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//go:build !windows
// Copyright (c) 2018, Ian Haken. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"crypto/sha1"
"flag"
"fmt"
"io"
"os"
"github.com/google/go-tpm/tpm"
)
func signAction() {
var tpmname = flag.String("tpm", "/dev/tpm0", "The path to the TPM device to use")
var keyblobPath = flag.String("keyblob", "keyblob", "Input path of the keyblob to use")
var signaturePath = flag.String("signature", "sig.data", "Output path of the signature")
var hashAlgArg = flag.String("hash", "SHA256", "Hash algorithm to use when generating the signature")
var dataPath = flag.String("data", "", "Path to the data that will be signed. If empty or omitted, the data will be read from stdin.")
flag.CommandLine.Parse(os.Args[2:])
hashAlg, ok := hashNames[*hashAlgArg]
if !ok {
fmt.Fprintf(os.Stderr, "Invalid hash algorithm: %s\n", *hashAlgArg)
return
}
rwc, err := tpm.OpenTPM(*tpmname)
if err != nil {
fmt.Fprintf(os.Stderr, "Couldn't open the TPM file %s: %s\n", *tpmname, err)
return
}
defer rwc.Close()
// Compute the auth values as needed.
var srkAuth [20]byte
srkInput := os.Getenv(srkAuthEnvVar)
if srkInput != "" {
sa := sha1.Sum([]byte(srkInput))
copy(srkAuth[:], sa[:])
}
var usageAuth [20]byte
usageInput := os.Getenv(usageAuthEnvVar)
if usageInput != "" {
ua := sha1.Sum([]byte(usageInput))
copy(usageAuth[:], ua[:])
}
var migrationAuth [20]byte
migrationInput := os.Getenv(migrationAuthEnvVar)
if migrationInput != "" {
ma := sha1.Sum([]byte(migrationInput))
copy(migrationAuth[:], ma[:])
}
keyblob, err := os.ReadFile(*keyblobPath)
if err != nil {
fmt.Fprintf(os.Stderr, "Error reading keyblob file: %s\n", err)
return
}
keyHandle, err := tpm.LoadKey2(rwc, keyblob, srkAuth[:])
if err != nil {
fmt.Fprintf(os.Stderr, "Could not load keyblob: %s\n", err)
return
}
defer tpm.CloseKey(rwc, keyHandle)
var data []byte
if *dataPath == "" {
data, err = io.ReadAll(os.Stdin)
} else {
data, err = os.ReadFile(*dataPath)
}
if err != nil {
fmt.Fprintf(os.Stderr, "Error reading input data: %s\n", err)
return
}
hash := hashAlg.New()
if _, err = hash.Write(data); err != nil {
fmt.Fprintf(os.Stderr, "Error building hash of data: %s\n", err)
return
}
hashed := hash.Sum(nil)
signature, err := tpm.Sign(rwc, usageAuth[:], keyHandle, hashAlg, hashed[:])
if err != nil {
fmt.Fprintf(os.Stderr, "Could not perform sign operation: %s\n", err)
return
}
fmt.Printf("Writing signature to %s\n", *signaturePath)
if err = os.WriteFile(*signaturePath, signature, 0644); err != nil {
fmt.Fprintf(os.Stderr, "Unable to write signature to file: %s\n", err)
return
}
}
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