129 lines
3.9 KiB
Go
129 lines
3.9 KiB
Go
package storage
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import (
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"fmt"
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"net/url"
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"strings"
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"unicode"
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)
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// ObjectKeyFromCDNURL 将属于 cdnBase 的 HTTPS URL 转成原始 S3 对象 key。
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// cdnBase 可省略 scheme，也可带 base path。外站或不属于 base path 的 URL
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// 返回 owned=false 且不报错；格式非法或试图伪装路径的 URL 返回错误。
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func ObjectKeyFromCDNURL(rawURL, cdnBase string) (key string, owned bool, err error) {
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base, err := parseCDNBase(cdnBase)
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if err != nil {
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return "", false, err
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}
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parsed, err := parseCDNURL(rawURL, false)
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if err != nil {
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return "", false, err
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}
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if !strings.EqualFold(parsed.Host, base.Host) {
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return "", false, nil
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}
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basePath := base.Path
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if basePath != "" {
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if parsed.Path == basePath {
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return "", false, fmt.Errorf("CDN URL does not contain an object key")
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}
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prefix := basePath + "/"
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if !strings.HasPrefix(parsed.Path, prefix) {
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return "", false, nil
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}
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key = strings.TrimPrefix(parsed.Path, prefix)
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} else {
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key = strings.TrimPrefix(parsed.Path, "/")
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}
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if key == "" {
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return "", false, fmt.Errorf("CDN URL does not contain an object key")
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}
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// 只去掉 cdnBase 的路径和前导分隔符；不添加或移除 bucket，也不 Clean，
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// 因而返回的解码路径仍是实际 S3 key。
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return key, true, nil
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}
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func parseCDNBase(cdnBase string) (*url.URL, error) {
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if cdnBase == "" {
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return nil, fmt.Errorf("CDN base URL is empty")
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}
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rawBase := cdnBase
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if strings.HasPrefix(rawBase, "//") {
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rawBase = "https:" + rawBase
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} else if !strings.Contains(rawBase, "://") {
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rawBase = "https://" + rawBase
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}
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return parseCDNURL(rawBase, true)
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}
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func parseCDNURL(rawURL string, isBase bool) (*url.URL, error) {
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if rawURL == "" {
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return nil, fmt.Errorf("URL is empty")
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}
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if strings.Contains(rawURL, `\`) || containsControl(rawURL) {
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return nil, fmt.Errorf("URL contains a backslash or control character")
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}
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parsed, err := url.Parse(rawURL)
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if err != nil {
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return nil, fmt.Errorf("parse URL: %w", err)
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}
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if !parsed.IsAbs() || !strings.EqualFold(parsed.Scheme, "https") || parsed.Host == "" ||
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parsed.Hostname() == "" || parsed.Opaque != "" {
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return nil, fmt.Errorf("URL must be an absolute HTTPS URL")
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}
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if parsed.User != nil {
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return nil, fmt.Errorf("URL must not contain userinfo")
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}
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if parsed.RawQuery != "" || parsed.ForceQuery {
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return nil, fmt.Errorf("URL must not contain a query")
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}
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if parsed.Fragment != "" || strings.Contains(rawURL, "#") {
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return nil, fmt.Errorf("URL must not contain a fragment")
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}
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// 必须在 url.Parse 的 Path 解码之外检查 EscapedPath：编码斜杠在 Path 中
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// 与普通分隔符无法区分，若放行会导致 CDN 与 S3 对 key 的解释不一致。
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escapedPath := strings.ToLower(parsed.EscapedPath())
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if strings.Contains(escapedPath, "%2f") || strings.Contains(escapedPath, "%5c") {
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return nil, fmt.Errorf("URL path contains an encoded slash or backslash")
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}
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if strings.Contains(parsed.Path, `\`) || containsControl(parsed.Path) {
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return nil, fmt.Errorf("URL path contains a backslash or control character")
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}
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if isBase && strings.HasSuffix(parsed.Path, "/") {
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// 配置中的 CDN base 允许一个末尾斜杠；其余空路径段仍会被拒绝。
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parsed.Path = strings.TrimSuffix(parsed.Path, "/")
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parsed.RawPath = ""
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}
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if parsed.Path == "" {
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if isBase {
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return parsed, nil
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}
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return nil, fmt.Errorf("URL path is empty")
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}
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if !strings.HasPrefix(parsed.Path, "/") {
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return nil, fmt.Errorf("URL path must be absolute")
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}
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for _, segment := range strings.Split(strings.TrimPrefix(parsed.Path, "/"), "/") {
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if segment == "" {
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return nil, fmt.Errorf("URL path contains an empty segment")
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}
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if segment == "." || segment == ".." {
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return nil, fmt.Errorf("URL path contains a dot segment")
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}
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}
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return parsed, nil
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}
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func containsControl(value string) bool {
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for _, r := range value {
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if unicode.IsControl(r) {
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return true
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}
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}
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return false
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}
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