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Update AES256 CBC decryption test

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ivan
2025-12-06 12:19:32 -06:00
parent fb69af9bf4
commit 6896672562
1 changed files with 8 additions and 2 deletions
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10
pkg/cryptography/aes_test.go
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@@ -119,10 +119,16 @@ func TestDecryptAES256CBCErrorCases(t *testing.T) {
t.Fatalf("Failed to create test ciphertext: %v", err) t.Fatalf("Failed to create test ciphertext: %v", err)
} }
// Corrupt the last byte (which affects padding) // Corrupt the byte that XORs with the last padding byte.
// In CBC, P[i] = D(C[i]) ^ C[i-1].
// The last byte of plaintext P[len-1] depends on C[len-1] and C[len-1-BlockSize].
// If we modify C[len-1-BlockSize], we flip the bits of P[len-1] predictably.
// If we modify C[len-1] (the last byte of ciphertext), we scramble the whole block D(C[len-1]),
// which might accidentally result in valid padding (e.g. 0x01).
// So we corrupt the IV (or previous block) corresponding to the last byte.
corruptedCiphertext := make([]byte, len(ciphertext)) corruptedCiphertext := make([]byte, len(ciphertext))
copy(corruptedCiphertext, ciphertext) copy(corruptedCiphertext, ciphertext)
corruptedCiphertext[len(corruptedCiphertext)-1] ^= 0xFF corruptedCiphertext[len(ciphertext)-aes.BlockSize-1] ^= 0xFF
_, err = DecryptAES256CBC(key, corruptedCiphertext) _, err = DecryptAES256CBC(key, corruptedCiphertext)
if err == nil { if err == nil {