/* $OpenLDAP$ */
/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
 *
 * Copyright 2009-2021 The OpenLDAP Foundation.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted only as authorized by the OpenLDAP
 * Public License.
 *
 * A copy of this license is available in the file LICENSE in the
 * top-level directory of the distribution or, alternatively, at
 * <http://www.OpenLDAP.org/license.html>.
 */
/* ACKNOWLEDGEMENT:
 * This work was initially developed by HAMANO Tsukasa <hamano@osstech.co.jp>
 */

#define _GNU_SOURCE

#include "portable.h"
#include <ac/string.h>
#include "lber_pvt.h"
#include "lutil.h"
#include <stdio.h>
#include <stdlib.h>

#ifdef HAVE_OPENSSL
#include <openssl/evp.h>
#elif HAVE_GNUTLS
#include <nettle/pbkdf2.h>
#include <nettle/hmac.h>
typedef void (*pbkdf2_hmac_update)(void *, unsigned, const uint8_t *);
typedef void (*pbkdf2_hmac_digest)(void *, unsigned, uint8_t *);
#else
#error Unsupported crypto backend.
#endif

#define PBKDF2_ITERATION 10000
#define PBKDF2_SALT_SIZE 16
#define PBKDF2_SHA1_DK_SIZE 20
#define PBKDF2_SHA256_DK_SIZE 32
#define PBKDF2_SHA512_DK_SIZE 64
#define PBKDF2_MAX_DK_SIZE 64

const struct berval pbkdf2_scheme = BER_BVC("{PBKDF2}");
const struct berval pbkdf2_sha1_scheme = BER_BVC("{PBKDF2-SHA1}");
const struct berval pbkdf2_sha256_scheme = BER_BVC("{PBKDF2-SHA256}");
const struct berval pbkdf2_sha512_scheme = BER_BVC("{PBKDF2-SHA512}");

/*
 * Converting base64 string to adapted base64 string.
 * Adapted base64 encode is identical to general base64 encode except
 * that it uses '.' instead of '+', and omits trailing padding '=' and
 * whitepsace.
 * see http://pythonhosted.org/passlib/lib/passlib.utils.html
 * This is destructive function.
 */
static int b64_to_ab64(char *str)
{
	char *p = str;
	do {
		if(*p == '+'){
			*p = '.';
		}
		if(*p == '='){
			*p = '\0';
		}
	} while(*p++);
	return 0;
}

/*
 * Converting adapted base64 string to base64 string.
 * dstsize will require src length + 2, due to output string have
 * potential to append "=" or "==".
 * return -1 if few output buffer.
 */
static int ab64_to_b64(char *src, char *dst, size_t dstsize){
	int i;
	char *p = src;
	for(i=0; p[i] && p[i] != '$'; i++){
		if(i >= dstsize){
			dst[0] = '\0';
			return -1;
		}
		if(p[i] == '.'){
			dst[i] = '+';
		}else{
			dst[i] = p[i];
		}
	}
	for(;i%4;i++){
		if(i >= dstsize){
			dst[0] = '\0';
			return -1;
		}
		dst[i] = '=';
	}
	dst[i] = '\0';
	return 0;
}

static int pbkdf2_format(
	const struct berval *sc,
	int iteration,
	const struct berval *salt,
	const struct berval *dk,
	struct berval *msg)
{

	int rc, msg_len;
	char salt_b64[LUTIL_BASE64_ENCODE_LEN(PBKDF2_SALT_SIZE) + 1];
	char dk_b64[LUTIL_BASE64_ENCODE_LEN(PBKDF2_MAX_DK_SIZE) + 1];

	rc = lutil_b64_ntop((unsigned char *)salt->bv_val, salt->bv_len,
						salt_b64, sizeof(salt_b64));
	if(rc < 0){
		return LUTIL_PASSWD_ERR;
	}
	b64_to_ab64(salt_b64);
	rc = lutil_b64_ntop((unsigned char *)dk->bv_val, dk->bv_len,
						dk_b64, sizeof(dk_b64));
	if(rc < 0){
		return LUTIL_PASSWD_ERR;
	}
	b64_to_ab64(dk_b64);
	msg_len = asprintf(&msg->bv_val, "%s%d$%s$%s",
						   sc->bv_val, iteration,
						   salt_b64, dk_b64);
	if(msg_len < 0){
		msg->bv_len = 0;
		return LUTIL_PASSWD_ERR;
	}

	msg->bv_len = msg_len;
	return LUTIL_PASSWD_OK;
}

static int pbkdf2_encrypt(
	const struct berval *scheme,
	const struct berval *passwd,
	struct berval *msg,
	const char **text)
{
	unsigned char salt_value[PBKDF2_SALT_SIZE];
	struct berval salt;
	unsigned char dk_value[PBKDF2_MAX_DK_SIZE];
	struct berval dk;
	int iteration = PBKDF2_ITERATION;
	int rc;
#ifdef HAVE_OPENSSL
	const EVP_MD *md;
#elif HAVE_GNUTLS
	struct hmac_sha1_ctx sha1_ctx;
	struct hmac_sha256_ctx sha256_ctx;
	struct hmac_sha512_ctx sha512_ctx;
	void * current_ctx = NULL;
	pbkdf2_hmac_update current_hmac_update = NULL;
	pbkdf2_hmac_digest current_hmac_digest = NULL;
#endif

	salt.bv_val = (char *)salt_value;
	salt.bv_len = sizeof(salt_value);
	dk.bv_val = (char *)dk_value;

#ifdef HAVE_OPENSSL
	if(!ber_bvcmp(scheme, &pbkdf2_scheme)){
		dk.bv_len = PBKDF2_SHA1_DK_SIZE;
		md = EVP_sha1();
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha1_scheme)){
		dk.bv_len = PBKDF2_SHA1_DK_SIZE;
		md = EVP_sha1();
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha256_scheme)){
		dk.bv_len = PBKDF2_SHA256_DK_SIZE;
		md = EVP_sha256();
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha512_scheme)){
		dk.bv_len = PBKDF2_SHA512_DK_SIZE;
		md = EVP_sha512();
	}else{
		return LUTIL_PASSWD_ERR;
	}
#elif HAVE_GNUTLS
	if(!ber_bvcmp(scheme, &pbkdf2_scheme)){
		dk.bv_len = PBKDF2_SHA1_DK_SIZE;
		current_ctx = &sha1_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha1_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha1_digest;
		hmac_sha1_set_key(current_ctx, passwd->bv_len, (const uint8_t *) passwd->bv_val);
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha1_scheme)){
		dk.bv_len = PBKDF2_SHA1_DK_SIZE;
		current_ctx = &sha1_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha1_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha1_digest;
		hmac_sha1_set_key(current_ctx, passwd->bv_len, (const uint8_t *) passwd->bv_val);
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha256_scheme)){
		dk.bv_len = PBKDF2_SHA256_DK_SIZE;
		current_ctx = &sha256_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha256_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha256_digest;
		hmac_sha256_set_key(current_ctx, passwd->bv_len, (const uint8_t *) passwd->bv_val);
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha512_scheme)){
		dk.bv_len = PBKDF2_SHA512_DK_SIZE;
		current_ctx = &sha512_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha512_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha512_digest;
		hmac_sha512_set_key(current_ctx, passwd->bv_len, (const uint8_t *) passwd->bv_val);
	}else{
		return LUTIL_PASSWD_ERR;
	}
#endif

	if(lutil_entropy((unsigned char *)salt.bv_val, salt.bv_len) < 0){
		return LUTIL_PASSWD_ERR;
	}

#ifdef HAVE_OPENSSL
	if(!PKCS5_PBKDF2_HMAC(passwd->bv_val, passwd->bv_len,
						  (unsigned char *)salt.bv_val, salt.bv_len,
						  iteration, md, dk.bv_len, dk_value)){
		return LUTIL_PASSWD_ERR;
	}
#elif HAVE_GNUTLS
	PBKDF2(current_ctx, current_hmac_update, current_hmac_digest,
						  dk.bv_len, iteration,
						  salt.bv_len, (const uint8_t *) salt.bv_val,
						  dk.bv_len, dk_value);
#endif

#ifdef SLAPD_PBKDF2_DEBUG
	printf("Encrypt for %s\n", scheme->bv_val);
	printf("  Password:\t%s\n", passwd->bv_val);

	printf("  Salt:\t\t");
	int i;
	for(i=0; i<salt.bv_len; i++){
		printf("%02x", salt_value[i]);
	}
	printf("\n");
	printf("  Iteration:\t%d\n", iteration);

	printf("  DK:\t\t");
	for(i=0; i<dk.bv_len; i++){
		printf("%02x", dk_value[i]);
	}
	printf("\n");
#endif

	rc = pbkdf2_format(scheme, iteration, &salt, &dk, msg);

#ifdef SLAPD_PBKDF2_DEBUG
	printf("  Output:\t%s\n", msg->bv_val);
#endif

	return rc;
}

static int pbkdf2_check(
	const struct berval *scheme,
	const struct berval *passwd,
	const struct berval *cred,
	const char **text)
{
	int rc;
	int iteration;

	/* salt_value require PBKDF2_SALT_SIZE + 1 in lutil_b64_pton. */
	unsigned char salt_value[PBKDF2_SALT_SIZE + 1];
	char salt_b64[LUTIL_BASE64_ENCODE_LEN(PBKDF2_SALT_SIZE) + 1];
	/* dk_value require PBKDF2_MAX_DK_SIZE + 1 in lutil_b64_pton. */
	unsigned char dk_value[PBKDF2_MAX_DK_SIZE + 1];
	char dk_b64[LUTIL_BASE64_ENCODE_LEN(PBKDF2_MAX_DK_SIZE) + 1];
	unsigned char input_dk_value[PBKDF2_MAX_DK_SIZE];
	size_t dk_len;
#ifdef HAVE_OPENSSL
	const EVP_MD *md;
#elif HAVE_GNUTLS
	struct hmac_sha1_ctx sha1_ctx;
	struct hmac_sha256_ctx sha256_ctx;
	struct hmac_sha512_ctx sha512_ctx;
	void * current_ctx = NULL;
	pbkdf2_hmac_update current_hmac_update = NULL;
	pbkdf2_hmac_digest current_hmac_digest = NULL;
#endif

#ifdef SLAPD_PBKDF2_DEBUG
	printf("Checking for %s\n", scheme->bv_val);
	printf("  Stored Value:\t%s\n", passwd->bv_val);
	printf("  Input Cred:\t%s\n", cred->bv_val);
#endif

#ifdef HAVE_OPENSSL
	if(!ber_bvcmp(scheme, &pbkdf2_scheme)){
		dk_len = PBKDF2_SHA1_DK_SIZE;
		md = EVP_sha1();
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha1_scheme)){
		dk_len = PBKDF2_SHA1_DK_SIZE;
		md = EVP_sha1();
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha256_scheme)){
		dk_len = PBKDF2_SHA256_DK_SIZE;
		md = EVP_sha256();
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha512_scheme)){
		dk_len = PBKDF2_SHA512_DK_SIZE;
		md = EVP_sha512();
	}else{
		return LUTIL_PASSWD_ERR;
	}
#elif HAVE_GNUTLS
	if(!ber_bvcmp(scheme, &pbkdf2_scheme)){
		dk_len = PBKDF2_SHA1_DK_SIZE;
		current_ctx = &sha1_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha1_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha1_digest;
		hmac_sha1_set_key(current_ctx, cred->bv_len, (const uint8_t *) cred->bv_val);
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha1_scheme)){
		dk_len = PBKDF2_SHA1_DK_SIZE;
		current_ctx = &sha1_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha1_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha1_digest;
		hmac_sha1_set_key(current_ctx, cred->bv_len, (const uint8_t *) cred->bv_val);
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha256_scheme)){
		dk_len = PBKDF2_SHA256_DK_SIZE;
		current_ctx = &sha256_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha256_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha256_digest;
		hmac_sha256_set_key(current_ctx, cred->bv_len, (const uint8_t *) cred->bv_val);
	}else if(!ber_bvcmp(scheme, &pbkdf2_sha512_scheme)){
		dk_len = PBKDF2_SHA512_DK_SIZE;
		current_ctx = &sha512_ctx;
		current_hmac_update = (pbkdf2_hmac_update) &hmac_sha512_update;
		current_hmac_digest = (pbkdf2_hmac_digest) &hmac_sha512_digest;
		hmac_sha512_set_key(current_ctx, cred->bv_len, (const uint8_t *) cred->bv_val);
	}else{
		return LUTIL_PASSWD_ERR;
	}
#endif

	iteration = atoi(passwd->bv_val);
	if(iteration < 1){
		return LUTIL_PASSWD_ERR;
	}

	char *ptr;
	ptr = strchr(passwd->bv_val, '$');
	if(!ptr){
		return LUTIL_PASSWD_ERR;
	}
	ptr++; /* skip '$' */
	rc = ab64_to_b64(ptr, salt_b64, sizeof(salt_b64));
	if(rc < 0){
		return LUTIL_PASSWD_ERR;
	}

	ptr = strchr(ptr, '$');
	if(!ptr){
		return LUTIL_PASSWD_ERR;
	}
	ptr++; /* skip '$' */
	rc = ab64_to_b64(ptr, dk_b64, sizeof(dk_b64));
	if(rc < 0){
		return LUTIL_PASSWD_ERR;
	}

	/* The targetsize require PBKDF2_SALT_SIZE + 1 in lutil_b64_pton. */
	rc = lutil_b64_pton(salt_b64, salt_value, PBKDF2_SALT_SIZE + 1);
	if(rc < 0){
		return LUTIL_PASSWD_ERR;
	}

	/* consistency check */
	if(rc != PBKDF2_SALT_SIZE){
		return LUTIL_PASSWD_ERR;
	}

	/* The targetsize require PBKDF2_MAX_DK_SIZE + 1 in lutil_b64_pton. */
	rc = lutil_b64_pton(dk_b64, dk_value, sizeof(dk_value));
	if(rc < 0){
		return LUTIL_PASSWD_ERR;
	}

	/* consistency check */
	if(rc != dk_len){
		return LUTIL_PASSWD_ERR;
	}

#ifdef HAVE_OPENSSL
	if(!PKCS5_PBKDF2_HMAC(cred->bv_val, cred->bv_len,
						  salt_value, PBKDF2_SALT_SIZE,
						  iteration, md, dk_len, input_dk_value)){
		return LUTIL_PASSWD_ERR;
	}
#elif HAVE_GNUTLS
	PBKDF2(current_ctx, current_hmac_update, current_hmac_digest,
						  dk_len, iteration,
						  PBKDF2_SALT_SIZE, salt_value,
						  dk_len, input_dk_value);
#endif

	rc = memcmp(dk_value, input_dk_value, dk_len);
#ifdef SLAPD_PBKDF2_DEBUG
	printf("  Iteration:\t%d\n", iteration);
	printf("  Base64 Salt:\t%s\n", salt_b64);
	printf("  Base64 DK:\t%s\n", dk_b64);
	int i;
	printf("  Stored Salt:\t");
	for(i=0; i<PBKDF2_SALT_SIZE; i++){
		printf("%02x", salt_value[i]);
	}
	printf("\n");

	printf("  Stored DK:\t");
	for(i=0; i<dk_len; i++){
		printf("%02x", dk_value[i]);
	}
	printf("\n");

	printf("  Input DK:\t");
	for(i=0; i<dk_len; i++){
		printf("%02x", input_dk_value[i]);
	}
	printf("\n");
	printf("  Result:\t%d\n", rc);
#endif
	return rc?LUTIL_PASSWD_ERR:LUTIL_PASSWD_OK;
}

int init_module(int argc, char *argv[]) {
	int rc;
	rc = lutil_passwd_add((struct berval *)&pbkdf2_scheme,
						  pbkdf2_check, pbkdf2_encrypt);
	if(rc) return rc;
	rc = lutil_passwd_add((struct berval *)&pbkdf2_sha1_scheme,
						  pbkdf2_check, pbkdf2_encrypt);
	if(rc) return rc;

	rc = lutil_passwd_add((struct berval *)&pbkdf2_sha256_scheme,
						  pbkdf2_check, pbkdf2_encrypt);
	if(rc) return rc;

	rc = lutil_passwd_add((struct berval *)&pbkdf2_sha512_scheme,
						  pbkdf2_check, pbkdf2_encrypt);
	return rc;
}

/*
 * Local variables:
 * indent-tabs-mode: t
 * tab-width: 4
 * c-basic-offset: 4
 * End:
 */