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We're trying to nail down error reporting for TLS version mismatches, and we're seeing a couple of puzzling behaviors. First, and most puzzling... assume these two command lines:
That is, I have a server that won't accept TLSv1.0, and a client that will only accept TLSv1.0. On the server side I see
which makes perfect sense. On the client side I see
which isn't as good, but is still sort of sensible. But when I look at the packets exchanged, I see that the client sends a Client Hello, and the server responds with an ACK and then a FIN-ACK, with no data. It just hangs up the phone. This seems to violate RFC 5246 section E.1: "If server supports (or is willing to use) only versions greater than client_version, it MUST send a "protocol_version" alert message and close the connection.". Where's my protocol version alert? Of course my real case does not involve the sample client and server - it involves my own clients and servers - but I seem to see the same behavior with several servers (notably including the Apache httpd). This looks like it's the same as https://rt.openssl.org/Ticket/Display.html?id=2777 . I'm using 1.0.2o. (But I don't see anything relevant-looking in the 1.0.2p changes.) I've seen similar behavior from 1.0.2o-fips. Am I missing something here, or is this a server-side bug?
And then, on the client side... SSL_connect returns zero. Exactly how that failure differs from a less-than-zero error is not clear, but OK. The docs say to call SSL_get_error(). SSL_get_error() returns 5, SSL_ERROR_SYSCALL. (That seems a little strange, since I don't think there's any system call errors here.) The docs say to consult the error queue and errno. ERR_peek_last_error( ) returns zero. Errno is zero. It failed, but nobody will tell me why. Am I missing something here, or is this a client library bug?
(I have not tracked down exactly how the s_client tool ends up with a message. It seems to use a more intricate mechanism than SSL_connect.)
-- Jordan Brown, Oracle Solaris |
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