X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=website%2Fdoc.mdwn;h=6a978ce49d61a0ae93057bd921ee818bb4996944;hb=e7a65d28df1b843acd486cc16756d7e0764d85f2;hp=7081ee4d37f630277c223e9386ec7b7f2d80a5ad;hpb=c329ccb6fd64234ec64fed0f0a4262a5522e8f58;p=monkeysphere.git diff --git a/website/doc.mdwn b/website/doc.mdwn index 7081ee4..6a978ce 100644 --- a/website/doc.mdwn +++ b/website/doc.mdwn @@ -1,15 +1,143 @@ [[!template id="nav"]] +[[meta title="Documentation"]] -# Monkeysphere Documentation # +# Dependencies # +Monkeysphere relies on: -## Dependencies ## + * [GnuTLS](http://gnutls.org/) version 2.4.0 or later + * [OpenSSH](http://openssh.com/) + * [GnuPG](http://gnupg.org/) - * Monkeysphere relies on [GnuTLS](http://gnutls.org/) version 2.4.0 or later. +# Getting started # -## References ## + * Getting started as a [user](/getting-started-user) + * Getting started as a [server admin](/getting-started-admin) + +# References # * [Initial specifications at CMRG](http://cmrg.fifthhorseman.net/wiki/OpenPGPandSSH) * [OpenPGP (RFC 4880)](http://tools.ietf.org/html/rfc4880) * [Secure Shell Authentication Protocol (RFC 4252)](http://tools.ietf.org/html/rfc4252) -* [URI scheme for SSH, RFC draft](http://tools.ietf.org/wg/secsh/draft-ietf-secsh-scp-sftp-ssh-uri/) + * [URI scheme for SSH, RFC draft](http://tools.ietf.org/wg/secsh/draft-ietf-secsh-scp-sftp-ssh-uri/) + +# Similar Projects # + +The monkeysphere isn't the only project intending to implement a PKI +for OpenSSH. We provide links to these other projects because they're +interesting, though we have concerns with their approaches. + +All of the other projects we've found so far require a patched version +of OpenSSH, which makes adoption more difficult. Most people don't +build their own software, and simply overlaying a patched binary is +associated with significant maintenance (and therefore security) +problems. + +While ultimately contributing a patch to +[OpenSSH](http://openssh.com/) (or any +[free](http://www.chiark.greenend.org.uk/~sgtatham/putty/) +[SSH](http://www.lysator.liu.se/~nisse/lsh/) +[implementation](http://matt.ucc.asn.au/dropbear/dropbear.html)) is +not a bad thing, we hope to be able to better establish the use of a +PKI without resorting to source modification. + +### openssh-gpg ### + +[openssh-gpg](http://www.red-bean.com/~nemo/openssh-gpg/) is a patch +against OpenSSH to support OpenPGP certificates. According to its +documentation, it is intended to support [`pgp-sign-rsa` and +`pgp-sign-dss` public key algorithms for hosts, as specified by the +IETF](http://tools.ietf.org/html/rfc4253#section-6.6). + +Some concerns with `openssh-gpg`: + + * This patch is old; it doesn't appear to have been maintained beyond + OpenSSH 3.6p1. As of this writing, OpenSSH 5.1p1 is current. + + * It only provides infrastructure in one direction: the user + authenticating the host by name. There doesn't seem to be a + mechanism for dealing with identifying users by name, or allowing + users to globally revoke or update keys. + + * The choice of User ID (`anything goes here (and here!) + `) for host keys overlaps with the current use + of the User ID space. While it's unlikely that someone actually + uses this e-mail address in the web of trust, it would be a nasty + collision, as the holder of that key could impersonate the server + in question. The monkeysphere uses [User IDs of the form + `ssh://foo.example.net`](http://tools.ietf.org/wg/secsh/draft-ietf-secsh-scp-sftp-ssh-uri/) + to avoid collisions with existing use. + + * It's not clear that `openssh-gpg` acknowledges or respects the + [usage flags](http://tools.ietf.org/html/rfc4880#section-5.2.3.21) + on the host keys. This means that it could accept a "sign-only" + key as suitable for authenticating a host, despite the + clearly-marked intentions of the key-holder. + +### Perspectives OpenSSH client ### + +[The Perspectives project](http://www.cs.cmu.edu/~perspectives/) at +CMU has released an [openssh client that uses network +notaries](http://www.cs.cmu.edu/~perspectives/openssh.html) to bolster +your confidence in newly-seen keys. This offers a defense against a +narrow MITM attack (e.g. by someone who controls your local gateway) +by simply verifying that other machines from around the network see +the same keys for the remote host that you're seeing. + +This tactic is quite useful, but doesn't take the system as far as it +could go, and doesn't tie into any existing web of trust. + +Some concerns with the Perspectives OpenSSH client: + + * This client won't help if you are connecting to machines behind + firewalls, on NAT'ed LANs, with source IP filtering, or otherwise + in a restricted network state. + + * There is still a question of why you should trust these particular + notaries during your verification. Who are the notaries? How + could they be compromised? + + * It only provides infrastructure in one direction: the user + authenticating the host by name. There is no mechanism for dealing + with identifying users by name, or allowing users to globally + revoke or change keys. + + * It doesn't provide any mechanism for key rotation or revocation: + Perspectives won't help you if you need to re-key your machine. + +### OpenSSH with X.509v3 certificates ### + +Roumen Petrov [maintains a patch to OpenSSH that works with the X.509 +PKI model](http://www.roumenpetrov.info/openssh/). This is the +certificate hierarchy commonly used by TLS (and SSL). + +Some concerns about OpenSSH with X.509v3: + + * the X.509 certificate specification itself [encourages corporate + consolidation and centralized global "trust" because of its + single-issuer architectural + limitation](http://lair.fifthhorseman.net/~dkg/tls-centralization/). + This results in an expensive and cumbersome system for smaller + players, and it also doesn't correspond to the true distributed + nature of human-to-human trust. Furthermore, centralized global + "trusted authorities" create a tempting target for attack, and a + single-point-of-failure if an attack is successful. + + Depending on how you declare your trust relationships, OpenPGP is + capable of providing the same hierarchical structure as X.509, but + it is not limited to such a structure. The OpenPGP Web of Trust + model is more flexible and more adaptable to represent real-world + trust than X.509's rigid hierarchy. + + * X.509 certificates can identify hosts by name, but not by + individual service. This means that a compromised web or e-mail + server with access to the X.509 key for that service could re-use + its certificate as an SSH server, and it would be able to + masquerade successfully. + + The monkeysphere uses [User IDs of the form + `ssh://foo.example.net`](http://tools.ietf.org/wg/secsh/draft-ietf-secsh-scp-sftp-ssh-uri/), + so they are not by-default shared across services on the same host + (you can still share a key across services on the same host if you + like, but the service User IDs can be certified independently of + one another).