utils.go

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2016 Gin-Gonic
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.

 * This file may have been modified by CloudWeGo authors. All CloudWeGo
 * Modifications are Copyright 2022 CloudWeGo Authors.
 */

package cors

import (
	"bytes"
	"reflect"
	"strconv"
	"strings"
	"time"
	"unsafe"
)

type converter func(string) string

func generateNormalHeaders(c Config) map[string]string {
	headers := make(map[string]string)
	if c.AllowCredentials {
		headers["Access-Control-Allow-Credentials"] = "true"
	}
	if len(c.ExposeHeaders) > 0 {
		exposeHeaders := convert(normalize(c.ExposeHeaders), normalizeHeaderKey)
		headers["Access-Control-Expose-Headers"] = strings.Join(exposeHeaders, ",")
	}
	if c.AllowAllOrigins {
		headers["Access-Control-Allow-Origin"] = "*"
	} else {
		headers["Vary"] = "Origin"
	}
	return headers
}

func generatePreflightHeaders(c Config) map[string]string {
	headers := make(map[string]string)
	if c.AllowCredentials {
		headers["Access-Control-Allow-Credentials"] = "true"
	}
	if len(c.AllowMethods) > 0 {
		allowMethods := convert(normalize(c.AllowMethods), strings.ToUpper)
		value := strings.Join(allowMethods, ",")
		headers["Access-Control-Allow-Methods"] = value
	}
	if len(c.AllowHeaders) > 0 {
		allowHeaders := convert(normalize(c.AllowHeaders), normalizeHeaderKey)
		value := strings.Join(allowHeaders, ",")
		headers["Access-Control-Allow-Headers"] = value
	}
	if c.MaxAge > time.Duration(0) {
		value := strconv.FormatInt(int64(c.MaxAge/time.Second), 10)
		headers["Access-Control-Max-Age"] = value
	}
	if c.AllowAllOrigins {
		headers["Access-Control-Allow-Origin"] = "*"
	} else {
		// Always set Vary headers
		// see https://github.com/rs/cors/issues/10,
		// https://github.com/rs/cors/commit/dbdca4d95feaa7511a46e6f1efb3b3aa505bc43f#commitcomment-12352001

		headers["Vary"] = "Origin"
	}
	return headers
}

func normalize(values []string) []string {
	if values == nil {
		return nil
	}
	distinctMap := make(map[string]bool, len(values))
	normalized := make([]string, 0, len(values))
	for _, value := range values {
		value = strings.TrimSpace(value)
		value = strings.ToLower(value)
		if _, seen := distinctMap[value]; !seen {
			normalized = append(normalized, value)
			distinctMap[value] = true
		}
	}
	return normalized
}

func convert(s []string, c converter) []string {
	var out []string
	for _, i := range s {
		out = append(out, c(i))
	}
	return out
}

func str2bytes(s string) (b []byte) {
	/* #nosec G103 */
	bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
	/* #nosec G103 */
	sh := (*reflect.StringHeader)(unsafe.Pointer(&s))
	bh.Data = sh.Data
	bh.Len = sh.Len
	bh.Cap = sh.Len
	return b
}

func bytes2str(b []byte) string {
	return *(*string)(unsafe.Pointer(&b))
}

func compareByteSlices(origin []byte, patterns ...[]byte) int {
	cmp := make([]byte, 0, len(origin))
	for _, v := range patterns {
		cmp = append(cmp, v...)
	}
	return bytes.Compare(origin, cmp)
}

func normalizeHeaderKey(s string) string {
	b := []byte(s)

	n := len(b)
	if n == 0 {
		return ""
	}

	b[0] = toUpperTable[b[0]]
	for i := 1; i < n; i++ {
		p := &b[i]
		if *p == '-' {
			i++
			if i < n {
				b[i] = toUpperTable[b[i]]
			}
			continue
		}
		*p = toLowerTable[*p]
	}
	return bytes2str(b)
}

const (
	toLowerTable = "\x00\x01\x02\x03\x04\x05\x06\a\b\t\n\v\f\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\"#$%&'()*+,-./0123456789:;<=>?@abcdefghijklmnopqrstuvwxyz[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\u007f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff"
	toUpperTable = "\x00\x01\x02\x03\x04\x05\x06\a\b\t\n\v\f\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`ABCDEFGHIJKLMNOPQRSTUVWXYZ{|}~\u007f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff"
)