在 Go 中使用 a.pem 文件私钥对带有 RSASSA-PSS 的字符串进行签名

Question

I'm trying to set up Amazon Pay, and following their guide for signing requests: https://amazonpaycheckoutintegrationguide.s3.amazonaws.com/amazon-pay-api-v2/signing-requests.html

I'm stuck on Step 3. I have a.pem file from Amazon containing a private key. It looks like:

-----BEGIN PRIVATE KEY-----
M...
-----END PRIVATE KEY-----

I'm supposed to sign a string I created earlier using the RSASSA-PSS algorithm with SHA256 hashing and a salt length of 20. I see that Go has a function to do so ( https://golang.org/pkg/crypto/rsa/#SignPSS ), but I'm not sure how to take my.pem file private key and use it in this function. It wants an *rsa.PrivateKey by the looks of it...

I've tried this...

var privateKeyString = `-----BEGIN PRIVATE KEY-----...`
decoded, _ := pem.Decode([]byte(privateKeyString))
parsed, _ := x509.ParsePKCS8PrivateKey(decoded.Bytes)
privateKey := parsed.(*rsa.PrivateKey)

But pem.Decode is returning nil. I've also tried:

parsed, _ := x509.ParsePKCS8PrivateKey([]byte(privateKeyString))

But this returns nil as well. I'm not familiar with crypto type stuff at all, so if anybody could provide some guidance it would be much appreciated!

Answer 1

Decode was returning nil because of how the private key string in back ticks was auto-indented. Removing all the indentation fixed the issue.