assuan.go

Documentation: github.com/sassoftware/relic/lib/assuan

     1  //
     2  // Copyright (c) SAS Institute Inc.
     3  //
     4  // Licensed under the Apache License, Version 2.0 (the "License");
     5  // you may not use this file except in compliance with the License.
     6  // You may obtain a copy of the License at
     7  //
     8  //     http://www.apache.org/licenses/LICENSE-2.0
     9  //
    10  // Unless required by applicable law or agreed to in writing, software
    11  // distributed under the License is distributed on an "AS IS" BASIS,
    12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  //
    16  
    17  package assuan
    18  
    19  import (
    20  	"bufio"
    21  	"errors"
    22  	"fmt"
    23  	"net"
    24  	"net/url"
    25  	"strings"
    26  	"sync"
    27  
    28  	"github.com/sassoftware/relic/lib/dlog"
    29  )
    30  
    31  // Simple libassuan client
    32  //
    33  // See: https://www.gnupg.org/software/libassuan/index.html
    34  
    35  const (
    36  	StatusOk      = "OK"
    37  	StatusErr     = "ERR"
    38  	StatusInquire = "INQUIRE"
    39  	StatusData    = "D"
    40  	StatusLines   = "S"
    41  	StatusComment = "#"
    42  )
    43  
    44  type Conn struct {
    45  	conn net.Conn
    46  	r    *bufio.Reader
    47  	mu   sync.Mutex
    48  }
    49  
    50  type Response struct {
    51  	Status        string
    52  	StatusMessage string
    53  	Lines         []string
    54  	Blob          []byte
    55  }
    56  
    57  func (r Response) Error() string {
    58  	return fmt.Sprintf("response error: %s", r.StatusMessage)
    59  }
    60  
    61  type InquireFunc func(inquireLine string, msgLines []string) (string, error)
    62  
    63  var InquireCancel = errors.New("inquiry cancelled")
    64  
    65  func Dial(path string) (*Conn, error) {
    66  	conn, err := net.Dial("unix", path)
    67  	if err != nil {
    68  		return nil, err
    69  	}
    70  	s := &Conn{
    71  		conn: conn,
    72  		r:    bufio.NewReader(conn),
    73  	}
    74  	status, msg, err := s.readLine()
    75  	if err != nil {
    76  		conn.Close()
    77  		return nil, err
    78  	} else if status != StatusOk {
    79  		conn.Close()
    80  		return nil, fmt.Errorf("failed to connect to %s: %s", path, msg)
    81  	}
    82  	return s, nil
    83  }
    84  
    85  func (c *Conn) write(cmd string) error {
    86  	dlog.Printf(7, "> %#v", cmd)
    87  	_, err := c.conn.Write([]byte(cmd))
    88  	return err
    89  }
    90  
    91  func (c *Conn) data(data string) error {
    92  	data = url.PathEscape(data)
    93  	for len(data) > 0 {
    94  		n := 512
    95  		if n > len(data) {
    96  			n = len(data)
    97  		}
    98  		chunk := data[:n]
    99  		data = data[n:]
   100  		if err := c.write(fmt.Sprintf("D %s\n", chunk)); err != nil {
   101  			return err
   102  		}
   103  	}
   104  	return c.write("END\n")
   105  }
   106  
   107  func (c *Conn) readLine() (string, string, error) {
   108  	line, err := c.r.ReadString('\n')
   109  	if err != nil {
   110  		return "", "", err
   111  	}
   112  	line = line[:len(line)-1]
   113  	dlog.Printf(7, "< %#v", line)
   114  	parts := strings.SplitN(line, " ", 2)
   115  	status := parts[0]
   116  	if len(parts) > 1 {
   117  		return status, parts[1], nil
   118  	}
   119  	return status, "", nil
   120  }
   121  
   122  func (c *Conn) read(inquire InquireFunc) (res Response, err error) {
   123  	var quotedBlob string
   124  	var saved error
   125  readloop:
   126  	for {
   127  		status, msg, err := c.readLine()
   128  		if err != nil {
   129  			return res, err
   130  		}
   131  		switch status {
   132  		case StatusData:
   133  			quotedBlob += msg
   134  		case StatusLines:
   135  			msg, err := url.PathUnescape(msg)
   136  			if err != nil {
   137  				return res, err
   138  			}
   139  			res.Lines = append(res.Lines, msg)
   140  		case StatusInquire:
   141  			if inquire != nil {
   142  				d, err := inquire(msg, res.Lines)
   143  				if err != nil {
   144  					c.write("CANCEL\n")
   145  					if err != InquireCancel {
   146  						// raise this once the ERR has been received
   147  						saved = err
   148  					}
   149  				} else {
   150  					if err := c.data(d); err != nil {
   151  						return res, err
   152  					}
   153  				}
   154  			} else {
   155  				c.write("CANCEL\n")
   156  			}
   157  		case StatusComment:
   158  			// no-op
   159  		default:
   160  			res.Status = status
   161  			res.StatusMessage = msg
   162  			break readloop
   163  		}
   164  	}
   165  	if len(quotedBlob) > 0 {
   166  		blob, err := url.PathUnescape(quotedBlob)
   167  		if err != nil {
   168  			return res, err
   169  		}
   170  		res.Blob = []byte(blob)
   171  	}
   172  	err = saved
   173  	return
   174  }
   175  
   176  // Execute a command and retrieve the result.
   177  //
   178  // If an INQUIRE is received then inquire() will be invoked with the text after
   179  // INQUIRE and all status lines received so far. It should return data to send,
   180  // or it can return an err of InquireCancel which will cause a CANCEL to be
   181  // sent and the resulting response to be returned. If inquire is nil then a
   182  // CANCEL is always sent.
   183  func (c *Conn) Transact(command string, inquire InquireFunc) (res Response, err error) {
   184  	c.mu.Lock()
   185  	defer c.mu.Unlock()
   186  	if c.conn == nil {
   187  		return res, errors.New("connection is closed")
   188  	}
   189  	if err := c.write(command + "\n"); err != nil {
   190  		return res, err
   191  	}
   192  	res, err = c.read(inquire)
   193  	if err == nil && res.Status != StatusOk {
   194  		err = res
   195  	}
   196  	return
   197  }
   198  
   199  func (c *Conn) Close() error {
   200  	c.mu.Lock()
   201  	defer c.mu.Unlock()
   202  	if c.conn != nil {
   203  		c.conn.Close()
   204  		c.conn = nil
   205  		c.r = nil
   206  	}
   207  	return nil
   208  }
   209
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