command@ubuntu# grep "AuthorizedKeysFile" /etc/ssh/sshd_config 
AuthorizedKeysFile %h/.ssh/me.pro

not using default authorized_keys file, after upgrade it not work...

You put a tab in the authorized_keys file itself or after the directive in sshd_config?

(In reply to Darren Tucker from comment #2)
> You put a tab in the authorized_keys file itself or after the
> directive in sshd_config?

authorized_keys file itself

$ cat .ssh/authorized_keys_renamed
xxxx{\tab}sign
xxxx{\tab}sign
xxxx{\tab}sign

Created attachment 2878 [details]
Allow a single tab instead of space between key type and key.

Looks like the code in question is in sshkey.c:sshkey_read(), and that tabs are accepted in many places but not all.  In that code's defense, the sshd(8) man page specifies that these things are space-separated.

        case KEY_UNSPEC:
[...]
                space = strchr(cp, ' ');
... but later:
                        while (*space == ' ' || *space == '\t')
                                space++;

Please try the attached patch, which should allow a single tab character instead of a space.

(In reply to Darren Tucker from comment #4)
> Created attachment 2878 [details]
> Allow a single tab instead of space between key type and key.

Looks like this causes a regression test failure so further investigation is needed.

*** Bug 2294 has been marked as a duplicate of this bug. ***