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103 lines
2.5 KiB
Go
103 lines
2.5 KiB
Go
package util
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import (
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"crypto/aes"
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"crypto/cipher"
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"encoding/binary"
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"errors"
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"io"
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prand "math/rand"
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"net"
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"strconv"
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)
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func AESGCMEncrypt(nonce []byte, key []byte, plaintext []byte) ([]byte, error) {
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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aesgcm, err := cipher.NewGCM(block)
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if err != nil {
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return nil, err
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}
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return aesgcm.Seal(nil, nonce, plaintext, nil), nil
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}
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func AESGCMDecrypt(nonce []byte, key []byte, ciphertext []byte) ([]byte, error) {
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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aesgcm, err := cipher.NewGCM(block)
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if err != nil {
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return nil, err
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}
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plain, err := aesgcm.Open(nil, nonce, ciphertext, nil)
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if err != nil {
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return nil, err
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}
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return plain, nil
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}
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// PsudoRandBytes returns a byte slice filled with psudorandom bytes generated by the seed
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func PsudoRandBytes(length int, seed int64) []byte {
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r := prand.New(prand.NewSource(seed))
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ret := make([]byte, length)
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r.Read(ret)
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return ret
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}
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// ReadTLS reads TLS data according to its record layer
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func ReadTLS(conn net.Conn, buffer []byte) (n int, err error) {
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// TCP is a stream. Multiple TLS messages can arrive at the same time,
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// a single message can also be segmented due to MTU of the IP layer.
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// This function guareentees a single TLS message to be read and everything
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// else is left in the buffer.
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i, err := io.ReadFull(conn, buffer[:5])
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if err != nil {
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return
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}
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dataLength := int(binary.BigEndian.Uint16(buffer[3:5]))
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if dataLength > len(buffer) {
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err = errors.New("Reading TLS message: message size greater than buffer. message size: " + strconv.Itoa(dataLength))
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return
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}
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left := dataLength
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readPtr := 5
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for left != 0 {
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// If left > buffer size (i.e. our message got segmented), the entire MTU is read
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// if left = buffer size, the entire buffer is all there left to read
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// if left < buffer size (i.e. multiple messages came together),
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// only the message we want is read
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i, err = io.ReadFull(conn, buffer[readPtr:readPtr+left])
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if err != nil {
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return
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}
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left -= i
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readPtr += i
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}
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n = 5 + dataLength
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return
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}
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// AddRecordLayer adds record layer to data
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func AddRecordLayer(input []byte, typ []byte, ver []byte) []byte {
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length := make([]byte, 2)
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binary.BigEndian.PutUint16(length, uint16(len(input)))
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ret := make([]byte, 5+len(input))
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copy(ret[0:1], typ)
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copy(ret[1:3], ver)
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copy(ret[3:5], length)
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copy(ret[5:], input)
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return ret
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}
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// PeelRecordLayer peels off the record layer
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func PeelRecordLayer(data []byte) []byte {
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ret := data[5:]
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return ret
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}
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