auth2-chall.c revision 1.21
1 /* $NetBSD: auth2-chall.c,v 1.21 2026/04/08 18:58:40 christos Exp $ */ 2 /* $OpenBSD: auth2-chall.c,v 1.60 2026/03/03 09:57:25 dtucker Exp $ */ 3 4 /* 5 * Copyright (c) 2001 Markus Friedl. All rights reserved. 6 * Copyright (c) 2001 Per Allansson. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #include "includes.h" 30 __RCSID("$NetBSD: auth2-chall.c,v 1.21 2026/04/08 18:58:40 christos Exp $"); 31 #include <sys/types.h> 32 33 #include <stdlib.h> 34 #include <stdio.h> 35 #include <string.h> 36 #include <stdarg.h> 37 38 #include "xmalloc.h" 39 #include "ssh2.h" 40 #include "sshkey.h" 41 #include "hostfile.h" 42 #include "auth.h" 43 #include "sshbuf.h" 44 #include "packet.h" 45 #include "dispatch.h" 46 #include "ssherr.h" 47 #include "log.h" 48 #include "misc.h" 49 #include "servconf.h" 50 51 /* import */ 52 extern ServerOptions options; 53 54 static int auth2_challenge_start(struct ssh *); 55 static int send_userauth_info_request(struct ssh *); 56 static int input_userauth_info_response(int, uint32_t, struct ssh *); 57 58 #ifdef BSD_AUTH 59 extern KbdintDevice mm_bsdauth_device; 60 #else 61 #ifdef USE_PAM 62 extern KbdintDevice sshpam_device; 63 #endif 64 #ifdef SKEY 65 extern KbdintDevice skey_device; 66 #endif 67 #endif 68 69 KbdintDevice *devices[] = { 70 #ifdef BSD_AUTH 71 &bsdauth_device, 72 #else 73 #ifdef USE_PAM 74 &sshpam_device, 75 #endif 76 #ifdef SKEY 77 &skey_device, 78 #endif 79 #endif 80 NULL 81 }; 82 83 typedef struct KbdintAuthctxt KbdintAuthctxt; 84 struct KbdintAuthctxt 85 { 86 char *devices; 87 void *ctxt; 88 KbdintDevice *device; 89 u_int nreq; 90 u_int devices_done; 91 }; 92 93 #ifdef USE_PAM 94 void remove_kbdint_device(const char *); 95 void 96 remove_kbdint_device(const char *xdevname) 97 { 98 int i, j; 99 100 for (i = 0; devices[i] != NULL; i++) 101 if (strcmp(devices[i]->name, xdevname) == 0) { 102 for (j = i; devices[j] != NULL; j++) 103 devices[j] = devices[j+1]; 104 i--; 105 } 106 } 107 #endif 108 109 static KbdintAuthctxt * 110 kbdint_alloc(const char *devs) 111 { 112 KbdintAuthctxt *kbdintctxt; 113 struct sshbuf *b; 114 int i, r; 115 116 #ifdef USE_PAM 117 if (!options.use_pam) 118 remove_kbdint_device("pam"); 119 #endif 120 121 kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt)); 122 if (strcmp(devs, "") == 0) { 123 if ((b = sshbuf_new()) == NULL) 124 fatal_f("sshbuf_new failed"); 125 for (i = 0; devices[i]; i++) { 126 if ((r = sshbuf_putf(b, "%s%s", 127 sshbuf_len(b) ? "," : "", devices[i]->name)) != 0) 128 fatal_fr(r, "buffer error"); 129 } 130 if ((kbdintctxt->devices = sshbuf_dup_string(b)) == NULL) 131 fatal_f("sshbuf_dup_string failed"); 132 sshbuf_free(b); 133 } else { 134 kbdintctxt->devices = xstrdup(devs); 135 } 136 debug("kbdint_alloc: devices '%s'", kbdintctxt->devices); 137 kbdintctxt->ctxt = NULL; 138 kbdintctxt->device = NULL; 139 kbdintctxt->nreq = 0; 140 141 return kbdintctxt; 142 } 143 static void 144 kbdint_reset_device(KbdintAuthctxt *kbdintctxt) 145 { 146 if (kbdintctxt->ctxt) { 147 kbdintctxt->device->free_ctx(kbdintctxt->ctxt); 148 kbdintctxt->ctxt = NULL; 149 } 150 kbdintctxt->device = NULL; 151 } 152 static void 153 kbdint_free(KbdintAuthctxt *kbdintctxt) 154 { 155 if (kbdintctxt->device) 156 kbdint_reset_device(kbdintctxt); 157 free(kbdintctxt->devices); 158 freezero(kbdintctxt, sizeof(*kbdintctxt)); 159 } 160 /* get next device */ 161 static int 162 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt) 163 { 164 size_t len; 165 char *t; 166 size_t i; 167 168 if (kbdintctxt->device) 169 kbdint_reset_device(kbdintctxt); 170 do { 171 len = kbdintctxt->devices ? 172 strcspn(kbdintctxt->devices, ",") : 0; 173 174 if (len == 0) 175 break; 176 for (i = 0; devices[i]; i++) { 177 if (i >= sizeof(kbdintctxt->devices_done) * 8 || 178 i >= sizeof(devices) / sizeof(devices[0])) 179 fatal_f("internal error: too many devices"); 180 if ((kbdintctxt->devices_done & (1 << i)) != 0 || 181 !auth2_method_allowed(authctxt, 182 "keyboard-interactive", devices[i]->name)) 183 continue; 184 if (strlen(devices[i]->name) == len && 185 memcmp(kbdintctxt->devices, devices[i]->name, 186 len) == 0) { 187 kbdintctxt->device = devices[i]; 188 kbdintctxt->devices_done |= 1 << i; 189 } 190 } 191 t = kbdintctxt->devices; 192 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL; 193 free(t); 194 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ? 195 kbdintctxt->devices : "<empty>"); 196 } while (kbdintctxt->devices && !kbdintctxt->device); 197 198 return kbdintctxt->device ? 1 : 0; 199 } 200 201 /* 202 * try challenge-response, set authctxt->postponed if we have to 203 * wait for the response. 204 */ 205 int 206 auth2_challenge(struct ssh *ssh, char *devs) 207 { 208 Authctxt *authctxt = ssh->authctxt; 209 debug("auth2_challenge: user=%s devs=%s", 210 authctxt->user ? authctxt->user : "<nouser>", 211 devs ? devs : "<no devs>"); 212 213 if (authctxt->user == NULL || !devs) 214 return 0; 215 if (authctxt->kbdintctxt == NULL) 216 authctxt->kbdintctxt = kbdint_alloc(devs); 217 return auth2_challenge_start(ssh); 218 } 219 220 /* unregister kbd-int callbacks and context */ 221 void 222 auth2_challenge_stop(struct ssh *ssh) 223 { 224 Authctxt *authctxt = ssh->authctxt; 225 /* unregister callback */ 226 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL); 227 if (authctxt->kbdintctxt != NULL) { 228 kbdint_free(authctxt->kbdintctxt); 229 authctxt->kbdintctxt = NULL; 230 } 231 } 232 233 /* side effect: sets authctxt->postponed if a reply was sent*/ 234 static int 235 auth2_challenge_start(struct ssh *ssh) 236 { 237 Authctxt *authctxt = ssh->authctxt; 238 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt; 239 240 debug2("auth2_challenge_start: devices %s", 241 kbdintctxt->devices ? kbdintctxt->devices : "<empty>"); 242 243 if (kbdint_next_device(authctxt, kbdintctxt) == 0) { 244 auth2_challenge_stop(ssh); 245 return 0; 246 } 247 debug("auth2_challenge_start: trying authentication method '%s'", 248 kbdintctxt->device->name); 249 250 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) { 251 auth2_challenge_stop(ssh); 252 return 0; 253 } 254 if (send_userauth_info_request(ssh) == 0) { 255 auth2_challenge_stop(ssh); 256 return 0; 257 } 258 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, 259 &input_userauth_info_response); 260 261 authctxt->postponed = 1; 262 return 0; 263 } 264 265 static int 266 send_userauth_info_request(struct ssh *ssh) 267 { 268 Authctxt *authctxt = ssh->authctxt; 269 KbdintAuthctxt *kbdintctxt; 270 char *name, *instr, **prompts; 271 int r; 272 u_int i, *echo_on; 273 274 kbdintctxt = authctxt->kbdintctxt; 275 if (kbdintctxt->device->query(kbdintctxt->ctxt, 276 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on)) 277 return 0; 278 279 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST)) != 0 || 280 (r = sshpkt_put_cstring(ssh, name)) != 0 || 281 (r = sshpkt_put_cstring(ssh, instr)) != 0 || 282 (r = sshpkt_put_cstring(ssh, "")) != 0 || /* language not used */ 283 (r = sshpkt_put_u32(ssh, kbdintctxt->nreq)) != 0) 284 fatal_fr(r, "start packet"); 285 for (i = 0; i < kbdintctxt->nreq; i++) { 286 if ((r = sshpkt_put_cstring(ssh, prompts[i])) != 0 || 287 (r = sshpkt_put_u8(ssh, echo_on[i])) != 0) 288 fatal_fr(r, "assemble packet"); 289 } 290 if ((r = sshpkt_send(ssh)) != 0 || 291 (r = ssh_packet_write_wait(ssh)) < 0) 292 fatal_fr(r, "send packet"); 293 294 for (i = 0; i < kbdintctxt->nreq; i++) 295 free(prompts[i]); 296 free(prompts); 297 free(echo_on); 298 free(name); 299 free(instr); 300 return 1; 301 } 302 303 static int 304 input_userauth_info_response(int type, uint32_t seq, struct ssh *ssh) 305 { 306 Authctxt *authctxt = ssh->authctxt; 307 KbdintAuthctxt *kbdintctxt; 308 int authenticated = 0, res; 309 int r; 310 u_int i, nresp; 311 const char *devicename = NULL; 312 char **response = NULL; 313 314 if (authctxt == NULL) 315 fatal_f("no authctxt"); 316 kbdintctxt = authctxt->kbdintctxt; 317 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL) 318 fatal_f("no kbdintctxt"); 319 if (kbdintctxt->device == NULL) 320 fatal_f("no device"); 321 322 authctxt->postponed = 0; /* reset */ 323 if ((r = sshpkt_get_u32(ssh, &nresp)) != 0) 324 fatal_fr(r, "parse packet"); 325 if (nresp != kbdintctxt->nreq) 326 fatal_f("wrong number of replies"); 327 if (nresp > 100) 328 fatal_f("too many replies"); 329 if (nresp > 0) { 330 response = xcalloc(nresp, sizeof(char *)); 331 for (i = 0; i < nresp; i++) { 332 if ((r = sshpkt_get_cstring(ssh, &response[i], NULL)) != 0) 333 fatal_fr(r, "parse response"); 334 } 335 } 336 if ((r = sshpkt_get_end(ssh)) != 0) 337 fatal_fr(r, "parse packet"); 338 339 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response); 340 341 for (i = 0; i < nresp; i++) { 342 explicit_bzero(response[i], strlen(response[i])); 343 free(response[i]); 344 } 345 free(response); 346 347 switch (res) { 348 case 0: 349 /* Success! */ 350 authenticated = authctxt->valid ? 1 : 0; 351 break; 352 case 1: 353 /* Authentication needs further interaction */ 354 if (send_userauth_info_request(ssh) == 1) 355 authctxt->postponed = 1; 356 break; 357 default: 358 /* Failure! */ 359 break; 360 } 361 devicename = kbdintctxt->device->name; 362 if (!authctxt->postponed) { 363 if (authenticated) { 364 auth2_challenge_stop(ssh); 365 } else { 366 /* start next device */ 367 /* may set authctxt->postponed */ 368 auth2_challenge_start(ssh); 369 } 370 } 371 userauth_finish(ssh, authenticated, "keyboard-interactive", 372 devicename); 373 return 0; 374 } 375
Indexes created Fri Apr 24 00:22:58 UTC 2026