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Fix slicing error when data is too short #63

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Fix slicing error when data is too short #63

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18 changes: 16 additions & 2 deletions aesutils/aesutils.go
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,11 @@ func DecryptLegacy(data, key []byte) ([]byte, error) {
}

func prepareCMAC(data, key []byte) ([]byte, error) {
// Validate data length to avoid slicing error
if len(data) < 16 {
return nil, errors.New("data too short for CMAC computation")
}

// Create AES cipher
block, err := aes.NewCipher(key)
if err != nil {
Expand All @@ -117,10 +122,19 @@ func prepareCMAC(data, key []byte) ([]byte, error) {
}

// Update CMAC with parts of the data
cmacObj.Write(data[:16])
cmacObj.Write(data[4:])
if _, err := cmacObj.Write(data[:16]); err != nil {
return nil, err
}
if len(data) > 4 {
if _, err := cmacObj.Write(data[4:]); err != nil {
return nil, err
}
}

// Compute MAC and return the first 4 bytes (MAC length of 4 bytes)
mac := cmacObj.Sum(nil)
if len(mac) < 4 {
return nil, errors.New("computed CMAC too short")
}
return mac[:4], nil
}