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https://issues.apache.org/jira/browse/DIRMINA-1143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17354300#comment-17354300
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Thomas Wolf commented on DIRMINA-1143:
--------------------------------------
Interesting. We had a similar bug report in [Eclipse bug
545939|https://bugs.eclipse.org/bugs/show_bug.cgi?id=545939] two years ago, but
we never identified the root cause. We just made that
{{doReadIdentification()}} more lenient and since then that problem seems to
have disappeared. (See [JGit commit
b8a514f|https://git.eclipse.org/r/c/jgit/jgit/+/146047/].) At least we never
had any report about this problem anymore.
JGit didn't submit this upstream at MINA sshd since we never figured out what
the real cause of the problem was, so it's unclear whether the JGit "fix" for
this is really the right fix.
If you can reproduce this easily: what kind of server is this? Does it send any
preamble lines before its SSH identification string? Do you have any traces for
cases when the problem occurs vs. cases when the problem does _not_ occur? Why
is that server sending NULs before its SSH identification?
Off-topic: there's a separate Jira project "MINA SSHD". Unfortunately I cannot
move this issue to the correct project. Normally Jira has a "Move Issue"
command, but here I don't see it.
> sftp authentication fails with "Incorrect identification (null characters not
> allowed) - at line 1 character #1 after ''
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: DIRMINA-1143
> URL: https://issues.apache.org/jira/browse/DIRMINA-1143
> Project: MINA
> Issue Type: Bug
> Components: Core
> Environment: Ubuntu Linux 18.04, Java 11.
> Reporter: Frits Jalvingh
> Priority: Major
>
> I am having this intermittent error when authenticating to an sftp server. It
> is always the same server and always the same program; connecting fails about
> once every 5 times with this error coming from SessionHelper.java, method
> doReadIdentification. I had this error before and upgraded to Mina 2.6.0 from
> maven (org.apache.sshd, sshd-core et al) but that changed nothing. The code
> runs on Ubuntu Linux 18.04 (Azure, sigh) with Java 11.I tried to do some
> debugging and for that I changed SessionHelper so that it dumps the
> information that it is trying to read at that time from its buffer. Because
> that always died with that NUL character as the first character read I made
> the code continue to read a bit so that there might be some context.. What is
> present in that buffer at this time is this:
>
> {{0000: 00 00 01 d4 0b 14 8a e8 5f 65 22 7b 97 4f 2d 61 ........_e"{.O-a}}
> {{0010: 12 75 19 81 6e 1a 00 00 00 47 64 69 66 66 69 65 .u..n....Gdiffie}}
> {{0020: 2d 68 65 6c 6c 6d 61 6e 2d 67 72 6f 75 70 2d 65 -hellman-group-e}}
> {{0030: 78 63 68 61 6e 67 65 2d 73 68 61 32 35 36 2c 64 xchange-sha256,d}}
> {{0040: 69 66 66 69 65 2d 68 65 6c 6c 6d 61 6e 2d 67 72 iffie-hellman-gr}}
> {{0050: 6f 75 70 2d 65 78 63 68 61 6e 67 65 2d 73 68 61 oup-exchange-sha}}
> {{0060: 31 00 00 00 0f 73 73 68 2d 72 73 61 2c 73 73 68 1....ssh-rsa,ssh}}
> {{0070: 2d 64 73 73 00 00 00 41 61 65 73 31 32 38 2d 63 -dss...Aaes128-c}}
> {{0080: 74 72 2c 61 65 73 31 39 32 2d 63 74 72 2c 61 65 tr,aes192-ctr,ae}}
> {{0090: 73 32 35 36 2d 63 74 72 2c 61 65 73 31 32 38 2d s256-ctr,aes128-}}
> {{00a0: 63 62 63 2c 61 65 73 31 39 32 2d 63 62 63 2c 61 cbc,aes192-cbc,a}}
> {{00b0: 65 73 32 35 36 2d 63 62 63 00 00 00 41 61 65 73 es256-cbc...Aaes}}
> {{00c0: 31 32 38 2d 63 74 72 2c 61 65 73 31 39 32 2d 63 128-ctr,aes192-c}}
> {{00d0: 74 72 2c 61 65 73 32 35 36 2d 63 74 72 2c 61 65 tr,aes256-ctr,ae}}
> {{00e0: 73 31 32 38 2d 63 62 63 2c 61 65 73 31 39 32 2d s128-cbc,aes192-}}
> {{00f0: 63 62 63 2c 61 65 73 32 35 36 2d 63 62 63 00 cbc,aes256-cbc.}}
>
> The error occurs when reading that 00 at offset 0000; the rest of the data is
> there by looking into the rest of that buffer..
> I can quite easily reproduce this, so if more data is needed I should be able
> to provide it..
>
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