source: trunk/third/openssh/hostfile.c @ 18759

/*
 * 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 "includes.h"
RCSID("$OpenBSD: hostfile.c,v 1.30 2002/07/24 16:11:18 markus Exp $");

#include "packet.h"
#include "match.h"
#include "key.h"
#include "hostfile.h"
#include "log.h"

/*
 * 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, 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)) {
                log("Warning: %s, line %d: keysize mismatch for host %s: "
                    "actual %d vs. announced %d.",
                    filename, linenum, host, BN_num_bits(key->rsa->n), bits);
                log("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, Key *key, int keytype, Key *found, int *numret)
{
        FILE *f;
        char line[8192];
        int linenum = 0;
        u_int kbits;
        char *cp, *cp2;
        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)
                        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)
                                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, 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, Key *key)
{
        FILE *f;
        int success = 0;
        if (key == NULL)
                return 1;       /* XXX ? */
        f = fopen(filename, "a");
        if (!f)
                return 0;
        fprintf(f, "%s ", 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;
}