// Copyright (C) 2017. See AUTHORS.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package openssl

// #include "shim.h"
import "C"

import (
	"errors"
	"io/ioutil"
	"runtime"
	"unsafe"
)

type Method *C.EVP_MD

var (
	SHA1_Method   Method = C.X_EVP_sha1()
	SHA256_Method Method = C.X_EVP_sha256()
	SHA512_Method Method = C.X_EVP_sha512()
)

// Constants for the various key types.
// Mapping of name -> NID taken from openssl/evp.h
const (
	KeyTypeNone    = NID_undef
	KeyTypeRSA     = NID_rsaEncryption
	KeyTypeRSA2    = NID_rsa
	KeyTypeDSA     = NID_dsa
	KeyTypeDSA1    = NID_dsa_2
	KeyTypeDSA2    = NID_dsaWithSHA
	KeyTypeDSA3    = NID_dsaWithSHA1
	KeyTypeDSA4    = NID_dsaWithSHA1_2
	KeyTypeDH      = NID_dhKeyAgreement
	KeyTypeDHX     = NID_dhpublicnumber
	KeyTypeEC      = NID_X9_62_id_ecPublicKey
	KeyTypeHMAC    = NID_hmac
	KeyTypeCMAC    = NID_cmac
	KeyTypeTLS1PRF = NID_tls1_prf
	KeyTypeHKDF    = NID_hkdf
)

type PrivateKey interface {
	PublicKey

	// Signs the data using PKCS1.15
	SignPKCS1v15(Method, []byte) ([]byte, error)

	// MarshalPKCS1PrivateKeyPEM converts the private key to PEM-encoded PKCS1
	// format
	MarshalPKCS1PrivateKeyPEM() (pem_block []byte, err error)

	// MarshalPKCS1PrivateKeyDER converts the private key to DER-encoded PKCS1
	// format
	MarshalPKCS1PrivateKeyDER() (der_block []byte, err error)
}

type pKey struct {
	key *C.EVP_PKEY
}

func (key *pKey) evpPKey() *C.EVP_PKEY { return key.key }

func (key *pKey) SignPKCS1v15(method Method, data []byte) ([]byte, error) {
	ctx := C.X_EVP_MD_CTX_new()
	defer C.X_EVP_MD_CTX_free(ctx)

	if 1 != C.X_EVP_SignInit(ctx, method) {
		return nil, errors.New("signpkcs1v15: failed to init signature")
	}
	if len(data) > 0 {
		if 1 != C.X_EVP_SignUpdate(
			ctx, unsafe.Pointer(&data[0]), C.uint(len(data))) {
			return nil, errors.New("signpkcs1v15: failed to update signature")
		}
	}
	sig := make([]byte, C.X_EVP_PKEY_size(key.key))
	var sigblen C.uint
	if 1 != C.X_EVP_SignFinal(ctx,
		((*C.uchar)(unsafe.Pointer(&sig[0]))), &sigblen, key.key) {
		return nil, errors.New("signpkcs1v15: failed to finalize signature")
	}
	return sig[:sigblen], nil
}

func (key *pKey) VerifyPKCS1v15(method Method, data, sig []byte) error {
	ctx := C.X_EVP_MD_CTX_new()
	defer C.X_EVP_MD_CTX_free(ctx)

	if 1 != C.X_EVP_VerifyInit(ctx, method) {
		return errors.New("verifypkcs1v15: failed to init verify")
	}
	if len(data) > 0 {
		if 1 != C.X_EVP_VerifyUpdate(
			ctx, unsafe.Pointer(&data[0]), C.uint(len(data))) {
			return errors.New("verifypkcs1v15: failed to update verify")
		}
	}
	if 1 != C.X_EVP_VerifyFinal(ctx,
		((*C.uchar)(unsafe.Pointer(&sig[0]))), C.uint(len(sig)), key.key) {
		return errors.New("verifypkcs1v15: failed to finalize verify")
	}
	return nil
}

func (key *pKey) MarshalPKCS1PrivateKeyDER() (der_block []byte,
	err error) {
	bio := C.BIO_new(C.BIO_s_mem())
	if bio == nil {
		return nil, errors.New("failed to allocate memory BIO")
	}
	defer C.BIO_free(bio)

	if int(C.i2d_PrivateKey_bio(bio, key.key)) != 1 {
		return nil, errors.New("failed dumping private key der")
	}

	return ioutil.ReadAll(asAnyBio(bio))
}

func (key *pKey) MarshalPKIXPublicKeyPEM() (pem_block []byte,
	err error) {
	bio := C.BIO_new(C.BIO_s_mem())
	if bio == nil {
		return nil, errors.New("failed to allocate memory BIO")
	}
	defer C.BIO_free(bio)

	if int(C.PEM_write_bio_PUBKEY(bio, key.key)) != 1 {
		return nil, errors.New("failed dumping public key pem")
	}

	return ioutil.ReadAll(asAnyBio(bio))
}

func (key *pKey) MarshalPKIXPublicKeyDER() (der_block []byte,
	err error) {
	bio := C.BIO_new(C.BIO_s_mem())
	if bio == nil {
		return nil, errors.New("failed to allocate memory BIO")
	}
	defer C.BIO_free(bio)

	if int(C.i2d_PUBKEY_bio(bio, key.key)) != 1 {
		return nil, errors.New("failed dumping public key der")
	}

	return ioutil.ReadAll(asAnyBio(bio))
}

// LoadPrivateKeyFromPEM loads a private key from a PEM-encoded block.
func LoadPrivateKeyFromPEM(pem_block []byte) (PrivateKey, error) {
	if len(pem_block) == 0 {
		return nil, errors.New("empty pem block")
	}
	bio := C.BIO_new_mem_buf(unsafe.Pointer(&pem_block[0]),
		C.int(len(pem_block)))
	if bio == nil {
		return nil, errors.New("failed creating bio")
	}
	defer C.BIO_free(bio)

	key := C.PEM_read_bio_PrivateKey(bio, nil, nil, nil)
	if key == nil {
		return nil, errors.New("failed reading private key")
	}

	p := &pKey{key: key}
	runtime.SetFinalizer(p, func(p *pKey) {
		C.X_EVP_PKEY_free(p.key)
	})
	return p, nil
}

// LoadPrivateKeyFromPEMWithPassword loads a private key from a PEM-encoded block.
func LoadPrivateKeyFromPEMWithPassword(pem_block []byte, password string) (
	PrivateKey, error) {
	if len(pem_block) == 0 {
		return nil, errors.New("empty pem block")
	}
	bio := C.BIO_new_mem_buf(unsafe.Pointer(&pem_block[0]),
		C.int(len(pem_block)))
	if bio == nil {
		return nil, errors.New("failed creating bio")
	}
	defer C.BIO_free(bio)
	cs := C.CString(password)
	defer C.free(unsafe.Pointer(cs))
	key := C.PEM_read_bio_PrivateKey(bio, nil, nil, unsafe.Pointer(cs))
	if key == nil {
		return nil, errors.New("failed reading private key")
	}

	p := &pKey{key: key}
	runtime.SetFinalizer(p, func(p *pKey) {
		C.X_EVP_PKEY_free(p.key)
	})
	return p, nil
}

// LoadPrivateKeyFromDER loads a private key from a DER-encoded block.
func LoadPrivateKeyFromDER(der_block []byte) (PrivateKey, error) {
	if len(der_block) == 0 {
		return nil, errors.New("empty der block")
	}
	bio := C.BIO_new_mem_buf(unsafe.Pointer(&der_block[0]),
		C.int(len(der_block)))
	if bio == nil {
		return nil, errors.New("failed creating bio")
	}
	defer C.BIO_free(bio)

	key := C.d2i_PrivateKey_bio(bio, nil)
	if key == nil {
		return nil, errors.New("failed reading private key der")
	}

	p := &pKey{key: key}
	runtime.SetFinalizer(p, func(p *pKey) {
		C.X_EVP_PKEY_free(p.key)
	})
	return p, nil
}

// LoadPrivateKeyFromPEMWidthPassword loads a private key from a PEM-encoded block.
// Backwards-compatible with typo
func LoadPrivateKeyFromPEMWidthPassword(pem_block []byte, password string) (
	PrivateKey, error) {
	return LoadPrivateKeyFromPEMWithPassword(pem_block, password)
}

// LoadPublicKeyFromPEM loads a public key from a PEM-encoded block.
func LoadPublicKeyFromPEM(pem_block []byte) (PublicKey, error) {
	if len(pem_block) == 0 {
		return nil, errors.New("empty pem block")
	}
	bio := C.BIO_new_mem_buf(unsafe.Pointer(&pem_block[0]),
		C.int(len(pem_block)))
	if bio == nil {
		return nil, errors.New("failed creating bio")
	}
	defer C.BIO_free(bio)

	key := C.PEM_read_bio_PUBKEY(bio, nil, nil, nil)
	if key == nil {
		return nil, errors.New("failed reading public key der")
	}

	p := &pKey{key: key}
	runtime.SetFinalizer(p, func(p *pKey) {
		C.X_EVP_PKEY_free(p.key)
	})
	return p, nil
}

// LoadPublicKeyFromDER loads a public key from a DER-encoded block.
func LoadPublicKeyFromDER(der_block []byte) (PublicKey, error) {
	if len(der_block) == 0 {
		return nil, errors.New("empty der block")
	}
	bio := C.BIO_new_mem_buf(unsafe.Pointer(&der_block[0]),
		C.int(len(der_block)))
	if bio == nil {
		return nil, errors.New("failed creating bio")
	}
	defer C.BIO_free(bio)

	key := C.d2i_PUBKEY_bio(bio, nil)
	if key == nil {
		return nil, errors.New("failed reading public key der")
	}

	p := &pKey{key: key}
	runtime.SetFinalizer(p, func(p *pKey) {
		C.X_EVP_PKEY_free(p.key)
	})
	return p, nil
}

// GenerateRSAKey generates a new RSA private key with an exponent of 3.
func GenerateRSAKey(bits int) (PrivateKey, error) {
	return GenerateRSAKeyWithExponent(bits, 3)
}

// GenerateRSAKeyWithExponent generates a new RSA private key.
func GenerateRSAKeyWithExponent(bits int, exponent int) (PrivateKey, error) {
	rsa := C.RSA_generate_key(C.int(bits), C.ulong(exponent), nil, nil)
	if rsa == nil {
		return nil, errors.New("failed to generate RSA key")
	}
	key := C.X_EVP_PKEY_new()
	if key == nil {
		return nil, errors.New("failed to allocate EVP_PKEY")
	}
	if C.X_EVP_PKEY_assign_charp(key, C.EVP_PKEY_RSA, (*C.char)(unsafe.Pointer(rsa))) != 1 {
		C.X_EVP_PKEY_free(key)
		return nil, errors.New("failed to assign RSA key")
	}
	p := &pKey{key: key}
	runtime.SetFinalizer(p, func(p *pKey) {
		C.X_EVP_PKEY_free(p.key)
	})
	return p, nil
}