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