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