moonD4rk/HackBrowserData · error

decrypt: %w

Error message

decrypt: %w

What it means

At this throw site the error means CBC decryption completed but PKCS#5 un-padding of the decrypted plaintext failed: the final block's last byte was not a valid padding length (zero, greater than the block size, or the padding bytes did not all match that length). cbcDecrypt itself is a generic helper guarding decrypted output, so the faulting input is the plaintext produced by AES-CBC or 3DES-CBC decryption — almost always the result of a wrong key or IV rather than a malformed buffer. It fires whenever the caller passes a cipher key that does not match the one used to encrypt, an incorrect IV, or a corrupted/truncated-then-repadded ciphertext.

Source

Thrown at crypto/crypto.go:168

dst := make([]byte, len(ciphertext))
cipher.NewCBCDecrypter(block, iv).CryptBlocks(dst, ciphertext)

dst, err := pkcs5UnPadding(dst, bs)
if err != nil {
	return nil, fmt.Errorf("decrypt: %w", err)
}
return dst, nil

View on GitHub (pinned to 0503d04d7a)

Solutions

1. Confirm the decryption key is the exact one used at encryption time (re-derive profile keys, re-decrypt OS-level key stores).
2. Verify the IV matches the one used for encryption and has the same length as the cipher block size.
3. Ensure the ciphertext is intact and block-aligned (length is a multiple of 16 for AES, 8 for 3DES) and was not truncated or re-padded.
4. Check the plaintext was encrypted with PKCS#5/PKCS#7 padding, not zero padding or an AEAD mode like GCM.
5. Log (never print) a short hash of key/IV/ciphertext to correlate failing inputs, and surface the wrapped cause with errors.Is/As.

Example fix

Verify key and IV derivation before decrypting: key, err := getAESKey(); if err != nil { return nil, err }; plain, err := AESCBCDecrypt(key, iv, ciphertext); if err != nil { return nil, fmt.Errorf("read cookies: %w", err) } — confirm the key matches the profile that encrypted the data and the ciphertext was produced with PKCS#5 padding.

When it happens

Trigger: Wrong or mis-derived decryption key (e.g. wrong DPAPI-decrypted key, wrong passcode for 3DES); incorrect IV (wrong 'salt'/nonce source); ciphertext corrupted, truncated then re-blocked, or encrypted with a different scheme (GCM/zero-padding) than PKCS#5.

Common situations: Decrypting browser cookies/passwords with a key fetched for a different browser profile or version; Chrome v80+ key migration mismatches; hand-crafted test ciphertext without PKCS#5 padding; reusing an IV blob from another record.

AI-assisted analysis of moonD4rk/HackBrowserData@0503d04d7a (2026-09-06). Data as JSON: /api/errors/b9b37610c06413ea. Report an issue: GitHub.