/* $OpenBSD: hostfile.c,v 1.45 2006/08/03 03:34:42 deraadt Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland * All rights reserved * Functions for manipulating the known hosts files. * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". * * * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. * Copyright (c) 1999 Niels Provos. 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. */ #include <sys/types.h> #include <netinet/in.h> #include <openssl/hmac.h> #include <openssl/sha.h> #include <resolv.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include "xmalloc.h" #include "match.h" #include "key.h" #include "hostfile.h" #include "log.h" static int extract_salt(const char *s, u_int l, char *salt, size_t salt_len) { char *p, *b64salt; u_int b64len; int ret; if (l < sizeof(HASH_MAGIC) - 1) { debug2("extract_salt: string too short"); return (-1); } if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { debug2("extract_salt: invalid magic identifier"); return (-1); } s += sizeof(HASH_MAGIC) - 1; l -= sizeof(HASH_MAGIC) - 1; if ((p = memchr(s, HASH_DELIM, l)) == NULL) { debug2("extract_salt: missing salt termination character"); return (-1); } b64len = p - s; /* Sanity check */ if (b64len == 0 || b64len > 1024) { debug2("extract_salt: bad encoded salt length %u", b64len); return (-1); } b64salt = xmalloc(1 + b64len); memcpy(b64salt, s, b64len); b64salt[b64len] = '\0'; ret = __b64_pton(b64salt, salt, salt_len); xfree(b64salt); if (ret == -1) { debug2("extract_salt: salt decode error"); return (-1); } if (ret != SHA_DIGEST_LENGTH) { debug2("extract_salt: expected salt len %d, got %d", SHA_DIGEST_LENGTH, ret); return (-1); } return (0); } char * host_hash(const char *host, const char *name_from_hostfile, u_int src_len) { const EVP_MD *md = EVP_sha1(); HMAC_CTX mac_ctx; char salt[256], result[256], uu_salt[512], uu_result[512]; static char encoded[1024]; u_int i, len; len = EVP_MD_size(md); if (name_from_hostfile == NULL) { /* Create new salt */ for (i = 0; i < len; i++) salt[i] = arc4random(); } else { /* Extract salt from known host entry */ if (extract_salt(name_from_hostfile, src_len, salt, sizeof(salt)) == -1) return (NULL); } HMAC_Init(&mac_ctx, salt, len, md); HMAC_Update(&mac_ctx, host, strlen(host)); HMAC_Final(&mac_ctx, result, NULL); HMAC_cleanup(&mac_ctx); if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) fatal("host_hash: __b64_ntop failed"); snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, HASH_DELIM, uu_result); return (encoded); } /* * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the * pointer over the key. Skips any whitespace at the beginning and at end. */ int hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) { char *cp; /* Skip leading whitespace. */ for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) ; if (key_read(ret, &cp) != 1) return 0; /* Skip trailing whitespace. */ for (; *cp == ' ' || *cp == '\t'; cp++) ; /* Return results. */ *cpp = cp; *bitsp = key_size(ret); return 1; } static int hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum) { if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) return 1; if (bits != BN_num_bits(key->rsa->n)) { logit("Warning: %s, line %d: keysize mismatch for host %s: " "actual %d vs. announced %d.", filename, linenum, host, BN_num_bits(key->rsa->n), bits); logit("Warning: replace %d with %d in %s, line %d.", bits, BN_num_bits(key->rsa->n), filename, linenum); } return 1; } /* * Checks whether the given host (which must be in all lowercase) is already * in the list of our known hosts. Returns HOST_OK if the host is known and * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED * if the host is known but used to have a different host key. * * If no 'key' has been specified and a key of type 'keytype' is known * for the specified host, then HOST_FOUND is returned. */ static HostStatus check_host_in_hostfile_by_key_or_type(const char *filename, const char *host, const Key *key, int keytype, Key *found, int *numret) { FILE *f; char line[8192]; int linenum = 0; u_int kbits; char *cp, *cp2, *hashed_host; HostStatus end_return; debug3("check_host_in_hostfile: filename %s", filename); /* Open the file containing the list of known hosts. */ f = fopen(filename, "r"); if (!f) return HOST_NEW; /* * Return value when the loop terminates. This is set to * HOST_CHANGED if we have seen a different key for the host and have * not found the proper one. */ end_return = HOST_NEW; /* Go through the file. */ while (fgets(line, sizeof(line), f)) { cp = line; linenum++; /* Skip any leading whitespace, comments and empty lines. */ for (; *cp == ' ' || *cp == '\t'; cp++) ; if (!*cp || *cp == '#' || *cp == '\n') continue; /* Find the end of the host name portion. */ for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) ; /* Check if the host name matches. */ if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { if (*cp != HASH_DELIM) continue; hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); if (hashed_host == NULL) { debug("Invalid hashed host line %d of %s", linenum, filename); continue; } if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) continue; } /* Got a match. Skip host name. */ cp = cp2; /* * Extract the key from the line. This will skip any leading * whitespace. Ignore badly formatted lines. */ if (!hostfile_read_key(&cp, &kbits, found)) continue; if (numret != NULL) *numret = linenum; if (key == NULL) { /* we found a key of the requested type */ if (found->type == keytype) { fclose(f); return HOST_FOUND; } continue; } if (!hostfile_check_key(kbits, found, host, filename, linenum)) continue; /* Check if the current key is the same as the given key. */ if (key_equal(key, found)) { /* Ok, they match. */ debug3("check_host_in_hostfile: match line %d", linenum); fclose(f); return HOST_OK; } /* * They do not match. We will continue to go through the * file; however, we note that we will not return that it is * new. */ end_return = HOST_CHANGED; } /* Clear variables and close the file. */ fclose(f); /* * Return either HOST_NEW or HOST_CHANGED, depending on whether we * saw a different key for the host. */ return end_return; } HostStatus check_host_in_hostfile(const char *filename, const char *host, const Key *key, Key *found, int *numret) { if (key == NULL) fatal("no key to look up"); return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0, found, numret)); } int lookup_key_in_hostfile_by_type(const char *filename, const char *host, int keytype, Key *found, int *numret) { return (check_host_in_hostfile_by_key_or_type(filename, host, NULL, keytype, found, numret) == HOST_FOUND); } /* * Appends an entry to the host file. Returns false if the entry could not * be appended. */ int add_host_to_hostfile(const char *filename, const char *host, const Key *key, int store_hash) { FILE *f; int success = 0; char *hashed_host = NULL; if (key == NULL) return 1; /* XXX ? */ f = fopen(filename, "a"); if (!f) return 0; if (store_hash) { if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { error("add_host_to_hostfile: host_hash failed"); fclose(f); return 0; } } fprintf(f, "%s ", store_hash ? hashed_host : host); if (key_write(key, f)) { success = 1; } else { error("add_host_to_hostfile: saving key in %s failed", filename); } fprintf(f, "\n"); fclose(f); return success; }