug("Delegating credentials"); 213 } 214 215 ctx->major = gss_init_sec_context(&ctx->minor, 216 GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid, 217 GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag, 218 0, NULL, recv_tok, NULL, send_tok, flags, NULL); 219 220 if (GSS_ERROR(ctx->major)) 221 ssh_gssapi_error(ctx); 222 223 return (ctx->major); 224 } 225 226 /* Create a service name for the given host */ 227 OM_uint32 228 ssh_gssapi_import_name(Gssctxt *ctx, const char *host) 229 { 230 gss_buffer_desc gssbuf; 231 char *val; 232 233 xasprintf(&val, "host@%s", host); 234 gssbuf.value = val; 235 gssbuf.length = strlen(gssbuf.value); 236 237 if ((ctx->major = gss_import_name(&ctx->minor, 238 &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name))) 239 ssh_gssapi_error(ctx); 240 241 free(gssbuf.value); 242 return (ctx->major); 243 } 244 245 OM_uint32 246 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash) 247 { 248 if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context, 249 GSS_C_QOP_DEFAULT, buffer, hash))) 250 ssh_gssapi_error(ctx); 251 252 return (ctx->major); 253 } 254 255 void 256 ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service, 257 const char *context) 258 { 259 int r; 260 261 sshbuf_reset(b); 262 if ((r = sshbuf_put_string(b, session_id2, session_id2_len)) != 0 || 263 (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 264 (r = sshbuf_put_cstring(b, user)) != 0 || 265 (r = sshbuf_put_cstring(b, service)) != 0 || 266 (r = sshbuf_put_cstring(b, context)) != 0) 267 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 268 } 269 270 int 271 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host) 272 { 273 gss_buffer_desc token = GSS_C_EMPTY_BUFFER; 274 OM_uint32 major, minor; 275 gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"}; 276 277 /* RFC 4462 says we MUST NOT do SPNEGO */ 278 if (oid->length == spnego_oid.length && 279 (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0)) 280 return 0; /* false */ 281 282 ssh_gssapi_build_ctx(ctx); 283 ssh_gssapi_set_oid(*ctx, oid); 284 major = ssh_gssapi_import_name(*ctx, host); 285 if (!GSS_ERROR(major)) { 286 major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, 287 NULL); 288 gss_release_buffer(&minor, &token); 289 if ((*ctx)->context != GSS_C_NO_CONTEXT) 290 gss_delete_sec_context(&minor, &(*ctx)->context, 291 GSS_C_NO_BUFFER); 292 } 293 294 if (GSS_ERROR(major)) 295 ssh_gssapi_delete_ctx(ctx); 296 297 return (!GSS_ERROR(major)); 298 } 299 300 #endif /* GSSAPI */ 301