Decrypting selling partner api reports

Question

I am trying to decrypt selling partner api reports but while decrypting I am getting this error near decipher.final() [Node] Error: error:0606506D:digital envelope routines:EVP_DecryptFinal_ex:wrong final block length. The api returns the key, iv and the url of the report. Selling Partner api reference

I tried the solutions mentioned in other threads but still facing issues. I checked the length of both key and iv and it is 32 and 16 respectively.

Here is the code:

var AESCrypt: any = {
            decrypt: function (cryptkey: any, iv: any, encryptdata: any) {
                var decipher = crypto.createDecipheriv('aes-256-cbc', cryptkey, iv);
                // decipher.setAutoPadding(true);
                return Buffer.concat([
                    decipher.update(encryptdata),
                    decipher.final()
                ]);
            }}
            
            
  const res = await processRequest({
        url: details.url                                                                                                     
    });
    
    let encrypted_buffer = Buffer.from(res);
    const key = Buffer.from(details.encryptionDetails.key, "base64");
    const iv = Buffer.from(details.encryptionDetails.initializationVector, "base64");
    const decryptedBuff = AESCrypt.decrypt(key, iv, encrypted_buffer);
    console.log(decryptedBuff);

Lettie

Where do you use the URL or have you already downloaded the report and just want to decrypt it? What encoding does the report use? If it is contained in a buffer, Buffer.from() is not necessary. If it is Base64 encoded, the specification of 'base64' is missing. Currently with UTF8 (the default) the wrong encoding is applied. – Laskowski

The encoding is AES. Where do I need to add 'base64'?decipher.final('base64')? – Lettie

I mean the encoding. AES is not an encoding but an encryption. I refer to res. – Laskowski

I don't know much about decryption. The key and iv are base64 encoded. Can you have a look at this github.com/amzn/selling-partner-api-docs/blob/main/guides/en-US/… – Lettie

My question is not about encryption/decryption, but encoding. I mean is res an ArrayBuffer, Base64 encoded etc. or what does processRequest() return. Maybe you are converting wrong, but this is only a guess. The link does not answer that. – Laskowski

This processRequest is getting the encoded data from the url they have sent. How do I check whether it is base64 encoded or not? – Lettie

Did you output res to the console? Is ArrayBuffer, Uint8Array [...], <Buffer...>, an alphanumeric string (plus +/=) or some gibberish displayed? – Laskowski

No, its not a buffer. Its like this �ځ��P}Z��☺ow�e':g>��z>��@♥9��♂e4z�=��☼♣�O& – Lettie

This looks more like a binary string . If so, Buffer.from(res) would corrupt the ciphertext, because UTF-8 is used as encoding by default, which damages the ciphertext. You could try Buffer.from(res, 'binary'). – Laskowski

Buffer.from(res, 'binary') this is also giving the same error – Lettie

Maybe, but Buffer.from() with a string as ciphertext is wrong in any case. Probably there are other problems. – Laskowski

Did you figure this out? I'm struggling with the same issue – Unfair

Yes, I was able to but I don't remember it now. You can take help of this npmjs.com/package/amazon-sp-api – Lettie