/*
Copyright 2014 The Kubernetes 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 cert

import (
	"crypto/ecdsa"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"errors"
	"fmt"
)

const (

	// ECPrivateKeyBlockType is a possible value for pem.Block.Type.
	ECPrivateKeyBlockType = "EC PRIVATE KEY"
	// RSAPrivateKeyBlockType is a possible value for pem.Block.Type.
	RSAPrivateKeyBlockType = "RSA PRIVATE KEY"
	// CertificateRequestBlockType is a possible value for pem.Block.Type.
	CertificateRequestBlockType = "CERTIFICATE REQUEST"
	// CertificateBlockType is a possible value for pem.Block.Type.
	CertificateBlockType = "CERTIFICATE"
	// PrivateKeyBlockType is a possible value for pem.Block.Type.
	PrivateKeyBlockType = "PRIVATE KEY"
)

// ParsePrivateKeyPEM returns a private key parsed from a PEM block in the supplied data.
// Recognizes PEM blocks for "EC PRIVATE KEY", "RSA PRIVATE KEY", or "PRIVATE KEY"
func ParsePrivateKeyPEM(keyData []byte) (interface{}, error) {
	var privateKeyPemBlock *pem.Block
	for {
		privateKeyPemBlock, keyData = pem.Decode(keyData)
		if privateKeyPemBlock == nil {
			break
		}

		switch privateKeyPemBlock.Type {
		case ECPrivateKeyBlockType:
			// ECDSA Private Key in ASN.1 format
			if key, err := x509.ParseECPrivateKey(privateKeyPemBlock.Bytes); err == nil {
				return key, nil
			}
		case RSAPrivateKeyBlockType:
			// RSA Private Key in PKCS#1 format
			if key, err := x509.ParsePKCS1PrivateKey(privateKeyPemBlock.Bytes); err == nil {
				return key, nil
			}
		case PrivateKeyBlockType:
			// RSA or ECDSA Private Key in unencrypted PKCS#8 format
			if key, err := x509.ParsePKCS8PrivateKey(privateKeyPemBlock.Bytes); err == nil {
				return key, nil
			}
		}

		// tolerate non-key PEM blocks for compatibility with things like "EC PARAMETERS" blocks
		// originally, only the first PEM block was parsed and expected to be a key block
	}

	// we read all the PEM blocks and didn't recognize one
	return nil, fmt.Errorf("data does not contain a valid RSA or ECDSA private key")
}

// ParsePublicKeysPEM is a helper function for reading an array of rsa.PublicKey or ecdsa.PublicKey from a PEM-encoded byte array.
// Reads public keys from both public and private key files.
func ParsePublicKeysPEM(keyData []byte) ([]interface{}, error) {
	var block *pem.Block
	keys := []interface{}{}
	for {
		// read the next block
		block, keyData = pem.Decode(keyData)
		if block == nil {
			break
		}

		// test block against parsing functions
		if privateKey, err := parseRSAPrivateKey(block.Bytes); err == nil {
			keys = append(keys, &privateKey.PublicKey)
			continue
		}
		if publicKey, err := parseRSAPublicKey(block.Bytes); err == nil {
			keys = append(keys, publicKey)
			continue
		}
		if privateKey, err := parseECPrivateKey(block.Bytes); err == nil {
			keys = append(keys, &privateKey.PublicKey)
			continue
		}
		if publicKey, err := parseECPublicKey(block.Bytes); err == nil {
			keys = append(keys, publicKey)
			continue
		}

		// tolerate non-key PEM blocks for backwards compatibility
		// originally, only the first PEM block was parsed and expected to be a key block
	}

	if len(keys) == 0 {
		return nil, fmt.Errorf("data does not contain any valid RSA or ECDSA public keys")
	}
	return keys, nil
}

// EncodePrivateKeyPEM returns PEM-encoded private key data
func EncodePrivateKeyPEM(key *rsa.PrivateKey) []byte {
	block := pem.Block{
		Type:  RSAPrivateKeyBlockType,
		Bytes: x509.MarshalPKCS1PrivateKey(key),
	}
	return pem.EncodeToMemory(&block)
}

// ParseCertsPEM returns the x509.Certificates contained in the given PEM-encoded byte array
// Returns an error if a certificate could not be parsed, or if the data does not contain any certificates
func ParseCertsPEM(pemCerts []byte) ([]*x509.Certificate, error) {
	ok := false
	certs := []*x509.Certificate{}
	for len(pemCerts) > 0 {
		var block *pem.Block
		block, pemCerts = pem.Decode(pemCerts)
		if block == nil {
			break
		}
		// Only use PEM "CERTIFICATE" blocks without extra headers
		if block.Type != CertificateBlockType || len(block.Headers) != 0 {
			continue
		}

		cert, err := x509.ParseCertificate(block.Bytes)
		if err != nil {
			return certs, err
		}

		certs = append(certs, cert)
		ok = true
	}

	if !ok {
		return certs, errors.New("data does not contain any valid RSA or ECDSA certificates")
	}
	return certs, nil
}

// parseRSAPublicKey parses a single RSA public key from the provided data
func parseRSAPublicKey(data []byte) (*rsa.PublicKey, error) {
	var err error

	// Parse the key
	var parsedKey interface{}
	if parsedKey, err = x509.ParsePKIXPublicKey(data); err != nil {
		if cert, err := x509.ParseCertificate(data); err == nil {
			parsedKey = cert.PublicKey
		} else {
			return nil, err
		}
	}

	// Test if parsed key is an RSA Public Key
	var pubKey *rsa.PublicKey
	var ok bool
	if pubKey, ok = parsedKey.(*rsa.PublicKey); !ok {
		return nil, fmt.Errorf("data doesn't contain valid RSA Public Key")
	}

	return pubKey, nil
}

// parseRSAPrivateKey parses a single RSA private key from the provided data
func parseRSAPrivateKey(data []byte) (*rsa.PrivateKey, error) {
	var err error

	// Parse the key
	var parsedKey interface{}
	if parsedKey, err = x509.ParsePKCS1PrivateKey(data); err != nil {
		if parsedKey, err = x509.ParsePKCS8PrivateKey(data); err != nil {
			return nil, err
		}
	}

	// Test if parsed key is an RSA Private Key
	var privKey *rsa.PrivateKey
	var ok bool
	if privKey, ok = parsedKey.(*rsa.PrivateKey); !ok {
		return nil, fmt.Errorf("data doesn't contain valid RSA Private Key")
	}

	return privKey, nil
}

// parseECPublicKey parses a single ECDSA public key from the provided data
func parseECPublicKey(data []byte) (*ecdsa.PublicKey, error) {
	var err error

	// Parse the key
	var parsedKey interface{}
	if parsedKey, err = x509.ParsePKIXPublicKey(data); err != nil {
		if cert, err := x509.ParseCertificate(data); err == nil {
			parsedKey = cert.PublicKey
		} else {
			return nil, err
		}
	}

	// Test if parsed key is an ECDSA Public Key
	var pubKey *ecdsa.PublicKey
	var ok bool
	if pubKey, ok = parsedKey.(*ecdsa.PublicKey); !ok {
		return nil, fmt.Errorf("data doesn't contain valid ECDSA Public Key")
	}

	return pubKey, nil
}

// parseECPrivateKey parses a single ECDSA private key from the provided data
func parseECPrivateKey(data []byte) (*ecdsa.PrivateKey, error) {
	var err error

	// Parse the key
	var parsedKey interface{}
	if parsedKey, err = x509.ParseECPrivateKey(data); err != nil {
		return nil, err
	}

	// Test if parsed key is an ECDSA Private Key
	var privKey *ecdsa.PrivateKey
	var ok bool
	if privKey, ok = parsedKey.(*ecdsa.PrivateKey); !ok {
		return nil, fmt.Errorf("data doesn't contain valid ECDSA Private Key")
	}

	return privKey, nil
}
