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/*
* ssh_known_hosts.c: parser for ~/.ssh/known_hosts
* Copyright (C) 2018 Iru Cai <mytbk920423@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "ssh_endian.h"
#include "ccan_base64.h"
#include "ssh_known_hosts.h"
static char *ssh_hosts_file = NULL;
static char *ssh_get_string(const char *buf, char *s, int size, char delim)
{
char *end = strchr(buf, delim);
if (end == NULL)
return NULL;
int l = end - buf;
if (l >= size)
return NULL;
memcpy(s, buf, l);
s[l] = 0;
return end;
}
struct ssh_host *parse_hosts_file(const char *fn, int *list_sz)
{
FILE *fp;
char linebuf[1536];
int nHosts;
struct ssh_host *hosts;
fp = fopen(fn, "r");
if (fp == NULL) {
*list_sz = 0;
return NULL;
}
fseek(fp, 0, SEEK_END); // seek to end of file
long size = ftell(fp); // get current file pointer
fseek(fp, 0, SEEK_SET); // seek back to beginning of file
/* use file size/64 to estimate # of hosts */
hosts = (struct ssh_host *)malloc(sizeof(struct ssh_host) *
(size / 64 + 1));
nHosts = 0;
while (fgets(linebuf, sizeof(linebuf), fp)) {
char *host_end = ssh_get_string(linebuf, hosts[nHosts].hostname,
256, ' ');
if (host_end == NULL)
continue;
char *type_end = ssh_get_string(host_end + 1,
hosts[nHosts].keytype, 32, ' ');
if (type_end == NULL)
continue;
char *key_end = ssh_get_string(
type_end + 1, hosts[nHosts].pubkey, 1024, '\n');
if (key_end == NULL)
continue;
if (key_end - linebuf < 64) /* too short */
continue;
nHosts++;
}
fclose(fp);
*list_sz = nHosts;
return hosts;
}
int find_ssh_host(struct ssh_host *h, int n, const char *hostname, int port)
{
int L = strlen(hostname);
for (int i = 0; i < n; i++) {
const char *hn = h[i].hostname;
const char *hn_end;
int hlen;
if (port == 22 && hn[0] == '[')
continue;
if (port != 22 && hn[0] != '[')
continue;
if (port == 22) {
hn_end = strchr(hn, ',');
if (hn_end == NULL)
hlen = strlen(hn);
else
hlen = hn_end - hn;
} else {
hn_end = strchr(hn, ':');
if (hn_end == NULL || atoi(hn_end + 1) != port)
continue;
hn++;
hlen = hn_end - hn - 1;
}
/* TODO: match IP address */
if (hlen != L || memcmp(hostname, hn, L) != 0)
continue;
else
return i;
}
return -1;
}
int key_matches(struct ssh_host *h, const unsigned char *K_S, int K_S_len)
{
int algo_len = ntohu32(K_S);
int h_keylen = strlen(h->pubkey);
char buf[1536];
if (strlen(h->keytype) == algo_len &&
memcmp(h->keytype, K_S + 4, algo_len) == 0) {
if (base64_encoded_length(K_S_len) != h_keylen)
return 0;
base64_encode(buf, sizeof(buf), K_S, K_S_len);
if (memcmp(buf, h->pubkey, h_keylen) == 0)
return 1;
else
return 0;
} else {
return 0;
}
}
void append_hostkey(const char *fn, const char *hostname, const unsigned char *K_S, int K_S_len)
{
FILE *fp = fopen(fn, "a");
if (fp == NULL)
return;
char algo[32];
char buf[1536];
int algo_len = ntohu32(K_S);
if (algo_len >= sizeof(algo))
goto end;
memcpy(algo, K_S + 4, algo_len);
algo[algo_len] = 0;
int b64len = base64_encoded_length(K_S_len);
if (b64len >= sizeof(buf))
goto end;
base64_encode(buf, sizeof(buf), K_S, K_S_len);
buf[b64len] = 0;
fprintf(fp, "%s %s %s\n", hostname, algo, buf);
end:
fclose(fp);
return;
}
const char *ssh_hosts_filename(void)
{
if (ssh_hosts_file != NULL)
return ssh_hosts_file;
char *myhome = getenv("HOME");
ssh_hosts_file = malloc(strlen(myhome) + 20);
strcpy(ssh_hosts_file, myhome);
strcat(ssh_hosts_file, "/.ssh/known_hosts");
return ssh_hosts_file;
}
struct ssh_host *parse_unix_hosts_file(int *nhosts)
{
const char *hosts_file = ssh_hosts_filename();
return parse_hosts_file(hosts_file, nhosts);
}
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