/*
 * Copyright (C) 2016 Andreas Steffen
 * HSR Hochschule fuer Technik Rapperswil
 *
 * 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * 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.
 */

#include <library.h>
#include <utils/debug.h>
#include <utils/optionsfrom.h>
#include <asn1/asn1.h>
#include <asn1/oid.h>

#include <tss2/tpm20.h>

#include <syslog.h>
#include <getopt.h>
#include <errno.h>

/* default directory where AIK keys are stored */
#define AIK_DIR							IPSEC_CONFDIR "/pts/"


/* default name of AIK private key blob */
#define DEFAULT_FILENAME_AIKPUBKEY		AIK_DIR "aikPub.der"

/* logging */
static bool log_to_stderr = TRUE;
static bool log_to_syslog = TRUE;
static level_t default_loglevel = 1;

/* options read by optionsfrom */
options_t *options;

/* global variables */
chunk_t aik_pubkey;
chunk_t aik_keyid;

/**
 * logging function for aikpub2
 */
static void aikpub2_dbg(debug_t group, level_t level, char *fmt, ...)
{
	char buffer[8192];
	char *current = buffer, *next;
	va_list args;

	if (level <= default_loglevel)
	{
		if (log_to_stderr)
		{
			va_start(args, fmt);
			vfprintf(stderr, fmt, args);
			va_end(args);
			fprintf(stderr, "\n");
		}
		if (log_to_syslog)
		{
			/* write in memory buffer first */
			va_start(args, fmt);
			vsnprintf(buffer, sizeof(buffer), fmt, args);
			va_end(args);

			/* do a syslog with every line */
			while (current)
			{
				next = strchr(current, '\n');
				if (next)
				{
					*(next++) = '\0';
				}
				syslog(LOG_INFO, "%s\n", current);
				current = next;
			}
		}
	}
}

/**
 * Initialize logging to stderr/syslog
 */
static void init_log(const char *program)
{
	dbg = aikpub2_dbg;

	if (log_to_stderr)
	{
		setbuf(stderr, NULL);
	}
	if (log_to_syslog)
	{
		openlog(program, LOG_CONS | LOG_NDELAY | LOG_PID, LOG_AUTHPRIV);
	}
}

/**
 * @brief exit aikgen
 *
 * @param status 0 = OK, 1 = general discomfort
 */
static void exit_aikpub2(err_t message, ...)
{
	int status = 0;

	free(aik_pubkey.ptr);
	free(aik_keyid.ptr);
	options->destroy(options);

	/* print any error message to stderr */
	if (message != NULL && *message != '\0')
	{
		va_list args;
		char m[8192];

		va_start(args, message);
		vsnprintf(m, sizeof(m), message, args);
		va_end(args);

		fprintf(stderr, "error: %s\n", m);
		status = -1;
	}
	library_deinit();
	exit(status);
}

/**
 * @brief prints the usage of the program to the stderr output
 *
 * If message is set, program is exited with 1 (error)
 * @param message message in case of an error
 */
static void usage(const char *message)
{
	fprintf(stderr,
		"Usage: aikpub2  [--in <filename>] [--out <filename>]\n"
		"                [--force] [--quiet] [--debug <level>]\n"
		"       aikpub2 --help\n"
		"\n"
		"Options:\n"
		" --in (-i)         TSS 2.0 AIK public key blob\n"
		" --out (-o)        AIK public key in PKCS#1 format\n"
		" --force (-f)      force to overwrite existing files\n"
		" --help (-h)       show usage and exit\n"
		"\n"
		"Debugging output:\n"
		" --debug (-l)      changes the log level (-1..4, default: 1)\n"
		" --quiet (-q)      do not write log output to stderr\n"
		);
	exit_aikpub2(message);
}

/**
 * @brief main of aikpub2 which generates an Attestation Identity Key (AIK)
 *
 * @param argc number of arguments
 * @param argv pointer to the argument values
 */
int main(int argc, char *argv[])
{
	/* external values */
	extern char * optarg;
	extern int optind;

	char *aikblob_filename   = NULL;
	char *aikpubkey_filename = DEFAULT_FILENAME_AIKPUBKEY;
	bool force = FALSE;
	chunk_t *aikblob;
	hasher_t *hasher;

	/* TSS 2.0 variables */
	TPM2B_PUBLIC public;

	atexit(library_deinit);
	if (!library_init(NULL, "aikpub2"))
	{
		exit(SS_RC_LIBSTRONGSWAN_INTEGRITY);
	}
	if (lib->integrity &&
		!lib->integrity->check_file(lib->integrity, "aikpub2", argv[0]))
	{
		fprintf(stderr, "integrity check of aikpub2 failed\n");
		exit(SS_RC_DAEMON_INTEGRITY);
	}

	/* initialize global variables */
	options = options_create();

	for (;;)
	{
		static const struct option long_opts[] = {
			/* name, has_arg, flag, val */
			{ "help", no_argument, NULL, 'h' },
			{ "optionsfrom", required_argument, NULL, '+' },
			{ "in", required_argument, NULL, 'i' },
			{ "out", required_argument, NULL, 'o' },
			{ "force", no_argument, NULL, 'f' },
			{ "quiet", no_argument, NULL, 'q' },
			{ "debug", required_argument, NULL, 'l' },
			{ 0,0,0,0 }
		};

		/* parse next option */
		int c = getopt_long(argc, argv, "ho:c:b:p:fqd:", long_opts, NULL);

		switch (c)
		{
			case EOF:       /* end of flags */
				break;

			case 'h':       /* --help */
				usage(NULL);

			case '+':       /* --optionsfrom <filename> */
				if (!options->from(options, optarg, &argc, &argv, optind))
				{
					exit_aikpub2("optionsfrom failed");
				}
				continue;

			case 'i':       /* --in <filename> */
				aikblob_filename = optarg;
				continue;

			case 'o':       /* --out <filename> */
				aikpubkey_filename = optarg;
				continue;

			case 'f':       /* --force */
				force = TRUE;
				continue;

			case 'q':       /* --quiet */
				log_to_stderr = FALSE;
				continue;

			case 'l':		/* --debug <level> */
				default_loglevel = atoi(optarg);
				continue;

			default:
				usage("unknown option");
		}
		/* break from loop */
		break;
	}

	init_log("aikpub2");

	if (!lib->plugins->load(lib->plugins,
			lib->settings->get_str(lib->settings, "aikpub2.load", PLUGINS)))
	{
		exit_aikpub2("plugin loading failed");
	}

	/* read TSS 2.0 AIK public key blob */
	if (!aikblob_filename)
	{
		usage("--aikblob is required");
	}
	aikblob = chunk_map(aikblob_filename, FALSE);
	if (!aikblob)
	{
		exit_aikpub2("could not read TSS 2.0 public key file '%s'",
					  aikblob_filename);
	}
	DBG3(DBG_LIB, "aikblob: %B", aikblob);

	if (aikblob->len != sizeof(TPM2B_PUBLIC))
	{
		chunk_unmap(aikblob);
		exit_aikpub2("size of aikblob is not %d bytes", sizeof(TPM2B_PUBLIC));
	}
	public = *(TPM2B_PUBLIC*)aikblob->ptr;
	chunk_unmap(aikblob);

	switch (public.t.publicArea.type)
	{
		case TPM_ALG_RSA:
		{
			TPM2B_PUBLIC_KEY_RSA *rsa;
			chunk_t aik_exponent, aik_modulus;

			rsa = &public.t.publicArea.unique.rsa;
			aik_modulus = chunk_create(rsa->t.buffer, rsa->t.size);
			aik_exponent = chunk_from_chars(0x01, 0x00, 0x01);

			/* subjectPublicKeyInfo encoding of AIK RSA key */
			if (!lib->encoding->encode(lib->encoding, PUBKEY_SPKI_ASN1_DER,
					NULL, &aik_pubkey, CRED_PART_RSA_MODULUS, aik_modulus,
					CRED_PART_RSA_PUB_EXP, aik_exponent, CRED_PART_END))
			{
				exit_aikpub2("subjectPublicKeyInfo encoding of AIK key failed");
			}
			break;
		}
		case TPM_ALG_ECC:
		{
			TPMS_ECC_POINT *ecc;
			chunk_t ecc_point;
			uint8_t *pos;

			ecc = &public.t.publicArea.unique.ecc;

			/* allocate space for bit string */
			pos = asn1_build_object(&ecc_point, ASN1_BIT_STRING,
									2 + ecc->x.t.size + ecc->y.t.size);
			/* bit string length is a multiple of octets */
			*pos++ = 0x00;
			/* uncompressed ECC point format */
			*pos++ = 0x04;
			/* copy x coordinate of ECC point */
			memcpy(pos, ecc->x.t.buffer, ecc->x.t.size);
			pos += ecc->x.t.size;
			/* copy y coordinate of ECC point */
			memcpy(pos, ecc->y.t.buffer, ecc->y.t.size);
			/* subjectPublicKeyInfo encoding of AIK ECC key */
			aik_pubkey = asn1_wrap(ASN1_SEQUENCE, "mm",
							asn1_wrap(ASN1_SEQUENCE, "mm",
								asn1_build_known_oid(OID_EC_PUBLICKEY),
								asn1_build_known_oid(ecc->x.t.size == 32 ?
										OID_PRIME256V1 : OID_SECT384R1)),
							ecc_point);
			break;
		}
		default:
			exit_aikpub2("unsupported key type");
	}

	/* store AIK subjectPublicKeyInfo to file */
	if (!chunk_write(aik_pubkey, aikpubkey_filename, 0022, force))
	{
		exit_aikpub2("could not write AIK public key file '%s': %s",
					  aikpubkey_filename, strerror(errno));
	}
	DBG1(DBG_LIB, "AIK public key written to '%s' (%u bytes)",
				   aikpubkey_filename, aik_pubkey.len);

	/* AIK keyid derived from subjectPublicKeyInfo encoding */
	hasher = lib->crypto->create_hasher(lib->crypto, HASH_SHA1);
	if (!hasher)
	{
		exit_aikpub2("SHA1 hash algorithm not supported");
	}
	if (!hasher->allocate_hash(hasher, aik_pubkey, &aik_keyid))
	{
		hasher->destroy(hasher);
		exit_aikpub2("computing SHA1 fingerprint failed");
	}
	hasher->destroy(hasher);

	DBG1(DBG_LIB, "AIK keyid: %#B", &aik_keyid);

	exit_aikpub2(NULL);
	return -1; /* should never be reached */
}