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client.go
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client.go
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package mau
import (
"context"
"crypto/rsa"
"crypto/sha256"
"crypto/tls"
"crypto/x509"
"encoding/json"
"errors"
"fmt"
"io"
"log"
"net/http"
"os"
"path"
"time"
"github.com/hashicorp/mdns"
"golang.org/x/crypto/openpgp/packet"
)
var (
ErrFriendNotFollowed = errors.New("Friend is not being followed.")
ErrCantFindFriend = errors.New("Couldn't find friend.")
ErrIncorrectPeerCertificate = errors.New("Incorrect Peer certificate.")
)
type Client struct {
account *Account
httpClient *http.Client
}
func NewClient(account *Account, peer Fingerprint) (*Client, error) {
cert, err := account.Certificate()
if err != nil {
return nil, err
}
c := Client{
account: account,
httpClient: &http.Client{
// Prevent Redirects
CheckRedirect: func(_ *http.Request, _ []*http.Request) error { return http.ErrUseLastResponse },
Transport: &http.Transport{
TLSClientConfig: &tls.Config{
Certificates: []tls.Certificate{cert},
InsecureSkipVerify: true,
VerifyPeerCertificate: func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
for _, rawcert := range rawCerts {
certs, err := x509.ParseCertificates(rawcert)
if err != nil {
continue
}
var id Fingerprint
for _, c := range certs {
switch c.PublicKeyAlgorithm {
case x509.RSA:
pubkey := c.PublicKey.(*rsa.PublicKey)
id = packet.NewRSAPublicKey(c.NotBefore, pubkey).Fingerprint
if id == peer {
return nil
}
default:
return x509.ErrUnsupportedAlgorithm
}
}
}
return ErrIncorrectPeerCertificate
},
CipherSuites: []uint16{
tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
tls.TLS_RSA_WITH_AES_256_CBC_SHA,
tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
},
},
},
},
}
return &c, nil
}
func (account *Account) DownloadFriend(ctx context.Context, address string, fingerprint Fingerprint, after time.Time, client *Client) error {
followed := path.Join(account.path, fingerprint.String())
if _, err := os.Stat(followed); err != nil {
return ErrFriendNotFollowed
}
// if no address is provided we'll search for it with MDNS
if address == "" {
addresses := make(chan string, 1)
go findFriend(ctx, fingerprint, addresses)
select {
case address = <-addresses:
case <-ctx.Done():
return ErrCantFindFriend
}
close(addresses)
}
// TODO if we still don't have an address lets search on the internet with Kad
// Get list of remote files since the last modification we have
url := fmt.Sprintf("%s/p2p/%s", address, fingerprint)
req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
if err != nil {
return err
}
req.Header.Add("If-Modified-Since", after.UTC().Format(http.TimeFormat))
resp, err := client.httpClient.Do(req)
if err != nil {
return err
}
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("Peer responded with error: %s", resp.Status)
}
var list []FileListItem
err = json.NewDecoder(resp.Body).Decode(&list)
resp.Body.Close()
if err != nil {
return err
}
// Download each file in order
for i := range list {
select {
case <-ctx.Done():
return nil
default:
err = account.DownloadFile(ctx, address, fingerprint, &list[i], client)
if err != nil {
log.Printf("Error: Downloading File %s\n\t%s", url, err)
}
}
}
return nil
}
func (account *Account) DownloadFile(ctx context.Context, address string, fingerprint Fingerprint, file *FileListItem, client *Client) error {
fpath := path.Join(account.path, fingerprint.String(), file.Name)
f := File{
Path: fpath,
version: false,
}
// check if it's the same file first by checking the size if it's not the same size then we can download it
// if it's the same size then lets double check by summing it
s, err := f.Size()
if err == nil && s == file.Size {
h, err := f.Hash()
if err == nil && h == file.Sum {
return nil
}
}
url := fmt.Sprintf("%s/p2p/%s/%s", address, fingerprint, file.Name)
req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
if err != nil {
return err
}
resp, err := client.httpClient.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("Server returned unsuccessful response %s for %s", resp.Status, url)
}
content, err := io.ReadAll(resp.Body)
if err != nil {
return err
}
if len(content) != int(file.Size) {
return fmt.Errorf("Size is different for %s\nexpected %d received %d\ncontent:\n%s", url, file.Size, len(content), content)
}
hash := sha256.Sum256(content)
h := fmt.Sprintf("%x", hash)
if h != file.Sum {
return fmt.Errorf("Hash sum is different received %s", h)
}
// TODO: check for file signature
// TODO: check for file encrypted to current user
// TODO: keep existing version
err = os.WriteFile(fpath, content, 0600)
if err != nil {
return err
}
return nil
}
func findFriend(ctx context.Context, fingerprint Fingerprint, addresses chan<- string) error {
name := fmt.Sprintf("%s.%s.%s.", fingerprint, MDNSServiceName, MDNSDomain)
entriesCh := make(chan *mdns.ServiceEntry, cap(addresses))
err := mdns.Lookup(MDNSServiceName, entriesCh)
if err != nil {
return err
}
for {
select {
case entry := <-entriesCh:
if entry.Name == name {
addresses <- fmt.Sprintf("%s://%s:%d", URIProtocolName, entry.AddrV4, entry.Port)
}
case <-ctx.Done():
return nil
}
}
}