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upstream: fix miscellaneous text problems; ok djm@

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OpenBSD-Commit-ID: 0cbf411a14d8fa0b269b69cbb1b4fc0ca699fe9f
This commit is contained in:
naddy@openbsd.org 2019-11-01 12:10:43 +00:00 committed by Damien Miller
parent 9cac151c2d
commit ad38406fc9
1 changed files with 8 additions and 8 deletions
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16
PROTOCOL.u2f
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@ -22,13 +22,13 @@ given key is backed by hardware. Finally the signature format includes
a monotonic signature counter that can be used (at scale) to detect a monotonic signature counter that can be used (at scale) to detect
concurrent use of a private key, should it be extracted from hardware. concurrent use of a private key, should it be extracted from hardware.
U2F private keys are generatted through an enrollment operation, U2F private keys are generated through an enrollment operation,
which takes an application ID - a URL-like string, typically "ssh:" which takes an application ID - a URL-like string, typically "ssh:"
in this case, but a HTTP origin for the case of web authentication, in this case, but a HTTP origin for the case of web authentication,
and a challenge string (typically randomly generated). The enrollment and a challenge string (typically randomly generated). The enrollment
operation returns a public key, a key handle that must be used to invoke operation returns a public key, a key handle that must be used to invoke
the hardware-backed private key, some flags and signed attestation the hardware-backed private key, some flags and signed attestation
information that may be used to verify that private key is hosted on a information that may be used to verify that a private key is hosted on a
particular hardware instance. particular hardware instance.
It is common for U2F hardware to derive private keys from the key handle It is common for U2F hardware to derive private keys from the key handle
@ -73,7 +73,7 @@ The corresponding private key contains:
The certificate form of a SSH U2F key appends the usual certificate The certificate form of a SSH U2F key appends the usual certificate
information to the public key: information to the public key:
string "sk-ecdsa-sha2-nistp256@openssh.com" string "sk-ecdsa-sha2-nistp256-cert-v01@openssh.com"
string nonce string nonce
ec_point Q ec_point Q
string application string application
@ -98,7 +98,7 @@ choose not to include this information in the public key or save it by
default. default.
Attestation information is very useful however in an organisational Attestation information is very useful however in an organisational
context, where it may be used by an CA as part of certificate context, where it may be used by a CA as part of certificate
issuance. In this case, exposure to the CA of hardware identity is issuance. In this case, exposure to the CA of hardware identity is
desirable. To support this case, OpenSSH optionally allows retaining the desirable. To support this case, OpenSSH optionally allows retaining the
attestation information at the time of key generation. It will take the attestation information at the time of key generation. It will take the
@ -151,16 +151,16 @@ ecdsa_signature field returned from the hardware.
ssh-agent protocol extensions ssh-agent protocol extensions
----------------------------- -----------------------------
ssh-agent requires some protocol extension to support U2F keys. At ssh-agent requires a protocol extension to support U2F keys. At
present the closest analogue to Security Keys in ssh-agent are PKCS#11 present the closest analogue to Security Keys in ssh-agent are PKCS#11
tokens, insofar as they require a middleware library to communicate with tokens, insofar as they require a middleware library to communicate with
the device that holds the keys. Unfortunately, the protocol message used the device that holds the keys. Unfortunately, the protocol message used
to add PKCS#11 keys to ssh-agent does not include any way to send the to add PKCS#11 keys to ssh-agent does not include any way to send the
key handle to the agent as U2F keys require. key handle to the agent as U2F keys require.
To avoid this, without having to add wholy new messages to the agent To avoid this, without having to add wholly new messages to the agent
protocol we will use the existing SSH2_AGENTC_ADD_ID_CONSTRAINED message protocol, we will use the existing SSH2_AGENTC_ADD_ID_CONSTRAINED message
with a new a key constraint extension to encode a path to the middleware with a new key constraint extension to encode a path to the middleware
library for the key. The format of this constraint extension would be: library for the key. The format of this constraint extension would be:
byte SSH_AGENT_CONSTRAIN_EXTENSION byte SSH_AGENT_CONSTRAIN_EXTENSION