SSL-PROBLEMS: describes common curl+SSL problems

docs/Makefile.am

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-# Copyright (C) 1998 - 2013, Daniel Stenberg, <daniel@haxx.se>, et al.
+# Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
 #
 # This software is licensed as described in the file COPYING, which
 # you should have received as part of this distribution. The terms
@@ -37,7 +37,8 @@ EXTRA_DIST = MANUAL BUGS CONTRIBUTE FAQ FEATURES INTERNALS SSLCERTS	 \
  README.win32 RESOURCES TODO TheArtOfHttpScripting THANKS VERSIONS	 \
  KNOWN_BUGS BINDINGS $(man_MANS) $(HTMLPAGES) HISTORY INSTALL		 \
  $(PDFPAGES) LICENSE-MIXING README.netware DISTRO-DILEMMA INSTALL.devcpp \
- MAIL-ETIQUETTE HTTP-COOKIES LIBCURL-STRUCTS SECURITY RELEASE-PROCEDURE
+ MAIL-ETIQUETTE HTTP-COOKIES LIBCURL-STRUCTS SECURITY RELEASE-PROCEDURE  \
+ SSL-PROBLEMS
 
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docs/SSL-PROBLEMS

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+SSL problems
+
+  First, let's establish that we often refer to TLS and SSL interchangably as
+  SSL here. The current protocol is called TLS, it was called SSL a long time
+  ago.
+
+  There are several known reasons why a connection that involves SSL might
+  fail. This is a document that attempts to details the most common ones and
+  how to mitigate them.
+
+CA certs
+
+  CA certs are used to digitally verify the server's certificate. You need a
+  "ca bundle" for this. See lots of more details on this in the SSLCERTS
+  document.
+
+SSL version
+
+  Some broken servers fail to support the protocol negotiation properly that
+  SSL servers are supposed to handle. This may cause the connection to fail
+  completely. Sometimes you may need to explicity select a SSL version to use
+  when connecting to make the connection succeed.
+
+  An additional complication can be that modern SSL libraries sometimes are
+  built with support for older SSL and TLS versions disabled!
+
+SSL ciphers
+
+  Clients give servers a list of ciphers to select from. If the list doens't
+  include any ciphers the server wants/can use, the connection handshake
+  fails.
+
+  curl has recently disabled the user of a whole bunch of seriously insecure
+  ciphers from its default set (slightly depending on SSL backend in use).
+
+  You may have to explicitly provide an alternative list of ciphers for curl
+  to use to allow the server to use a WEAK cipher for you.
+
+  Note that these weak ciphers are identified as flawed. For example, this
+  includes symmetric ciphers with less than 128 bit keys and RC4.
+
+  References:
+
+  http://tools.ietf.org/html/draft-popov-tls-prohibiting-rc4-01
+  
+Allow BEAST
+
+  BEAST is the name of a TLS 1.0 attack that surfaced 2011. When adding means
+  to mitigate this attack, it turned out that some broken servers out there in
+  the wild didn't work properly with the BEAST mitigation in place.
+
+  To make such broken servers work, the --ssl-allow-beast option was
+  introduced. Exactly as it sounds, it re-introduces the BEAST vulnerability
+  but on the other hand it allows curl to connect to that kind of strange
+  servers.