Annotation of src/usr.bin/ssh/auth1.c, Revision 1.65
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"
13:
14: #include "xmalloc.h"
15: #include "rsa.h"
1.12 markus 16: #include "ssh1.h"
1.1 markus 17: #include "packet.h"
18: #include "buffer.h"
1.13 markus 19: #include "log.h"
1.1 markus 20: #include "servconf.h"
21: #include "compat.h"
22: #include "auth.h"
1.35 markus 23: #include "channels.h"
1.1 markus 24: #include "session.h"
1.25 dugsong 25: #include "uidswap.h"
1.38 provos 26: #include "monitor_wrap.h"
1.1 markus 27:
28: /* import */
29: extern ServerOptions options;
30:
1.60 djm 31: static int auth1_process_password(Authctxt *, char *, size_t);
32: static int auth1_process_rsa(Authctxt *, char *, size_t);
33: static int auth1_process_rhosts_rsa(Authctxt *, char *, size_t);
34: static int auth1_process_tis_challenge(Authctxt *, char *, size_t);
35: static int auth1_process_tis_response(Authctxt *, char *, size_t);
36:
37: struct AuthMethod1 {
38: int type;
39: char *name;
40: int *enabled;
41: int (*method)(Authctxt *, char *, size_t);
42: };
43:
44: const struct AuthMethod1 auth1_methods[] = {
45: {
46: SSH_CMSG_AUTH_PASSWORD, "password",
47: &options.password_authentication, auth1_process_password
48: },
49: {
50: SSH_CMSG_AUTH_RSA, "rsa",
51: &options.rsa_authentication, auth1_process_rsa
52: },
53: {
54: SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa",
55: &options.rhosts_rsa_authentication, auth1_process_rhosts_rsa
56: },
57: {
58: SSH_CMSG_AUTH_TIS, "challenge-response",
59: &options.challenge_response_authentication,
60: auth1_process_tis_challenge
61: },
62: {
63: SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response",
64: &options.challenge_response_authentication,
65: auth1_process_tis_response
66: },
67: { -1, NULL, NULL, NULL}
68: };
69:
70: static const struct AuthMethod1
71: *lookup_authmethod1(int type)
72: {
73: int i;
74:
1.64 deraadt 75: for (i = 0; auth1_methods[i].name != NULL; i++)
1.60 djm 76: if (auth1_methods[i].type == type)
77: return (&(auth1_methods[i]));
78:
79: return (NULL);
80: }
81:
1.24 itojun 82: static char *
1.1 markus 83: get_authname(int type)
84: {
1.60 djm 85: const struct AuthMethod1 *a;
86: static char buf[64];
87:
88: if ((a = lookup_authmethod1(type)) != NULL)
89: return (a->name);
90: snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type);
91: return (buf);
92: }
93:
1.65 ! deraadt 94: /*ARGSUSED*/
1.60 djm 95: static int
96: auth1_process_password(Authctxt *authctxt, char *info, size_t infolen)
97: {
98: int authenticated = 0;
99: char *password;
100: u_int dlen;
101:
102: /*
103: * Read user password. It is in plain text, but was
104: * transmitted over the encrypted channel so it is
105: * not visible to an outside observer.
106: */
107: password = packet_get_string(&dlen);
108: packet_check_eom();
109:
110: /* Try authentication with the password. */
111: authenticated = PRIVSEP(auth_password(authctxt, password));
112:
113: memset(password, 0, dlen);
114: xfree(password);
115:
116: return (authenticated);
117: }
118:
1.65 ! deraadt 119: /*ARGSUSED*/
1.60 djm 120: static int
121: auth1_process_rsa(Authctxt *authctxt, char *info, size_t infolen)
122: {
123: int authenticated = 0;
124: BIGNUM *n;
125:
126: /* RSA authentication requested. */
127: if ((n = BN_new()) == NULL)
128: fatal("do_authloop: BN_new failed");
129: packet_get_bignum(n);
130: packet_check_eom();
131: authenticated = auth_rsa(authctxt, n);
132: BN_clear_free(n);
133:
134: return (authenticated);
135: }
136:
1.65 ! deraadt 137: /*ARGSUSED*/
1.60 djm 138: static int
139: auth1_process_rhosts_rsa(Authctxt *authctxt, char *info, size_t infolen)
140: {
1.61 djm 141: int keybits, authenticated = 0;
1.60 djm 142: u_int bits;
143: char *client_user;
144: Key *client_host_key;
145: u_int ulen;
146:
147: /*
148: * Get client user name. Note that we just have to
149: * trust the client; root on the client machine can
150: * claim to be any user.
151: */
152: client_user = packet_get_string(&ulen);
153:
154: /* Get the client host key. */
155: client_host_key = key_new(KEY_RSA1);
156: bits = packet_get_int();
157: packet_get_bignum(client_host_key->rsa->e);
158: packet_get_bignum(client_host_key->rsa->n);
159:
1.61 djm 160: keybits = BN_num_bits(client_host_key->rsa->n);
161: if (keybits < 0 || bits != (u_int)keybits) {
1.60 djm 162: verbose("Warning: keysize mismatch for client_host_key: "
163: "actual %d, announced %d",
164: BN_num_bits(client_host_key->rsa->n), bits);
1.1 markus 165: }
1.60 djm 166: packet_check_eom();
167:
168: authenticated = auth_rhosts_rsa(authctxt, client_user,
169: client_host_key);
170: key_free(client_host_key);
171:
172: snprintf(info, infolen, " ruser %.100s", client_user);
173: xfree(client_user);
1.62 djm 174:
1.60 djm 175: return (authenticated);
176: }
177:
1.65 ! deraadt 178: /*ARGSUSED*/
1.60 djm 179: static int
180: auth1_process_tis_challenge(Authctxt *authctxt, char *info, size_t infolen)
181: {
182: char *challenge;
1.62 djm 183:
1.60 djm 184: if ((challenge = get_challenge(authctxt)) == NULL)
185: return (0);
186:
187: debug("sending challenge '%s'", challenge);
188: packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
189: packet_put_cstring(challenge);
190: xfree(challenge);
191: packet_send();
192: packet_write_wait();
193:
194: return (-1);
195: }
196:
1.65 ! deraadt 197: /*ARGSUSED*/
1.60 djm 198: static int
199: auth1_process_tis_response(Authctxt *authctxt, char *info, size_t infolen)
200: {
201: int authenticated = 0;
202: char *response;
203: u_int dlen;
204:
205: response = packet_get_string(&dlen);
206: packet_check_eom();
207: authenticated = verify_response(authctxt, response);
208: memset(response, 'r', dlen);
209: xfree(response);
210:
211: return (authenticated);
1.1 markus 212: }
213:
214: /*
1.11 markus 215: * read packets, try to authenticate the user and
216: * return only if authentication is successful
1.1 markus 217: */
1.24 itojun 218: static void
1.11 markus 219: do_authloop(Authctxt *authctxt)
1.1 markus 220: {
1.5 markus 221: int authenticated = 0;
1.11 markus 222: char info[1024];
1.1 markus 223: int type = 0;
1.60 djm 224: const struct AuthMethod1 *meth;
1.11 markus 225:
226: debug("Attempting authentication for %s%.100s.",
1.59 markus 227: authctxt->valid ? "" : "invalid user ", authctxt->user);
1.11 markus 228:
229: /* If the user has no password, accept authentication immediately. */
230: if (options.password_authentication &&
1.49 markus 231: #ifdef KRB5
1.11 markus 232: (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
233: #endif
1.38 provos 234: PRIVSEP(auth_password(authctxt, ""))) {
1.11 markus 235: auth_log(authctxt, 1, "without authentication", "");
236: return;
237: }
1.27 deraadt 238:
1.1 markus 239: /* Indicate that authentication is needed. */
240: packet_start(SSH_SMSG_FAILURE);
241: packet_send();
242: packet_write_wait();
243:
1.11 markus 244: for (;;) {
1.5 markus 245: /* default to fail */
246: authenticated = 0;
247:
1.11 markus 248: info[0] = '\0';
1.1 markus 249:
250: /* Get a packet from the client. */
1.34 markus 251: type = packet_read();
1.60 djm 252: if ((meth = lookup_authmethod1(type)) == NULL) {
253: logit("Unknown message during authentication: "
254: "type %d", type);
255: goto skip;
256: }
1.1 markus 257:
1.60 djm 258: if (!*(meth->enabled)) {
259: verbose("%s authentication disabled.", meth->name);
260: goto skip;
1.1 markus 261: }
1.60 djm 262:
263: authenticated = meth->method(authctxt, info, sizeof(info));
264: if (authenticated == -1)
265: continue; /* "postponed" */
266:
1.20 markus 267: #ifdef BSD_AUTH
268: if (authctxt->as) {
269: auth_close(authctxt->as);
270: authctxt->as = NULL;
271: }
272: #endif
1.11 markus 273: if (!authctxt->valid && authenticated)
274: fatal("INTERNAL ERROR: authenticated invalid user %s",
275: authctxt->user);
276:
277: /* Special handling for root */
1.47 markus 278: if (authenticated && authctxt->pw->pw_uid == 0 &&
1.60 djm 279: !auth_root_allowed(meth->name))
1.11 markus 280: authenticated = 0;
1.1 markus 281:
1.60 djm 282: skip:
1.11 markus 283: /* Log before sending the reply */
284: auth_log(authctxt, authenticated, get_authname(type), info);
1.1 markus 285:
286: if (authenticated)
287: return;
288:
1.57 dtucker 289: if (authctxt->failures++ > options.max_authtries)
1.11 markus 290: packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
1.1 markus 291:
292: packet_start(SSH_SMSG_FAILURE);
293: packet_send();
294: packet_write_wait();
295: }
296: }
297:
298: /*
299: * Performs authentication of an incoming connection. Session key has already
300: * been exchanged and encryption is enabled.
301: */
1.53 markus 302: void
303: do_authentication(Authctxt *authctxt)
1.1 markus 304: {
1.8 markus 305: u_int ulen;
1.40 markus 306: char *user, *style = NULL;
1.1 markus 307:
308: /* Get the name of the user that we wish to log in as. */
1.34 markus 309: packet_read_expect(SSH_CMSG_USER);
1.1 markus 310:
311: /* Get the user name. */
312: user = packet_get_string(&ulen);
1.32 markus 313: packet_check_eom();
1.1 markus 314:
1.11 markus 315: if ((style = strchr(user, ':')) != NULL)
1.25 dugsong 316: *style++ = '\0';
1.27 deraadt 317:
1.11 markus 318: authctxt->user = user;
319: authctxt->style = style;
320:
1.1 markus 321: /* Verify that the user is a valid user. */
1.39 markus 322: if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
1.11 markus 323: authctxt->valid = 1;
1.51 markus 324: else {
1.59 markus 325: debug("do_authentication: invalid user %s", user);
1.51 markus 326: authctxt->pw = fakepw();
327: }
1.17 markus 328:
1.58 djm 329: setproctitle("%s%s", authctxt->valid ? user : "unknown",
1.38 provos 330: use_privsep ? " [net]" : "");
1.1 markus 331:
332: /*
333: * If we are not running as root, the user must have the same uid as
334: * the server.
335: */
1.39 markus 336: if (!use_privsep && getuid() != 0 && authctxt->pw &&
337: authctxt->pw->pw_uid != getuid())
1.1 markus 338: packet_disconnect("Cannot change user when server not running as root.");
339:
1.11 markus 340: /*
341: * Loop until the user has been authenticated or the connection is
342: * closed, do_authloop() returns only if authentication is successful
343: */
344: do_authloop(authctxt);
1.1 markus 345:
346: /* The user has been authenticated and accepted. */
347: packet_start(SSH_SMSG_SUCCESS);
348: packet_send();
349: packet_write_wait();
350: }
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