/* $OpenBSD: hostfile.c,v 1.100 2025/11/25 00:57:04 djm 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 <sys/stat.h>

#include <netinet/in.h>

#include <errno.h>
#include <resolv.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "xmalloc.h"
#include "match.h"
#include "sshkey.h"
#include "hostfile.h"
#include "log.h"
#include "misc.h"
#include "pathnames.h"
#include "ssherr.h"
#include "digest.h"
#include "hmac.h"
#include "sshbuf.h"

/* XXX hmac is too easy to dictionary attack; use bcrypt? */

static int
extract_salt(const char *s, u_int l, u_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);
        free(b64salt);
        if (ret == -1) {
                debug2("extract_salt: salt decode error");
                return (-1);
        }
        if (ret != (int)ssh_hmac_bytes(SSH_DIGEST_SHA1)) {
                debug2("extract_salt: expected salt len %zd, got %d",
                    ssh_hmac_bytes(SSH_DIGEST_SHA1), ret);
                return (-1);
        }

        return (0);
}

char *
host_hash(const char *host, const char *name_from_hostfile, u_int src_len)
{
        struct ssh_hmac_ctx *ctx;
        u_char salt[256], result[256];
        char uu_salt[512], uu_result[512];
        char *encoded = NULL;
        u_int len;

        len = ssh_digest_bytes(SSH_DIGEST_SHA1);

        if (name_from_hostfile == NULL) {
                /* Create new salt */
                arc4random_buf(salt, len);
        } else {
                /* Extract salt from known host entry */
                if (extract_salt(name_from_hostfile, src_len, salt,
                    sizeof(salt)) == -1)
                        return (NULL);
        }

        if ((ctx = ssh_hmac_start(SSH_DIGEST_SHA1)) == NULL ||
            ssh_hmac_init(ctx, salt, len) < 0 ||
            ssh_hmac_update(ctx, host, strlen(host)) < 0 ||
            ssh_hmac_final(ctx, result, sizeof(result)))
                fatal_f("ssh_hmac failed");
        ssh_hmac_free(ctx);

        if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 ||
            __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1)
                fatal_f("__b64_ntop failed");
        xasprintf(&encoded, "%s%s%c%s", HASH_MAGIC, uu_salt, HASH_DELIM,
            uu_result);

        return (encoded);
}

/*
 * Parses an RSA 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, struct sshkey *ret)
{
        char *cp;

        /* Skip leading whitespace. */
        for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
                ;

        if (sshkey_read(ret, &cp) != 0)
                return 0;

        /* Skip trailing whitespace. */
        for (; *cp == ' ' || *cp == '\t'; cp++)
                ;

        /* Return results. */
        *cpp = cp;
        if (bitsp != NULL)
                *bitsp = sshkey_size(ret);
        return 1;
}

static HostkeyMarker
check_markers(char **cpp)
{
        char marker[32], *sp, *cp = *cpp;
        int ret = MRK_NONE;

        while (*cp == '@') {
                /* Only one marker is allowed */
                if (ret != MRK_NONE)
                        return MRK_ERROR;
                /* Markers are terminated by whitespace */
                if ((sp = strchr(cp, ' ')) == NULL &&
                    (sp = strchr(cp, '\t')) == NULL)
                        return MRK_ERROR;
                /* Extract marker for comparison */
                if (sp <= cp + 1 || sp >= cp + sizeof(marker))
                        return MRK_ERROR;
                memcpy(marker, cp, sp - cp);
                marker[sp - cp] = '\0';
                if (strcmp(marker, CA_MARKER) == 0)
                        ret = MRK_CA;
                else if (strcmp(marker, REVOKE_MARKER) == 0)
                        ret = MRK_REVOKE;
                else
                        return MRK_ERROR;

                /* Skip past marker and any whitespace that follows it */
                cp = sp;
                for (; *cp == ' ' || *cp == '\t'; cp++)
                        ;
        }
        *cpp = cp;
        return ret;
}

struct hostkeys *
init_hostkeys(void)
{
        struct hostkeys *ret = xcalloc(1, sizeof(*ret));

        ret->entries = NULL;
        return ret;
}

struct load_callback_ctx {
        const char *host;
        u_long num_loaded;
        struct hostkeys *hostkeys;
};

static int
record_hostkey(struct hostkey_foreach_line *l, void *_ctx)
{
        struct load_callback_ctx *ctx = (struct load_callback_ctx *)_ctx;
        struct hostkeys *hostkeys = ctx->hostkeys;
        struct hostkey_entry *tmp;

        if (l->status == HKF_STATUS_INVALID) {
                /* XXX make this verbose() in the future */
                debug("%s:%ld: parse error in hostkeys file",
                    l->path, l->linenum);
                return 0;
        }

        debug3_f("found %skey type %s in file %s:%lu",
            l->marker == MRK_NONE ? "" :
            (l->marker == MRK_CA ? "ca " : "revoked "),
            sshkey_type(l->key), l->path, l->linenum);
        if ((tmp = recallocarray(hostkeys->entries, hostkeys->num_entries,
            hostkeys->num_entries + 1, sizeof(*hostkeys->entries))) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        hostkeys->entries = tmp;
        hostkeys->entries[hostkeys->num_entries].host = xstrdup(ctx->host);
        hostkeys->entries[hostkeys->num_entries].file = xstrdup(l->path);
        hostkeys->entries[hostkeys->num_entries].line = l->linenum;
        hostkeys->entries[hostkeys->num_entries].key = l->key;
        l->key = NULL; /* steal it */
        hostkeys->entries[hostkeys->num_entries].marker = l->marker;
        hostkeys->entries[hostkeys->num_entries].note = l->note;
        hostkeys->num_entries++;
        ctx->num_loaded++;

        return 0;
}

void
load_hostkeys_file(struct hostkeys *hostkeys, const char *host,
    const char *path, FILE *f, u_int note)
{
        int r;
        struct load_callback_ctx ctx;

        ctx.host = host;
        ctx.num_loaded = 0;
        ctx.hostkeys = hostkeys;

        if ((r = hostkeys_foreach_file(path, f, record_hostkey, &ctx, host,
            NULL, HKF_WANT_MATCH|HKF_WANT_PARSE_KEY, note)) != 0) {
                if (r != SSH_ERR_SYSTEM_ERROR && errno != ENOENT)
                        debug_fr(r, "hostkeys_foreach failed for %s", path);
        }
        if (ctx.num_loaded != 0)
                debug3_f("loaded %lu keys from %s", ctx.num_loaded, host);
}

void
load_hostkeys(struct hostkeys *hostkeys, const char *host, const char *path,
    u_int note)
{
        FILE *f;

        if ((f = fopen(path, "r")) == NULL) {
                debug_f("fopen %s: %s", path, strerror(errno));
                return;
        }

        load_hostkeys_file(hostkeys, host, path, f, note);
        fclose(f);
}

void
free_hostkeys(struct hostkeys *hostkeys)
{
        u_int i;

        for (i = 0; i < hostkeys->num_entries; i++) {
                free(hostkeys->entries[i].host);
                free(hostkeys->entries[i].file);
                sshkey_free(hostkeys->entries[i].key);
                explicit_bzero(hostkeys->entries + i, sizeof(*hostkeys->entries));
        }
        free(hostkeys->entries);
        freezero(hostkeys, sizeof(*hostkeys));
}

static int
check_key_not_revoked(struct hostkeys *hostkeys, struct sshkey *k)
{
        int is_cert = sshkey_is_cert(k);
        u_int i;

        for (i = 0; i < hostkeys->num_entries; i++) {
                if (hostkeys->entries[i].marker != MRK_REVOKE)
                        continue;
                if (sshkey_equal_public(k, hostkeys->entries[i].key))
                        return -1;
                if (is_cert && k != NULL &&
                    sshkey_equal_public(k->cert->signature_key,
                    hostkeys->entries[i].key))
                        return -1;
        }
        return 0;
}

/*
 * Match keys against a specified key, or look one up by key type.
 *
 * If looking for a keytype (key == NULL) and one is found then return
 * HOST_FOUND, otherwise HOST_NEW.
 *
 * If looking for a key (key != NULL):
 *  1. If the key is a cert and a matching CA is found, return HOST_OK
 *  2. If the key is not a cert and a matching key is found, return HOST_OK
 *  3. If no key matches but a key with a different type is found, then
 *     return HOST_CHANGED
 *  4. If no matching keys are found, then return HOST_NEW.
 *
 * Finally, check any found key is not revoked.
 */
static HostStatus
check_hostkeys_by_key_or_type(struct hostkeys *hostkeys,
    struct sshkey *k, int keytype, int nid, const struct hostkey_entry **found)
{
        u_int i;
        HostStatus end_return = HOST_NEW;
        int want_cert = sshkey_is_cert(k);
        HostkeyMarker want_marker = want_cert ? MRK_CA : MRK_NONE;

        if (found != NULL)
                *found = NULL;

        for (i = 0; i < hostkeys->num_entries; i++) {
                if (hostkeys->entries[i].marker != want_marker)
                        continue;
                if (k == NULL) {
                        if (hostkeys->entries[i].key->type != keytype)
                                continue;
                        if (nid != -1 &&
                            sshkey_type_plain(keytype) == KEY_ECDSA &&
                            hostkeys->entries[i].key->ecdsa_nid != nid)
                                continue;
                        end_return = HOST_FOUND;
                        if (found != NULL)
                                *found = hostkeys->entries + i;
                        k = hostkeys->entries[i].key;
                        break;
                }
                if (want_cert) {
                        if (sshkey_equal_public(k->cert->signature_key,
                            hostkeys->entries[i].key)) {
                                /* A matching CA exists */
                                end_return = HOST_OK;
                                if (found != NULL)
                                        *found = hostkeys->entries + i;
                                break;
                        }
                } else {
                        if (sshkey_equal(k, hostkeys->entries[i].key)) {
                                end_return = HOST_OK;
                                if (found != NULL)
                                        *found = hostkeys->entries + i;
                                break;
                        }
                        /* A non-matching key exists */
                        end_return = HOST_CHANGED;
                        if (found != NULL)
                                *found = hostkeys->entries + i;
                }
        }
        if (check_key_not_revoked(hostkeys, k) != 0) {
                end_return = HOST_REVOKED;
                if (found != NULL)
                        *found = NULL;
        }
        return end_return;
}

HostStatus
check_key_in_hostkeys(struct hostkeys *hostkeys, struct sshkey *key,
    const struct hostkey_entry **found)
{
        if (key == NULL)
                fatal("no key to look up");
        return check_hostkeys_by_key_or_type(hostkeys, key, 0, -1, found);
}

int
lookup_key_in_hostkeys_by_type(struct hostkeys *hostkeys, int keytype, int nid,
    const struct hostkey_entry **found)
{
        return (check_hostkeys_by_key_or_type(hostkeys, NULL, keytype, nid,
            found) == HOST_FOUND);
}

int
lookup_marker_in_hostkeys(struct hostkeys *hostkeys, int want_marker)
{
        u_int i;

        for (i = 0; i < hostkeys->num_entries; i++) {
                if (hostkeys->entries[i].marker == (HostkeyMarker)want_marker)
                        return 1;
        }
        return 0;
}

static int
format_host_entry(struct sshbuf *entry, const char *host, const char *ip,
    const struct sshkey *key, int store_hash)
{
        int r, success = 0;
        char *hashed_host = NULL, *lhost;

        lhost = xstrdup(host);
        lowercase(lhost);

        if (store_hash) {
                if ((hashed_host = host_hash(lhost, NULL, 0)) == NULL) {
                        error_f("host_hash failed");
                        free(lhost);
                        return 0;
                }
                if ((r = sshbuf_putf(entry, "%s ", hashed_host)) != 0)
                        fatal_fr(r, "sshbuf_putf");
        } else if (ip != NULL) {
                if ((r = sshbuf_putf(entry, "%s,%s ", lhost, ip)) != 0)
                        fatal_fr(r, "sshbuf_putf");
        } else {
                if ((r = sshbuf_putf(entry, "%s ", lhost)) != 0)
                        fatal_fr(r, "sshbuf_putf");
        }
        free(hashed_host);
        free(lhost);
        if ((r = sshkey_format_text(key, entry)) == 0)
                success = 1;
        else
                error_fr(r, "sshkey_write");
        if ((r = sshbuf_putf(entry, "\n")) != 0)
                fatal_fr(r, "sshbuf_putf");

        /* If hashing is enabled, the IP address needs to go on its own line */
        if (success && store_hash && ip != NULL)
                success = format_host_entry(entry, ip, NULL, key, 1);
        return success;
}

static int
write_host_entry(FILE *f, const char *host, const char *ip,
    const struct sshkey *key, int store_hash)
{
        int r, success = 0;
        struct sshbuf *entry = NULL;

        if ((entry = sshbuf_new()) == NULL)
                fatal_f("allocation failed");
        if ((r = format_host_entry(entry, host, ip, key, store_hash)) != 1) {
                debug_f("failed to format host entry");
                goto out;
        }
        if ((r = fwrite(sshbuf_ptr(entry), sshbuf_len(entry), 1, f)) != 1) {
                error_f("fwrite: %s", strerror(errno));
                goto out;
        }
        success = 1;
 out:
        sshbuf_free(entry);
        return success;
}

/*
 * Create user ~/.ssh directory if it doesn't exist and we want to write to it.
 * If notify is set, a message will be emitted if the directory is created.
 */
void
hostfile_create_user_ssh_dir(const char *filename, int notify)
{
        char *dotsshdir = NULL, *p;
        size_t len;
        struct stat st;

        if ((p = strrchr(filename, '/')) == NULL)
                return;
        len = p - filename;
        dotsshdir = tilde_expand_filename("~/" _PATH_SSH_USER_DIR, getuid());
        if (strlen(dotsshdir) > len || strncmp(filename, dotsshdir, len) != 0)
                goto out; /* not ~/.ssh prefixed */
        if (stat(dotsshdir, &st) == 0)
                goto out; /* dir already exists */
        else if (errno != ENOENT)
                error("Could not stat %s: %s", dotsshdir, strerror(errno));
        else {
                if (mkdir(dotsshdir, 0700) == -1)
                        error("Could not create directory '%.200s' (%s).",
                            dotsshdir, strerror(errno));
                else if (notify)
                        logit("Created directory '%s'.", dotsshdir);
        }
 out:
        free(dotsshdir);
}


/*
 * 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 struct sshkey *key, int store_hash)
{
        FILE *f;
        int success, addnl = 0;

        if (key == NULL)
                return 1;       /* XXX ? */
        hostfile_create_user_ssh_dir(filename, 0);
        if ((f = fopen(filename, "a+")) == NULL)
                return 0;
        setvbuf(f, NULL, _IONBF, 0);
        /* Make sure we have a terminating newline. */
        if (fseek(f, -1L, SEEK_END) == 0 && fgetc(f) != '\n')
                addnl = 1;
        if (fseek(f, 0L, SEEK_END) != 0 || (addnl && fputc('\n', f) != '\n')) {
                error("Failed to add terminating newline to %s: %s",
                   filename, strerror(errno));
                fclose(f);
                return 0;
        }
        success = write_host_entry(f, host, NULL, key, store_hash);
        fclose(f);
        return success;
}

struct host_delete_ctx {
        FILE *out;
        int quiet;
        const char *host, *ip;
        u_int *match_keys;      /* mask of HKF_MATCH_* for this key */
        struct sshkey * const *keys;
        size_t nkeys;
        int modified;
};

static int
host_delete(struct hostkey_foreach_line *l, void *_ctx)
{
        struct host_delete_ctx *ctx = (struct host_delete_ctx *)_ctx;
        int loglevel = ctx->quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
        size_t i;

        /* Don't remove CA and revocation lines */
        if (l->status == HKF_STATUS_MATCHED && l->marker == MRK_NONE) {
                /*
                 * If this line contains one of the keys that we will be
                 * adding later, then don't change it and mark the key for
                 * skipping.
                 */
                for (i = 0; i < ctx->nkeys; i++) {
                        if (!sshkey_equal(ctx->keys[i], l->key))
                                continue;
                        ctx->match_keys[i] |= l->match;
                        fprintf(ctx->out, "%s\n", l->line);
                        debug3_f("%s key already at %s:%ld",
                            sshkey_type(l->key), l->path, l->linenum);
                        return 0;
                }

                /*
                 * Hostname matches and has no CA/revoke marker, delete it
                 * by *not* writing the line to ctx->out.
                 */
                do_log2(loglevel, "%s%s%s:%ld: Removed %s key for host %s",
                    ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
                    l->path, l->linenum, sshkey_type(l->key), ctx->host);
                ctx->modified = 1;
                return 0;
        }
        /* Retain non-matching hosts and invalid lines when deleting */
        if (l->status == HKF_STATUS_INVALID) {
                do_log2(loglevel, "%s%s%s:%ld: invalid known_hosts entry",
                    ctx->quiet ? __func__ : "", ctx->quiet ? ": " : "",
                    l->path, l->linenum);
        }
        fprintf(ctx->out, "%s\n", l->line);
        return 0;
}

int
hostfile_replace_entries(const char *filename, const char *host, const char *ip,
    struct sshkey **keys, size_t nkeys, int store_hash, int quiet, int hash_alg)
{
        int r, fd, oerrno = 0;
        int loglevel = quiet ? SYSLOG_LEVEL_DEBUG1 : SYSLOG_LEVEL_VERBOSE;
        struct host_delete_ctx ctx;
        char *fp = NULL, *temp = NULL, *back = NULL;
        const char *what;
        mode_t omask;
        size_t i;
        u_int want;

        omask = umask(077);

        memset(&ctx, 0, sizeof(ctx));
        ctx.host = host;
        ctx.ip = ip;
        ctx.quiet = quiet;

        if ((ctx.match_keys = calloc(nkeys, sizeof(*ctx.match_keys))) == NULL)
                return SSH_ERR_ALLOC_FAIL;
        ctx.keys = keys;
        ctx.nkeys = nkeys;
        ctx.modified = 0;

        /*
         * Prepare temporary file for in-place deletion.
         */
        if ((r = asprintf(&temp, "%s.XXXXXXXXXXX", filename)) == -1 ||
            (r = asprintf(&back, "%s.old", filename)) == -1) {
                r = SSH_ERR_ALLOC_FAIL;
                goto fail;
        }

        if ((fd = mkstemp(temp)) == -1) {
                oerrno = errno;
                error_f("mkstemp: %s", strerror(oerrno));
                r = SSH_ERR_SYSTEM_ERROR;
                goto fail;
        }
        if ((ctx.out = fdopen(fd, "w")) == NULL) {
                oerrno = errno;
                close(fd);
                error_f("fdopen: %s", strerror(oerrno));
                r = SSH_ERR_SYSTEM_ERROR;
                goto fail;
        }

        /* Remove stale/mismatching entries for the specified host */
        if ((r = hostkeys_foreach(filename, host_delete, &ctx, host, ip,
            HKF_WANT_PARSE_KEY, 0)) != 0) {
                oerrno = errno;
                error_fr(r, "hostkeys_foreach");
                goto fail;
        }

        /* Re-add the requested keys */
        want = HKF_MATCH_HOST | (ip == NULL ? 0 : HKF_MATCH_IP);
        for (i = 0; i < nkeys; i++) {
                if (keys[i] == NULL || (want & ctx.match_keys[i]) == want)
                        continue;
                if ((fp = sshkey_fingerprint(keys[i], hash_alg,
                    SSH_FP_DEFAULT)) == NULL) {
                        r = SSH_ERR_ALLOC_FAIL;
                        goto fail;
                }
                /* write host/ip */
                what = "";
                if (ctx.match_keys[i] == 0) {
                        what = "Adding new key";
                        if (!write_host_entry(ctx.out, host, ip,
                            keys[i], store_hash)) {
                                r = SSH_ERR_INTERNAL_ERROR;
                                goto fail;
                        }
                } else if ((want & ~ctx.match_keys[i]) == HKF_MATCH_HOST) {
                        what = "Fixing match (hostname)";
                        if (!write_host_entry(ctx.out, host, NULL,
                            keys[i], store_hash)) {
                                r = SSH_ERR_INTERNAL_ERROR;
                                goto fail;
                        }
                } else if ((want & ~ctx.match_keys[i]) == HKF_MATCH_IP) {
                        what = "Fixing match (address)";
                        if (!write_host_entry(ctx.out, ip, NULL,
                            keys[i], store_hash)) {
                                r = SSH_ERR_INTERNAL_ERROR;
                                goto fail;
                        }
                }
                do_log2(loglevel, "%s%s%s for %s%s%s to %s: %s %s",
                    quiet ? __func__ : "", quiet ? ": " : "", what,
                    host, ip == NULL ? "" : ",", ip == NULL ? "" : ip, filename,
                    sshkey_ssh_name(keys[i]), fp);
                free(fp);
                fp = NULL;
                ctx.modified = 1;
        }
        fclose(ctx.out);
        ctx.out = NULL;

        if (ctx.modified) {
                /* Backup the original file and replace it with the temporary */
                if (unlink(back) == -1 && errno != ENOENT) {
                        oerrno = errno;
                        error_f("unlink %.100s: %s", back, strerror(errno));
                        r = SSH_ERR_SYSTEM_ERROR;
                        goto fail;
                }
                if (link(filename, back) == -1) {
                        oerrno = errno;
                        error_f("link %.100s to %.100s: %s", filename,
                            back, strerror(errno));
                        r = SSH_ERR_SYSTEM_ERROR;
                        goto fail;
                }
                if (rename(temp, filename) == -1) {
                        oerrno = errno;
                        error_f("rename \"%s\" to \"%s\": %s", temp,
                            filename, strerror(errno));
                        r = SSH_ERR_SYSTEM_ERROR;
                        goto fail;
                }
        } else {
                /* No changes made; just delete the temporary file */
                if (unlink(temp) != 0)
                        error_f("unlink \"%s\": %s", temp, strerror(errno));
        }

        /* success */
        r = 0;
 fail:
        if (temp != NULL && r != 0)
                unlink(temp);
        free(temp);
        free(back);
        free(fp);
        if (ctx.out != NULL)
                fclose(ctx.out);
        free(ctx.match_keys);
        umask(omask);
        if (r == SSH_ERR_SYSTEM_ERROR)
                errno = oerrno;
        return r;
}

static int
match_maybe_hashed(const char *host, const char *names, int *was_hashed)
{
        int hashed = *names == HASH_DELIM, ret;
        char *hashed_host = NULL;
        size_t nlen = strlen(names);

        if (was_hashed != NULL)
                *was_hashed = hashed;
        if (hashed) {
                if ((hashed_host = host_hash(host, names, nlen)) == NULL)
                        return -1;
                ret = (nlen == strlen(hashed_host) &&
                    strncmp(hashed_host, names, nlen) == 0);
                free(hashed_host);
                return ret;
        }
        return match_hostname(host, names) == 1;
}

int
hostkeys_foreach_file(const char *path, FILE *f, hostkeys_foreach_fn *callback,
    void *ctx, const char *host, const char *ip, u_int options, u_int note)
{
        char *line = NULL, ktype[128];
        u_long linenum = 0;
        char *cp, *cp2;
        u_int kbits;
        int hashed;
        int s, r = 0;
        struct hostkey_foreach_line lineinfo;
        size_t linesize = 0, l;

        memset(&lineinfo, 0, sizeof(lineinfo));
        if (host == NULL && (options & HKF_WANT_MATCH) != 0)
                return SSH_ERR_INVALID_ARGUMENT;

        while (getline(&line, &linesize, f) != -1) {
                linenum++;
                line[strcspn(line, "\n")] = '\0';

                free(lineinfo.line);
                sshkey_free(lineinfo.key);
                memset(&lineinfo, 0, sizeof(lineinfo));
                lineinfo.path = path;
                lineinfo.linenum = linenum;
                lineinfo.line = xstrdup(line);
                lineinfo.marker = MRK_NONE;
                lineinfo.status = HKF_STATUS_OK;
                lineinfo.keytype = KEY_UNSPEC;
                lineinfo.note = note;

                /* Skip any leading whitespace, comments and empty lines. */
                for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
                        ;
                if (!*cp || *cp == '#' || *cp == '\n') {
                        if ((options & HKF_WANT_MATCH) == 0) {
                                lineinfo.status = HKF_STATUS_COMMENT;
                                if ((r = callback(&lineinfo, ctx)) != 0)
                                        break;
                        }
                        continue;
                }

                if ((lineinfo.marker = check_markers(&cp)) == MRK_ERROR) {
                        verbose_f("invalid marker at %s:%lu", path, linenum);
                        if ((options & HKF_WANT_MATCH) == 0)
                                goto bad;
                        continue;
                }

                /* Find the end of the host name portion. */
                for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
                        ;
                if (*cp2 == '\0') {
                        verbose_f("truncated line at %s:%lu", path, linenum);
                        if ((options & HKF_WANT_MATCH) == 0)
                                goto bad;
                        continue;
                }
                lineinfo.hosts = cp;
                *cp2++ = '\0';

                /* Check if the host name matches. */
                if (host != NULL) {
                        if ((s = match_maybe_hashed(host, lineinfo.hosts,
                            &hashed)) == -1) {
                                debug2_f("%s:%ld: bad host hash \"%.32s\"",
                                    path, linenum, lineinfo.hosts);
                                goto bad;
                        }
                        if (s == 1) {
                                lineinfo.status = HKF_STATUS_MATCHED;
                                lineinfo.match |= HKF_MATCH_HOST |
                                    (hashed ? HKF_MATCH_HOST_HASHED : 0);
                        }
                        /* Try matching IP address if supplied */
                        if (ip != NULL) {
                                if ((s = match_maybe_hashed(ip, lineinfo.hosts,
                                    &hashed)) == -1) {
                                        debug2_f("%s:%ld: bad ip hash "
                                            "\"%.32s\"", path, linenum,
                                            lineinfo.hosts);
                                        goto bad;
                                }
                                if (s == 1) {
                                        lineinfo.status = HKF_STATUS_MATCHED;
                                        lineinfo.match |= HKF_MATCH_IP |
                                            (hashed ? HKF_MATCH_IP_HASHED : 0);
                                }
                        }
                        /*
                         * Skip this line if host matching requested and
                         * neither host nor address matched.
                         */
                        if ((options & HKF_WANT_MATCH) != 0 &&
                            lineinfo.status != HKF_STATUS_MATCHED)
                                continue;
                }

                /* Got a match.  Skip host name and any following whitespace */
                for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
                        ;
                if (*cp2 == '\0' || *cp2 == '#') {
                        debug2("%s:%ld: truncated before key type",
                            path, linenum);
                        goto bad;
                }
                lineinfo.rawkey = cp = cp2;

                if ((options & HKF_WANT_PARSE_KEY) != 0) {
                        /*
                         * Extract the key from the line.  This will skip
                         * any leading whitespace.  Ignore badly formatted
                         * lines.
                         */
                        if ((lineinfo.key = sshkey_new(KEY_UNSPEC)) == NULL) {
                                error_f("sshkey_new failed");
                                r = SSH_ERR_ALLOC_FAIL;
                                break;
                        }
                        if (!hostfile_read_key(&cp, &kbits, lineinfo.key)) {
                                goto bad;
                        }
                        lineinfo.keytype = lineinfo.key->type;
                        lineinfo.comment = cp;
                } else {
                        /* Extract and parse key type */
                        l = strcspn(lineinfo.rawkey, " \t");
                        if (l <= 1 || l >= sizeof(ktype) ||
                            lineinfo.rawkey[l] == '\0')
                                goto bad;
                        memcpy(ktype, lineinfo.rawkey, l);
                        ktype[l] = '\0';
                        lineinfo.keytype = sshkey_type_from_name(ktype);

                        /*
                         * Assume legacy RSA1 if the first component is a short
                         * decimal number.
                         */
                        if (lineinfo.keytype == KEY_UNSPEC && l < 8 &&
                            strspn(ktype, "0123456789") == l)
                                goto bad;

                        /*
                         * Check that something other than whitespace follows
                         * the key type. This won't catch all corruption, but
                         * it does catch trivial truncation.
                         */
                        cp2 += l; /* Skip past key type */
                        for (; *cp2 == ' ' || *cp2 == '\t'; cp2++)
                                ;
                        if (*cp2 == '\0' || *cp2 == '#') {
                                debug2("%s:%ld: truncated after key type",
                                    path, linenum);
                                lineinfo.keytype = KEY_UNSPEC;
                        }
                        if (lineinfo.keytype == KEY_UNSPEC) {
 bad:
                                sshkey_free(lineinfo.key);
                                lineinfo.key = NULL;
                                lineinfo.status = HKF_STATUS_INVALID;
                                if ((r = callback(&lineinfo, ctx)) != 0)
                                        break;
                                continue;
                        }
                }
                if ((r = callback(&lineinfo, ctx)) != 0)
                        break;
        }
        sshkey_free(lineinfo.key);
        free(lineinfo.line);
        free(line);
        return r;
}

int
hostkeys_foreach(const char *path, hostkeys_foreach_fn *callback, void *ctx,
    const char *host, const char *ip, u_int options, u_int note)
{
        FILE *f;
        int r, oerrno;

        if ((f = fopen(path, "r")) == NULL)
                return SSH_ERR_SYSTEM_ERROR;

        debug3_f("reading file \"%s\"", path);
        r = hostkeys_foreach_file(path, f, callback, ctx, host, ip,
            options, note);
        oerrno = errno;
        fclose(f);
        errno = oerrno;
        return r;
}