Disallow use of DES encryption functions in new programs.

The functions encrypt, setkey, encrypt_r, setkey_r, cbc_crypt,
ecb_crypt, and des_setparity should not be used in new programs,
because they use the DES block cipher, which is unacceptably weak by
modern standards.  Demote all of them to compatibility symbols, and
remove their prototypes from installed headers.  cbc_crypt, ecb_crypt,
and des_setparity were already compat symbols when glibc was
configured with --disable-obsolete-rpc.

POSIX requires encrypt and setkey to be available when _XOPEN_CRYPT
is defined, so this change also removes the definition of X_OPEN_CRYPT
from <unistd.h>.

The entire "DES Encryption" section is dropped from the manual, as is
the mention of AUTH_DES and FIPS 140-2 in the introduction to
crypt.texi.  The documentation of 'memfrob' cross-referenced the DES
Encryption section, which is replaced by a hyperlink to libgcrypt, and
while I was in there I spruced up the actual documentation of
'memfrob' and 'strfry' a little.  It's still fairly jokey, because
those functions _are_ jokes, but they do also have real use cases, so
people trying to use them for real should have all the information
they need.

DES-based authentication for Sun RPC is also insecure and should be
deprecated or even removed, but maybe that can be left as TI-RPC's
problem.

1 files changed, 2 insertions, 0 deletions

diff --git a/manual/conf.texi b/manual/conf.texi
index f1dce4a..dbd1d30 100644
--- a/manual/conf.texi
+++ b/manual/conf.texi
@@ -778,6 +778,8 @@ Inquire about the parameter corresponding to @code{_XOPEN_LEGACY}.
 @item _SC_XOPEN_CRYPT
 @standards{X/Open, unistd.h}
 Inquire about the parameter corresponding to @code{_XOPEN_CRYPT}.
+@Theglibc no longer implements the @code{_XOPEN_CRYPT} extensions,
+so @samp{sysconf (_SC_XOPEN_CRYPT)} always returns @code{-1}.
 
 @item _SC_XOPEN_ENH_I18N
 @standards{X/Open, unistd.h}