WeKnora deployment source with the reviewed wiki identity, summary and recovery fixes

internal/im/wechat/crypto.go

@@ -0,0 +1,72 @@
+// Package wechat implements the WeChat personal account IM adapter for WeKnora
+// via the Tencent iLink Bot API (ilinkai.weixin.qq.com).
+package wechat
+
+import (
+	"crypto/aes"
+	"fmt"
+)
+
+// decryptAES128ECB decrypts data encrypted with AES-128-ECB (no padding removal).
+// iLink media files are encrypted with a 16-byte AES key using ECB mode.
+func decryptAES128ECB(ciphertext, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, fmt.Errorf("new aes cipher: %w", err)
+	}
+
+	bs := block.BlockSize()
+	if len(ciphertext) == 0 || len(ciphertext)%bs != 0 {
+		return nil, fmt.Errorf("ciphertext length %d is not a multiple of block size %d", len(ciphertext), bs)
+	}
+
+	plaintext := make([]byte, len(ciphertext))
+	for i := 0; i < len(ciphertext); i += bs {
+		block.Decrypt(plaintext[i:i+bs], ciphertext[i:i+bs])
+	}
+
+	// Remove PKCS#7 padding if present
+	if len(plaintext) > 0 {
+		padLen := int(plaintext[len(plaintext)-1])
+		if padLen > 0 && padLen <= bs && padLen <= len(plaintext) {
+			valid := true
+			for i := 0; i < padLen; i++ {
+				if plaintext[len(plaintext)-1-i] != byte(padLen) {
+					valid = false
+					break
+				}
+			}
+			if valid {
+				plaintext = plaintext[:len(plaintext)-padLen]
+			}
+		}
+	}
+
+	return plaintext, nil
+}
+
+// encryptAES128ECB encrypts data with AES-128-ECB and PKCS#7 padding.
+// Used for uploading media files to the iLink CDN.
+func encryptAES128ECB(plaintext, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, fmt.Errorf("new aes cipher: %w", err)
+	}
+
+	bs := block.BlockSize()
+
+	// PKCS#7 padding
+	padLen := bs - len(plaintext)%bs
+	padded := make([]byte, len(plaintext)+padLen)
+	copy(padded, plaintext)
+	for i := len(plaintext); i < len(padded); i++ {
+		padded[i] = byte(padLen)
+	}
+
+	ciphertext := make([]byte, len(padded))
+	for i := 0; i < len(padded); i += bs {
+		block.Encrypt(ciphertext[i:i+bs], padded[i:i+bs])
+	}
+
+	return ciphertext, nil
+}