Product Capability API Dictionary Interface Rules Access Specification FAQs Terms Update Log

Signature check

Update Time：2024.09.19

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	●Is the signature method of the V2 and V3 interface the same?
	No. The signature at V2 interface is MD5 or HMAC-SHA256, and the signature at V3 interface is asymmetric key SHA256-RSA.

●Why is the WeChat Pay callback missing several HTTP headers?

●Accept or User-Agent is missing in Http

●How to Load a Private Key in a Program?

We recommend using the SDK provided by WeChat Pay. You can also view the sample codes in the following programming languages.

JAVA

1/**
2  * 获取私钥。
3  *
4  * @param filename 私钥文件路径  (required)  * @return 私钥对象
5  */
6public static PrivateKey getPrivateKey(String filename) throws IOException {
7
8  String content = new String(Files.readAllBytes(Paths.get(filename)), "utf-8");
9  try {
10    String privateKey = content.replace("-----BEGIN PRIVATE KEY-----", "")
11        .replace("-----END PRIVATE KEY-----", "")
12        .replaceAll("\\s+", "");
13
14    KeyFactory kf = KeyFactory.getInstance("RSA");
15    return kf.generatePrivate(
16        new PKCS8EncodedKeySpec(Base64.getDecoder().decode(privateKey)));
17  } catch (NoSuchAlgorithmException e) {
18    throw new RuntimeException("当前Java环境不支持RSA", e);
19  } catch (InvalidKeySpecException e) {
20    throw new RuntimeException("无效的密钥格式");
21  }
22}
23

PHP

1/**
2* Read private key from file*
3* @param string    $filepath     PEM encoded private key file path
4* 
5* @return resource|bool     Private key resource identifier on success, or FALSE on error
6*/
7public static function getPrivateKey($filepath) {
8    return openssl_get_privatekey(file_get_contents($filepath));
9}
10

.NET

1protected string sign(string message)
2{
3    // 需去除私钥文件中的-----BEGIN/END PRIVATE KEY-----
4    string privateKey = "MIIEvgIBADANBgkqhkiG...30HBe+GD1tntZgf6I1Y0ZpHZ";
5    byte[] keyData = Convert.FromBase64String(privateKey);
6    using (CngKey cngKey = CngKey.Import(keyData, CngKeyBlobFormat.Pkcs8PrivateBlob))
7    using (RSACng rsa = new RSACng(cngKey))
8    {
9        byte[] data = System.Text.Encoding.UTF8.GetBytes(message);
10        return Convert.ToBase64String(rsa.SignData(data, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1));
11    }
12}
13

GO

1package main
2import (
3  "crypto/x509"
4  "encoding/pem"  "fmt"
5  "log"
6)
7
8func main() {
9  var pemData = []byte(`
10-----BEGIN PRIVATE KEY-----
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
12-----END PRIVATE KEY-----`)
13
14  block, rest := pem.Decode(pemData)
15  if block == nil || block.Type != "PRIVATE KEY" {
16    log.Fatal("failed to decode PEM block containing public key")
17  }
18
19  pri, err := x509.ParsePKCS8PrivateKey(block.Bytes)
20  if err != nil {
21    log.Fatal(err)
22  }
23
24  fmt.Printf("Got a %T, with remaining data: %q", pri, rest)
25}
26

●Why is 401 Unauthorized Returned in the Request?

Please find the cause of the error and the corresponding solution in the table below according to the message.

Error description	Cause	Solution
The merchant has not set an APIv3 key.	The merchant has not set an APIv3 key	Please log in to the merchant platform to set an APIv3 key
The merchant has not applied for a certificate.	The merchant has not applied for an API certificate	Please refer to Private key and certificate
The merchant certificate serial number is incorrect.	A wrong merchant certificate was used, or a merchant certificate that has expired was used, or the serial number of the obtained merchant certificate is incorrect.	Please check the merchant certificate. You can log in to the merchant platform to view the correct certificate serial number.
The merchant certificate has expired.	Expired merchant certificate and private key were used.	Please log in to the merchant platform to renew the certificate for use.
The merchant certificate has been invalidated.	The merchant certificate and private key invalidated by the merchant owner are used.	Please log in to the merchant platform to apply for the certificate again, and use the new certificate.
Verification failed due to wrong signature.	A wrong merchant private key was used, or the signature string was incorrectly constructed.	See the next question.
Http header Authorization value format error	The Authorization header is missing, or its format is incorrect.	Please check the Authorization sent.
Http header Authorization authentication type is incorrect.	The signature algorithm declared in Authorization is not supported.	Please check the Authorization sent. Currently, it only supports WECHATPAY2-SHA256-RSA2048.
The timestamp in the Http header Authorization and the time for initiating the request must not exceed 5 minutes	The time indicated by the timestamp in the Authorization header is more than 5 minutes away from the current time.	Please check whether the system time is accurate, or whether the logic for obtaining the time is correct.
The certificate has been replaced. Please use the new certificate.	The merchant reapplied for a merchant API certificate.	Please use the new merchant API certificate.

●How to Locate the Error of"Verification Failed Due to Wrong Signature"?

In order to help developers locate the error, we will add the verification information to the error detail detail of the response when there is a verification failure. The verification information is a variety of information we request Constructing a signature string based on the merchant's HTTP.

Method, HTTP request method
Url, requested URL
Truncated_sign_message, the signature string used during WeChat Pay verification (the line break is displayed as \n). For easy viewing, we truncated the body of the final request message.
sign_message_length, byte length of the signature string used in WeChat Pay verification

1{
2"code": "SIGN_ERROR",
3"message": "Verification failed due to wrong signature",
4"detail": {
5    "field": "signature",
6    "issue": "sign not match",
7    "location": "authorization",
8    "sign_information": {
9        "method": "GET",
10        "url": "/payscore/user-service-state?service_id=500001&appid=wxeaf7bf1de621b0c2&openid=oWm9Z5JQwgV7BKAQUeKsUMVSjTpQ",
11        "truncated_sign_message": "GET\n/payscore/user-service-state?service_id=500001&appid=wxeaf7bf1de621b0c2&openid=oWm9Z5JQwgV7BKAQUeKsUMVSjTpQ\n1559194069\n18a427e78d2344e1a71156a2690cc4d6\n\n",
12        "sign_message_length": 157
13    }
14}
15}
16

We recommend that developers export the signature string they have assembled and the byte length of the signature string in the debugging information in the program, and carefully compare the verification information returned by WeChat Pay to check for the following common errors:

No line break character added to the last line of the signature string

If the body of the request message is empty (such as a GET request), the last line should be a line break character.

The parameters in the signature string are inconsistent with the actual requested parameters.

The manually spliced URL is inconsistent with the actual request sent. We recommend using the HTTP library to construct the request object or URL object, then use the corresponding method to obtain the URL.

Two timestamps generated at different time were used when you sign and set the Authorization header.

Two different random strings generated at different time were used when you sign and set the Authorization header.

The JSON strings serialized at different time were used as the request subject during signing and request.

Notice

Developers of merchants can generate and save key parameters in variables, and use them for signing and sending requests to avoid inconsistencies in information generated at different time.

Inconsistent text encoding

The generated signature string uses non-UTF-8 encoding or no specific encoding is set.

Wrong signature string construction sequence

The signature string was not constructed in the order required by the document.

Wrong merchant private key

Developers can use the following openssl command to check whether the private key and the modulus (the product of the two large prime numbers p and q) in the merchant certificate are consistent. If yes, the private key and certificate are paired.

1$ openssl x509 -noout -modulus -in 1900009191_20180326_cert.pem
2Modulus=C6D43C87B991...
3$ openssl rsa -noout -modulus -in 1900009191_20180326_key.pem
4Modulus=C6D43C87B991...
5

Notice

The modulus length is 2048 bits, and the output is 512 bytes.
Before checking the key matching, please check the certificate serial number to check whether it is the correct merchant certificate.

●Why is the Callback of WeChat Pay Missing Several HTTP Headers?