git-crypt/commands.cpp

/*
 * Copyright 2012, 2014 Andrew Ayer
 *
 * This file is part of git-crypt.
 *
 * git-crypt 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 3 of the License, or
 * (at your option) any later version.
 *
 * git-crypt 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 git-crypt.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Additional permission under GNU GPL version 3 section 7:
 *
 * If you modify the Program, or any covered work, by linking or
 * combining it with the OpenSSL project's OpenSSL library (or a
 * modified version of that library), containing parts covered by the
 * terms of the OpenSSL or SSLeay licenses, the licensors of the Program
 * grant you additional permission to convey the resulting work.
 * Corresponding Source for a non-source form of such a combination
 * shall include the source code for the parts of OpenSSL used as well
 * as that of the covered work.
 */

#include "commands.hpp"
#include "crypto.hpp"
#include "util.hpp"
#include "key.hpp"
#include "gpg.hpp"
#include "parse_options.hpp"
#include <unistd.h>
#include <stdint.h>
#include <algorithm>
#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
#include <cstddef>
#include <cstring>
#include <cctype>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <vector>

static void git_config (const std::string& name, const std::string& value)
{
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("config");
	command.push_back(name);
	command.push_back(value);

	if (!successful_exit(exec_command(command))) {
		throw Error("'git config' failed");
	}
}

static void configure_git_filters (const char* key_name)
{
	std::string	escaped_git_crypt_path(escape_shell_arg(our_exe_path()));

	if (key_name) {
		// Note: key_name contains only shell-safe characters so it need not be escaped.
		git_config(std::string("filter.git-crypt-") + key_name + ".smudge",
		           escaped_git_crypt_path + " smudge --key-name=" + key_name);
		git_config(std::string("filter.git-crypt-") + key_name + ".clean",
		           escaped_git_crypt_path + " clean --key-name=" + key_name);
		git_config(std::string("diff.git-crypt-") + key_name + ".textconv",
		           escaped_git_crypt_path + " diff --key-name=" + key_name);
	} else {
		git_config("filter.git-crypt.smudge", escaped_git_crypt_path + " smudge");
		git_config("filter.git-crypt.clean", escaped_git_crypt_path + " clean");
		git_config("diff.git-crypt.textconv", escaped_git_crypt_path + " diff");
	}
}

static bool same_key_name (const char* a, const char* b)
{
	return (!a && !b) || (a && b && std::strcmp(a, b) == 0);
}

static void validate_key_name_or_throw (const char* key_name)
{
	std::string			reason;
	if (!validate_key_name(key_name, &reason)) {
		throw Error(reason);
	}
}

static std::string get_internal_key_path (const char* key_name)
{
	// git rev-parse --git-dir
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("rev-parse");
	command.push_back("--git-dir");

	std::stringstream		output;

	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git rev-parse --git-dir' failed - is this a Git repository?");
	}

	std::string			path;
	std::getline(output, path);
	path += "/git-crypt/keys/";
	path += key_name ? key_name : "default";
	return path;
}

static std::string get_repo_keys_path ()
{
	// git rev-parse --show-toplevel
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("rev-parse");
	command.push_back("--show-toplevel");

	std::stringstream		output;

	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git rev-parse --show-toplevel' failed - is this a Git repository?");
	}

	std::string			path;
	std::getline(output, path);

	if (path.empty()) {
		// could happen for a bare repo
		throw Error("Could not determine Git working tree - is this a non-bare repo?");
	}

	path += "/.git-crypt/keys";
	return path;
}

static std::string get_path_to_top ()
{
	// git rev-parse --show-cdup
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("rev-parse");
	command.push_back("--show-cdup");

	std::stringstream		output;

	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git rev-parse --show-cdup' failed - is this a Git repository?");
	}

	std::string			path_to_top;
	std::getline(output, path_to_top);

	return path_to_top;
}

static void get_git_status (std::ostream& output)
{
	// git status -uno --porcelain
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("status");
	command.push_back("-uno"); // don't show untracked files
	command.push_back("--porcelain");

	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git status' failed - is this a Git repository?");
	}
}

static bool check_if_head_exists ()
{
	// git rev-parse HEAD
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("rev-parse");
	command.push_back("HEAD");

	std::stringstream		output;
	return successful_exit(exec_command(command, output));
}

// returns filter and diff attributes as a pair
static std::pair<std::string, std::string> get_file_attributes (const std::string& filename)
{
	// git check-attr filter diff -- filename
	// TODO: pass -z to get machine-parseable output (this requires Git 1.8.5 or higher, which was released on 27 Nov 2013)
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("check-attr");
	command.push_back("filter");
	command.push_back("diff");
	command.push_back("--");
	command.push_back(filename);

	std::stringstream		output;
	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git check-attr' failed - is this a Git repository?");
	}

	std::string			filter_attr;
	std::string			diff_attr;

	std::string			line;
	// Example output:
	// filename: filter: git-crypt
	// filename: diff: git-crypt
	while (std::getline(output, line)) {
		// filename might contain ": ", so parse line backwards
		// filename: attr_name: attr_value
		//         ^name_pos  ^value_pos
		const std::string::size_type	value_pos(line.rfind(": "));
		if (value_pos == std::string::npos || value_pos == 0) {
			continue;
		}
		const std::string::size_type	name_pos(line.rfind(": ", value_pos - 1));
		if (name_pos == std::string::npos) {
			continue;
		}

		const std::string		attr_name(line.substr(name_pos + 2, value_pos - (name_pos + 2)));
		const std::string		attr_value(line.substr(value_pos + 2));

		if (attr_value != "unspecified" && attr_value != "unset" && attr_value != "set") {
			if (attr_name == "filter") {
				filter_attr = attr_value;
			} else if (attr_name == "diff") {
				diff_attr = attr_value;
			}
		}
	}

	return std::make_pair(filter_attr, diff_attr);
}

static bool check_if_blob_is_encrypted (const std::string& object_id)
{
	// git cat-file blob object_id

	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("cat-file");
	command.push_back("blob");
	command.push_back(object_id);

	// TODO: do this more efficiently - don't read entire command output into buffer, only read what we need
	std::stringstream		output;
	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git cat-file' failed - is this a Git repository?");
	}

	char				header[10];
	output.read(header, sizeof(header));
	return output.gcount() == sizeof(header) && std::memcmp(header, "\0GITCRYPT\0", 10) == 0;
}

static bool check_if_file_is_encrypted (const std::string& filename)
{
	// git ls-files -sz filename
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("ls-files");
	command.push_back("-sz");
	command.push_back("--");
	command.push_back(filename);

	std::stringstream		output;
	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git ls-files' failed - is this a Git repository?");
	}

	if (output.peek() == -1) {
		return false;
	}

	std::string			mode;
	std::string			object_id;
	output >> mode >> object_id;

	return check_if_blob_is_encrypted(object_id);
}

static void load_key (Key_file& key_file, const char* key_name, const char* key_path =0, const char* legacy_path =0)
{
	if (legacy_path) {
		std::ifstream		key_file_in(legacy_path, std::fstream::binary);
		if (!key_file_in) {
			throw Error(std::string("Unable to open key file: ") + legacy_path);
		}
		key_file.load_legacy(key_file_in);
	} else if (key_path) {
		std::ifstream		key_file_in(key_path, std::fstream::binary);
		if (!key_file_in) {
			throw Error(std::string("Unable to open key file: ") + key_path);
		}
		key_file.load(key_file_in);
	} else {
		std::ifstream		key_file_in(get_internal_key_path(key_name).c_str(), std::fstream::binary);
		if (!key_file_in) {
			// TODO: include key name in error message
			throw Error("Unable to open key file - have you unlocked/initialized this repository yet?");
		}
		key_file.load(key_file_in);
	}
}

static bool decrypt_repo_key (Key_file& key_file, const char* key_name, uint32_t key_version, const std::vector<std::string>& secret_keys, const std::string& keys_path)
{
	for (std::vector<std::string>::const_iterator seckey(secret_keys.begin()); seckey != secret_keys.end(); ++seckey) {
		std::ostringstream		path_builder;
		path_builder << keys_path << '/' << (key_name ? key_name : "default") << '/' << key_version << '/' << *seckey << ".gpg";
		std::string			path(path_builder.str());
		if (access(path.c_str(), F_OK) == 0) {
			std::stringstream	decrypted_contents;
			gpg_decrypt_from_file(path, decrypted_contents);
			Key_file		this_version_key_file;
			this_version_key_file.load(decrypted_contents);
			const Key_file::Entry*	this_version_entry = this_version_key_file.get(key_version);
			if (!this_version_entry) {
				throw Error("GPG-encrypted keyfile is malformed because it does not contain expected key version");
			}
			if (!same_key_name(key_name, this_version_key_file.get_key_name())) {
				throw Error("GPG-encrypted keyfile is malformed because it does not contain expected key name");
			}
			key_file.set_key_name(key_name);
			key_file.add(*this_version_entry);
			return true;
		}
	}
	return false;
}

static bool decrypt_repo_keys (std::vector<Key_file>& key_files, uint32_t key_version, const std::vector<std::string>& secret_keys, const std::string& keys_path)
{
	bool				successful = false;
	std::vector<std::string>	dirents;

	if (access(keys_path.c_str(), F_OK) == 0) {
		dirents = get_directory_contents(keys_path.c_str());
	}

	for (std::vector<std::string>::const_iterator dirent(dirents.begin()); dirent != dirents.end(); ++dirent) {
		const char*		key_name = 0;
		if (*dirent != "default") {
			if (!validate_key_name(dirent->c_str())) {
				continue;
			}
			key_name = dirent->c_str();
		}

		Key_file	key_file;
		if (decrypt_repo_key(key_file, key_name, key_version, secret_keys, keys_path)) {
			key_files.push_back(key_file);
			successful = true;
		}
	}
	return successful;
}

static void encrypt_repo_key (const char* key_name, const Key_file::Entry& key, const std::vector<std::string>& collab_keys, const std::string& keys_path, std::vector<std::string>* new_files)
{
	std::string	key_file_data;
	{
		Key_file this_version_key_file;
		this_version_key_file.set_key_name(key_name);
		this_version_key_file.add(key);
		key_file_data = this_version_key_file.store_to_string();
	}

	for (std::vector<std::string>::const_iterator collab(collab_keys.begin()); collab != collab_keys.end(); ++collab) {
		std::ostringstream	path_builder;
		path_builder << keys_path << '/' << (key_name ? key_name : "default") << '/' << key.version << '/' << *collab << ".gpg";
		std::string		path(path_builder.str());

		if (access(path.c_str(), F_OK) == 0) {
			continue;
		}

		mkdir_parent(path);
		gpg_encrypt_to_file(path, *collab, key_file_data.data(), key_file_data.size());
		new_files->push_back(path);
	}
}

static int parse_plumbing_options (const char** key_name, const char** key_file, int argc, const char** argv)
{
	Options_list	options;
	options.push_back(Option_def("-k", key_name));
	options.push_back(Option_def("--key-name", key_name));
	options.push_back(Option_def("--key-file", key_file));

	return parse_options(options, argc, argv);
}



// Encrypt contents of stdin and write to stdout
int clean (int argc, const char** argv)
{
	const char*		key_name = 0;
	const char*		key_path = 0;
	const char*		legacy_key_path = 0;

	int			argi = parse_plumbing_options(&key_name, &key_path, argc, argv);
	if (argc - argi == 0) {
	} else if (!key_name && !key_path && argc - argi == 1) { // Deprecated - for compatibility with pre-0.4
		legacy_key_path = argv[argi];
	} else {
		std::clog << "Usage: git-crypt clean [--key-name=NAME] [--key-file=PATH]" << std::endl;
		return 2;
	}
	Key_file		key_file;
	load_key(key_file, key_name, key_path, legacy_key_path);

	const Key_file::Entry*	key = key_file.get_latest();
	if (!key) {
		std::clog << "git-crypt: error: key file is empty" << std::endl;
		return 1;
	}

	// Read the entire file

	Hmac_sha1_state	hmac(key->hmac_key, HMAC_KEY_LEN); // Calculate the file's SHA1 HMAC as we go
	uint64_t		file_size = 0;	// Keep track of the length, make sure it doesn't get too big
	std::string		file_contents;	// First 8MB or so of the file go here
	temp_fstream		temp_file;	// The rest of the file spills into a temporary file on disk
	temp_file.exceptions(std::fstream::badbit);

	char			buffer[1024];

	while (std::cin && file_size < Aes_ctr_encryptor::MAX_CRYPT_BYTES) {
		std::cin.read(buffer, sizeof(buffer));

		const size_t	bytes_read = std::cin.gcount();

		hmac.add(reinterpret_cast<unsigned char*>(buffer), bytes_read);
		file_size += bytes_read;

		if (file_size <= 8388608) {
			file_contents.append(buffer, bytes_read);
		} else {
			if (!temp_file.is_open()) {
				temp_file.open(std::fstream::in | std::fstream::out | std::fstream::binary | std::fstream::app);
			}
			temp_file.write(buffer, bytes_read);
		}
	}

	// Make sure the file isn't so large we'll overflow the counter value (which would doom security)
	if (file_size >= Aes_ctr_encryptor::MAX_CRYPT_BYTES) {
		std::clog << "git-crypt: error: file too long to encrypt securely" << std::endl;
		return 1;
	}

	// We use an HMAC of the file as the encryption nonce (IV) for CTR mode.
	// By using a hash of the file we ensure that the encryption is
	// deterministic so git doesn't think the file has changed when it really
	// hasn't.  CTR mode with a synthetic IV is provably semantically secure
	// under deterministic CPA as long as the synthetic IV is derived from a
	// secure PRF applied to the message.  Since HMAC-SHA1 is a secure PRF, this
	// encryption scheme is semantically secure under deterministic CPA.
	// 
	// Informally, consider that if a file changes just a tiny bit, the IV will
	// be completely different, resulting in a completely different ciphertext
	// that leaks no information about the similarities of the plaintexts.  Also,
	// since we're using the output from a secure hash function plus a counter
	// as the input to our block cipher, we should never have a situation where
	// two different plaintext blocks get encrypted with the same CTR value.  A
	// nonce will be reused only if the entire file is the same, which leaks no
	// information except that the files are the same.
	//
	// To prevent an attacker from building a dictionary of hash values and then
	// looking up the nonce (which must be stored in the clear to allow for
	// decryption), we use an HMAC as opposed to a straight hash.

	// Note: Hmac_sha1_state::LEN >= Aes_ctr_encryptor::NONCE_LEN

	unsigned char		digest[Hmac_sha1_state::LEN];
	hmac.get(digest);

	// Write a header that...
	std::cout.write("\0GITCRYPT\0", 10); // ...identifies this as an encrypted file
	std::cout.write(reinterpret_cast<char*>(digest), Aes_ctr_encryptor::NONCE_LEN); // ...includes the nonce

	// Now encrypt the file and write to stdout
	Aes_ctr_encryptor	aes(key->aes_key, digest);

	// First read from the in-memory copy
	const unsigned char*	file_data = reinterpret_cast<const unsigned char*>(file_contents.data());
	size_t			file_data_len = file_contents.size();
	while (file_data_len > 0) {
		const size_t	buffer_len = std::min(sizeof(buffer), file_data_len);
		aes.process(file_data, reinterpret_cast<unsigned char*>(buffer), buffer_len);
		std::cout.write(buffer, buffer_len);
		file_data += buffer_len;
		file_data_len -= buffer_len;
	}

	// Then read from the temporary file if applicable
	if (temp_file.is_open()) {
		temp_file.seekg(0);
		while (temp_file.peek() != -1) {
			temp_file.read(buffer, sizeof(buffer));

			const size_t	buffer_len = temp_file.gcount();

			aes.process(reinterpret_cast<unsigned char*>(buffer),
			            reinterpret_cast<unsigned char*>(buffer),
			            buffer_len);
			std::cout.write(buffer, buffer_len);
		}
	}

	return 0;
}

// Decrypt contents of stdin and write to stdout
int smudge (int argc, const char** argv)
{
	const char*		key_name = 0;
	const char*		key_path = 0;
	const char*		legacy_key_path = 0;

	int			argi = parse_plumbing_options(&key_name, &key_path, argc, argv);
	if (argc - argi == 0) {
	} else if (!key_name && !key_path && argc - argi == 1) { // Deprecated - for compatibility with pre-0.4
		legacy_key_path = argv[argi];
	} else {
		std::clog << "Usage: git-crypt smudge [--key-name=NAME] [--key-file=PATH]" << std::endl;
		return 2;
	}
	Key_file		key_file;
	load_key(key_file, key_name, key_path, legacy_key_path);

	// Read the header to get the nonce and make sure it's actually encrypted
	unsigned char		header[10 + Aes_ctr_decryptor::NONCE_LEN];
	std::cin.read(reinterpret_cast<char*>(header), sizeof(header));
	if (std::cin.gcount() != sizeof(header) || std::memcmp(header, "\0GITCRYPT\0", 10) != 0) {
		std::clog << "git-crypt: error: file not encrypted" << std::endl;
		return 1;
	}
	const unsigned char*	nonce = header + 10;
	uint32_t		key_version = 0; // TODO: get the version from the file header

	const Key_file::Entry*	key = key_file.get(key_version);
	if (!key) {
		std::clog << "git-crypt: error: key version " << key_version << " not available - please unlock with the latest version of the key." << std::endl;
		return 1;
	}

	Aes_ctr_decryptor::process_stream(std::cin, std::cout, key->aes_key, nonce);
	return 0;
}

int diff (int argc, const char** argv)
{
	const char*		key_name = 0;
	const char*		key_path = 0;
	const char*		filename = 0;
	const char*		legacy_key_path = 0;

	int			argi = parse_plumbing_options(&key_name, &key_path, argc, argv);
	if (argc - argi == 1) {
		filename = argv[argi];
	} else if (!key_name && !key_path && argc - argi == 2) { // Deprecated - for compatibility with pre-0.4
		legacy_key_path = argv[argi];
		filename = argv[argi + 1];
	} else {
		std::clog << "Usage: git-crypt diff [--key-name=NAME] [--key-file=PATH] FILENAME" << std::endl;
		return 2;
	}
	Key_file		key_file;
	load_key(key_file, key_name, key_path, legacy_key_path);

	// Open the file
	std::ifstream		in(filename, std::fstream::binary);
	if (!in) {
		std::clog << "git-crypt: " << filename << ": unable to open for reading" << std::endl;
		return 1;
	}
	in.exceptions(std::fstream::badbit);

	// Read the header to get the nonce and determine if it's actually encrypted
	unsigned char		header[10 + Aes_ctr_decryptor::NONCE_LEN];
	in.read(reinterpret_cast<char*>(header), sizeof(header));
	if (in.gcount() != sizeof(header) || std::memcmp(header, "\0GITCRYPT\0", 10) != 0) {
		// File not encrypted - just copy it out to stdout
		std::cout.write(reinterpret_cast<char*>(header), in.gcount()); // don't forget to include the header which we read!
		std::cout << in.rdbuf();
		return 0;
	}

	// Go ahead and decrypt it
	const unsigned char*	nonce = header + 10;
	uint32_t		key_version = 0; // TODO: get the version from the file header

	const Key_file::Entry*	key = key_file.get(key_version);
	if (!key) {
		std::clog << "git-crypt: error: key version " << key_version << " not available - please unlock with the latest version of the key." << std::endl;
		return 1;
	}

	Aes_ctr_decryptor::process_stream(in, std::cout, key->aes_key, nonce);
	return 0;
}

int init (int argc, const char** argv)
{
	const char*	key_name = 0;
	Options_list	options;
	options.push_back(Option_def("-k", &key_name));
	options.push_back(Option_def("--key-name", &key_name));

	int		argi = parse_options(options, argc, argv);

	if (!key_name && argc - argi == 1) {
		std::clog << "Warning: 'git-crypt init' with a key file is deprecated as of git-crypt 0.4" << std::endl;
		std::clog << "and will be removed in a future release. Please get in the habit of using" << std::endl;
		std::clog << "'git-crypt unlock KEYFILE' instead." << std::endl;
		return unlock(argc, argv);
	}
	if (argc - argi != 0) {
		std::clog << "Usage: git-crypt init [-k KEYNAME]" << std::endl;
		return 2;
	}

	if (key_name) {
		validate_key_name_or_throw(key_name);
	}

	std::string		internal_key_path(get_internal_key_path(key_name));
	if (access(internal_key_path.c_str(), F_OK) == 0) {
		// TODO: add a -f option to reinitialize the repo anyways (this should probably imply a refresh)
		// TODO: include key_name in error message
		std::clog << "Error: this repository has already been initialized with git-crypt." << std::endl;
		return 1;
	}

	// 1. Generate a key and install it
	std::clog << "Generating key..." << std::endl;
	Key_file		key_file;
	key_file.set_key_name(key_name);
	key_file.generate();

	mkdir_parent(internal_key_path);
	if (!key_file.store_to_file(internal_key_path.c_str())) {
		std::clog << "Error: " << internal_key_path << ": unable to write key file" << std::endl;
		return 1;
	}

	// 2. Configure git for git-crypt
	configure_git_filters(key_name);

	return 0;
}

int unlock (int argc, const char** argv)
{
	// 0. Make sure working directory is clean (ignoring untracked files)
	// We do this because we run 'git checkout -f HEAD' later and we don't
	// want the user to lose any changes.  'git checkout -f HEAD' doesn't touch
	// untracked files so it's safe to ignore those.

	// Running 'git status' also serves as a check that the Git repo is accessible.

	std::stringstream	status_output;
	get_git_status(status_output);

	// 1. Check to see if HEAD exists.  See below why we do this.
	bool			head_exists = check_if_head_exists();

	if (status_output.peek() != -1 && head_exists) {
		// We only care that the working directory is dirty if HEAD exists.
		// If HEAD doesn't exist, we won't be resetting to it (see below) so
		// it doesn't matter that the working directory is dirty.
		std::clog << "Error: Working directory not clean." << std::endl;
		std::clog << "Please commit your changes or 'git stash' them before running 'git-crypt' unlock." << std::endl;
		return 1;
	}

	// 2. Determine the path to the top of the repository.  We pass this as the argument
	// to 'git checkout' below. (Determine the path now so in case it fails we haven't already
	// mucked with the git config.)
	std::string		path_to_top(get_path_to_top());

	// 3. Load the key(s)
	std::vector<Key_file>	key_files;
	if (argc > 0) {
		// Read from the symmetric key file(s)
		// TODO: command line flag to accept legacy key format?

		for (int argi = 0; argi < argc; ++argi) {
			const char*	symmetric_key_file = argv[argi];
			Key_file	key_file;

			try {
				if (std::strcmp(symmetric_key_file, "-") == 0) {
					key_file.load(std::cin);
				} else {
					if (!key_file.load_from_file(symmetric_key_file)) {
						std::clog << "Error: " << symmetric_key_file << ": unable to read key file" << std::endl;
						return 1;
					}
				}
			} catch (Key_file::Incompatible) {
				std::clog << "Error: " << symmetric_key_file << " is in an incompatible format" << std::endl;
				std::clog << "Please upgrade to a newer version of git-crypt." << std::endl;
				return 1;
			} catch (Key_file::Malformed) {
				std::clog << "Error: " << symmetric_key_file << ": not a valid git-crypt key file" << std::endl;
				std::clog << "If this key was created prior to git-crypt 0.4, you need to migrate it" << std::endl;
				std::clog << "by running 'git-crypt migrate-key /path/to/key/file'." << std::endl;
				return 1;
			}

			key_files.push_back(key_file);
		}
	} else {
		// Decrypt GPG key from root of repo
		std::string			repo_keys_path(get_repo_keys_path());
		std::vector<std::string>	gpg_secret_keys(gpg_list_secret_keys());
		// TODO: command-line option to specify the precise secret key to use
		// TODO: don't hard code key version 0 here - instead, determine the most recent version and try to decrypt that, or decrypt all versions if command-line option specified
		// TODO: command line option to only unlock specific key instead of all of them
		// TODO: avoid decrypting repo keys which are already unlocked in the .git directory
		if (!decrypt_repo_keys(key_files, 0, gpg_secret_keys, repo_keys_path)) {
			std::clog << "Error: no GPG secret key available to unlock this repository." << std::endl;
			std::clog << "To unlock with a shared symmetric key instead, specify the path to the symmetric key as an argument to 'git-crypt unlock'." << std::endl;
			std::clog << "To see a list of GPG keys authorized to unlock this repository, run 'git-crypt ls-collabs'." << std::endl;
			return 1;
		}
	}


	// 4. Install the key(s) and configure the git filters
	for (std::vector<Key_file>::iterator key_file(key_files.begin()); key_file != key_files.end(); ++key_file) {
		std::string		internal_key_path(get_internal_key_path(key_file->get_key_name()));
		// TODO: croak if internal_key_path already exists???
		mkdir_parent(internal_key_path);
		if (!key_file->store_to_file(internal_key_path.c_str())) {
			std::clog << "Error: " << internal_key_path << ": unable to write key file" << std::endl;
			return 1;
		}

		configure_git_filters(key_file->get_key_name());
	}

	// 5. Do a force checkout so any files that were previously checked out encrypted
	//    will now be checked out decrypted.
	// If HEAD doesn't exist (perhaps because this repo doesn't have any files yet)
	// just skip the checkout.
	if (head_exists) {
		// git checkout -f HEAD -- path/to/top
		std::vector<std::string>	command;
		command.push_back("git");
		command.push_back("checkout");
		command.push_back("-f");
		command.push_back("HEAD");
		command.push_back("--");
		if (path_to_top.empty()) {
			command.push_back(".");
		} else {
			command.push_back(path_to_top);
		}

		if (!successful_exit(exec_command(command))) {
			std::clog << "Error: 'git checkout' failed" << std::endl;
			std::clog << "git-crypt has been set up but existing encrypted files have not been decrypted" << std::endl;
			return 1;
		}
	}

	return 0;
}

int add_gpg_key (int argc, const char** argv)
{
	const char*		key_name = 0;
	Options_list		options;
	options.push_back(Option_def("-k", &key_name));
	options.push_back(Option_def("--key-name", &key_name));

	int			argi = parse_options(options, argc, argv);
	if (argc - argi == 0) {
		std::clog << "Usage: git-crypt add-collab [-k KEYNAME] GPG_USER_ID [...]" << std::endl;
		return 2;
	}

	// build a list of key fingerprints for every collaborator specified on the command line
	std::vector<std::string>	collab_keys;

	for (int i = argi; i < argc; ++i) {
		std::vector<std::string> keys(gpg_lookup_key(argv[i]));
		if (keys.empty()) {
			std::clog << "Error: public key for '" << argv[i] << "' not found in your GPG keyring" << std::endl;
			return 1;
		}
		if (keys.size() > 1) {
			std::clog << "Error: more than one public key matches '" << argv[i] << "' - please be more specific" << std::endl;
			return 1;
		}
		collab_keys.push_back(keys[0]);
	}

	// TODO: have a retroactive option to grant access to all key versions, not just the most recent
	Key_file			key_file;
	load_key(key_file, key_name);
	const Key_file::Entry*		key = key_file.get_latest();
	if (!key) {
		std::clog << "Error: key file is empty" << std::endl;
		return 1;
	}

	std::string			keys_path(get_repo_keys_path());
	std::vector<std::string>	new_files;

	encrypt_repo_key(key_name, *key, collab_keys, keys_path, &new_files);

	// add/commit the new files
	if (!new_files.empty()) {
		// git add NEW_FILE ...
		std::vector<std::string>	command;
		command.push_back("git");
		command.push_back("add");
		command.push_back("--");
		command.insert(command.end(), new_files.begin(), new_files.end());
		if (!successful_exit(exec_command(command))) {
			std::clog << "Error: 'git add' failed" << std::endl;
			return 1;
		}

		// git commit ...
		// TODO: add a command line option (-n perhaps) to inhibit committing
		// TODO: include key_name in commit message
		std::ostringstream	commit_message_builder;
		commit_message_builder << "Add " << collab_keys.size() << " git-crypt collaborator" << (collab_keys.size() != 1 ? "s" : "") << "\n\nNew collaborators:\n\n";
		for (std::vector<std::string>::const_iterator collab(collab_keys.begin()); collab != collab_keys.end(); ++collab) {
			commit_message_builder << '\t' << gpg_shorten_fingerprint(*collab) << ' ' << gpg_get_uid(*collab) << '\n';
		}

		// git commit -m MESSAGE NEW_FILE ...
		command.clear();
		command.push_back("git");
		command.push_back("commit");
		command.push_back("-m");
		command.push_back(commit_message_builder.str());
		command.push_back("--");
		command.insert(command.end(), new_files.begin(), new_files.end());

		if (!successful_exit(exec_command(command))) {
			std::clog << "Error: 'git commit' failed" << std::endl;
			return 1;
		}
	}

	return 0;
}

int rm_gpg_key (int argc, const char** argv) // TODO
{
	std::clog << "Error: rm-gpg-key is not yet implemented." << std::endl;
	return 1;
}

int ls_gpg_keys (int argc, const char** argv) // TODO
{
	// Sketch:
	// Scan the sub-directories in .git-crypt/keys, outputting something like this:
	// ====
	// Key version 0:
	//  0x143DE9B3F7316900 Andrew Ayer <andrew@example.com>
	//  0x4E386D9C9C61702F ???
	// Key version 1:
	//  0x143DE9B3F7316900 Andrew Ayer <andrew@example.com>
	//  0x1727274463D27F40 John Smith <smith@example.com>
	//  0x4E386D9C9C61702F ???
	// ====
	// To resolve a long hex ID, use a command like this:
	//  gpg --options /dev/null --fixed-list-mode --batch --with-colons --list-keys 0x143DE9B3F7316900

	std::clog << "Error: ls-gpg-keys is not yet implemented." << std::endl;
	return 1;
}

int export_key (int argc, const char** argv)
{
	// TODO: provide options to export only certain key versions
	const char*		key_name = 0;
	Options_list		options;
	options.push_back(Option_def("-k", &key_name));
	options.push_back(Option_def("--key-name", &key_name));

	int			argi = parse_options(options, argc, argv);

	if (argc - argi != 1) {
		std::clog << "Usage: git-crypt export-key [-k KEYNAME] FILENAME" << std::endl;
		return 2;
	}

	Key_file		key_file;
	load_key(key_file, key_name);

	const char*		out_file_name = argv[argi];

	if (std::strcmp(out_file_name, "-") == 0) {
		key_file.store(std::cout);
	} else {
		if (!key_file.store_to_file(out_file_name)) {
			std::clog << "Error: " << out_file_name << ": unable to write key file" << std::endl;
			return 1;
		}
	}

	return 0;
}

int keygen (int argc, const char** argv)
{
	if (argc != 1) {
		std::clog << "Usage: git-crypt keygen KEYFILE" << std::endl;
		return 2;
	}

	const char*		key_file_name = argv[0];

	if (std::strcmp(key_file_name, "-") != 0 && access(key_file_name, F_OK) == 0) {
		std::clog << key_file_name << ": File already exists" << std::endl;
		return 1;
	}

	std::clog << "Generating key..." << std::endl;
	Key_file		key_file;
	key_file.generate();

	if (std::strcmp(key_file_name, "-") == 0) {
		key_file.store(std::cout);
	} else {
		if (!key_file.store_to_file(key_file_name)) {
			std::clog << "Error: " << key_file_name << ": unable to write key file" << std::endl;
			return 1;
		}
	}
	return 0;
}

int migrate_key (int argc, const char** argv)
{
	if (argc != 1) {
		std::clog << "Usage: git-crypt migrate-key KEYFILE" << std::endl;
		return 2;
	}

	const char*		key_file_name = argv[0];
	Key_file		key_file;

	try {
		if (std::strcmp(key_file_name, "-") == 0) {
			key_file.load_legacy(std::cin);
			key_file.store(std::cout);
		} else {
			std::ifstream	in(key_file_name, std::fstream::binary);
			if (!in) {
				std::clog << "Error: " << key_file_name << ": unable to open for reading" << std::endl;
				return 1;
			}
			key_file.load_legacy(in);
			in.close();

			std::string	new_key_file_name(key_file_name);
			new_key_file_name += ".new";

			if (access(new_key_file_name.c_str(), F_OK) == 0) {
				std::clog << new_key_file_name << ": File already exists" << std::endl;
				return 1;
			}

			if (!key_file.store_to_file(new_key_file_name.c_str())) {
				std::clog << "Error: " << new_key_file_name << ": unable to write key file" << std::endl;
				return 1;
			}

			if (util_rename(new_key_file_name.c_str(), key_file_name) == -1) {
				std::clog << "Error: " << key_file_name << ": " << strerror(errno) << std::endl;
				unlink(new_key_file_name.c_str());
				return 1;
			}
		}
	} catch (Key_file::Malformed) {
		std::clog << "Error: " << key_file_name << ": not a valid legacy git-crypt key file" << std::endl;
		return 1;
	}

	return 0;
}

int refresh (int argc, const char** argv) // TODO: do a force checkout, much like in unlock
{
	std::clog << "Error: refresh is not yet implemented." << std::endl;
	return 1;
}

int status (int argc, const char** argv)
{
	// Usage:
	//  git-crypt status -r [-z]			Show repo status
	//  git-crypt status [-e | -u] [-z] [FILE ...]	Show encrypted status of files
	//  git-crypt status -f				Fix unencrypted blobs

	// TODO: help option / usage output

	bool		repo_status_only = false;	// -r show repo status only
	bool		show_encrypted_only = false;	// -e show encrypted files only
	bool		show_unencrypted_only = false;	// -u show unencrypted files only
	bool		fix_problems = false;		// -f fix problems
	bool		machine_output = false;		// -z machine-parseable output

	Options_list	options;
	options.push_back(Option_def("-r", &repo_status_only));
	options.push_back(Option_def("-e", &show_encrypted_only));
	options.push_back(Option_def("-u", &show_unencrypted_only));
	options.push_back(Option_def("-f", &fix_problems));
	options.push_back(Option_def("--fix", &fix_problems));
	options.push_back(Option_def("-z", &machine_output));

	int		argi = parse_options(options, argc, argv);

	if (repo_status_only) {
		if (show_encrypted_only || show_unencrypted_only) {
			std::clog << "Error: -e and -u options cannot be used with -r" << std::endl;
			return 2;
		}
		if (fix_problems) {
			std::clog << "Error: -f option cannot be used with -r" << std::endl;
			return 2;
		}
		if (argc - argi != 0) {
			std::clog << "Error: filenames cannot be specified when -r is used" << std::endl;
			return 2;
		}
	}

	if (show_encrypted_only && show_unencrypted_only) {
		std::clog << "Error: -e and -u options are mutually exclusive" << std::endl;
		return 2;
	}

	if (fix_problems && (show_encrypted_only || show_unencrypted_only)) {
		std::clog << "Error: -e and -u options cannot be used with -f" << std::endl;
		return 2;
	}

	if (machine_output) {
		// TODO: implement machine-parseable output
		std::clog << "Sorry, machine-parseable output is not yet implemented" << std::endl;
		return 2;
	}

	if (argc - argi == 0) {
		// TODO: check repo status:
		//	is it set up for git-crypt?
		//	which keys are unlocked?
		//	--> check for filter config (see configure_git_filters()) and corresponding internal key

		if (repo_status_only) {
			return 0;
		}
	}

	// git ls-files -cotsz --exclude-standard ...
	std::vector<std::string>	command;
	command.push_back("git");
	command.push_back("ls-files");
	command.push_back("-cotsz");
	command.push_back("--exclude-standard");
	command.push_back("--");
	if (argc - argi == 0) {
		const std::string	path_to_top(get_path_to_top());
		if (!path_to_top.empty()) {
			command.push_back(path_to_top);
		}
	} else {
		for (int i = argi; i < argc; ++i) {
			command.push_back(argv[i]);
		}
	}

	std::stringstream		output;
	if (!successful_exit(exec_command(command, output))) {
		throw Error("'git ls-files' failed - is this a Git repository?");
	}

	// Output looks like (w/o newlines):
	// ? .gitignore\0
	// H 100644 06ec22e5ed0de9280731ef000a10f9c3fbc26338 0     afile\0

	std::vector<std::string>	files;
	bool				attribute_errors = false;
	bool				unencrypted_blob_errors = false;
	unsigned int			nbr_of_fixed_blobs = 0;
	unsigned int			nbr_of_fix_errors = 0;

	while (output.peek() != -1) {
		std::string		tag;
		std::string		object_id;
		std::string		filename;
		output >> tag;
		if (tag != "?") {
			std::string	mode;
			std::string	stage;
			output >> mode >> object_id >> stage;
		}
		output >> std::ws;
		std::getline(output, filename, '\0');

		// TODO: get file attributes en masse for efficiency... unfortunately this requires machine-parseable output from git check-attr to be workable, and this is only supported in Git 1.8.5 and above (released 27 Nov 2013)
		const std::pair<std::string, std::string> file_attrs(get_file_attributes(filename));

		if (file_attrs.first == "git-crypt") { // TODO: key_name support
			// File is encrypted
			const bool	blob_is_unencrypted = !object_id.empty() && !check_if_blob_is_encrypted(object_id);

			if (fix_problems && blob_is_unencrypted) {
				if (access(filename.c_str(), F_OK) != 0) {
					std::clog << "Error: " << filename << ": cannot stage encrypted version because not present in working tree - please 'git rm' or 'git checkout' it" << std::endl;
					++nbr_of_fix_errors;
				} else {
					touch_file(filename);
					std::vector<std::string>	git_add_command;
					git_add_command.push_back("git");
					git_add_command.push_back("add");
					git_add_command.push_back("--");
					git_add_command.push_back(filename);
					if (!successful_exit(exec_command(git_add_command))) {
						throw Error("'git-add' failed");
					}
					if (check_if_file_is_encrypted(filename)) {
						std::cout << filename << ": staged encrypted version" << std::endl;
						++nbr_of_fixed_blobs;
					} else {
						std::clog << "Error: " << filename << ": still unencrypted even after staging" << std::endl;
						++nbr_of_fix_errors;
					}
				}
			} else if (!fix_problems && !show_unencrypted_only) {
				std::cout << "    encrypted: " << filename;
				if (file_attrs.second != file_attrs.first) {
					// but diff filter is not properly set
					std::cout << " *** WARNING: diff=" << file_attrs.first << " attribute not set ***";
					attribute_errors = true;
				}
				if (blob_is_unencrypted) {
					// File not actually encrypted
					std::cout << " *** WARNING: staged/committed version is NOT ENCRYPTED! ***";
					unencrypted_blob_errors = true;
				}
				std::cout << std::endl;
			}
		} else {
			// File not encrypted
			if (!fix_problems && !show_encrypted_only) {
				std::cout << "not encrypted: " << filename << std::endl;
			}
		}
	}

	int				exit_status = 0;

	if (attribute_errors) {
		std::cout << std::endl;
		std::cout << "Warning: one or more files has a git-crypt filter attribute but not a" << std::endl;
		std::cout << "corresponding git-crypt diff attribute.  For proper 'git diff' operation" << std::endl;
		std::cout << "you should fix the .gitattributes file to specify the correct diff attribute." << std::endl;
		std::cout << "Consult the git-crypt documentation for help." << std::endl;
		exit_status = 1;
	}
	if (unencrypted_blob_errors) {
		std::cout << std::endl;
		std::cout << "Warning: one or more files is marked for encryption via .gitattributes but" << std::endl;
		std::cout << "was staged and/or committed before the .gitattributes file was in effect." << std::endl;
		std::cout << "Run 'git-crypt status' with the '-f' option to stage an encrypted version." << std::endl;
		exit_status = 1;
	}
	if (nbr_of_fixed_blobs) {
		std::cout << "Staged " << nbr_of_fixed_blobs << " encrypted file" << (nbr_of_fixed_blobs != 1 ? "s" : "") << "." << std::endl;
		std::cout << "Warning: if these files were previously committed, unencrypted versions still exist in the repository's history." << std::endl;
	}
	if (nbr_of_fix_errors) {
		std::cout << "Unable to stage " << nbr_of_fix_errors << " file" << (nbr_of_fix_errors != 1 ? "s" : "") << "." << std::endl;
		exit_status = 1;
	}

	return exit_status;
}