1 /* $OpenBSD: gss-genr.c,v 1.28 2021/01/27 10:05:28 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 /* sshbuf_get for gss_buffer_desc */ 48 int 49 ssh_gssapi_get_buffer_desc(struct sshbuf *b, gss_buffer_desc *g) 50 { 51 int r; 52 u_char *p; 53 size_t len; 54 55 if ((r = sshbuf_get_string(b, &p, &len)) != 0) 56 return r; 57 g->value = p; 58 g->length = len; 59 return 0; 60 } 61 62 /* Check that the OID in a data stream matches that in the context */ 63 int 64 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len) 65 { 66 return (ctx != NULL && ctx->oid != GSS_C_NO_OID && 67 ctx->oid->length == len && 68 memcmp(ctx->oid->elements, data, len) == 0); 69 } 70 71 /* Set the contexts OID from a data stream */ 72 void 73 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len) 74 { 75 if (ctx->oid != GSS_C_NO_OID) { 76 free(ctx->oid->elements); 77 free(ctx->oid); 78 } 79 ctx->oid = xcalloc(1, sizeof(gss_OID_desc)); 80 ctx->oid->length = len; 81 ctx->oid->elements = xmalloc(len); 82 memcpy(ctx->oid->elements, data, len); 83 } 84 85 /* Set the contexts OID */ 86 void 87 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid) 88 { 89 ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length); 90 } 91 92 /* All this effort to report an error ... */ 93 void 94 ssh_gssapi_error(Gssctxt *ctxt) 95 { 96 char *s; 97 98 s = ssh_gssapi_last_error(ctxt, NULL, NULL); 99 debug("%s", s); 100 free(s); 101 } 102 103 char * 104 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status, 105 OM_uint32 *minor_status) 106 { 107 OM_uint32 lmin; 108 gss_buffer_desc msg = GSS_C_EMPTY_BUFFER; 109 OM_uint32 ctx; 110 struct sshbuf *b; 111 char *ret; 112 int r; 113 114 if ((b = sshbuf_new()) == NULL) 115 fatal_f("sshbuf_new failed"); 116 117 if (major_status != NULL) 118 *major_status = ctxt->major; 119 if (minor_status != NULL) 120 *minor_status = ctxt->minor; 121 122 ctx = 0; 123 /* The GSSAPI error */ 124 do { 125 gss_display_status(&lmin, ctxt->major, 126 GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg); 127 128 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 || 129 (r = sshbuf_put_u8(b, '\n')) != 0) 130 fatal_fr(r, "assemble GSS_CODE"); 131 132 gss_release_buffer(&lmin, &msg); 133 } while (ctx != 0); 134 135 /* The mechanism specific error */ 136 do { 137 gss_display_status(&lmin, ctxt->minor, 138 GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg); 139 140 if ((r = sshbuf_put(b, msg.value, msg.length)) != 0 || 141 (r = sshbuf_put_u8(b, '\n')) != 0) 142 fatal_fr(r, "assemble MECH_CODE"); 143 144 gss_release_buffer(&lmin, &msg); 145 } while (ctx != 0); 146 147 if ((r = sshbuf_put_u8(b, '\n')) != 0) 148 fatal_fr(r, "assemble newline"); 149 ret = xstrdup((const char *)sshbuf_ptr(b)); 150 sshbuf_free(b); 151 return (ret); 152 } 153 154 /* 155 * Initialise our GSSAPI context. We use this opaque structure to contain all 156 * of the data which both the client and server need to persist across 157 * {accept,init}_sec_context calls, so that when we do it from the userauth 158 * stuff life is a little easier 159 */ 160 void 161 ssh_gssapi_build_ctx(Gssctxt **ctx) 162 { 163 *ctx = xcalloc(1, sizeof (Gssctxt)); 164 (*ctx)->context = GSS_C_NO_CONTEXT; 165 (*ctx)->name = GSS_C_NO_NAME; 166 (*ctx)->oid = GSS_C_NO_OID; 167 (*ctx)->creds = GSS_C_NO_CREDENTIAL; 168 (*ctx)->client = GSS_C_NO_NAME; 169 (*ctx)->client_creds = GSS_C_NO_CREDENTIAL; 170 } 171 172 /* Delete our context, providing it has been built correctly */ 173 void 174 ssh_gssapi_delete_ctx(Gssctxt **ctx) 175 { 176 OM_uint32 ms; 177 178 if ((*ctx) == NULL) 179 return; 180 if ((*ctx)->context != GSS_C_NO_CONTEXT) 181 gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER); 182 if ((*ctx)->name != GSS_C_NO_NAME) 183 gss_release_name(&ms, &(*ctx)->name); 184 if ((*ctx)->oid != GSS_C_NO_OID) { 185 free((*ctx)->oid->elements); 186 free((*ctx)->oid); 187 (*ctx)->oid = GSS_C_NO_OID; 188 } 189 if ((*ctx)->creds != GSS_C_NO_CREDENTIAL) 190 gss_release_cred(&ms, &(*ctx)->creds); 191 if ((*ctx)->client != GSS_C_NO_NAME) 192 gss_release_name(&ms, &(*ctx)->client); 193 if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL) 194 gss_release_cred(&ms, &(*ctx)->client_creds); 195 196 free(*ctx); 197 *ctx = NULL; 198 } 199 200 /* 201 * Wrapper to init_sec_context 202 * Requires that the context contains: 203 * oid 204 * server name (from ssh_gssapi_import_name) 205 */ 206 OM_uint32 207 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok, 208 gss_buffer_desc* send_tok, OM_uint32 *flags) 209 { 210 int deleg_flag = 0; 211 212 if (deleg_creds) { 213 deleg_flag = GSS_C_DELEG_FLAG; 214 debug("Delegating credentials"); 215 } 216 217 ctx->major = gss_init_sec_context(&ctx->minor, 218 GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid, 219 GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag, 220 0, NULL, recv_tok, NULL, send_tok, flags, NULL); 221 222 if (GSS_ERROR(ctx->major)) 223 ssh_gssapi_error(ctx); 224 225 return (ctx->major); 226 } 227 228 /* Create a service name for the given host */ 229 OM_uint32 230 ssh_gssapi_import_name(Gssctxt *ctx, const char *host) 231 { 232 gss_buffer_desc gssbuf; 233 char *val; 234 235 xasprintf(&val, "host@%s", host); 236 gssbuf.value = val; 237 gssbuf.length = strlen(gssbuf.value); 238 239 if ((ctx->major = gss_import_name(&ctx->minor, 240 &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name))) 241 ssh_gssapi_error(ctx); 242 243 free(gssbuf.value); 244 return (ctx->major); 245 } 246 247 OM_uint32 248 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash) 249 { 250 if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context, 251 GSS_C_QOP_DEFAULT, buffer, hash))) 252 ssh_gssapi_error(ctx); 253 254 return (ctx->major); 255 } 256 257 void 258 ssh_gssapi_buildmic(struct sshbuf *b, const char *user, const char *service, 259 const char *context, const struct sshbuf *session_id) 260 { 261 int r; 262 263 sshbuf_reset(b); 264 if ((r = sshbuf_put_stringb(b, session_id)) != 0 || 265 (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 266 (r = sshbuf_put_cstring(b, user)) != 0 || 267 (r = sshbuf_put_cstring(b, service)) != 0 || 268 (r = sshbuf_put_cstring(b, context)) != 0) 269 fatal_fr(r, "assemble buildmic"); 270 } 271 272 int 273 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host) 274 { 275 gss_buffer_desc token = GSS_C_EMPTY_BUFFER; 276 OM_uint32 major, minor; 277 gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"}; 278 279 /* RFC 4462 says we MUST NOT do SPNEGO */ 280 if (oid->length == spnego_oid.length && 281 (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0)) 282 return 0; /* false */ 283 284 ssh_gssapi_build_ctx(ctx); 285 ssh_gssapi_set_oid(*ctx, oid); 286 major = ssh_gssapi_import_name(*ctx, host); 287 if (!GSS_ERROR(major)) { 288 major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, 289 NULL); 290 gss_release_buffer(&minor, &token); 291 if ((*ctx)->context != GSS_C_NO_CONTEXT) 292 gss_delete_sec_context(&minor, &(*ctx)->context, 293 GSS_C_NO_BUFFER); 294 } 295 296 if (GSS_ERROR(major)) 297 ssh_gssapi_delete_ctx(ctx); 298 299 return (!GSS_ERROR(major)); 300 } 301 302 #endif /* GSSAPI */ 303