auth2-pubkey.c revision 1.1.1.1
1/* $NetBSD: auth2-pubkey.c,v 1.1.1.1 2009/06/07 22:19:03 christos Exp $ */ 2/* $OpenBSD: auth2-pubkey.c,v 1.19 2008/07/03 21:46:58 otto Exp $ */ 3/* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 28#include <sys/types.h> 29#include <sys/stat.h> 30 31#include <fcntl.h> 32#include <pwd.h> 33#include <stdio.h> 34#include <stdarg.h> 35#include <unistd.h> 36 37#include "xmalloc.h" 38#include "ssh.h" 39#include "ssh2.h" 40#include "packet.h" 41#include "buffer.h" 42#include "log.h" 43#include "servconf.h" 44#include "compat.h" 45#include "key.h" 46#include "hostfile.h" 47#include "auth.h" 48#include "pathnames.h" 49#include "uidswap.h" 50#include "auth-options.h" 51#include "canohost.h" 52#ifdef GSSAPI 53#include "ssh-gss.h" 54#endif 55#include "monitor_wrap.h" 56#include "misc.h" 57 58/* import */ 59extern ServerOptions options; 60extern u_char *session_id2; 61extern u_int session_id2_len; 62 63static int 64userauth_pubkey(Authctxt *authctxt) 65{ 66 Buffer b; 67 Key *key = NULL; 68 char *pkalg; 69 u_char *pkblob, *sig; 70 u_int alen, blen, slen; 71 int have_sig, pktype; 72 int authenticated = 0; 73 74 if (!authctxt->valid) { 75 debug2("userauth_pubkey: disabled because of invalid user"); 76 return 0; 77 } 78 have_sig = packet_get_char(); 79 if (datafellows & SSH_BUG_PKAUTH) { 80 debug2("userauth_pubkey: SSH_BUG_PKAUTH"); 81 /* no explicit pkalg given */ 82 pkblob = packet_get_string(&blen); 83 buffer_init(&b); 84 buffer_append(&b, pkblob, blen); 85 /* so we have to extract the pkalg from the pkblob */ 86 pkalg = buffer_get_string(&b, &alen); 87 buffer_free(&b); 88 } else { 89 pkalg = packet_get_string(&alen); 90 pkblob = packet_get_string(&blen); 91 } 92 pktype = key_type_from_name(pkalg); 93 if (pktype == KEY_UNSPEC) { 94 /* this is perfectly legal */ 95 logit("userauth_pubkey: unsupported public key algorithm: %s", 96 pkalg); 97 goto done; 98 } 99 key = key_from_blob(pkblob, blen); 100 if (key == NULL) { 101 error("userauth_pubkey: cannot decode key: %s", pkalg); 102 goto done; 103 } 104 if (key->type != pktype) { 105 error("userauth_pubkey: type mismatch for decoded key " 106 "(received %d, expected %d)", key->type, pktype); 107 goto done; 108 } 109 if (have_sig) { 110 sig = packet_get_string(&slen); 111 packet_check_eom(); 112 buffer_init(&b); 113 if (datafellows & SSH_OLD_SESSIONID) { 114 buffer_append(&b, session_id2, session_id2_len); 115 } else { 116 buffer_put_string(&b, session_id2, session_id2_len); 117 } 118 /* reconstruct packet */ 119 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); 120 buffer_put_cstring(&b, authctxt->user); 121 buffer_put_cstring(&b, 122 datafellows & SSH_BUG_PKSERVICE ? 123 "ssh-userauth" : 124 authctxt->service); 125 if (datafellows & SSH_BUG_PKAUTH) { 126 buffer_put_char(&b, have_sig); 127 } else { 128 buffer_put_cstring(&b, "publickey"); 129 buffer_put_char(&b, have_sig); 130 buffer_put_cstring(&b, pkalg); 131 } 132 buffer_put_string(&b, pkblob, blen); 133#ifdef DEBUG_PK 134 buffer_dump(&b); 135#endif 136 /* test for correct signature */ 137 authenticated = 0; 138 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) && 139 PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), 140 buffer_len(&b))) == 1) 141 authenticated = 1; 142 buffer_free(&b); 143 xfree(sig); 144 } else { 145 debug("test whether pkalg/pkblob are acceptable"); 146 packet_check_eom(); 147 148 /* XXX fake reply and always send PK_OK ? */ 149 /* 150 * XXX this allows testing whether a user is allowed 151 * to login: if you happen to have a valid pubkey this 152 * message is sent. the message is NEVER sent at all 153 * if a user is not allowed to login. is this an 154 * issue? -markus 155 */ 156 if (PRIVSEP(user_key_allowed(authctxt->pw, key))) { 157 packet_start(SSH2_MSG_USERAUTH_PK_OK); 158 packet_put_string(pkalg, alen); 159 packet_put_string(pkblob, blen); 160 packet_send(); 161 packet_write_wait(); 162 authctxt->postponed = 1; 163 } 164 } 165 if (authenticated != 1) 166 auth_clear_options(); 167done: 168 debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg); 169 if (key != NULL) 170 key_free(key); 171 xfree(pkalg); 172 xfree(pkblob); 173 return authenticated; 174} 175 176/* return 1 if user allows given key */ 177static int 178user_key_allowed2(struct passwd *pw, Key *key, char *file) 179{ 180 char line[SSH_MAX_PUBKEY_BYTES]; 181 int found_key = 0; 182 FILE *f; 183 u_long linenum = 0; 184 Key *found; 185 char *fp; 186 187 /* Temporarily use the user's uid. */ 188 temporarily_use_uid(pw); 189 190 debug("trying public key file %s", file); 191 f = auth_openkeyfile(file, pw, options.strict_modes); 192 193 if (!f) { 194 restore_uid(); 195 return 0; 196 } 197 198 found_key = 0; 199 found = key_new(key->type); 200 201 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { 202 char *cp, *key_options = NULL; 203 204 /* Skip leading whitespace, empty and comment lines. */ 205 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 206 ; 207 if (!*cp || *cp == '\n' || *cp == '#') 208 continue; 209 210 if (key_read(found, &cp) != 1) { 211 /* no key? check if there are options for this key */ 212 int quoted = 0; 213 debug2("user_key_allowed: check options: '%s'", cp); 214 key_options = cp; 215 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { 216 if (*cp == '\\' && cp[1] == '"') 217 cp++; /* Skip both */ 218 else if (*cp == '"') 219 quoted = !quoted; 220 } 221 /* Skip remaining whitespace. */ 222 for (; *cp == ' ' || *cp == '\t'; cp++) 223 ; 224 if (key_read(found, &cp) != 1) { 225 debug2("user_key_allowed: advance: '%s'", cp); 226 /* still no key? advance to next line*/ 227 continue; 228 } 229 } 230 if (key_equal(found, key) && 231 auth_parse_options(pw, key_options, file, linenum) == 1) { 232 found_key = 1; 233 debug("matching key found: file %s, line %lu", 234 file, linenum); 235 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 236 verbose("Found matching %s key: %s", 237 key_type(found), fp); 238 xfree(fp); 239 break; 240 } 241 } 242 restore_uid(); 243 fclose(f); 244 key_free(found); 245 if (!found_key) 246 debug2("key not found"); 247 return found_key; 248} 249 250/* check whether given key is in .ssh/authorized_keys* */ 251int 252user_key_allowed(struct passwd *pw, Key *key) 253{ 254 int success; 255 char *file; 256 257 file = authorized_keys_file(pw); 258 success = user_key_allowed2(pw, key, file); 259 xfree(file); 260 if (success) 261 return success; 262 263 /* try suffix "2" for backward compat, too */ 264 file = authorized_keys_file2(pw); 265 success = user_key_allowed2(pw, key, file); 266 xfree(file); 267 return success; 268} 269 270Authmethod method_pubkey = { 271 "publickey", 272 userauth_pubkey, 273 &options.pubkey_authentication 274}; 275