Annotation of src/usr.bin/ssh/auth1.c, Revision 1.25
1.1 markus 1: /*
2: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
3: * All rights reserved
1.4 deraadt 4: *
5: * As far as I am concerned, the code I have written for this software
6: * can be used freely for any purpose. Any derived versions of this
7: * software must be clearly marked as such, and if the derived work is
8: * incompatible with the protocol description in the RFC file, it must be
9: * called by a name other than "ssh" or "Secure Shell".
1.1 markus 10: */
11:
12: #include "includes.h"
1.25 ! dugsong 13: RCSID("$OpenBSD: auth1.c,v 1.24 2001/06/23 15:12:17 itojun Exp $");
1.1 markus 14:
15: #include "xmalloc.h"
16: #include "rsa.h"
1.12 markus 17: #include "ssh1.h"
1.1 markus 18: #include "packet.h"
19: #include "buffer.h"
20: #include "mpaux.h"
1.13 markus 21: #include "log.h"
1.1 markus 22: #include "servconf.h"
23: #include "compat.h"
24: #include "auth.h"
25: #include "session.h"
1.18 markus 26: #include "misc.h"
1.25 ! dugsong 27: #include "uidswap.h"
1.1 markus 28:
29: /* import */
30: extern ServerOptions options;
31:
32: /*
33: * convert ssh auth msg type into description
34: */
1.24 itojun 35: static char *
1.1 markus 36: get_authname(int type)
37: {
38: static char buf[1024];
39: switch (type) {
40: case SSH_CMSG_AUTH_PASSWORD:
41: return "password";
42: case SSH_CMSG_AUTH_RSA:
43: return "rsa";
44: case SSH_CMSG_AUTH_RHOSTS_RSA:
45: return "rhosts-rsa";
46: case SSH_CMSG_AUTH_RHOSTS:
47: return "rhosts";
1.11 markus 48: case SSH_CMSG_AUTH_TIS:
49: case SSH_CMSG_AUTH_TIS_RESPONSE:
50: return "challenge-response";
1.25 ! dugsong 51: #if defined(KRB4) || defined(KRB5)
1.1 markus 52: case SSH_CMSG_AUTH_KERBEROS:
53: return "kerberos";
54: #endif
55: }
56: snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
57: return buf;
58: }
59:
60: /*
1.11 markus 61: * read packets, try to authenticate the user and
62: * return only if authentication is successful
1.1 markus 63: */
1.24 itojun 64: static void
1.11 markus 65: do_authloop(Authctxt *authctxt)
1.1 markus 66: {
1.5 markus 67: int authenticated = 0;
1.8 markus 68: u_int bits;
1.1 markus 69: RSA *client_host_key;
70: BIGNUM *n;
71: char *client_user, *password;
1.11 markus 72: char info[1024];
1.8 markus 73: u_int dlen;
1.1 markus 74: int plen, nlen, elen;
1.8 markus 75: u_int ulen;
1.1 markus 76: int type = 0;
1.11 markus 77: struct passwd *pw = authctxt->pw;
78:
79: debug("Attempting authentication for %s%.100s.",
80: authctxt->valid ? "" : "illegal user ", authctxt->user);
81:
82: /* If the user has no password, accept authentication immediately. */
83: if (options.password_authentication &&
1.25 ! dugsong 84: #if defined(KRB4) || defined(KRB5)
1.11 markus 85: (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
86: #endif
1.20 markus 87: auth_password(authctxt, "")) {
1.11 markus 88: auth_log(authctxt, 1, "without authentication", "");
89: return;
90: }
1.25 ! dugsong 91:
1.1 markus 92: /* Indicate that authentication is needed. */
93: packet_start(SSH_SMSG_FAILURE);
94: packet_send();
95: packet_write_wait();
96:
1.11 markus 97: for (;;) {
1.5 markus 98: /* default to fail */
99: authenticated = 0;
100:
1.11 markus 101: info[0] = '\0';
1.1 markus 102:
103: /* Get a packet from the client. */
104: type = packet_read(&plen);
105:
106: /* Process the packet. */
107: switch (type) {
108:
1.25 ! dugsong 109: #if defined(KRB4) || defined(KRB5)
1.1 markus 110: case SSH_CMSG_AUTH_KERBEROS:
111: if (!options.kerberos_authentication) {
112: verbose("Kerberos authentication disabled.");
113: } else {
1.25 ! dugsong 114: char *kdata = packet_get_string(&dlen);
! 115:
! 116: packet_integrity_check(plen, 4 + dlen, type);
! 117:
! 118: if (kdata[0] == 4) { /* KRB_PROT_VERSION */
! 119: #ifdef KRB4
! 120: KTEXT_ST tkt;
! 121:
! 122: tkt.length = dlen;
! 123: if (tkt.length < MAX_KTXT_LEN)
! 124: memcpy(tkt.dat, kdata, tkt.length);
! 125:
! 126: if (auth_krb4(authctxt, &tkt, &client_user)) {
! 127: authenticated = 1;
! 128: snprintf(info, sizeof(info),
! 129: " tktuser %.100s",
! 130: client_user);
! 131: xfree(client_user);
1.5 markus 132: }
1.25 ! dugsong 133: #endif /* KRB4 */
! 134: } else {
! 135: #ifdef KRB5
! 136: krb5_data tkt;
! 137: tkt.length = dlen;
! 138: tkt.data = kdata;
! 139:
! 140: if (auth_krb5(authctxt, &tkt, &client_user)) {
! 141: authenticated = 1;
! 142: snprintf(info, sizeof(info),
! 143: " tktuser %.100s",
! 144: client_user);
! 145: xfree(client_user);
! 146: }
! 147: #endif /* KRB5 */
1.1 markus 148: }
1.11 markus 149: xfree(kdata);
1.1 markus 150: }
151: break;
1.25 ! dugsong 152: #endif /* KRB4 || KRB5 */
! 153:
! 154: #if defined(AFS) || defined(KRB5)
! 155: /* XXX - punt on backward compatibility here. */
! 156: case SSH_CMSG_HAVE_KERBEROS_TGT:
! 157: packet_send_debug("Kerberos TGT passing disabled before authentication.");
! 158: break;
! 159: #ifdef AFS
! 160: case SSH_CMSG_HAVE_AFS_TOKEN:
! 161: packet_send_debug("AFS token passing disabled before authentication.");
! 162: break;
! 163: #endif /* AFS */
! 164: #endif /* AFS || KRB5 */
! 165:
1.1 markus 166: case SSH_CMSG_AUTH_RHOSTS:
167: if (!options.rhosts_authentication) {
168: verbose("Rhosts authentication disabled.");
169: break;
170: }
171: /*
172: * Get client user name. Note that we just have to
173: * trust the client; this is one reason why rhosts
174: * authentication is insecure. (Another is
175: * IP-spoofing on a local network.)
176: */
177: client_user = packet_get_string(&ulen);
178: packet_integrity_check(plen, 4 + ulen, type);
179:
1.5 markus 180: /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
1.1 markus 181: authenticated = auth_rhosts(pw, client_user);
182:
1.11 markus 183: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 184: xfree(client_user);
185: break;
186:
187: case SSH_CMSG_AUTH_RHOSTS_RSA:
188: if (!options.rhosts_rsa_authentication) {
189: verbose("Rhosts with RSA authentication disabled.");
190: break;
191: }
192: /*
193: * Get client user name. Note that we just have to
194: * trust the client; root on the client machine can
195: * claim to be any user.
196: */
197: client_user = packet_get_string(&ulen);
198:
199: /* Get the client host key. */
200: client_host_key = RSA_new();
201: if (client_host_key == NULL)
202: fatal("RSA_new failed");
203: client_host_key->e = BN_new();
204: client_host_key->n = BN_new();
205: if (client_host_key->e == NULL || client_host_key->n == NULL)
206: fatal("BN_new failed");
207: bits = packet_get_int();
208: packet_get_bignum(client_host_key->e, &elen);
209: packet_get_bignum(client_host_key->n, &nlen);
210:
211: if (bits != BN_num_bits(client_host_key->n))
1.5 markus 212: verbose("Warning: keysize mismatch for client_host_key: "
1.2 markus 213: "actual %d, announced %d", BN_num_bits(client_host_key->n), bits);
1.1 markus 214: packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
215:
216: authenticated = auth_rhosts_rsa(pw, client_user, client_host_key);
217: RSA_free(client_host_key);
218:
1.11 markus 219: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 220: xfree(client_user);
221: break;
222:
223: case SSH_CMSG_AUTH_RSA:
224: if (!options.rsa_authentication) {
225: verbose("RSA authentication disabled.");
226: break;
227: }
228: /* RSA authentication requested. */
229: n = BN_new();
230: packet_get_bignum(n, &nlen);
231: packet_integrity_check(plen, nlen, type);
232: authenticated = auth_rsa(pw, n);
233: BN_clear_free(n);
234: break;
235:
236: case SSH_CMSG_AUTH_PASSWORD:
237: if (!options.password_authentication) {
238: verbose("Password authentication disabled.");
239: break;
240: }
241: /*
242: * Read user password. It is in plain text, but was
243: * transmitted over the encrypted channel so it is
244: * not visible to an outside observer.
245: */
246: password = packet_get_string(&dlen);
247: packet_integrity_check(plen, 4 + dlen, type);
248:
249: /* Try authentication with the password. */
1.20 markus 250: authenticated = auth_password(authctxt, password);
1.1 markus 251:
252: memset(password, 0, strlen(password));
253: xfree(password);
254: break;
255:
256: case SSH_CMSG_AUTH_TIS:
257: debug("rcvd SSH_CMSG_AUTH_TIS");
1.23 markus 258: if (options.challenge_response_authentication == 1) {
259: char *challenge = get_challenge(authctxt);
1.11 markus 260: if (challenge != NULL) {
261: debug("sending challenge '%s'", challenge);
1.1 markus 262: packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
1.11 markus 263: packet_put_cstring(challenge);
1.23 markus 264: xfree(challenge);
1.1 markus 265: packet_send();
266: packet_write_wait();
267: continue;
268: }
269: }
270: break;
271: case SSH_CMSG_AUTH_TIS_RESPONSE:
272: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
1.23 markus 273: if (options.challenge_response_authentication == 1) {
1.1 markus 274: char *response = packet_get_string(&dlen);
1.11 markus 275: debug("got response '%s'", response);
1.1 markus 276: packet_integrity_check(plen, 4 + dlen, type);
1.11 markus 277: authenticated = verify_response(authctxt, response);
278: memset(response, 'r', dlen);
1.1 markus 279: xfree(response);
280: }
281: break;
282:
283: default:
284: /*
285: * Any unknown messages will be ignored (and failure
286: * returned) during authentication.
287: */
288: log("Unknown message during authentication: type %d", type);
289: break;
290: }
1.20 markus 291: #ifdef BSD_AUTH
292: if (authctxt->as) {
293: auth_close(authctxt->as);
294: authctxt->as = NULL;
295: }
296: #endif
1.11 markus 297: if (!authctxt->valid && authenticated)
298: fatal("INTERNAL ERROR: authenticated invalid user %s",
299: authctxt->user);
300:
301: /* Special handling for root */
1.16 markus 302: if (authenticated && authctxt->pw->pw_uid == 0 &&
303: !auth_root_allowed(get_authname(type)))
1.11 markus 304: authenticated = 0;
1.1 markus 305:
1.11 markus 306: /* Log before sending the reply */
307: auth_log(authctxt, authenticated, get_authname(type), info);
1.1 markus 308:
309: if (authenticated)
310: return;
311:
1.11 markus 312: if (authctxt->failures++ > AUTH_FAIL_MAX)
313: packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
1.1 markus 314:
315: packet_start(SSH_SMSG_FAILURE);
316: packet_send();
317: packet_write_wait();
318: }
319: }
320:
321: /*
322: * Performs authentication of an incoming connection. Session key has already
323: * been exchanged and encryption is enabled.
324: */
325: void
326: do_authentication()
327: {
1.11 markus 328: Authctxt *authctxt;
329: struct passwd *pw;
1.1 markus 330: int plen;
1.8 markus 331: u_int ulen;
1.25 ! dugsong 332: char *p, *user, *style = NULL;
1.1 markus 333:
334: /* Get the name of the user that we wish to log in as. */
335: packet_read_expect(&plen, SSH_CMSG_USER);
336:
337: /* Get the user name. */
338: user = packet_get_string(&ulen);
339: packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
340:
1.11 markus 341: if ((style = strchr(user, ':')) != NULL)
1.25 ! dugsong 342: *style++ = '\0';
1.11 markus 343:
1.25 ! dugsong 344: /* XXX - SSH.com Kerberos v5 braindeath. */
! 345: if ((p = strchr(user, '@')) != NULL)
! 346: *p = '\0';
! 347:
1.11 markus 348: authctxt = authctxt_new();
349: authctxt->user = user;
350: authctxt->style = style;
351:
1.1 markus 352: /* Verify that the user is a valid user. */
353: pw = getpwnam(user);
1.5 markus 354: if (pw && allowed_user(pw)) {
1.11 markus 355: authctxt->valid = 1;
356: pw = pwcopy(pw);
1.5 markus 357: } else {
1.11 markus 358: debug("do_authentication: illegal user %s", user);
1.5 markus 359: pw = NULL;
360: }
1.11 markus 361: authctxt->pw = pw;
1.17 markus 362:
363: setproctitle("%s", pw ? user : "unknown");
1.1 markus 364:
365: /*
366: * If we are not running as root, the user must have the same uid as
367: * the server.
368: */
1.5 markus 369: if (getuid() != 0 && pw && pw->pw_uid != getuid())
1.1 markus 370: packet_disconnect("Cannot change user when server not running as root.");
371:
1.11 markus 372: /*
373: * Loop until the user has been authenticated or the connection is
374: * closed, do_authloop() returns only if authentication is successful
375: */
376: do_authloop(authctxt);
1.1 markus 377:
378: /* The user has been authenticated and accepted. */
379: packet_start(SSH_SMSG_SUCCESS);
380: packet_send();
381: packet_write_wait();
382:
383: /* Perform session preparation. */
1.21 markus 384: do_authenticated(authctxt);
1.1 markus 385: }
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