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Fix renegotiation on OpenSSL versions that backport RFC5746.

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Our code assumed that any version of OpenSSL before 0.9.8l could not
possibly require SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION.  This is
so... except that many vendors have backported the flag from later
versions of openssl when they backported the RFC5476 renegotiation
feature.

The new behavior is particularly annoying to detect.  Previously,
leaving SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION unset meant that
clients would fail to renegotiate.  People noticed that one fast!
Now, OpenSSL's RFC5476 support means that clients will happily talk to
any servers there are, but servers won't accept renegotiation requests
from unpatched clients unless SSL_OP_ALLOW_etc is set.  More fun:
servers send back a "no renegotiation for you!" error, which unpatched
clients respond to by stalling, and generally producing no useful
error message.

This might not be _the_ cause of bug 1346, but it is quite likely _a_
cause for bug 1346.
This commit is contained in:
Nick Mathewson 2010-04-13 14:58:30 -04:00
parent 5e679acc72
commit 6ad09cc6af
2 changed files with 11 additions and 4 deletions
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5
changes/use_ssl_option_everywhere Normal file
View file

@ -0,0 +1,5 @@
o Major bugfixes:
- Fix SSL renegotiation behavior on OpenSSL versions that claim to
be earlier than 0.9.8m, but which have in reality backported huge
swaths of 0.9.8m or 0.9.8n renegotiation behavior. Possibly fix
for some cases of bug 1346.

10
src/common/tortls.c
View file

@ -345,8 +345,8 @@ tor_tls_init(void)
* OpenSSL 0.9.8l.
*
* No, we can't just set flag 0x0010 everywhere. It breaks Tor with
* OpenSSL 1.0.0beta3 and later. No, we can't just set option
* 0x00040000L everywhere: before 0.9.8m, it meant something else.
* OpenSSL 1.0.0beta3 and later. On the other hand, we might be able to
* set option 0x00040000L everywhere.
*
* No, we can't simply detect whether the flag or the option is present
* in the headers at build-time: some vendors (notably Apple) like to
@ -370,10 +370,12 @@ tor_tls_init(void)
} else if (version < 0x009080c0L) {
log_notice(LD_GENERAL, "OpenSSL %s [%lx] looks like it's older than "
"0.9.8l, but some vendors have backported 0.9.8l's "
"renegotiation code to earlier versions. I'll set "
"SSL3_FLAGS just to be safe.",
"renegotiation code to earlier versions, and some have "
"backported the code from 0.9.8m or 0.9.8n. I'll set both "
"SSL3_FLAGS and SSL_OP just to be safe.",
SSLeay_version(SSLEAY_VERSION), version);
use_unsafe_renegotiation_flag = 1;
use_unsafe_renegotiation_op = 1;
} else {
log_info(LD_GENERAL, "OpenSSL %s has version %lx",
SSLeay_version(SSLEAY_VERSION), version);