Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2000 Markus Friedl. All rights reserved. |
| 3 | * |
| 4 | * Redistribution and use in source and binary forms, with or without |
| 5 | * modification, are permitted provided that the following conditions |
| 6 | * are met: |
| 7 | * 1. Redistributions of source code must retain the above copyright |
| 8 | * notice, this list of conditions and the following disclaimer. |
| 9 | * 2. Redistributions in binary form must reproduce the above copyright |
| 10 | * notice, this list of conditions and the following disclaimer in the |
| 11 | * documentation and/or other materials provided with the distribution. |
| 12 | * |
| 13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 23 | */ |
| 24 | |
| 25 | #include "includes.h" |
Darren Tucker | 22cc741 | 2004-12-06 22:47:41 +1100 | [diff] [blame^] | 26 | RCSID("$OpenBSD: auth2-pubkey.c,v 1.8 2004/12/06 11:41:03 dtucker Exp $"); |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 27 | |
Darren Tucker | 22cc741 | 2004-12-06 22:47:41 +1100 | [diff] [blame^] | 28 | #include "ssh.h" |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 29 | #include "ssh2.h" |
| 30 | #include "xmalloc.h" |
| 31 | #include "packet.h" |
| 32 | #include "buffer.h" |
| 33 | #include "log.h" |
| 34 | #include "servconf.h" |
| 35 | #include "compat.h" |
| 36 | #include "bufaux.h" |
| 37 | #include "auth.h" |
| 38 | #include "key.h" |
| 39 | #include "pathnames.h" |
| 40 | #include "uidswap.h" |
| 41 | #include "auth-options.h" |
| 42 | #include "canohost.h" |
| 43 | #include "monitor_wrap.h" |
| 44 | |
| 45 | /* import */ |
| 46 | extern ServerOptions options; |
| 47 | extern u_char *session_id2; |
Darren Tucker | 502d384 | 2003-06-28 12:38:01 +1000 | [diff] [blame] | 48 | extern u_int session_id2_len; |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 49 | |
| 50 | static int |
| 51 | userauth_pubkey(Authctxt *authctxt) |
| 52 | { |
| 53 | Buffer b; |
| 54 | Key *key = NULL; |
| 55 | char *pkalg; |
| 56 | u_char *pkblob, *sig; |
| 57 | u_int alen, blen, slen; |
| 58 | int have_sig, pktype; |
| 59 | int authenticated = 0; |
| 60 | |
| 61 | if (!authctxt->valid) { |
| 62 | debug2("userauth_pubkey: disabled because of invalid user"); |
| 63 | return 0; |
| 64 | } |
| 65 | have_sig = packet_get_char(); |
| 66 | if (datafellows & SSH_BUG_PKAUTH) { |
| 67 | debug2("userauth_pubkey: SSH_BUG_PKAUTH"); |
| 68 | /* no explicit pkalg given */ |
| 69 | pkblob = packet_get_string(&blen); |
| 70 | buffer_init(&b); |
| 71 | buffer_append(&b, pkblob, blen); |
| 72 | /* so we have to extract the pkalg from the pkblob */ |
| 73 | pkalg = buffer_get_string(&b, &alen); |
| 74 | buffer_free(&b); |
| 75 | } else { |
| 76 | pkalg = packet_get_string(&alen); |
| 77 | pkblob = packet_get_string(&blen); |
| 78 | } |
| 79 | pktype = key_type_from_name(pkalg); |
| 80 | if (pktype == KEY_UNSPEC) { |
| 81 | /* this is perfectly legal */ |
Damien Miller | 996acd2 | 2003-04-09 20:59:48 +1000 | [diff] [blame] | 82 | logit("userauth_pubkey: unsupported public key algorithm: %s", |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 83 | pkalg); |
| 84 | goto done; |
| 85 | } |
| 86 | key = key_from_blob(pkblob, blen); |
| 87 | if (key == NULL) { |
| 88 | error("userauth_pubkey: cannot decode key: %s", pkalg); |
| 89 | goto done; |
| 90 | } |
| 91 | if (key->type != pktype) { |
| 92 | error("userauth_pubkey: type mismatch for decoded key " |
| 93 | "(received %d, expected %d)", key->type, pktype); |
| 94 | goto done; |
| 95 | } |
| 96 | if (have_sig) { |
| 97 | sig = packet_get_string(&slen); |
| 98 | packet_check_eom(); |
| 99 | buffer_init(&b); |
| 100 | if (datafellows & SSH_OLD_SESSIONID) { |
| 101 | buffer_append(&b, session_id2, session_id2_len); |
| 102 | } else { |
| 103 | buffer_put_string(&b, session_id2, session_id2_len); |
| 104 | } |
| 105 | /* reconstruct packet */ |
| 106 | buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST); |
| 107 | buffer_put_cstring(&b, authctxt->user); |
| 108 | buffer_put_cstring(&b, |
| 109 | datafellows & SSH_BUG_PKSERVICE ? |
| 110 | "ssh-userauth" : |
| 111 | authctxt->service); |
| 112 | if (datafellows & SSH_BUG_PKAUTH) { |
| 113 | buffer_put_char(&b, have_sig); |
| 114 | } else { |
| 115 | buffer_put_cstring(&b, "publickey"); |
| 116 | buffer_put_char(&b, have_sig); |
| 117 | buffer_put_cstring(&b, pkalg); |
| 118 | } |
| 119 | buffer_put_string(&b, pkblob, blen); |
| 120 | #ifdef DEBUG_PK |
| 121 | buffer_dump(&b); |
| 122 | #endif |
| 123 | /* test for correct signature */ |
| 124 | authenticated = 0; |
| 125 | if (PRIVSEP(user_key_allowed(authctxt->pw, key)) && |
| 126 | PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b), |
Damien Miller | fb1310e | 2004-01-21 11:02:50 +1100 | [diff] [blame] | 127 | buffer_len(&b))) == 1) |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 128 | authenticated = 1; |
Damien Miller | fb1310e | 2004-01-21 11:02:50 +1100 | [diff] [blame] | 129 | buffer_free(&b); |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 130 | xfree(sig); |
| 131 | } else { |
| 132 | debug("test whether pkalg/pkblob are acceptable"); |
| 133 | packet_check_eom(); |
| 134 | |
| 135 | /* XXX fake reply and always send PK_OK ? */ |
| 136 | /* |
| 137 | * XXX this allows testing whether a user is allowed |
| 138 | * to login: if you happen to have a valid pubkey this |
| 139 | * message is sent. the message is NEVER sent at all |
| 140 | * if a user is not allowed to login. is this an |
| 141 | * issue? -markus |
| 142 | */ |
| 143 | if (PRIVSEP(user_key_allowed(authctxt->pw, key))) { |
| 144 | packet_start(SSH2_MSG_USERAUTH_PK_OK); |
| 145 | packet_put_string(pkalg, alen); |
| 146 | packet_put_string(pkblob, blen); |
| 147 | packet_send(); |
| 148 | packet_write_wait(); |
| 149 | authctxt->postponed = 1; |
| 150 | } |
| 151 | } |
| 152 | if (authenticated != 1) |
| 153 | auth_clear_options(); |
| 154 | done: |
| 155 | debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg); |
| 156 | if (key != NULL) |
| 157 | key_free(key); |
| 158 | xfree(pkalg); |
| 159 | xfree(pkblob); |
| 160 | #ifdef HAVE_CYGWIN |
| 161 | if (check_nt_auth(0, authctxt->pw) == 0) |
Damien Miller | 4765679 | 2004-09-11 22:42:09 +1000 | [diff] [blame] | 162 | authenticated = 0; |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 163 | #endif |
| 164 | return authenticated; |
| 165 | } |
| 166 | |
| 167 | /* return 1 if user allows given key */ |
| 168 | static int |
| 169 | user_key_allowed2(struct passwd *pw, Key *key, char *file) |
| 170 | { |
Darren Tucker | 22cc741 | 2004-12-06 22:47:41 +1100 | [diff] [blame^] | 171 | char line[SSH_MAX_PUBKEY_BYTES]; |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 172 | int found_key = 0; |
| 173 | FILE *f; |
| 174 | u_long linenum = 0; |
| 175 | struct stat st; |
| 176 | Key *found; |
| 177 | char *fp; |
| 178 | |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 179 | /* Temporarily use the user's uid. */ |
| 180 | temporarily_use_uid(pw); |
| 181 | |
| 182 | debug("trying public key file %s", file); |
| 183 | |
| 184 | /* Fail quietly if file does not exist */ |
| 185 | if (stat(file, &st) < 0) { |
| 186 | /* Restore the privileged uid. */ |
| 187 | restore_uid(); |
| 188 | return 0; |
| 189 | } |
| 190 | /* Open the file containing the authorized keys. */ |
| 191 | f = fopen(file, "r"); |
| 192 | if (!f) { |
| 193 | /* Restore the privileged uid. */ |
| 194 | restore_uid(); |
| 195 | return 0; |
| 196 | } |
| 197 | if (options.strict_modes && |
| 198 | secure_filename(f, file, pw, line, sizeof(line)) != 0) { |
| 199 | fclose(f); |
Damien Miller | 996acd2 | 2003-04-09 20:59:48 +1000 | [diff] [blame] | 200 | logit("Authentication refused: %s", line); |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 201 | restore_uid(); |
| 202 | return 0; |
| 203 | } |
| 204 | |
| 205 | found_key = 0; |
| 206 | found = key_new(key->type); |
| 207 | |
Darren Tucker | 22cc741 | 2004-12-06 22:47:41 +1100 | [diff] [blame^] | 208 | while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { |
Darren Tucker | 3f9fdc7 | 2004-06-22 12:56:01 +1000 | [diff] [blame] | 209 | char *cp, *key_options = NULL; |
Darren Tucker | 22cc741 | 2004-12-06 22:47:41 +1100 | [diff] [blame^] | 210 | |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 211 | /* Skip leading whitespace, empty and comment lines. */ |
| 212 | for (cp = line; *cp == ' ' || *cp == '\t'; cp++) |
| 213 | ; |
| 214 | if (!*cp || *cp == '\n' || *cp == '#') |
| 215 | continue; |
| 216 | |
| 217 | if (key_read(found, &cp) != 1) { |
| 218 | /* no key? check if there are options for this key */ |
| 219 | int quoted = 0; |
| 220 | debug2("user_key_allowed: check options: '%s'", cp); |
Darren Tucker | 3f9fdc7 | 2004-06-22 12:56:01 +1000 | [diff] [blame] | 221 | key_options = cp; |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 222 | for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { |
| 223 | if (*cp == '\\' && cp[1] == '"') |
| 224 | cp++; /* Skip both */ |
| 225 | else if (*cp == '"') |
| 226 | quoted = !quoted; |
| 227 | } |
| 228 | /* Skip remaining whitespace. */ |
| 229 | for (; *cp == ' ' || *cp == '\t'; cp++) |
| 230 | ; |
| 231 | if (key_read(found, &cp) != 1) { |
| 232 | debug2("user_key_allowed: advance: '%s'", cp); |
| 233 | /* still no key? advance to next line*/ |
| 234 | continue; |
| 235 | } |
| 236 | } |
| 237 | if (key_equal(found, key) && |
Darren Tucker | 3f9fdc7 | 2004-06-22 12:56:01 +1000 | [diff] [blame] | 238 | auth_parse_options(pw, key_options, file, linenum) == 1) { |
Ben Lindstrom | 855bf3a | 2002-06-06 20:27:55 +0000 | [diff] [blame] | 239 | found_key = 1; |
| 240 | debug("matching key found: file %s, line %lu", |
| 241 | file, linenum); |
| 242 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); |
| 243 | verbose("Found matching %s key: %s", |
| 244 | key_type(found), fp); |
| 245 | xfree(fp); |
| 246 | break; |
| 247 | } |
| 248 | } |
| 249 | restore_uid(); |
| 250 | fclose(f); |
| 251 | key_free(found); |
| 252 | if (!found_key) |
| 253 | debug2("key not found"); |
| 254 | return found_key; |
| 255 | } |
| 256 | |
| 257 | /* check whether given key is in .ssh/authorized_keys* */ |
| 258 | int |
| 259 | user_key_allowed(struct passwd *pw, Key *key) |
| 260 | { |
| 261 | int success; |
| 262 | char *file; |
| 263 | |
| 264 | file = authorized_keys_file(pw); |
| 265 | success = user_key_allowed2(pw, key, file); |
| 266 | xfree(file); |
| 267 | if (success) |
| 268 | return success; |
| 269 | |
| 270 | /* try suffix "2" for backward compat, too */ |
| 271 | file = authorized_keys_file2(pw); |
| 272 | success = user_key_allowed2(pw, key, file); |
| 273 | xfree(file); |
| 274 | return success; |
| 275 | } |
| 276 | |
| 277 | Authmethod method_pubkey = { |
| 278 | "publickey", |
| 279 | userauth_pubkey, |
| 280 | &options.pubkey_authentication |
| 281 | }; |