http.c

/*
 * http posting routines
 *
 * Copyright (C) 2014-2016 LastPass.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * In addition, as a special exception, the copyright holders give
 * permission to link the code of portions of this program with the
 * OpenSSL library under certain conditions as described in each
 * individual source file, and distribute linked combinations
 * including the two.
 *
 * You must obey the GNU General Public License in all respects
 * for all of the code used other than OpenSSL.  If you modify
 * file(s) with this exception, you may extend this exception to your
 * version of the file(s), but you are not obligated to do so.  If you
 * do not wish to do so, delete this exception statement from your
 * version.  If you delete this exception statement from all source
 * files in the program, then also delete it here.
 *
 * See LICENSE.OpenSSL for more details regarding this exception.
 */
#include "http.h"
#include "log.h"
#include "util.h"
#include "version.h"
#include "pins.h"
#include "cipher.h"
#include <stdarg.h>
#include <stdint.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <openssl/ssl.h>
#include <curl/curl.h>

struct mem_chunk {
	char *ptr;
	size_t len;
};

static bool interrupted = false;
static sig_t previous_handler = SIG_DFL;
static void interruption_detected(int signal)
{
	UNUSED(signal);
	interrupted = true;
}
static void set_interrupt_detect(void)
{
	interrupted = false;
	previous_handler = signal(SIGINT, interruption_detected);
}
static void unset_interrupt_detect(void)
{
	interrupted = false;
	signal(SIGINT, previous_handler);
}
static int check_interruption(void *p, double dltotal, double dlnow, double ultotal, double ulnow)
{
	UNUSED(p);
	UNUSED(dltotal);
	UNUSED(dlnow);
	UNUSED(ultotal);
	UNUSED(ulnow);
	return interrupted;
}

static size_t write_data(char *ptr, size_t size, size_t nmemb, void *data)
{
	size_t len, new_len;
	struct mem_chunk *mem = (struct mem_chunk *)data;
	if ((nmemb >= MUL_NO_OVERFLOW || size >= MUL_NO_OVERFLOW) && nmemb > 0 && SIZE_MAX / nmemb < size) {
		errno = ENOMEM;
		return 0;
	}
	len = size * nmemb;
	new_len = len + mem->len + 1;
	if (new_len <= mem->len || new_len <= len || new_len < 1) {
		errno = ENOMEM;
		return 0;
	}

	mem->ptr = xrealloc(mem->ptr, new_len);
	memcpy(mem->ptr + mem->len, ptr, len);
	mem->len += len;
	mem->ptr[mem->len] = '\0';

	return len;
}

static char *hash_subject_pubkey_info(X509 *cert)
{
	_cleanup_free_ unsigned char *spki = NULL;
	char *hash = NULL;
	EVP_PKEY *pkey;
	int len;

	pkey = X509_get_pubkey(cert);
	if (!pkey)
		return NULL;

	len = i2d_PUBKEY(pkey, &spki);
	if (len <= 0)
		goto free_pkey;

	hash = cipher_sha256_b64(spki, len);
free_pkey:
	EVP_PKEY_free(pkey);
	return hash;
}

static int verify_callback(int preverify_ok, X509_STORE_CTX *ctx)
{
	int i, j;

	/*
	 * Preverify checks the platform's certificate store; don't
	 * allow any chain that doesn't already validate according to
	 * that.
	 */
	if (!preverify_ok)
		return 0;

	/* check each certificate in the chain against our built-in pinlist. */
	STACK_OF(X509) *chain = X509_STORE_CTX_get_chain(ctx);
	if (!chain)
		die("No certificate chain available");

	bool found = false;
	for (i=0; i < sk_X509_num(chain); i++) {
		_cleanup_free_ char *spki_hash = NULL;
		spki_hash = hash_subject_pubkey_info(sk_X509_value(chain, i));
		if (!spki_hash)
			continue;

		for (j=0; j < (int) ARRAY_SIZE(PK_PINS); j++) {
			if (strcmp(PK_PINS[j], spki_hash) == 0) {
				found = true;
				break;
			}
		}
	}

	return found;
}

static CURLcode pin_keys(CURL *curl, void *sslctx, void *parm)
{
	UNUSED(curl);
	UNUSED(parm);
	SSL_CTX_set_verify((SSL_CTX *)sslctx, SSL_VERIFY_PEER,
			   verify_callback);
	return CURLE_OK;
}

static
void vhttp_post_add_params(struct http_param_set *param_set, va_list args)
{
	char **argv_ptr;
	char *arg;
	size_t count = 0;

	if (!param_set->argv) {
		param_set->n_alloced = 2;
		param_set->argv = xcalloc(param_set->n_alloced, sizeof(char *));
	}
	argv_ptr = param_set->argv;
	while (*argv_ptr) {
		argv_ptr++;
		count++;
	}

	while ((arg = va_arg(args, char *))) {
		if (count == param_set->n_alloced - 1) {
			param_set->n_alloced += 2;
			param_set->argv = xreallocarray(param_set->argv,
				param_set->n_alloced, sizeof(char *));
			argv_ptr = &param_set->argv[count];
		}
		*argv_ptr++ = arg;
		count++;
	}
	*argv_ptr = 0;
}

int http_init()
{
	curl_global_cleanup();
	return curl_global_init(CURL_GLOBAL_DEFAULT);
}

void http_post_add_params(struct http_param_set *param_set, ...)
{
	va_list args;
	va_start(args, param_set);
	vhttp_post_add_params(param_set, args);
	va_end(args);
}

char *http_post_lastpass(const char *page, const struct session *session, size_t *final_len, ...)
{
	va_list args;
	struct http_param_set params = {
		.argv = NULL,
		.n_alloced = 0
	};

	va_start(args, final_len);
	vhttp_post_add_params(&params, args);
	char *result = http_post_lastpass_param_set(page, session, final_len, &params);
	free(params.argv);
	return result;
}

char *http_post_lastpass_v_noexit(const char *server, const char *page, const struct session *session, size_t *final_len, char **argv, int *curl_ret, long *http_code)
{
	_cleanup_free_ char *url = NULL;
	_cleanup_free_ char *postdata = NULL;
	_cleanup_free_ char *cookie = NULL;
	_cleanup_fclose_ FILE *logstream = NULL;
	char *param, *encoded_param;
	CURL *curl = NULL;
	char separator;
	size_t len, new_len;
	int ret;
	struct mem_chunk result;
	const char *login_server;

	/* if we have a session, use that server, otherwise use whatever was passed */
	login_server = session ? session->server : server;

	/* if nothing passed, use lastpass */
	if (!login_server)
		login_server = LASTPASS_SERVER;

	xasprintf(&url, "https://%s/%s", login_server, page);

	lpass_log(LOG_DEBUG, "Making request to %s\n", url);

	curl = curl_easy_init();
	if (!curl)
		die("Could not init curl");

	len = 0;
	for (separator = '=', param = *argv;
	     param;
	     separator = (separator == '=') ? '&' : '=', param = *(++argv)) {
		encoded_param = curl_easy_escape(curl, param, 0);
		if (!encoded_param)
			die("Could not escape %s with curl", param);
		new_len = strlen(encoded_param) + 1 /* separator */;
		postdata = xrealloc(postdata, len + new_len + 1 /* null */);
		snprintf(postdata + len, new_len + 1, "%s%c", encoded_param, separator);
		len += new_len;
		curl_free(encoded_param);
	}
	if (len && postdata)
		postdata[len - 1] = '\0';

	memset(&result, 0, sizeof(result));
	curl_easy_setopt(curl, CURLOPT_URL, url);
	curl_easy_setopt(curl, CURLOPT_USERAGENT, LASTPASS_CLI_USERAGENT);

	if (lpass_log_level() >= LOG_VERBOSE) {
		logstream = lpass_log_open();
		if (logstream) {
			curl_easy_setopt(curl, CURLOPT_STDERR, logstream);
			curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
		}
	}
#if defined(DO_NOT_ENABLE_ME_MITM_PROXY_FOR_DEBUGGING_ONLY)
	curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0);
	curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
	curl_easy_setopt(curl, CURLOPT_PROXY, "http://localhost:8080");
#else
	curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2);
	curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1);
	curl_easy_setopt(curl, CURLOPT_SSL_CTX_FUNCTION, pin_keys);
#endif
	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
	curl_easy_setopt(curl, CURLOPT_WRITEDATA, &result);
	curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1);
	curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, check_interruption);
	curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0);
	if (postdata)
		curl_easy_setopt(curl, CURLOPT_POSTFIELDS, postdata);
	if (session) {
		xasprintf(&cookie, "PHPSESSID=%s", session->sessionid);
		curl_easy_setopt(curl, CURLOPT_COOKIE, cookie);
	}

	set_interrupt_detect();
	ret = curl_easy_perform(curl);
	unset_interrupt_detect();

	curl_easy_cleanup(curl);
	curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, http_code);
	*curl_ret = ret;

	if (ret != CURLE_OK) {
		result.len = 0;
		free(result.ptr);
		result.ptr = NULL;
	} else if (!result.ptr)
		result.ptr = xstrdup("");
	if (final_len)
		*final_len = result.len;

	return result.ptr;
}

char *http_post_lastpass_v(const char *server, const char *page, const struct session *session, size_t *final_len, char **argv)
{
	char *result;
	int ret;
	long http_code;

	result = http_post_lastpass_v_noexit(server, page, session, final_len,
					     argv, &ret, &http_code);

	if (ret != CURLE_OK && ret != CURLE_ABORTED_BY_CALLBACK)
		die("%s.", curl_easy_strerror(ret));

	return result;
}


char *http_post_lastpass_param_set(const char *page, const struct session *session, size_t *final_len, struct http_param_set *param_set) {
	return http_post_lastpass_v(NULL, page, session, final_len, param_set->argv);
}