commit 2cd7bff3bf00550fbed88472c2f67b3e04c5d54a Author: Damian Johnson atagar@torproject.org Date: Wed Feb 27 14:42:37 2019 -0800

Demonstrate how to use SAFECOOKIE authentication

Wonderful demo for authenticating using SAFECOOKIE by hand (thanks wagon!).

https://trac.torproject.org/projects/tor/ticket/28300#comment:9 --- docs/faq.rst | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 54 insertions(+), 4 deletions(-)

diff --git a/docs/faq.rst b/docs/faq.rst index 4a555d02..3aa7b02a 100644 --- a/docs/faq.rst +++ b/docs/faq.rst @@ -181,10 +181,9 @@ of authentication (including the cookie file's location) by calling 250-VERSION Tor="0.2.5.1-alpha-dev" 250 OK

-Cookie authentication has two flavors: **COOKIE** and **SAFECOOKIE**. Below -we'll show you how to authenticate via COOKIE. SAFECOOKIE authentication is a -lot more involved, and not something you will want to do by hand (though Stem -supports it transparently). +Cookie authentication has two flavors: **COOKIE** and **SAFECOOKIE**. First +we will demonstrate **COOKIE** authentication which is quite a bit simpler, +though Stem supports both transparently.

To get the credential for your AUTHENTICATE command we will use **hexdump**...

@@ -206,6 +205,57 @@ To get the credential for your AUTHENTICATE command we will use **hexdump**... 250 closing connection Connection closed by foreign host.

+**I'm using safe cookie authentication** +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Password and cookie authentication both disclose your credential. This makes +you vulnerable to replay attacks if you accidently connect to a malicious port +or have a man-in-the-middle. **SAFECOOKIE** authentication avoids this through +a two way handshake, but authenticating by hand requires some extra work. + +This demonstration will use **xxd** to for hex conversion and **openssl** for +crypto. First we need to call **AUTHCHALLENGE** with a random one-time token... + +:: + + % CookieString="$(xxd -u -p -c32 < /home/atagar/.tor/control_auth_cookie)" + % ClientNonce="$(xxd -u -p -l32 -c32 < /dev/urandom)" + % printf '%s\n' "${ClientNonce}" + 9C653314CC4CC2C695999CE84EB1B0045E3D59B6AFFE615D624DB4870DD7041E + + % telnet localhost 9051 + Trying 127.0.0.1... + Connected to localhost. + Escape character is '^]'. + AUTHCHALLENGE SAFECOOKIE 9C653314CC4CC2C695999CE84EB1B0045E3D59B6AFFE615D624DB4870DD7041E + 250 AUTHCHALLENGE SERVERHASH=16274D83FC2240DF9D50D74009D9AE107B77EA317F0034D3638C7942F350D1F9 + SERVERNONCE=1C2E73C41FA8537FDD3A59C2ECBE26DFC85E0A05389373AD8C130C0F5795A036 + +Next combine the server challenge with our cookie content. This token will +prove to Tor that we have our authentication cookie without divulging its +content... + +:: + + % ServerNonce="1C2E73C41FA8537FDD3A59C2ECBE26DFC85E0A05389373AD8C130C0F5795A036" + % printf '%s%s%s\n' "${CookieString}" "${ClientNonce}" "${ServerNonce}" | xxd -r -p \ + > | openssl dgst -sha256 -binary -hmac "Tor safe cookie authentication controller-to-server hash" \ + > | xxd -p -u -c32 + A733E09A65E2A6030BF6710D800370FC3AD28E1D2545E1692D160545D93CEE68 + +We can now authenticate using this token... + +:: + + AUTHENTICATE A733E09A65E2A6030BF6710D800370FC3AD28E1D2545E1692D160545D93CEE68 + 250 OK + GETINFO version + 250-version=0.2.5.1-alpha-dev (git-245ecfff36c0cecc) + 250 OK + QUIT + 250 closing connection + Connection closed by foreign host. + **I'm using password authentication** ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~