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authormarha <marha@users.sourceforge.net>2014-06-26 09:35:54 +0200
committermarha <marha@users.sourceforge.net>2014-06-26 09:35:54 +0200
commitd47db8d4713de42ccca071c9e8401fc7a213ed49 (patch)
tree7189b3c025315c514ae9d2835810b94d0e4e0e01 /openssl/doc/crypto/CMS_decrypt.pod
parent880395e8c3f451bf34b96da76fcee133b356e966 (diff)
parentc30d5eefc96925b4bef781806c7a0114eca1b8e0 (diff)
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Merge remote-tracking branch 'origin/released'
* origin/released: Opdated to openssl-1.0.1h xkeyboard-config fontconfig libX11 libxcb xcb-proto mesa xserver git update 26 June 2014 Conflicts: openssl/Makefile
Diffstat (limited to 'openssl/doc/crypto/CMS_decrypt.pod')
-rw-r--r--openssl/doc/crypto/CMS_decrypt.pod16
1 files changed, 15 insertions, 1 deletions
diff --git a/openssl/doc/crypto/CMS_decrypt.pod b/openssl/doc/crypto/CMS_decrypt.pod
index d857e4f93..3fa9212af 100644
--- a/openssl/doc/crypto/CMS_decrypt.pod
+++ b/openssl/doc/crypto/CMS_decrypt.pod
@@ -27,7 +27,21 @@ function or errors about unknown algorithms will occur.
Although the recipients certificate is not needed to decrypt the data it is
needed to locate the appropriate (of possible several) recipients in the CMS
-structure. If B<cert> is set to NULL all possible recipients are tried.
+structure.
+
+If B<cert> is set to NULL all possible recipients are tried. This case however
+is problematic. To thwart the MMA attack (Bleichenbacher's attack on
+PKCS #1 v1.5 RSA padding) all recipients are tried whether they succeed or
+not. If no recipient succeeds then a random symmetric key is used to decrypt
+the content: this will typically output garbage and may (but is not guaranteed
+to) ultimately return a padding error only. If CMS_decrypt() just returned an
+error when all recipient encrypted keys failed to decrypt an attacker could
+use this in a timing attack. If the special flag B<CMS_DEBUG_DECRYPT> is set
+then the above behaviour is modified and an error B<is> returned if no
+recipient encrypted key can be decrypted B<without> generating a random
+content encryption key. Applications should use this flag with
+B<extreme caution> especially in automated gateways as it can leave them
+open to attack.
It is possible to determine the correct recipient key by other means (for
example looking them up in a database) and setting them in the CMS structure