62 lines
1.6 KiB
Go
62 lines
1.6 KiB
Go
package captcha
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import (
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"bytes"
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"encoding/base64"
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"fmt"
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"io"
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"time"
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)
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// GenerateEncryptedSceneID 按阿里云文档生成 EncryptedSceneId（仅适用于 V3 架构加密模式）。
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// 明文格式: sceneId×tamp&expireTime
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// 加密: AES-256-CBC + PKCS7Padding，结果为 Base64( IV(16字节) + ciphertext )
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func GenerateEncryptedSceneID(sceneId, ekey string, expireSeconds int) (string, error) {
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if expireSeconds <= 0 || expireSeconds > 86400 {
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expireSeconds = 3600
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}
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ts := time.Now().Unix() // 秒级时间戳
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plaintext := fmt.Sprintf("%s&%d&%d", sceneId, ts, expireSeconds)
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keyBytes, err := base64.StdEncoding.DecodeString(ekey)
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if err != nil {
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return "", fmt.Errorf("decode ekey error: %w", err)
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}
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if len(keyBytes) != 32 {
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return "", fmt.Errorf("invalid ekey length, need 32 bytes after base64 decode, got %d", len(keyBytes))
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}
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block, err := aes.NewCipher(keyBytes)
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if err != nil {
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return "", fmt.Errorf("new cipher error: %w", err)
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}
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iv := make([]byte, aes.BlockSize)
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if _, err := io.ReadFull(rand.Reader, iv); err != nil {
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return "", fmt.Errorf("read iv error: %w", err)
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}
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padded := pkcs7Pad([]byte(plaintext), aes.BlockSize)
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ciphertext := make([]byte, len(padded))
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mode := cipher.NewCBCEncrypter(block, iv)
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mode.CryptBlocks(ciphertext, padded)
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out := append(iv, ciphertext...)
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return base64.StdEncoding.EncodeToString(out), nil
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}
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func pkcs7Pad(src []byte, blockSize int) []byte {
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padLen := blockSize - len(src)%blockSize
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if padLen == 0 {
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padLen = blockSize
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}
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pad := bytes.Repeat([]byte{byte(padLen)}, padLen)
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return append(src, pad...)
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}
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