vitess.io/vitess@v0.16.2/go/vt/grpcoptionaltls/tls_detector.go (about)

     1  /*
     2  Copyright 2019 The Vitess Authors.
     3  Licensed under the Apache License, Version 2.0 (the "License");
     4  you may not use this file except in compliance with the License.
     5  You may obtain a copy of the License at
     6  
     7  	http://www.apache.org/licenses/LICENSE-2.0
     8  
     9  Unless required by applicable law or agreed to in writing, software
    10  distributed under the License is distributed on an "AS IS" BASIS,
    11  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  See the License for the specific language governing permissions and
    13  limitations under the License.
    14  */
    15  package grpcoptionaltls
    16  
    17  import "io"
    18  
    19  const TLSPeekedBytes = 6
    20  
    21  func looksLikeTLS(bytes []byte) bool {
    22  	if len(bytes) < TLSPeekedBytes {
    23  		return false
    24  	}
    25  	// TLS starts as
    26  	// 0: 0x16 - handshake protocol magic
    27  	// 1: 0x03 - SSL version major
    28  	// 2: 0x00 to 0x03 - SSL version minor (SSLv3 or TLS1.0 through TLS1.3)
    29  	// 3-4: length (2 bytes)
    30  	// 5: 0x01 - handshake type (ClientHello)
    31  	// 6-8: handshake len (3 bytes), equals value from offset 3-4 minus 4
    32  	// HTTP2 initial frame bytes
    33  	// https://tools.ietf.org/html/rfc7540#section-3.4
    34  
    35  	// Definitely not TLS
    36  	if bytes[0] != 0x16 || bytes[1] != 0x03 || bytes[5] != 0x01 {
    37  		return false
    38  	}
    39  	return true
    40  }
    41  
    42  // DetectTLS reads necessary number of bytes from io.Reader
    43  // returns result, bytes read from Reader and error
    44  // No matter if error happens or what flag value is
    45  // returned bytes should be checked
    46  func DetectTLS(r io.Reader) (bool, []byte, error) {
    47  	var bytes = make([]byte, TLSPeekedBytes)
    48  	if n, err := io.ReadFull(r, bytes); err != nil {
    49  		return false, bytes[:n], err
    50  	}
    51  	return looksLikeTLS(bytes), bytes, nil
    52  }