ptth/bare_minimum_crypto/cpp/bmc_main.cpp

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#include <chrono>
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#include <filesystem>
#include <fstream>
#include <iostream>
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#include <optional>
#include <stdint.h>
#include <string>
#include <vector>
#include "cxxopts.hpp"
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#include "json.hpp"
#include "expiring_signature.h"
#include "receiver.h"
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#include "sender.h"
#include "signing_key.h"
#include "sodium_helpers.h"
#include "string_helpers.h"
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#include "time_helpers.h"
using namespace std;
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using nlohmann::json;
using namespace BareMinimumCrypto;
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namespace fs = std::filesystem;
int file (const string & file_path) {
cout << "Reading `" << file_path << "`" << endl;
const auto j = std::move (*try_load_msgpack_file (file_path));
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if (! j.contains ("app")) {
cout << "Can't find app magic string. This file was probably not made by BMC." << endl;
return 1;
}
const string app = j ["app"];
if (app != "4B27CL32") {
cout << "Can't find app magic string. This file was probably not made by BMC." << endl;
return 1;
}
const string schema = j ["schema"];
cout << "Schema: " << schema << endl;
if (schema == "3T6XF5DZ") {
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cout << "File is a secret key for humans. (It's passphrase-protected)" << endl;
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// Read msgpack fields
const auto key = std::move (*HumanKeyFile::try_from_msgpack (j));
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// Read data from other places
const auto now = Instant::now ();
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// Print normal stuff
cout << "Generated at Unix time " << key.time_created.x
<< " (" << now.x - key.time_created.x << " seconds ago)"
<< endl;
cout << "Generated on machine ID " << key.machine_id << endl;
cout << "Claims to have Base64 pubkey `" << base64_encode (key.pubkey) << "`" << endl;
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// Print warnings
if (now.x < key.time_created.x) {
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cout << "* The key was generated in the past. Someone's clock is wrong." << endl;
}
if (get_machine_id () != key.machine_id) {
cout << "* The key was generated on another machine. You should report this." << endl;
}
if (fs::status (file_path).permissions () != fs::perms::owner_read) {
cout << "* The key doesn't have the right permissions. Try `chmod 400` on it." << endl;
}
}
else if (schema == "2PVHIKMA") {
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cout << "File is a secret key for machines. (No passphrase)" << endl;
// Read msgpack fields
const auto key = std::move (*MachineKeyFile::try_from_msgpack (j));
// Read data from other places
const auto now = Instant::now ();
// Print normal stuff
cout << "Generated at Unix time " << key.time_created.x
<< " (" << now.x - key.time_created.x << " seconds ago)"
<< endl;
cout << "Generated on machine ID " << key.machine_id << endl;
cout << "Claims to have Base64 pubkey `" << base64_encode (key.pubkey ()) << "`" << endl;
// Print warnings
if (now.x < key.time_created.x) {
cout << "* The key was generated in the past. Someone's clock is wrong." << endl;
}
if (get_machine_id () != key.machine_id) {
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cout << "* The key was generated on another machine. You should report this." << endl;
}
if (fs::status (file_path).permissions () != fs::perms::owner_read) {
cout << "* The key doesn't have the right permissions. Try `chmod 400` on it." << endl;
}
}
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else if (schema == "MSYZGDBI") {
cout << "File is a signed certificate, possibly for a pubkey." << endl;
cout << "Claims to be signed by pubkey `" << base64_encode (j ["signer_pubkey"].get_binary ()) << "`" << endl;
const auto cert_bytes = j ["cert"].get_binary ();
const auto cert = json::from_msgpack (cert_bytes);
const TimeRange tr {
cert ["not_before"],
cert ["not_after"],
};
const auto now = Instant::now ();
if (! tr.contains (now)) {
cout << "Cert is NOT valid." << endl;
if (now.x <= tr.not_before) {
cout << "Cert is from the future. Is your clock behind? Is the signer's clock ahead?" << endl;
}
else if (now.x >= tr.not_after) {
cout << "Cert expired " << now.x - tr.not_after << " seconds ago. Don't trust it." << endl;
}
return 1;
}
cout << "Cert is valid for another " << tr.not_after - now.x << " seconds." << endl;
const auto payload = cert ["payload"].get_binary ();
if (payload.size () == crypto_sign_PUBLICKEYBYTES) {
cout << "Payload might be the pubkey `" << base64_encode (payload) << "`" << endl;
}
else {
cout << "Payload doesn't have the right size to be a pubkey." << endl;
}
}
else {
cout << "Unknown schema. Maybe this file is from a newer version of BMC?" << endl;
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return 1;
}
return 0;
}
int test () {
if (test_base64 () != 0) {
return 1;
}
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cerr << "crypto_sign_PUBLICKEYBYTES = " << crypto_sign_PUBLICKEYBYTES << endl;
cerr << "crypto_sign_SECRETKEYBYTES = " << crypto_sign_SECRETKEYBYTES << endl;
// We generate a root key and keep it somewhere safe
// (offline, hopefully)
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SigningKey root_key;
cerr << "Root pub key " << base64_encode (root_key.pubkey ()) << endl;
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if (test_time () != 0) {
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return 1;
}
const auto now = Instant::now ();
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// The sender generates a key
SigningKey sender_key;
cerr << "Sender key " << base64_encode (sender_key.pubkey ()) << endl;
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// The root signs the sender key
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const auto sender_cert = std::move (*root_key.sign_key (sender_key.pubkey (), now));
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const auto sender = std::move (*Sender::create (sender_key, sender_cert));
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// The sender signs some important data
const auto important_data = copy_to_bytes ("Nikolai, Anna, Ivan, Mikhail, Ivan, Nikolai, Anna. 7 4 1 4 3 5 7 4");
const auto signed_data = std::move (*sender.sign (important_data));
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// The receiver verifies the data by the root public key,
// even though the receiver has never seen the sender-key.
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auto verified_opt = Receiver::verify_cert_and_data (root_key.pubkey (), signed_data);
if (! verified_opt) {
cerr << "Receiver couldn't verify cert and data" << endl;
return 1;
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}
const auto verified = std::move (*verified_opt);
if (verified != important_data) {
cerr << "Verified payload did not match expected payload" << endl;
return 1;
}
return 0;
}
int main (int argc, char ** argv) {
cxxopts::Options options ("BareMinimumCrypto", "Simple crypto things you might need.");
options.add_options ()
// Commands
("help", "Print usage")
("file", "Print info about any file generated by BMC", cxxopts::value <string> ())
("generate-human-key", "Generate a passphrase-protected key for human use", cxxopts::value <string> ())
("generate-machine-key", "Generate a key for machine use, with no passphrase", cxxopts::value <string> ())
("generate-key-cert", "Certify a key for 3 months and save the cert here", cxxopts::value <string> ())
// cxxopts nonsense
("using-key", "Key to load for other operations", cxxopts::value <string> ())
// Other stuff
("test", "Run self-test")
;
auto result = options.parse (argc, argv);
if (result.count ("help")) {
cout << options.help () << endl;
}
else if (result.count ("file")) {
const auto file_path = result ["file"].as <string> ();
return file (file_path);
}
else if (result.count ("generate-human-key")) {
const auto file_path = result ["generate-human-key"].as <string> ();
const auto passphrase = get_passphrase_from_user ();
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auto key_opt = HumanKeyFile::generate (file_path, passphrase);
if (! key_opt) {
cerr << "Error. Key was not generated" << endl;
return 1;
}
cout << "The pubkey is `" << base64_encode (key_opt->pubkey ()) << "`" << endl;
}
else if (result.count ("generate-machine-key")) {
const auto file_path = result ["generate-machine-key"].as <string> ();
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auto key_opt = MachineKeyFile::generate (file_path);
if (! key_opt) {
cerr << "Error. Key was not generated" << endl;
return 1;
}
cout << "The pubkey is `" << base64_encode (key_opt->pubkey ()) << "`" << endl;
}
else if (result.count ("generate-key-cert")) {
if (! result.count ("using-key")) {
cerr << "Usage: bmc --generate-key-cert output.cert --using-key human.key" << endl;
return 1;
}
const auto key_path = result ["using-key"].as <string> ();
const auto output_path = result ["generate-key-cert"].as <string> ();
const auto passphrase = get_passphrase_from_user ();
auto key_opt = HumanKeyFile::load (key_path, passphrase);
if (! key_opt) {
cerr << "Error, could not load human key." << endl;
return 1;
}
const auto key = std::move (*key_opt);
cout << "Paste Base64-encoded public key" << endl;
string pubkey_b64;
cin >> pubkey_b64;
auto pubkey_opt = base64_decode (pubkey_b64);
const auto pubkey = std::move (*pubkey_opt);
auto sig_opt = key.sign (pubkey, TimeRange::from_start_and_dur (Instant::now (), about_3_months));
if (! sig_opt) {
cerr << "Error, could not sign pubkey." << endl;
return 1;
}
const auto sig = std::move (*sig_opt);
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const auto sig_bytes = sig.to_msgpack ();
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ofstream f;
f.open (output_path, ofstream::binary);
if (! f.is_open ()) {
cerr << "Error, could not open output file" << endl;
return 1;
}
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f.write ((const char *)sig_bytes.data (), sig_bytes.size ());
}
else if (result.count ("test")) {
if (test () != 0) {
return 1;
}
cerr << "All good." << endl;
}
return 0;
}