diff options
Diffstat (limited to 'usr.bin/ssh/PROTOCOL.certkeys')
| -rw-r--r-- | usr.bin/ssh/PROTOCOL.certkeys | 73 |
1 files changed, 44 insertions, 29 deletions
diff --git a/usr.bin/ssh/PROTOCOL.certkeys b/usr.bin/ssh/PROTOCOL.certkeys index 1ed9e206410..a2069f54767 100644 --- a/usr.bin/ssh/PROTOCOL.certkeys +++ b/usr.bin/ssh/PROTOCOL.certkeys @@ -16,7 +16,7 @@ These protocol extensions build on the simple public key authentication system already in SSH to allow certificate-based authentication. The certificates used are not traditional X.509 certificates, with numerous options and complex encoding rules, but something rather -more minimal: a key, some identity information and usage constraints +more minimal: a key, some identity information and usage options that have been signed with some other trusted key. A sshd server may be configured to allow authentication via certified @@ -27,7 +27,7 @@ of acceptance of certified host keys, by adding a similar ability to specify CA keys in ~/.ssh/known_hosts. Certified keys are represented using two new key types: -ssh-rsa-cert-v00@openssh.com and ssh-dss-cert-v00@openssh.com that +ssh-rsa-cert-v01@openssh.com and ssh-dss-cert-v01@openssh.com that include certification information along with the public key that is used to sign challenges. ssh-keygen performs the CA signing operation. @@ -47,7 +47,7 @@ in RFC4252 section 7. New public key formats ---------------------- -The ssh-rsa-cert-v00@openssh.com and ssh-dss-cert-v00@openssh.com key +The ssh-rsa-cert-v01@openssh.com and ssh-dss-cert-v01@openssh.com key types take a similar high-level format (note: data types and encoding are as per RFC4251 section 5). The serialised wire encoding of these certificates is also used for storing them on disk. @@ -57,42 +57,55 @@ these certificates is also used for storing them on disk. RSA certificate - string "ssh-rsa-cert-v00@openssh.com" + string "ssh-rsa-cert-v01@openssh.com" + string nonce mpint e mpint n + uint64 serial uint32 type string key id string valid principals uint64 valid after uint64 valid before - string constraints - string nonce + string critical options + string extensions string reserved string signature key string signature DSA certificate - string "ssh-dss-cert-v00@openssh.com" + string "ssh-dss-cert-v01@openssh.com" + string nonce mpint p mpint q mpint g mpint y + uint64 serial uint32 type string key id string valid principals uint64 valid after uint64 valid before - string constraints - string nonce + string critical options + string extensions string reserved string signature key string signature +The nonce field is a CA-provided random bitstring of arbitrary length +(but typically 16 or 32 bytes) included to make attacks that depend on +inducing collisions in the signature hash infeasible. + e and n are the RSA exponent and public modulus respectively. p, q, g, y are the DSA parameters as described in FIPS-186-2. +serial is an optional certificate serial number set by the CA to +provide an abbreviated way to refer to certificates from that CA. +If a CA does not with to number its certificates it must set this +field to zero. + type specifies whether this certificate is for identification of a user or a host using a SSH_CERT_TYPE_... value. @@ -112,13 +125,15 @@ certificate. Each represents a time in seconds since 1970-01-01 00:00:00. A certificate is considered valid if: valid after <= current time < valid before -constraints is a set of zero or more key constraints encoded as below. +criticial options is a set of zero or more key options encoded as +below. All such options are "critical" in the sense that an implementation +must refuse to authorise a key that has an unrecognised option. -The nonce field is a CA-provided random bitstring of arbitrary length -(but typically 16 or 32 bytes) included to make attacks that depend on -inducing collisions in the signature hash infeasible. +extensions is a set of zero or more optional extensions. These extensions +are not critical, and an implementation that encounters one that it does +not recognise may safely ignore it. No extensions are defined at present. -The reserved field is current unused and is ignored in this version of +The reserved field is currently unused and is ignored in this version of the protocol. signature key contains the CA key used to sign the certificate. @@ -132,22 +147,22 @@ up to, and including the signature key. Signatures are computed and encoded according to the rules defined for the CA's public key algorithm (RFC4253 section 6.6 for ssh-rsa and ssh-dss). -Constraints ------------ +Critical options +---------------- -The constraints section of the certificate specifies zero or more -constraints on the certificates validity. The format of this field +The critical options section of the certificate specifies zero or more +options on the certificates validity. The format of this field is a sequence of zero or more tuples: string name string data -The name field identifies the constraint and the data field encodes -constraint-specific information (see below). All constraints are -"critical", if an implementation does not recognise a constraint +The name field identifies the option and the data field encodes +option-specific information (see below). All options are +"critical", if an implementation does not recognise a option then the validating party should refuse to accept the certificate. -The supported constraints and the contents and structure of their +The supported options and the contents and structure of their data fields are: Name Format Description @@ -159,35 +174,35 @@ force-command string Specifies a command that is executed permit-X11-forwarding empty Flag indicating that X11 forwarding should be permitted. X11 forwarding will - be refused if this constraint is absent. + be refused if this option is absent. permit-agent-forwarding empty Flag indicating that agent forwarding should be allowed. Agent forwarding must not be permitted unless this - constraint is present. + option is present. permit-port-forwarding empty Flag indicating that port-forwarding - should be allowed. If this constraint is + should be allowed. If this option is not present then no port forwarding will be allowed. permit-pty empty Flag indicating that PTY allocation should be permitted. In the absence of - this constraint PTY allocation will be + this option PTY allocation will be disabled. permit-user-rc empty Flag indicating that execution of ~/.ssh/rc should be permitted. Execution of this script will not be permitted if - this constraint is not present. + this option is not present. source-address string Comma-separated list of source addresses from which this certificate is accepted for authentication. Addresses are specified in CIDR format (nn.nn.nn.nn/nn or hhhh::hhhh/nn). - If this constraint is not present then + If this option is not present then certificates may be presented from any source address. -$OpenBSD: PROTOCOL.certkeys,v 1.3 2010/03/03 22:50:40 djm Exp $ +$OpenBSD: PROTOCOL.certkeys,v 1.4 2010/04/16 01:47:25 djm Exp $ |