/* * Copyright (c) 2000 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* * Copyright 2007 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ #include "includes.h" RCSID("$OpenBSD: auth2-pubkey.c,v 1.2 2002/05/31 11:35:15 markus Exp $"); #pragma ident "%Z%%M% %I% %E% SMI" #include "ssh2.h" #include "xmalloc.h" #include "packet.h" #include "buffer.h" #include "log.h" #include "servconf.h" #include "compat.h" #include "bufaux.h" #include "auth.h" #include "key.h" #include "pathnames.h" #include "uidswap.h" #include "auth-options.h" #include "canohost.h" #ifdef USE_PAM #include #include "auth-pam.h" #endif /* USE_PAM */ /* import */ extern ServerOptions options; extern u_char *session_id2; extern int session_id2_len; static void userauth_pubkey(Authctxt *authctxt) { Buffer b; Key *key = NULL; char *pkalg; u_char *pkblob, *sig; u_int alen, blen, slen; int have_sig, pktype; int authenticated = 0; if (!authctxt || !authctxt->method) fatal("%s: missing context", __func__); have_sig = packet_get_char(); if (datafellows & SSH_BUG_PKAUTH) { debug2("userauth_pubkey: SSH_BUG_PKAUTH"); /* no explicit pkalg given */ pkblob = packet_get_string(&blen); buffer_init(&b); buffer_append(&b, pkblob, blen); /* so we have to extract the pkalg from the pkblob */ pkalg = buffer_get_string(&b, &alen); buffer_free(&b); } else { pkalg = packet_get_string(&alen); pkblob = packet_get_string(&blen); } pktype = key_type_from_name(pkalg); if (pktype == KEY_UNSPEC) { /* this is perfectly legal */ log("userauth_pubkey: unsupported public key algorithm: %s", pkalg); goto done; } key = key_from_blob(pkblob, blen); if (key == NULL) { error("userauth_pubkey: cannot decode key: %s", pkalg); goto done; } if (key->type != pktype) { error("userauth_pubkey: type mismatch for decoded key " "(received %d, expected %d)", key->type, pktype); goto done; } /* Detect and count abandonment */ if (authctxt->method->method_data) { Key *prev_key; unsigned char *prev_pkblob; int prev_blen; /* * Check for earlier test of a key that was allowed but * not followed up with a pubkey req for the same pubkey * and with a signature. */ prev_key = authctxt->method->method_data; if ((prev_blen = key_to_blob(prev_key, &prev_pkblob, NULL))) { if (prev_blen != blen || memcmp(prev_pkblob, pkblob, blen) != 0) { authctxt->method->abandons++; authctxt->method->attempts++; } } key_free(prev_key); authctxt->method->method_data = NULL; } if (have_sig) { sig = packet_get_string(&slen); packet_check_eom(); buffer_init(&b); if (datafellows & SSH_OLD_SESSIONID) { buffer_append(&b, session_id2, session_id2_len); } else { buffer_put_string(&b, session_id2, session_id2_len); } /* reconstruct packet */ buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); buffer_put_cstring(&b, authctxt->user); buffer_put_cstring(&b, datafellows & SSH_BUG_PKSERVICE ? "ssh-userauth" : authctxt->service); if (datafellows & SSH_BUG_PKAUTH) { buffer_put_char(&b, have_sig); } else { buffer_put_cstring(&b, "publickey"); buffer_put_char(&b, have_sig); buffer_put_cstring(&b, pkalg); } buffer_put_string(&b, pkblob, blen); #ifdef DEBUG_PK buffer_dump(&b); #endif /* test for correct signature */ if (user_key_allowed(authctxt->pw, key) && key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1) { authenticated = 1; } authctxt->method->postponed = 0; buffer_clear(&b); xfree(sig); } else { debug("test whether pkalg/pkblob are acceptable"); packet_check_eom(); /* XXX fake reply and always send PK_OK ? */ /* * XXX this allows testing whether a user is allowed * to login: if you happen to have a valid pubkey this * message is sent. the message is NEVER sent at all * if a user is not allowed to login. is this an * issue? -markus */ if (user_key_allowed(authctxt->pw, key)) { packet_start(SSH2_MSG_USERAUTH_PK_OK); packet_put_string(pkalg, alen); packet_put_string(pkblob, blen); packet_send(); packet_write_wait(); authctxt->method->postponed = 1; /* * Remember key that was tried so we can * correctly detect abandonment. See above. */ authctxt->method->method_data = (void *) key; key = NULL; } } if (authenticated != 1) auth_clear_options(); done: /* * XXX TODO: add config options for specifying users for whom * this userauth is insufficient and what userauths may * continue. */ #ifdef USE_PAM if (authenticated) { if (!do_pam_non_initial_userauth(authctxt)) authenticated = 0; } #endif /* USE_PAM */ debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg); if (key != NULL) key_free(key); xfree(pkalg); xfree(pkblob); #ifdef HAVE_CYGWIN if (check_nt_auth(0, authctxt->pw) == 0) return; #endif if (authenticated) authctxt->method->authenticated = 1; } /* return 1 if user allows given key */ static int user_key_allowed2(struct passwd *pw, Key *key, char *file) { char line[8192]; int found_key = 0; FILE *f; u_long linenum = 0; struct stat st; Key *found; char *fp; if (pw == NULL) return 0; /* Temporarily use the user's uid. */ temporarily_use_uid(pw); debug("trying public key file %s", file); /* Fail quietly if file does not exist */ if (stat(file, &st) < 0) { /* Restore the privileged uid. */ restore_uid(); return 0; } /* Open the file containing the authorized keys. */ f = fopen(file, "r"); if (!f) { /* Restore the privileged uid. */ restore_uid(); return 0; } if (options.strict_modes && secure_filename(f, file, pw, line, sizeof(line)) != 0) { (void) fclose(f); log("Authentication refused: %s", line); restore_uid(); return 0; } found_key = 0; found = key_new(key->type); while (fgets(line, sizeof(line), f)) { char *cp, *options = NULL; linenum++; /* Skip leading whitespace, empty and comment lines. */ for (cp = line; *cp == ' ' || *cp == '\t'; cp++) ; if (!*cp || *cp == '\n' || *cp == '#') continue; if (key_read(found, &cp) != 1) { /* no key? check if there are options for this key */ int quoted = 0; debug2("user_key_allowed: check options: '%s'", cp); options = cp; for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { if (*cp == '\\' && cp[1] == '"') cp++; /* Skip both */ else if (*cp == '"') quoted = !quoted; } /* Skip remaining whitespace. */ for (; *cp == ' ' || *cp == '\t'; cp++) ; if (key_read(found, &cp) != 1) { debug2("user_key_allowed: advance: '%s'", cp); /* still no key? advance to next line*/ continue; } } if (key_equal(found, key) && auth_parse_options(pw, options, file, linenum) == 1) { found_key = 1; debug("matching key found: file %s, line %lu", file, linenum); fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); verbose("Found matching %s key: %s", key_type(found), fp); xfree(fp); break; } } restore_uid(); (void) fclose(f); key_free(found); if (!found_key) debug2("key not found"); return found_key; } /* check whether given key is in .ssh/authorized_keys* */ int user_key_allowed(struct passwd *pw, Key *key) { int success; char *file; if (pw == NULL) return 0; file = authorized_keys_file(pw); success = user_key_allowed2(pw, key, file); xfree(file); if (success) return success; /* try suffix "2" for backward compat, too */ file = authorized_keys_file2(pw); success = user_key_allowed2(pw, key, file); xfree(file); return success; } static void userauth_pubkey_abandon(Authctxt *authctxt, Authmethod *method) { if (!authctxt || !method) return; if (method->method_data) { method->abandons++; method->attempts++; key_free((Key *) method->method_data); method->method_data = NULL; } } Authmethod method_pubkey = { "publickey", &options.pubkey_authentication, userauth_pubkey, userauth_pubkey_abandon, NULL, NULL, /* method data and hist data */ 0, /* not initial userauth */ 0, 0, 0, /* counters */ 0, 0, 0, 0, 0, 0 /* state */ };