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/* $OpenBSD: https.c,v 1.2 2018/12/06 17:43:30 tedu Exp $ */
/*
* Copyright (c) 2018 Ted Unangst <tedu@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* this file attempts to implement a client for RFC 8484:
* DNS Queries over HTTPS (DoH)
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <syslog.h>
#include <tls.h>
void logmsg(int prio, const char *msg, ...);
void __dead logerr(const char *msg, ...);
static struct tls_config *config;
static struct tls *ctx;
static int connected;
static const char *servername;
int
https_init(void)
{
int rv;
config = tls_config_new();
if (!config) {
logmsg(LOG_NOTICE, "failed to create tls config");
return -1;
}
tls_config_set_ca_file(config, tls_default_ca_cert_file());
ctx = tls_client();
if (!ctx) {
logmsg(LOG_NOTICE, "failed to create tls client");
goto fail;
}
rv = tls_configure(ctx, config);
if (rv != 0) {
logmsg(LOG_NOTICE, "failed to config tls client");
goto fail;
}
return 0;
fail:
tls_free(ctx);
ctx = NULL;
tls_config_free(config);
config = NULL;
return -1;
}
int
https_connect(const char *ip, const char *name)
{
const char *port = "443";
int rv;
if (!ctx)
return -1;
if (connected)
tls_close(ctx);
connected = 0;
tls_reset(ctx);
rv = tls_configure(ctx, config);
if (rv != 0) {
logmsg(LOG_NOTICE, "failed to reconfig tls client");
return -1;
}
rv = tls_connect_servername(ctx, ip, port, name);
if (rv != 0) {
logmsg(LOG_NOTICE, "failed to make tls connection: %s",
tls_error(ctx));
goto fail;
}
servername = name;
connected = 1;
return 0;
fail:
return -1;
}
static const char headerfmt[] =
"POST /dns-query HTTP/1.1\r\n"
"Host: %s\r\n"
"User-Agent: rebound 6.4\r\n"
"Accept: application/dns-message\r\n"
"Content-Type: application/dns-message\r\n"
"Content-Length: %zu\r\n"
"\r\n";
int
https_query(uint8_t *query, size_t qlen, uint8_t *resp, size_t *resplen)
{
char header[1024];
unsigned char buf[65536 + 1024];
unsigned char *two, *clptr, *endptr, *dataptr;
ssize_t amt, headerlen, have, needlen, contlen;
const char *errstr;
if (!connected)
return -1;
headerlen = snprintf(header, sizeof(header), headerfmt, servername, qlen);
amt = tls_write(ctx, header, headerlen);
if (amt != headerlen)
goto badwrite;
amt = tls_write(ctx, query, qlen);
if (amt != qlen)
goto badwrite;
amt = tls_read(ctx, buf, sizeof(buf) - 1);
/* what in the world is going on here? */
if (amt < 10)
goto bad1;
buf[amt] = 0;
two = buf;
while (*two && two < buf + 10 && *two != '2')
two++;
if (*two != '2')
goto bad1;
if (memcmp(two, "200", 3) != 0)
goto notok;
clptr = strcasestr(buf, "content-length:");
if (!clptr)
goto fail;
while (*clptr && !isdigit(*clptr))
clptr++;
if (!isdigit(*clptr))
goto fail;
endptr = clptr;
while (*endptr && *endptr != '\r')
endptr++;
if (*endptr != '\r')
goto fail;
*endptr = 0;
contlen = strtonum(clptr, 0, 65536, &errstr);
if (errstr)
goto fail;
dataptr = memmem(endptr + 1, amt - (endptr + 1 - buf), "\r\n\r\n", 4);
if (!dataptr)
goto fail;
dataptr += 4;
have = amt - (dataptr - buf);
if (have > contlen)
have = contlen;
memcpy(resp, dataptr, have);
needlen = contlen;
needlen -= have;
while (needlen > 0) {
amt = tls_read(ctx, buf, needlen);
if (amt <= 0)
break;
memcpy(resp + have, buf, amt);
have += amt;
needlen -= amt;
}
*resplen = have;
return 0;
badwrite:
logmsg(LOG_NOTICE, "unable to write request");
return -1;
bad1:
logmsg(LOG_NOTICE, "didn't receive enough data for anything");
return -1;
notok:
logmsg(LOG_NOTICE, "http response was not 200");
return -1;
fail:
logmsg(LOG_NOTICE, "some other problem with response");
return -1;
}
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