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// We compare against Go's built-in GCM implementation. Since stupidgcm only
// supports 128-bit IVs and Go only supports that from 1.5 onward, we cannot
// run these tests on older Go versions.
package stupidgcm
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/hex"
"log"
"testing"
)
// Get "n" random bytes from /dev/urandom or panic
func randBytes(n int) []byte {
b := make([]byte, n)
_, err := rand.Read(b)
if err != nil {
log.Panic("Failed to read random bytes: " + err.Error())
}
return b
}
// TestEncryptDecrypt encrypts and decrypts using both stupidgcm and Go's built-in
// GCM implemenatation and verifies that the results are identical.
func TestEncryptDecrypt(t *testing.T) {
key := randBytes(32)
sGCM := New(key)
authData := randBytes(24)
iv := randBytes(16)
dst := make([]byte, 71) // 71 = random length
gAES, err := aes.NewCipher(key)
if err != nil {
t.Fatal(err)
}
gGCM, err := cipher.NewGCMWithNonceSize(gAES, 16)
if err != nil {
t.Fatal(err)
}
// Check all block sizes from 1 to 5000
for i := 1; i < 5000; i++ {
in := make([]byte, i)
sOut := sGCM.Seal(dst, iv, in, authData)
gOut := gGCM.Seal(dst, iv, in, authData)
// Ciphertext must be identical to Go GCM
if !bytes.Equal(sOut, gOut) {
t.Fatalf("Compare failed for encryption, size %d", i)
t.Log("sOut:")
t.Log("\n" + hex.Dump(sOut))
t.Log("gOut:")
t.Log("\n" + hex.Dump(gOut))
}
sOut2, sErr := sGCM.Open(dst, iv, sOut[len(dst):], authData)
if sErr != nil {
t.Fatal(sErr)
}
gOut2, gErr := gGCM.Open(dst, iv, gOut[len(dst):], authData)
if gErr != nil {
t.Fatal(gErr)
}
// Plaintext must be identical to Go GCM
if !bytes.Equal(sOut2, gOut2) {
t.Fatalf("Compare failed for decryption, size %d", i)
}
}
}
// TestCorruption verifies that changes in the ciphertext result in a decryption
// error
func TestCorruption(t *testing.T) {
key := randBytes(32)
sGCM := New(key)
authData := randBytes(24)
iv := randBytes(16)
in := make([]byte, 354)
sOut := sGCM.Seal(nil, iv, in, authData)
sOut2, sErr := sGCM.Open(nil, iv, sOut, authData)
if sErr != nil {
t.Fatal(sErr)
}
if !bytes.Equal(in, sOut2) {
t.Fatalf("Compare failed")
}
// Corrupt first byte
sOut[0]++
sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
if sErr == nil || sOut2 != nil {
t.Fatalf("Should have gotten error")
}
sOut[0]--
// Corrupt last byte
sOut[len(sOut)-1]++
sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
if sErr == nil || sOut2 != nil {
t.Fatalf("Should have gotten error")
}
sOut[len(sOut)-1]--
// Append one byte
sOut = append(sOut, 0)
sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
if sErr == nil || sOut2 != nil {
t.Fatalf("Should have gotten error")
}
}
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