Re: [openssl-dev] [Bug] OpenSSL does not send short messages

[Viktor Dukhovni]

[ This question belongs on openssl-users, not openssl-dev.  Please
  reply only to openssl-users. ]

On Tue, Apr 26, 2016 at 05:17:46AM +0200, Alex Hultman wrote:

> SSL_write followed by SSL_shutdown does not actually send the data passed
> to SSL_write if the total data size sent is less than (on my system) 7-8
> bytes.

This does not happen in "openssl s_client".  You're likely doing
something wrong.

In one window I start an openssl server:

$ cipher=ADH-DES-CBC3-SHA
$ seclev= # Make that seclev=":@SECLEVEL=0" with OpenSSL 1.1.0 or later
$ openssl s_server -quiet -cipher "$cipher$seclev" -nocert -accept 12345

I another window I start a client:

$ cipher=ADH-DES-CBC3-SHA
$ seclev= # Make that seclev=":@SECLEVEL=0" with OpenSSL 1.1.0 or later
echo XXX | openssl s_client -debug -no_ign_eof -cipher "$cipher$seclev" 
-connect localhost:12345

On the server side I see the expected output:

XXX

On the client side after lots of handshake messages:

>>> ??? [length 0005]
17 03 03 00 24
write to 0x7f7f8bd003d0 [0x7f7f8c80b203] (41 bytes => 41 (0x29))
 - 17 03 03 00 24 c2 19 ea-c6 f1 a8 c7 74 31 50 3d   $...t1P=
0010 - a1 2f fb f0 d5 4d 2e 85-e0 6a 18 86 27 6a 09 1d   ./...M...j..'j..
0020 - de 98 4e 69 05 57 0f 4c-93..Ni.W.L.
DONE
>>> ??? [length 0005]
15 03 03 00 24
write to 0x7f7f8bd003d0 [0x7f7f8c80b203] (41 bytes => 41 (0x29))
 - 15 03 03 00 24 d2 94 f8-11 dd 69 81 f7 ab cc 8c   $.i.
0010 - c4 13 4c 80 24 d7 50 10-b9 62 74 d7 21 86 16 78   ..L.$.P..bt.!..x
0020 - b4 83 87 da 5e 2f d9 5d-34^/.]4
>>> TLS 1.2Alert [length 0002], warning close_notify
01 00

The first of these is the "XXX" encrypted to 16 bytes, and padded
with a 20-byte SHA1 MAC (the server and client negotiated TLS 1.2
with Encrypt-then-Mac).  The second is the encrypted shutdown alert.

> Is this known behavior?

No.

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Viktor.
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[openssl-dev] [Bug] OpenSSL does not send short messages

[Alex Hultman]

Hi,

I've found a very central bug that affects all my OpenSSL applications
including the official server example code, the vanilla Node.js HTTPs
server and my (arguably non-correct) own server project.

https://github.com/openssl/openssl/issues/992

SSL_write followed by SSL_shutdown does not actually send the data passed
to SSL_write if the total data size sent is less than (on my system) 7-8
bytes.

If you consider the official example:
https://wiki.openssl.org/index.php/Simple_TLS_Server

(Note: I removed "SSL_CTX_set_ecdh_auto(ctx, 1);" to make it compile)

It responds Chrome with ERR_RESPONSE_HEADERS_TRUNCATED, while changing the
text sent to "Hello there" works and shows "Hello there" in Chrome. Same
goes for Curl. I've tested self-signed certs and one "half-signed" (crap
signer).

This is on Linux (Fedora 24) and I have OpenSSL 1.1.0 but I'm pretty sure
Node.js 5.x uses OpenSSL 1.0.2g.

Is this known behavior?
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