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signature.go
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signature.go
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package jws
import (
"crypto/rsa"
"encoding/json"
"errors"
"strings"
"github.com/alexandru-ionut-balan/ing-jws/crypto"
"github.com/alexandru-ionut-balan/ing-jws/logging"
)
func generateEncodedHeader(jwsHeader *JwsHeader) (string, error) {
rawHeaderBytes, err := json.Marshal(jwsHeader)
logging.Info("Encoding jws header: " + string(rawHeaderBytes))
if err != nil {
logging.Error("Cannot marshal JWS Header into JSON.", nil)
return "", err
}
return crypto.ApplyExtraFormatting(crypto.Base64(rawHeaderBytes)), nil
}
func generateSignatureValue(encodedJwsHeader string, headerNames []string, httpHeaders map[string]string, privateKey *rsa.PrivateKey) (string, error) {
signatureInput := encodedJwsHeader + "."
for _, name := range headerNames {
value, ok := httpHeaders[name]
if !ok {
logging.Error("No http header was found for header name: "+name, nil)
return "", errors.New("header name present in sigD, but missing when generating signature")
}
signatureInput += strings.ToLower(name) + ": " + value + "\n"
}
logging.Info("Signing jws value: " + signatureInput[:len(signatureInput)-1])
signedInput, err := crypto.Sign(signatureInput[:len(signatureInput)-1], privateKey)
if err != nil {
logging.Error("Cannot generate signature value.", nil)
return "", err
}
return crypto.ApplyExtraFormatting(crypto.Base64(signedInput)), nil
}
func GenerateSignature(jwsHeader *JwsHeader, httpHeaders map[string]string, privateKey *rsa.PrivateKey) (string, error) {
encodedHeader, err := generateEncodedHeader(jwsHeader)
if err != nil {
logging.Error("Cannot create signature!", nil)
return "", err
}
signatureValue, err := generateSignatureValue(encodedHeader, jwsHeader.SigD.Pars, httpHeaders, privateKey)
if err != nil {
logging.Error("Cannot create signature!", nil)
return "", err
}
return encodedHeader + ".." + signatureValue, nil
}