Annotation of src/usr.bin/ssh/auth2-pubkey.c, Revision 1.1
1.1 ! markus 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"
! 26: RCSID("$OpenBSD: auth2.c,v 1.91 2002/05/13 02:37:39 itojun Exp $");
! 27:
! 28: #include "ssh2.h"
! 29: #include "xmalloc.h"
! 30: #include "packet.h"
! 31: #include "buffer.h"
! 32: #include "log.h"
! 33: #include "servconf.h"
! 34: #include "compat.h"
! 35: #include "bufaux.h"
! 36: #include "auth.h"
! 37: #include "key.h"
! 38: #include "pathnames.h"
! 39: #include "uidswap.h"
! 40: #include "auth-options.h"
! 41: #include "canohost.h"
! 42: #include "monitor_wrap.h"
! 43:
! 44: /* import */
! 45: extern ServerOptions options;
! 46: extern u_char *session_id2;
! 47: extern int session_id2_len;
! 48:
! 49: int
! 50: userauth_pubkey(Authctxt *authctxt)
! 51: {
! 52: Buffer b;
! 53: Key *key = NULL;
! 54: char *pkalg;
! 55: u_char *pkblob, *sig;
! 56: u_int alen, blen, slen;
! 57: int have_sig, pktype;
! 58: int authenticated = 0;
! 59:
! 60: if (!authctxt->valid) {
! 61: debug2("userauth_pubkey: disabled because of invalid user");
! 62: return 0;
! 63: }
! 64: have_sig = packet_get_char();
! 65: if (datafellows & SSH_BUG_PKAUTH) {
! 66: debug2("userauth_pubkey: SSH_BUG_PKAUTH");
! 67: /* no explicit pkalg given */
! 68: pkblob = packet_get_string(&blen);
! 69: buffer_init(&b);
! 70: buffer_append(&b, pkblob, blen);
! 71: /* so we have to extract the pkalg from the pkblob */
! 72: pkalg = buffer_get_string(&b, &alen);
! 73: buffer_free(&b);
! 74: } else {
! 75: pkalg = packet_get_string(&alen);
! 76: pkblob = packet_get_string(&blen);
! 77: }
! 78: pktype = key_type_from_name(pkalg);
! 79: if (pktype == KEY_UNSPEC) {
! 80: /* this is perfectly legal */
! 81: log("userauth_pubkey: unsupported public key algorithm: %s",
! 82: pkalg);
! 83: goto done;
! 84: }
! 85: key = key_from_blob(pkblob, blen);
! 86: if (key == NULL) {
! 87: error("userauth_pubkey: cannot decode key: %s", pkalg);
! 88: goto done;
! 89: }
! 90: if (key->type != pktype) {
! 91: error("userauth_pubkey: type mismatch for decoded key "
! 92: "(received %d, expected %d)", key->type, pktype);
! 93: goto done;
! 94: }
! 95: if (have_sig) {
! 96: sig = packet_get_string(&slen);
! 97: packet_check_eom();
! 98: buffer_init(&b);
! 99: if (datafellows & SSH_OLD_SESSIONID) {
! 100: buffer_append(&b, session_id2, session_id2_len);
! 101: } else {
! 102: buffer_put_string(&b, session_id2, session_id2_len);
! 103: }
! 104: /* reconstruct packet */
! 105: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
! 106: buffer_put_cstring(&b, authctxt->user);
! 107: buffer_put_cstring(&b,
! 108: datafellows & SSH_BUG_PKSERVICE ?
! 109: "ssh-userauth" :
! 110: authctxt->service);
! 111: if (datafellows & SSH_BUG_PKAUTH) {
! 112: buffer_put_char(&b, have_sig);
! 113: } else {
! 114: buffer_put_cstring(&b, "publickey");
! 115: buffer_put_char(&b, have_sig);
! 116: buffer_put_cstring(&b, pkalg);
! 117: }
! 118: buffer_put_string(&b, pkblob, blen);
! 119: #ifdef DEBUG_PK
! 120: buffer_dump(&b);
! 121: #endif
! 122: /* test for correct signature */
! 123: authenticated = 0;
! 124: if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
! 125: PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
! 126: buffer_len(&b))) == 1)
! 127: authenticated = 1;
! 128: buffer_clear(&b);
! 129: xfree(sig);
! 130: } else {
! 131: debug("test whether pkalg/pkblob are acceptable");
! 132: packet_check_eom();
! 133:
! 134: /* XXX fake reply and always send PK_OK ? */
! 135: /*
! 136: * XXX this allows testing whether a user is allowed
! 137: * to login: if you happen to have a valid pubkey this
! 138: * message is sent. the message is NEVER sent at all
! 139: * if a user is not allowed to login. is this an
! 140: * issue? -markus
! 141: */
! 142: if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
! 143: packet_start(SSH2_MSG_USERAUTH_PK_OK);
! 144: packet_put_string(pkalg, alen);
! 145: packet_put_string(pkblob, blen);
! 146: packet_send();
! 147: packet_write_wait();
! 148: authctxt->postponed = 1;
! 149: }
! 150: }
! 151: if (authenticated != 1)
! 152: auth_clear_options();
! 153: done:
! 154: debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
! 155: if (key != NULL)
! 156: key_free(key);
! 157: xfree(pkalg);
! 158: xfree(pkblob);
! 159: return authenticated;
! 160: }
! 161:
! 162: /* return 1 if user allows given key */
! 163: static int
! 164: user_key_allowed2(struct passwd *pw, Key *key, char *file)
! 165: {
! 166: char line[8192];
! 167: int found_key = 0;
! 168: FILE *f;
! 169: u_long linenum = 0;
! 170: struct stat st;
! 171: Key *found;
! 172: char *fp;
! 173:
! 174: if (pw == NULL)
! 175: return 0;
! 176:
! 177: /* Temporarily use the user's uid. */
! 178: temporarily_use_uid(pw);
! 179:
! 180: debug("trying public key file %s", file);
! 181:
! 182: /* Fail quietly if file does not exist */
! 183: if (stat(file, &st) < 0) {
! 184: /* Restore the privileged uid. */
! 185: restore_uid();
! 186: return 0;
! 187: }
! 188: /* Open the file containing the authorized keys. */
! 189: f = fopen(file, "r");
! 190: if (!f) {
! 191: /* Restore the privileged uid. */
! 192: restore_uid();
! 193: return 0;
! 194: }
! 195: if (options.strict_modes &&
! 196: secure_filename(f, file, pw, line, sizeof(line)) != 0) {
! 197: fclose(f);
! 198: log("Authentication refused: %s", line);
! 199: restore_uid();
! 200: return 0;
! 201: }
! 202:
! 203: found_key = 0;
! 204: found = key_new(key->type);
! 205:
! 206: while (fgets(line, sizeof(line), f)) {
! 207: char *cp, *options = NULL;
! 208: linenum++;
! 209: /* Skip leading whitespace, empty and comment lines. */
! 210: for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
! 211: ;
! 212: if (!*cp || *cp == '\n' || *cp == '#')
! 213: continue;
! 214:
! 215: if (key_read(found, &cp) != 1) {
! 216: /* no key? check if there are options for this key */
! 217: int quoted = 0;
! 218: debug2("user_key_allowed: check options: '%s'", cp);
! 219: options = cp;
! 220: for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
! 221: if (*cp == '\\' && cp[1] == '"')
! 222: cp++; /* Skip both */
! 223: else if (*cp == '"')
! 224: quoted = !quoted;
! 225: }
! 226: /* Skip remaining whitespace. */
! 227: for (; *cp == ' ' || *cp == '\t'; cp++)
! 228: ;
! 229: if (key_read(found, &cp) != 1) {
! 230: debug2("user_key_allowed: advance: '%s'", cp);
! 231: /* still no key? advance to next line*/
! 232: continue;
! 233: }
! 234: }
! 235: if (key_equal(found, key) &&
! 236: auth_parse_options(pw, options, file, linenum) == 1) {
! 237: found_key = 1;
! 238: debug("matching key found: file %s, line %lu",
! 239: file, linenum);
! 240: fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
! 241: verbose("Found matching %s key: %s",
! 242: key_type(found), fp);
! 243: xfree(fp);
! 244: break;
! 245: }
! 246: }
! 247: restore_uid();
! 248: fclose(f);
! 249: key_free(found);
! 250: if (!found_key)
! 251: debug2("key not found");
! 252: return found_key;
! 253: }
! 254:
! 255: /* check whether given key is in .ssh/authorized_keys* */
! 256: int
! 257: user_key_allowed(struct passwd *pw, Key *key)
! 258: {
! 259: int success;
! 260: char *file;
! 261:
! 262: file = authorized_keys_file(pw);
! 263: success = user_key_allowed2(pw, key, file);
! 264: xfree(file);
! 265: if (success)
! 266: return success;
! 267:
! 268: /* try suffix "2" for backward compat, too */
! 269: file = authorized_keys_file2(pw);
! 270: success = user_key_allowed2(pw, key, file);
! 271: xfree(file);
! 272: return success;
! 273: }
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