Annotation of src/usr.bin/ssh/auth1.c, Revision 1.54
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"
1.54 ! djm 13: RCSID("$OpenBSD: auth1.c,v 1.53 2003/09/23 20:17:11 markus 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"
1.35 markus 25: #include "channels.h"
1.1 markus 26: #include "session.h"
1.25 dugsong 27: #include "uidswap.h"
1.38 provos 28: #include "monitor_wrap.h"
1.1 markus 29:
30: /* import */
31: extern ServerOptions options;
32:
33: /*
34: * convert ssh auth msg type into description
35: */
1.24 itojun 36: static char *
1.1 markus 37: get_authname(int type)
38: {
39: static char buf[1024];
40: switch (type) {
41: case SSH_CMSG_AUTH_PASSWORD:
42: return "password";
43: case SSH_CMSG_AUTH_RSA:
44: return "rsa";
45: case SSH_CMSG_AUTH_RHOSTS_RSA:
46: return "rhosts-rsa";
47: case SSH_CMSG_AUTH_RHOSTS:
48: return "rhosts";
1.11 markus 49: case SSH_CMSG_AUTH_TIS:
50: case SSH_CMSG_AUTH_TIS_RESPONSE:
51: return "challenge-response";
1.1 markus 52: }
53: snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
54: return buf;
55: }
56:
57: /*
1.11 markus 58: * read packets, try to authenticate the user and
59: * return only if authentication is successful
1.1 markus 60: */
1.24 itojun 61: static void
1.11 markus 62: do_authloop(Authctxt *authctxt)
1.1 markus 63: {
1.5 markus 64: int authenticated = 0;
1.8 markus 65: u_int bits;
1.29 markus 66: Key *client_host_key;
1.1 markus 67: BIGNUM *n;
68: char *client_user, *password;
1.11 markus 69: char info[1024];
1.8 markus 70: u_int dlen;
71: u_int ulen;
1.1 markus 72: int type = 0;
1.11 markus 73: struct passwd *pw = authctxt->pw;
74:
75: debug("Attempting authentication for %s%.100s.",
1.27 deraadt 76: authctxt->valid ? "" : "illegal user ", authctxt->user);
1.11 markus 77:
78: /* If the user has no password, accept authentication immediately. */
79: if (options.password_authentication &&
1.49 markus 80: #ifdef KRB5
1.11 markus 81: (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
82: #endif
1.38 provos 83: PRIVSEP(auth_password(authctxt, ""))) {
1.11 markus 84: auth_log(authctxt, 1, "without authentication", "");
85: return;
86: }
1.27 deraadt 87:
1.1 markus 88: /* Indicate that authentication is needed. */
89: packet_start(SSH_SMSG_FAILURE);
90: packet_send();
91: packet_write_wait();
92:
1.11 markus 93: for (;;) {
1.5 markus 94: /* default to fail */
95: authenticated = 0;
96:
1.11 markus 97: info[0] = '\0';
1.1 markus 98:
99: /* Get a packet from the client. */
1.34 markus 100: type = packet_read();
1.1 markus 101:
102: /* Process the packet. */
103: switch (type) {
104: case SSH_CMSG_AUTH_RHOSTS_RSA:
105: if (!options.rhosts_rsa_authentication) {
106: verbose("Rhosts with RSA authentication disabled.");
107: break;
108: }
109: /*
110: * Get client user name. Note that we just have to
111: * trust the client; root on the client machine can
112: * claim to be any user.
113: */
114: client_user = packet_get_string(&ulen);
115:
116: /* Get the client host key. */
1.29 markus 117: client_host_key = key_new(KEY_RSA1);
1.1 markus 118: bits = packet_get_int();
1.33 markus 119: packet_get_bignum(client_host_key->rsa->e);
120: packet_get_bignum(client_host_key->rsa->n);
1.1 markus 121:
1.29 markus 122: if (bits != BN_num_bits(client_host_key->rsa->n))
1.5 markus 123: verbose("Warning: keysize mismatch for client_host_key: "
1.29 markus 124: "actual %d, announced %d",
1.41 deraadt 125: BN_num_bits(client_host_key->rsa->n), bits);
1.32 markus 126: packet_check_eom();
1.1 markus 127:
1.54 ! djm 128: authenticated = auth_rhosts_rsa(authctxt, client_user,
1.30 markus 129: client_host_key);
1.29 markus 130: key_free(client_host_key);
1.1 markus 131:
1.11 markus 132: snprintf(info, sizeof info, " ruser %.100s", client_user);
1.1 markus 133: xfree(client_user);
134: break;
135:
136: case SSH_CMSG_AUTH_RSA:
137: if (!options.rsa_authentication) {
138: verbose("RSA authentication disabled.");
139: break;
140: }
141: /* RSA authentication requested. */
1.29 markus 142: if ((n = BN_new()) == NULL)
143: fatal("do_authloop: BN_new failed");
1.33 markus 144: packet_get_bignum(n);
1.32 markus 145: packet_check_eom();
1.54 ! djm 146: authenticated = auth_rsa(authctxt, n);
1.1 markus 147: BN_clear_free(n);
148: break;
149:
150: case SSH_CMSG_AUTH_PASSWORD:
151: if (!options.password_authentication) {
152: verbose("Password authentication disabled.");
153: break;
154: }
155: /*
156: * Read user password. It is in plain text, but was
157: * transmitted over the encrypted channel so it is
158: * not visible to an outside observer.
159: */
160: password = packet_get_string(&dlen);
1.32 markus 161: packet_check_eom();
1.1 markus 162:
163: /* Try authentication with the password. */
1.38 provos 164: authenticated = PRIVSEP(auth_password(authctxt, password));
1.1 markus 165:
166: memset(password, 0, strlen(password));
167: xfree(password);
168: break;
169:
170: case SSH_CMSG_AUTH_TIS:
171: debug("rcvd SSH_CMSG_AUTH_TIS");
1.23 markus 172: if (options.challenge_response_authentication == 1) {
173: char *challenge = get_challenge(authctxt);
1.11 markus 174: if (challenge != NULL) {
175: debug("sending challenge '%s'", challenge);
1.1 markus 176: packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
1.11 markus 177: packet_put_cstring(challenge);
1.23 markus 178: xfree(challenge);
1.1 markus 179: packet_send();
180: packet_write_wait();
181: continue;
182: }
183: }
184: break;
185: case SSH_CMSG_AUTH_TIS_RESPONSE:
186: debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
1.23 markus 187: if (options.challenge_response_authentication == 1) {
1.1 markus 188: char *response = packet_get_string(&dlen);
1.32 markus 189: packet_check_eom();
1.11 markus 190: authenticated = verify_response(authctxt, response);
191: memset(response, 'r', dlen);
1.1 markus 192: xfree(response);
193: }
194: break;
195:
196: default:
197: /*
198: * Any unknown messages will be ignored (and failure
199: * returned) during authentication.
200: */
1.48 itojun 201: logit("Unknown message during authentication: type %d", type);
1.1 markus 202: break;
203: }
1.20 markus 204: #ifdef BSD_AUTH
205: if (authctxt->as) {
206: auth_close(authctxt->as);
207: authctxt->as = NULL;
208: }
209: #endif
1.11 markus 210: if (!authctxt->valid && authenticated)
211: fatal("INTERNAL ERROR: authenticated invalid user %s",
212: authctxt->user);
213:
214: /* Special handling for root */
1.47 markus 215: if (authenticated && authctxt->pw->pw_uid == 0 &&
1.16 markus 216: !auth_root_allowed(get_authname(type)))
1.11 markus 217: authenticated = 0;
1.1 markus 218:
1.11 markus 219: /* Log before sending the reply */
220: auth_log(authctxt, authenticated, get_authname(type), info);
1.1 markus 221:
222: if (authenticated)
223: return;
224:
1.11 markus 225: if (authctxt->failures++ > AUTH_FAIL_MAX)
226: packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
1.1 markus 227:
228: packet_start(SSH_SMSG_FAILURE);
229: packet_send();
230: packet_write_wait();
231: }
232: }
233:
234: /*
235: * Performs authentication of an incoming connection. Session key has already
236: * been exchanged and encryption is enabled.
237: */
1.53 markus 238: void
239: do_authentication(Authctxt *authctxt)
1.1 markus 240: {
1.8 markus 241: u_int ulen;
1.40 markus 242: char *user, *style = NULL;
1.1 markus 243:
244: /* Get the name of the user that we wish to log in as. */
1.34 markus 245: packet_read_expect(SSH_CMSG_USER);
1.1 markus 246:
247: /* Get the user name. */
248: user = packet_get_string(&ulen);
1.32 markus 249: packet_check_eom();
1.1 markus 250:
1.11 markus 251: if ((style = strchr(user, ':')) != NULL)
1.25 dugsong 252: *style++ = '\0';
1.27 deraadt 253:
1.11 markus 254: authctxt->user = user;
255: authctxt->style = style;
256:
1.1 markus 257: /* Verify that the user is a valid user. */
1.39 markus 258: if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
1.11 markus 259: authctxt->valid = 1;
1.51 markus 260: else {
1.11 markus 261: debug("do_authentication: illegal user %s", user);
1.51 markus 262: authctxt->pw = fakepw();
263: }
1.17 markus 264:
1.39 markus 265: setproctitle("%s%s", authctxt->pw ? user : "unknown",
1.38 provos 266: use_privsep ? " [net]" : "");
1.1 markus 267:
268: /*
269: * If we are not running as root, the user must have the same uid as
270: * the server.
271: */
1.39 markus 272: if (!use_privsep && getuid() != 0 && authctxt->pw &&
273: authctxt->pw->pw_uid != getuid())
1.1 markus 274: packet_disconnect("Cannot change user when server not running as root.");
275:
1.11 markus 276: /*
277: * Loop until the user has been authenticated or the connection is
278: * closed, do_authloop() returns only if authentication is successful
279: */
280: do_authloop(authctxt);
1.1 markus 281:
282: /* The user has been authenticated and accepted. */
283: packet_start(SSH_SMSG_SUCCESS);
284: packet_send();
285: packet_write_wait();
286: }
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