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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 09:44:07 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 09:44:07 +0000
commit39ce00b8d520cbecbd6af87257e8fb11df0ec273 (patch)
tree4c21a2674c19e5c44be3b3550b476b9e63d8ae3d /doc/cve-2016-9663
parentInitial commit. (diff)
downloadexim4-39ce00b8d520cbecbd6af87257e8fb11df0ec273.tar.xz
exim4-39ce00b8d520cbecbd6af87257e8fb11df0ec273.zip
Adding upstream version 4.94.2.upstream/4.94.2upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+CVE ID: CVE-2016-9963
+Date: 2016-12-15
+Credits: Bjoern Jacke <bjoern@j3e.de>
+Version(s): 4.69 -> 4.87
+Issue: If several conditions are met, Exim leaks private information
+ to a remote attacker.
+
+Conditions
+==========
+
+If *all* of the following conditions are met
+
+ Build options
+ -------------
+
+ * Exim is built with DKIM enabled (default for newer versions)
+ exim -bV | grep 'Support.*DKIM'
+
+ Runtime options
+ ---------------
+
+ * Exim uses DKIM signing (transport options dkim_private_key,
+ dkim_domain, and other)
+
+ * The dkim_private_key option names a file containing the key.
+
+ exim -bP transports | grep 'dkim_private_key = .'
+
+ * Exim uses PRDR (transport option hosts_try_prdr) (default
+ since 4.86)
+
+ exim -bP transports | grep 'hosts_try_prdr = .'
+
+ *OR*
+
+ Exim uses the LMTP protocol variant for SMTP transport.
+
+ exim -bP transports | grep 'protocol = lmtp'
+
+ Operation
+ ---------
+
+ * Exim transports a multi-recipient message
+
+ * The destination host supports PRDR
+ OR
+ the message transport uses LMTP
+
+ * One or more recipients are rejected after the DATA phase
+
+Impact
+======
+
+Exim leaks the private DKIM signing key to the log files. Additionally,
+if the build option EXPERIMENTAL_DSN_INFO=yes is used, the key material
+is included in the bounce message.
+
+Fix
+===
+
+Install a fixed Exim version:
+
+ 4.88
+ 4.87.1
+
+If you can't install one of the above versions, ask your package
+maintainer for a version containing the backported fix. On request and
+depending on our resources we will support you in backporting the fix.
+(Please note, that Exim project officially doesn't support versions
+prior the current stable version.)
+
+If you think that you MIGHT be affected, we HIGHLY recommend to create
+a new set of DKIM keys and fade out the previous DKIM key soon to make
+sure that a possibly leaked DKIM key can not be misused in the future.
+
+
+Workaround
+==========
+
+Disable PRDR in your outgoing transport(s): set hosts_try_prdr to an
+empty string.
+
+AND do not use the LMTP protocol variant of the SMTP driver.
+
+Indication
+==========
+
+You can check if you where affected already. The mainlog entries look like this:
+
+2016-12-17 09:44:33 10HmaX-0005vi-00 ** baduser@test.ex R=client T=send_to_server H=ip4.ip4.ip4.ip4 [ip4.ip4.ip4.ip4]: PRDR error after -----BEGIN RSA PRIVATE KEY-----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\nfKQax6vhiMq+0qIiEwLA1wavyLVKZ7Mfag+/4NTcDUVC\n-----END RSA PRIVATE KEY-----\n: 550 PRDR R=<baduser@test.ex> refusal
+
+Even if there is no evidence in the existing log files, that a DKIM key
+leakage happened this might have happened in the past, log files might
+have been deleted already but a key leak could have ended up via mail
+bounce in a user mail box