github.com/mholt/caddy-l4@v0.0.0-20241104153248-ec8fae209322/modules/l4ssh/matcher.go (about)

     1  // Copyright 2020 Matthew Holt
     2  //
     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 l4ssh
    16  
    17  import (
    18  	"bytes"
    19  	"io"
    20  
    21  	"github.com/caddyserver/caddy/v2"
    22  	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
    23  
    24  	"github.com/mholt/caddy-l4/layer4"
    25  )
    26  
    27  func init() {
    28  	caddy.RegisterModule(&MatchSSH{})
    29  }
    30  
    31  // MatchSSH is able to match SSH connections.
    32  type MatchSSH struct{}
    33  
    34  // CaddyModule returns the Caddy module information.
    35  func (*MatchSSH) CaddyModule() caddy.ModuleInfo {
    36  	return caddy.ModuleInfo{
    37  		ID:  "layer4.matchers.ssh",
    38  		New: func() caddy.Module { return new(MatchSSH) },
    39  	}
    40  }
    41  
    42  // Match returns true if the connection looks like SSH.
    43  func (m *MatchSSH) Match(cx *layer4.Connection) (bool, error) {
    44  	p := make([]byte, len(sshPrefix))
    45  	_, err := io.ReadFull(cx, p)
    46  	if err != nil {
    47  		return false, err
    48  	}
    49  	return bytes.Equal(p, sshPrefix), nil
    50  }
    51  
    52  var sshPrefix = []byte("SSH-")
    53  
    54  // UnmarshalCaddyfile sets up the MatchSSH from Caddyfile tokens. Syntax:
    55  //
    56  //	ssh
    57  func (m *MatchSSH) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
    58  	_, wrapper := d.Next(), d.Val() // consume wrapper name
    59  
    60  	// No same-line options are supported
    61  	if d.CountRemainingArgs() > 0 {
    62  		return d.ArgErr()
    63  	}
    64  
    65  	// No blocks are supported
    66  	if d.NextBlock(d.Nesting()) {
    67  		return d.Errf("malformed layer4 connection matcher '%s': blocks are not supported", wrapper)
    68  	}
    69  
    70  	return nil
    71  }
    72  
    73  // Interface guards
    74  var (
    75  	_ layer4.ConnMatcher    = (*MatchSSH)(nil)
    76  	_ caddyfile.Unmarshaler = (*MatchSSH)(nil)
    77  )