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// This package is intended to be compiled into a C shared library for
// use by non-Golang clients to perform certificate and signing operations.
//
// The shared library exports language-specific wrappers around the Golang
// client APIs.
//
// Example compilation command:
// go build -buildmode=c-shared -o signer.dylib main.go
package main
/*
#include <stdlib.h>
*/
import "C"
import (
"crypto"
"crypto/ecdsa"
"crypto/rsa"
"encoding/pem"
"io/ioutil"
"log"
"os"
"unsafe"
"github.com/googleapis/enterprise-certificate-proxy/client"
)
// If ECP Logging is enabled return true
// Otherwise return false
func enableECPLogging() bool {
if os.Getenv("ENABLE_ENTERPRISE_CERTIFICATE_LOGS") != "" {
return true
}
log.SetOutput(ioutil.Discard)
return false
}
func getCertPem(configFilePath string) []byte {
key, err := client.Cred(configFilePath)
if err != nil {
log.Printf("Could not create client using config %s: %v", configFilePath, err)
return nil
}
defer func() {
if err = key.Close(); err != nil {
log.Printf("Failed to clean up key. %v", err)
}
}()
certChain := key.CertificateChain()
certChainPem := []byte{}
for i := 0; i < len(certChain); i++ {
certPem := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certChain[i]})
certChainPem = append(certChainPem, certPem...)
}
return certChainPem
}
// GetCertPemForPython reads the contents of the certificate specified by configFilePath,
// storing the result inside a certHolder byte array of size certHolderLen.
//
// We must call it twice to get the cert. First time use nil for certHolder to get
// the cert length. Second time we pre-create an array in Python of the cert length and
// call this function again to load the cert into the array.
//
//export GetCertPemForPython
func GetCertPemForPython(configFilePath *C.char, certHolder *byte, certHolderLen int) int {
enableECPLogging()
pemBytes := getCertPem(C.GoString(configFilePath))
if certHolder != nil {
cert := unsafe.Slice(certHolder, certHolderLen)
copy(cert, pemBytes)
}
return len(pemBytes)
}
// SignForPython signs a message digest of length digestLen using a certificate private key
// specified by configFilePath, storing the result inside a sigHolder byte array of size sigHolderLen.
//
//export SignForPython
func SignForPython(configFilePath *C.char, digest *byte, digestLen int, sigHolder *byte, sigHolderLen int) int {
// First create a handle around the specified certificate and private key.
enableECPLogging()
key, err := client.Cred(C.GoString(configFilePath))
if err != nil {
log.Printf("Could not create client using config %s: %v", C.GoString(configFilePath), err)
return 0
}
defer func() {
if err = key.Close(); err != nil {
log.Printf("Failed to clean up key. %v", err)
}
}()
var isRsa bool
switch key.Public().(type) {
case *ecdsa.PublicKey:
isRsa = false
log.Print("the key is ecdsa key")
case *rsa.PublicKey:
isRsa = true
log.Print("the key is rsa key")
default:
log.Printf("unsupported key type")
return 0
}
// Compute the signature
digestSlice := unsafe.Slice(digest, digestLen)
var signature []byte
var signErr error
if isRsa {
// For RSA key, we need to create the padding and flags for RSASSA-SHA256
opts := rsa.PSSOptions{
SaltLength: digestLen,
Hash: crypto.SHA256,
}
signature, signErr = key.Sign(nil, digestSlice, &opts)
} else {
signature, signErr = key.Sign(nil, digestSlice, crypto.SHA256)
}
if signErr != nil {
log.Printf("failed to sign hash: %v", signErr)
return 0
}
// Create a Go buffer around the output buffer and copy the signature into the buffer
outBytes := unsafe.Slice(sigHolder, sigHolderLen)
if sigHolderLen < len(signature) {
log.Printf("The sigHolder buffer size %d is smaller than the signature size %d", sigHolderLen, len(signature))
return 0
}
for i := 0; i < len(signature); i++ {
outBytes[i] = signature[i]
}
return len(signature)
}
func main() {}
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