// Copyright 2021 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package cmd

import (
	"crypto/tls"
	"net/http"
	"os"
	"strings"

	"code.gitea.io/gitea/modules/graceful"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/setting"

	"github.com/klauspost/cpuid/v2"
)

var tlsVersionStringMap = map[string]uint16{
	"":        tls.VersionTLS12, // Default to tls.VersionTLS12
	"tlsv1.0": tls.VersionTLS10,
	"tlsv1.1": tls.VersionTLS11,
	"tlsv1.2": tls.VersionTLS12,
	"tlsv1.3": tls.VersionTLS13,
}

func toTLSVersion(version string) uint16 {
	tlsVersion, ok := tlsVersionStringMap[strings.TrimSpace(strings.ToLower(version))]
	if !ok {
		log.Warn("Unknown tls version: %s", version)
		return 0
	}
	return tlsVersion
}

var curveStringMap = map[string]tls.CurveID{
	"x25519": tls.X25519,
	"p256":   tls.CurveP256,
	"p384":   tls.CurveP384,
	"p521":   tls.CurveP521,
}

func toCurvePreferences(preferences []string) []tls.CurveID {
	ids := make([]tls.CurveID, 0, len(preferences))
	for _, pref := range preferences {
		id, ok := curveStringMap[strings.TrimSpace(strings.ToLower(pref))]
		if !ok {
			log.Warn("Unknown curve: %s", pref)
		}
		if id != 0 {
			ids = append(ids, id)
		}
	}
	return ids
}

var cipherStringMap = map[string]uint16{
	"rsa_with_rc4_128_sha":                      tls.TLS_RSA_WITH_RC4_128_SHA,
	"rsa_with_3des_ede_cbc_sha":                 tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA,
	"rsa_with_aes_128_cbc_sha":                  tls.TLS_RSA_WITH_AES_128_CBC_SHA,
	"rsa_with_aes_256_cbc_sha":                  tls.TLS_RSA_WITH_AES_256_CBC_SHA,
	"rsa_with_aes_128_cbc_sha256":               tls.TLS_RSA_WITH_AES_128_CBC_SHA256,
	"rsa_with_aes_128_gcm_sha256":               tls.TLS_RSA_WITH_AES_128_GCM_SHA256,
	"rsa_with_aes_256_gcm_sha384":               tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
	"ecdhe_ecdsa_with_rc4_128_sha":              tls.TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,
	"ecdhe_ecdsa_with_aes_128_cbc_sha":          tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
	"ecdhe_ecdsa_with_aes_256_cbc_sha":          tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
	"ecdhe_rsa_with_rc4_128_sha":                tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA,
	"ecdhe_rsa_with_3des_ede_cbc_sha":           tls.TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,
	"ecdhe_rsa_with_aes_128_cbc_sha":            tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
	"ecdhe_rsa_with_aes_256_cbc_sha":            tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
	"ecdhe_ecdsa_with_aes_128_cbc_sha256":       tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
	"ecdhe_rsa_with_aes_128_cbc_sha256":         tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
	"ecdhe_rsa_with_aes_128_gcm_sha256":         tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
	"ecdhe_ecdsa_with_aes_128_gcm_sha256":       tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
	"ecdhe_rsa_with_aes_256_gcm_sha384":         tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
	"ecdhe_ecdsa_with_aes_256_gcm_sha384":       tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
	"ecdhe_rsa_with_chacha20_poly1305_sha256":   tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256,
	"ecdhe_ecdsa_with_chacha20_poly1305_sha256": tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256,
	"ecdhe_rsa_with_chacha20_poly1305":          tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
	"ecdhe_ecdsa_with_chacha20_poly1305":        tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
	"aes_128_gcm_sha256":                        tls.TLS_AES_128_GCM_SHA256,
	"aes_256_gcm_sha384":                        tls.TLS_AES_256_GCM_SHA384,
	"chacha20_poly1305_sha256":                  tls.TLS_CHACHA20_POLY1305_SHA256,
}

func toTLSCiphers(cipherStrings []string) []uint16 {
	ciphers := make([]uint16, 0, len(cipherStrings))
	for _, cipherString := range cipherStrings {
		cipher, ok := cipherStringMap[strings.TrimSpace(strings.ToLower(cipherString))]
		if !ok {
			log.Warn("Unknown cipher: %s", cipherString)
		}
		if cipher != 0 {
			ciphers = append(ciphers, cipher)
		}
	}

	return ciphers
}

// defaultCiphers uses hardware support to check if AES is specifically
// supported by the CPU.
//
// If AES is supported AES ciphers will be preferred over ChaCha based ciphers
// (This code is directly inspired by the certmagic code.)
func defaultCiphers() []uint16 {
	if cpuid.CPU.Supports(cpuid.AESNI) {
		return defaultCiphersAESfirst
	}
	return defaultCiphersChaChaFirst
}

var (
	defaultCiphersAES = []uint16{
		tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
		tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
		tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
		tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
	}

	defaultCiphersChaCha = []uint16{
		tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
		tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
	}

	defaultCiphersAESfirst    = append(defaultCiphersAES, defaultCiphersChaCha...)
	defaultCiphersChaChaFirst = append(defaultCiphersChaCha, defaultCiphersAES...)
)

// runHTTPS listens on the provided network address and then calls
// Serve to handle requests on incoming TLS connections.
//
// Filenames containing a certificate and matching private key for the server must
// be provided. If the certificate is signed by a certificate authority, the
// certFile should be the concatenation of the server's certificate followed by the
// CA's certificate.
func runHTTPS(network, listenAddr, name, certFile, keyFile string, m http.Handler, useProxyProtocol, proxyProtocolTLSBridging bool) error {
	tlsConfig := &tls.Config{}
	if tlsConfig.NextProtos == nil {
		tlsConfig.NextProtos = []string{"h2", "http/1.1"}
	}

	if version := toTLSVersion(setting.SSLMinimumVersion); version != 0 {
		tlsConfig.MinVersion = version
	}
	if version := toTLSVersion(setting.SSLMaximumVersion); version != 0 {
		tlsConfig.MaxVersion = version
	}

	// Set curve preferences
	tlsConfig.CurvePreferences = []tls.CurveID{
		tls.X25519,
		tls.CurveP256,
	}
	if curves := toCurvePreferences(setting.SSLCurvePreferences); len(curves) > 0 {
		tlsConfig.CurvePreferences = curves
	}

	// Set cipher suites
	tlsConfig.CipherSuites = defaultCiphers()
	if ciphers := toTLSCiphers(setting.SSLCipherSuites); len(ciphers) > 0 {
		tlsConfig.CipherSuites = ciphers
	}

	tlsConfig.Certificates = make([]tls.Certificate, 1)

	certPEMBlock, err := os.ReadFile(certFile)
	if err != nil {
		log.Error("Failed to load https cert file %s for %s:%s: %v", certFile, network, listenAddr, err)
		return err
	}

	keyPEMBlock, err := os.ReadFile(keyFile)
	if err != nil {
		log.Error("Failed to load https key file %s for %s:%s: %v", keyFile, network, listenAddr, err)
		return err
	}

	tlsConfig.Certificates[0], err = tls.X509KeyPair(certPEMBlock, keyPEMBlock)
	if err != nil {
		log.Error("Failed to create certificate from cert file %s and key file %s for %s:%s: %v", certFile, keyFile, network, listenAddr, err)
		return err
	}

	return graceful.HTTPListenAndServeTLSConfig(network, listenAddr, name, tlsConfig, m, useProxyProtocol, proxyProtocolTLSBridging)
}

func runHTTPSWithTLSConfig(network, listenAddr, name string, tlsConfig *tls.Config, m http.Handler, useProxyProtocol, proxyProtocolTLSBridging bool) error {
	return graceful.HTTPListenAndServeTLSConfig(network, listenAddr, name, tlsConfig, m, useProxyProtocol, proxyProtocolTLSBridging)
}
