Bug 2026

Summary:	OpenSSH client leaks username to server
Product:	Portable OpenSSH	Reporter:	Longpoke <longpoke>
Component:	ssh	Assignee:	Assigned to nobody <unassigned-bugs>
Status:	CLOSED INVALID
Severity:	normal	CC:	djm
Priority:	P5
Version:	5.9p1
Hardware:	Other
OS:	Linux

Description Longpoke 2012-07-20 01:47:14 AEST

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Title: OpenSSH client leaks username to server
Context: Some issue tracker that includes portable openssh (https://bugzilla.mindrot.org)

When connecting to an SSH server, OpenSSH will send your username as the SSH username if you don't provide one explicitly. This is an information leak.

Why is this bad?
Imagine Bill Gates is using linux to hack into apple.com. He was told Linux is good, and he is planning on making the next release of windows be an open source Linux distribution. He gets the root password for the SSH server on apple.com. He tries to get on by running "ssh apple.com", it fails for wrong password, then he realizes he forgot to set the username so he runs "ssh root@apple.com". But now apple.com has a login attempt in their logs for the account "billgates" (he was using a botnet which is hardcoded in every Windows kernel, providing an anonymity network to Bill Gates, so apple.com didn't get his IP address). So after Bill Gates changed apple.com to show bad financial reports and say that they're closing down (making them lose all their investors/market share etc), Bill Gates gets arrested because of this irrefutable evidence left in the log file. Now Bill Gates hates Linux forever and will never make Windows be Linux based.
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Comment 1 Damien Miller 2012-07-20 10:14:47 AEST

Assuming this isn't an unsubtle joke:

echo "User notbillgates" > ~/.ssh/config

is all you need.

Comment 2 Damien Miller 2015-08-11 23:04:42 AEST

Set all RESOLVED bugs to CLOSED with release of OpenSSH 7.1