[Bug 2737] New: function identity_sign() assume private key's pub part as same as the .pub key.

[bugzilla-daemon at bugzilla.mindrot.org]

https://bugzilla.mindrot.org/show_bug.cgi?id=2737

            Bug ID: 2737
           Summary: function identity_sign() assume private key's pub part
                    as same as the .pub key.
           Product: Portable OpenSSH
           Version: 7.5p1
          Hardware: Other
                OS: Other
            Status: NEW
          Severity: enhancement
          Priority: P5
         Component: ssh
          Assignee: unassigned-bugs at mindrot.org
          Reporter: jj.net at 163.com

1: we use 'ssh-keygen' create two  rsa pub/pri key pair with empty
passphrase.
and names it to:
<id_rsa1, id_rsa1.pub>
<id_rsa2, id_rsa2.pub>

2: add two pub key to localhost sshd:
cat id_rsa1.pub >> ~/.ssh/authorized_keys
cat id_rsa2.pub >> ~/.ssh/authorized_keys

3: copy the unmatch pub/pri key to ~/.ssh directory
cp id_rsa1 ~/.ssh/id_rsa
cp id_rsa2.pub ~/.ssh/id_rsa.pub

4: login to localhost without agent.
SSH_AUTH_SOCK= ssh 127.0.0.1 -vvv
can see ssh prompt user input password because of
method pubkey failed. the reasion is identity_sign() used
the id_rsa2.pub as pubkey, and signed it by id_rsa1 private key. that
sshd verify signature failed.

but, if you remove ~/.ssh/id_rsa.pub,
ssh client will used full ~/.ssh/id_rsa (extract pubkey,privatekey)
through
userauth_pubkey()
 -->sign_and_send_pubkey()
    -->identity_sign()
and login success.

i think ssh designed to login use pubkey as possible we you can.
and if id_rsa unmatch id_rsa.pub, ssh should trust id_rsa and drop the
rsa.pub file,  try do login again as id_rsa.pub not exist.

-- 
You are receiving this mail because:
You are watching the assignee of the bug.