commit d9f777f236cb770a44a5f497cb50e17ed7ed1df5 Author: Yawning Angel <yawning@schwanenlied.me> Date: Thu Mar 12 22:26:30 2015 +0000 Read the ExtORPort cookie on every call to DialOr. This works around tor bug #15240, where the ExtORPort cookie is generated after the pluggable transports are launched, leading to a race condition and DialOr failures. 'ServerInfo.AuthCookie' is deprecated by this change, replaced by 'ServerInfo.AuthCookiePath', however nothing external to goptlib should be using either value in most situations. --- pt.go | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/pt.go b/pt.go index 468440e..d2e7dc1 100644 --- a/pt.go +++ b/pt.go @@ -566,7 +566,7 @@ type ServerInfo struct { Bindaddrs []Bindaddr OrAddr *net.TCPAddr ExtendedOrAddr *net.TCPAddr - AuthCookie []byte + AuthCookiePath string } // Check the server pluggable transports environment, emitting an error message @@ -612,17 +612,10 @@ func ServerSetup(star []string) (info ServerInfo, err error) { return } } - authCookieFilename := getenv("TOR_PT_AUTH_COOKIE_FILE") - if authCookieFilename != "" { - info.AuthCookie, err = readAuthCookieFile(authCookieFilename) - if err != nil { - err = envError(fmt.Sprintf("error reading TOR_PT_AUTH_COOKIE_FILE %q: %s", authCookieFilename, err.Error())) - return - } - } + info.AuthCookiePath = getenv("TOR_PT_AUTH_COOKIE_FILE") // Need either OrAddr or ExtendedOrAddr. - if info.OrAddr == nil && (info.ExtendedOrAddr == nil || info.AuthCookie == nil) { + if info.OrAddr == nil && (info.ExtendedOrAddr == nil || info.AuthCookiePath == "") { err = envError("need TOR_PT_ORPORT or TOR_PT_EXTENDED_SERVER_PORT environment variable") return } @@ -700,12 +693,20 @@ func extOrPortAuthenticate(s io.ReadWriter, info *ServerInfo) error { return err } - expectedServerHash := computeServerHash(info.AuthCookie, clientNonce, serverNonce) + // Work around tor bug #15240 where the auth cookie is generated after + // pluggable transports are launched, leading to a stale cookie getting + // cached forever if it is only read once as part of ServerSetup. + authCookie, err := readAuthCookieFile(info.AuthCookiePath) + if err != nil { + return fmt.Errorf("error reading TOR_PT_AUTH_COOKIE_FILE %q: %s", info.AuthCookiePath, err.Error()) + } + + expectedServerHash := computeServerHash(authCookie, clientNonce, serverNonce) if subtle.ConstantTimeCompare(serverHash, expectedServerHash) != 1 { return fmt.Errorf("mismatch in server hash") } - clientHash = computeClientHash(info.AuthCookie, clientNonce, serverNonce) + clientHash = computeClientHash(authCookie, clientNonce, serverNonce) _, err = s.Write(clientHash) if err != nil { return err @@ -845,7 +846,7 @@ func extOrPortSetup(s io.ReadWriter, addr, methodName string) error { // commands, respectively. If either is "", the corresponding command is not // sent. func DialOr(info *ServerInfo, addr, methodName string) (*net.TCPConn, error) { - if info.ExtendedOrAddr == nil || info.AuthCookie == nil { + if info.ExtendedOrAddr == nil || info.AuthCookiePath == "" { return net.DialTCP("tcp", nil, info.OrAddr) }