Commit message: Sanitize inputs to bookmark-cmd (#591)

Newsbeuter didn't properly shell-escape the arguments passed to
bookmarking command, which allows a remote attacker to perform remote
code execution by crafting an RSS item whose title and/or URL contain
something interpretable by the shell (most notably subshell
invocations.)

This has been reported by Jeriko One <jeriko.one@gmx.us>, complete with
PoC and a patch.

This vulnerability was assigned CVE-2017-12904.
CVE: CVE-2017-12904
CWE: CWE-787
Vulnerability description: Improper Neutralization of Special Elements used in an OS Command in bookmarking function of Newsbeuter versions 0.7 through 2.9 allows remote attackers to perform user-assisted code execution by crafting an RSS item that includes shell code in its title and/or URL.

Project: newsbeuter
File: controller.cpp

std::string controller::bookmark(
		const std::string& url,
		const std::string& title,
		const std::string& description,
		const std::string& feed_title)
{
	std::string bookmark_cmd = cfg.get_configvalue("bookmark-cmd");
	bool is_interactive = cfg.get_configvalue_as_bool("bookmark-interactive");
	if (bookmark_cmd.length() > 0) {
		std::string cmdline = strprintf::fmt("%s '%s' %s %s %s",
		                                       bookmark_cmd,
		                                       utils::replace_all(url,"'", "%27"),
		                                       quote_empty(stfl::quote(title)),
		                                       quote_empty(stfl::quote(description)),
		                                       quote_empty(stfl::quote(feed_title)));

		LOG(level::DEBUG, "controller::bookmark: cmd = %s", cmdline);

		if (is_interactive) {
			v->push_empty_formaction();
			stfl::reset();
			utils::run_interactively(cmdline, "controller::bookmark");
			v->pop_current_formaction();
			return "";
		} else {
			char * my_argv[4];
			my_argv[0] = const_cast<char *>("/bin/sh");
			my_argv[1] = const_cast<char *>("-c");
			my_argv[2] = const_cast<char *>(cmdline.c_str());
			my_argv[3] = nullptr;
			return utils::run_program(my_argv, "");
		}
	} else {
		return _("bookmarking support is not configured. Please set the configuration variable `bookmark-cmd' accordingly.");
	}
}

Project: newsbeuter
File: controller.cpp

std::string controller::bookmark(
		const std::string& url,
		const std::string& title,
		const std::string& description,
		const std::string& feed_title)
{
	std::string bookmark_cmd = cfg.get_configvalue("bookmark-cmd");
	bool is_interactive = cfg.get_configvalue_as_bool("bookmark-interactive");
	if (bookmark_cmd.length() > 0) {
		std::string cmdline = strprintf::fmt("%s '%s' '%s' '%s' '%s'",
		                                       bookmark_cmd,
		                                       utils::replace_all(url,"'", "%27"),
		                                       utils::replace_all(title,"'", "%27"),
		                                       utils::replace_all(description,"'", "%27"),
		                                       utils::replace_all(feed_title,"'", "%27"));

		LOG(level::DEBUG, "controller::bookmark: cmd = %s", cmdline);

		if (is_interactive) {
			v->push_empty_formaction();
			stfl::reset();
			utils::run_interactively(cmdline, "controller::bookmark");
			v->pop_current_formaction();
			return "";
		} else {
			char * my_argv[4];
			my_argv[0] = const_cast<char *>("/bin/sh");
			my_argv[1] = const_cast<char *>("-c");
			my_argv[2] = const_cast<char *>(cmdline.c_str());
			my_argv[3] = nullptr;
			return utils::run_program(my_argv, "");
		}
	} else {
		return _("bookmarking support is not configured. Please set the configuration variable `bookmark-cmd' accordingly.");
	}
}