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Diffstat (limited to 'website')
| -rw-r--r-- | website/doc.mdwn | 124 | ||||
| -rw-r--r-- | website/similar.mdwn | 121 |
2 files changed, 123 insertions, 122 deletions
diff --git a/website/doc.mdwn b/website/doc.mdwn index da955ac..cec29ec 100644 --- a/website/doc.mdwn +++ b/website/doc.mdwn @@ -1,8 +1,5 @@ [[!template id="nav"]] [[meta title="Documentation"]] -# Monkeysphere Documentation # -[[toc ]] - ## Dependencies ## Monkeysphere relies on: @@ -23,123 +20,6 @@ Monkeysphere relies on: * [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/) -## 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!) - <ssh@foo.example.net>`) 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. +## Other ## - 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). + * [Similar Projects](/similar) diff --git a/website/similar.mdwn b/website/similar.mdwn new file mode 100644 index 0000000..5bfd4b2 --- /dev/null +++ b/website/similar.mdwn @@ -0,0 +1,121 @@ +[[!template id="nav"]] +[[meta title="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!) + <ssh@foo.example.net>`) 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). |