go-ipp/adapter-socket.go

/*
	Copyright 2022 Dolysis Consulting Limited

	Licensed under the Apache License, Version 2.0 (the "License");
	you may not use this file except in compliance with the License.
	You may obtain a copy of the License at
		http://www.apache.org/licenses/LICENSE-2.0
	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.

	For changes see the git log
*/
package ipp

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"os"
	"strconv"
)

var SocketNotFoundError = errors.New("unable to locate CUPS socket")
var CertNotFoundError = errors.New("unable to locate CUPS certificate")

var (
	DefaultSocketSearchPaths = []string{"/var/run/cupsd", "/var/run/cups/cups.sock", "/run/cups/cups.sock"}
	DefaultCertSearchPaths   = []string{"/etc/cups/certs/0", "/run/cups/certs/0"}
)

const DefaultRequestRetryLimit = 3

type SocketAdapter struct {
	host              string
	useTLS            bool
	SocketSearchPaths []string
	CertSearchPaths   []string
	//RequestRetryLimit is the number of times a request will be retried when receiving an authorized status. This usually happens when a CUPs cert is expired, and a retry will use the newly generated cert. Default 3.
	RequestRetryLimit int
}

func NewSocketAdapter(host string, useTLS bool) *SocketAdapter {
	return &SocketAdapter{
		host:              host,
		useTLS:            useTLS,
		SocketSearchPaths: DefaultSocketSearchPaths,
		CertSearchPaths:   DefaultCertSearchPaths,
		RequestRetryLimit: DefaultRequestRetryLimit,
	}
}

//DoRequest performs the given IPP request to the given URL, returning the IPP response or an error if one occurred.
//Additional data will be written to an io.Writer if additionalData is not nil
func (h *SocketAdapter) SendRequest(url string, r *Request, additionalData io.Writer) (*Response, error) {
	for i := 0; i < h.RequestRetryLimit; i++ {
		// encode request
		payload, err := r.Encode()
		if err != nil {
			return nil, fmt.Errorf("unable to encode IPP request: %v", err)
		}

		var body io.Reader
		size := len(payload)

		if r.File != nil && r.FileSize != -1 {
			size += r.FileSize

			body = io.MultiReader(bytes.NewBuffer(payload), r.File)
		} else {
			body = bytes.NewBuffer(payload)
		}

		req, err := http.NewRequest("POST", url, body)
		if err != nil {
			return nil, fmt.Errorf("unable to create HTTP request: %v", err)
		}

		sock, err := h.GetSocket()
		if err != nil {
			return nil, err
		}

		// if cert isn't found, do a request to generate it
		cert, err := h.GetCert()
		if err != nil && err != CertNotFoundError {
			return nil, err
		}

		req.Header.Set("Content-Length", strconv.Itoa(size))
		req.Header.Set("Content-Type", ContentTypeIPP)
		req.Header.Set("Authorization", fmt.Sprintf("Local %s", cert))

		unixClient := http.Client{
			Transport: &http.Transport{
				DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
					return net.Dial("unix", sock)
				},
			},
		}

		// send request
		resp, err := unixClient.Do(req)
		if err != nil {
			return nil, fmt.Errorf("unable to perform HTTP request: %v", err)
		}

		if resp.StatusCode == http.StatusUnauthorized {
			// retry with newly generated cert
			resp.Body.Close()
			continue
		}

		if resp.StatusCode != http.StatusOK {
			resp.Body.Close()
			return nil, fmt.Errorf("server did not return Status OK: %d", resp.StatusCode)
		}

		// buffer response to avoid read issues
		buf := new(bytes.Buffer)
		if _, err := io.Copy(buf, resp.Body); err != nil {
			resp.Body.Close()
			return nil, fmt.Errorf("unable to buffer response: %v", err)
		}

		resp.Body.Close()

		// decode reply
		ippResp, err := NewResponseDecoder(bytes.NewReader(buf.Bytes())).Decode(additionalData)
		if err != nil {
			return nil, fmt.Errorf("unable to decode IPP response: %v", err)
		}

		if err = ippResp.CheckForErrors(); err != nil {
			return nil, fmt.Errorf("received error IPP response: %v", err)
		}

		return ippResp, nil
	}

	return nil, errors.New("request retry limit exceeded")
}

//GetSocket returns the path to the cupsd socket by searching SocketSearchPaths
func (h *SocketAdapter) GetSocket() (string, error) {
	for _, path := range h.SocketSearchPaths {
		fi, err := os.Stat(path)
		if err != nil {
			if os.IsNotExist(err) {
				continue
			} else if os.IsPermission(err) {
				return "", errors.New("unable to access socket: Access denied")
			}
			return "", fmt.Errorf("unable to access socket: %v", err)
		}

		if fi.Mode()&os.ModeSocket != 0 {
			return path, nil
		}
	}

	return "", SocketNotFoundError
}

//GetCert returns the current CUPs authentication certificate by searching CertSearchPaths
func (h *SocketAdapter) GetCert() (string, error) {
	for _, path := range h.CertSearchPaths {
		f, err := os.Open(path)
		if err != nil {
			if os.IsNotExist(err) {
				continue
			} else if os.IsPermission(err) {
				return "", errors.New("unable to access certificate: Access denied")
			}
			return "", fmt.Errorf("unable to access certificate: %v", err)
		}
		defer f.Close()

		buf := new(bytes.Buffer)
		if _, err := io.Copy(buf, f); err != nil {
			return "", fmt.Errorf("unable to access certificate: %v", err)
		}
		return buf.String(), nil
	}

	return "", CertNotFoundError
}

func (h *SocketAdapter) GetHttpUri(namespace string, object interface{}) string {
	proto := "http"
	if h.useTLS {
		proto = "https"
	}

	uri := fmt.Sprintf("%s://%s", proto, h.host)

	if namespace != "" {
		uri = fmt.Sprintf("%s/%s", uri, namespace)
	}

	if object != nil {
		uri = fmt.Sprintf("%s/%v", uri, object)
	}

	return uri
}

func (h *SocketAdapter) TestConnection() error {
	sock, err := h.GetSocket()
	if err != nil {
		return err
	}
	conn, err := net.Dial("unix", sock)
	if err != nil {
		return err
	}
	conn.Close()
	return nil
}