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.

16 files changed, 142 insertions, 303 deletions

diff --git a/ChangeLog b/ChangeLog
index 55d4f3a3c5..d3c4c423e1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,36 @@
+2018-06-29  Zack Weinberg  <zackw@panix.com>
+	    Florian Weimer <fweimer@redhat.com>
+
+	* posix/unistd.h: Do not declare encrypt.
+	(_XOPEN_CRYPT): Remove macro definition.
+	(crypt): Declare only for _USE_MISC.
+	* stdlib/stdlib.h: Do not declare setkey.
+	* crypt/crypt.h: Do not declare encrypt, setkey, encrypt_r, setkey_r.
+	* sunrpc/Makefile: Do not install des_crypt.h nor rpc_des.h.
+
+	* crypt/crypt-entry.c: Make fcrypt a compat symbol.
+	* crypt/crypt_util.c: Make encrypt, encrypt_r, setkey, setkey_r
+	into compat symbols.  Don't define initial_perm if it's not
+	going to be used.
+	* crypt/cert.c: Link explicitly with the expected versions for
+	setkey and encrypt.  If they are not available at all, mark
+	the test as unsupported.
+
+	* sunrpc/des_crypt.c: Unconditionally block linkage with
+	cbc_crypt and ecb_crypt for new binaries.
+	* sunrpc/des_soft.c: Unconditionally block linkage with
+	des_setparity for new binaries.
+
+	* manual/crypt.texi: Remove the entire "DES Encryption"
+	section.  Also remove the paragraph talking about FIPS 140-2
+	from the introduction.
+	* manual/string.texi (strfry, memfrob): Revise.	 Recommend use
+	of libgcrypt for "real" encryption, not DES.
+	* manual/conf.texi (Constants for Sysconf): Mention that
+	_XOPEN_CRYPT is no longer impelemented.
+
+	* conform/data/unistd.h-data: Remove crypt function declaration.
+
 2018-06-29  Florian Weimer  <fweimer@redhat.com>
 
 	[BZ #23351]
diff --git a/NEWS b/NEWS
index d1de6830a1..ebe63a2f40 100644
--- a/NEWS
+++ b/NEWS
@@ -116,6 +116,23 @@ Deprecated and removed features, and other changes affecting compatibility:
   fcntl and LFS support is handled transparently.  Also for Linux, the OFD
   locks act as a cancellation entrypoint.
 
+* The obsolete functions encrypt, encrypt_r, setkey, setkey_r, cbc_crypt,
+  ecb_crypt, and des_setparity are no longer available to newly linked
+  binaries, and the headers <rpc/des_crypt.h> and <rpc/rpc_des.h> are no
+  longer installed.  These functions encrypted and decrypted data with the
+  DES block cipher, which is no longer considered secure.  Software that
+  still uses these functions should switch to a modern cryptography library,
+  such as libgcrypt.
+
+* Reflecting the removal of the encrypt and setkey functions above, the
+  macro _XOPEN_CRYPT is no longer defined.  As a consequence, the crypt
+  function is no longer declared unless _DEFAULT_SOURCE or _GNU_SOURCE is
+  enabled.
+
+* The obsolete function fcrypt is no longer available to newly linked
+  binaries.  It was just another name for the standard function crypt,
+  and it has not appeared in any header file in many years.
+
 Changes to build and runtime requirements:
 
   [Add changes to build and runtime requirements here]
diff --git a/conform/data/stdlib.h-data b/conform/data/stdlib.h-data
index d8fcccc2fb..6913828196 100644
--- a/conform/data/stdlib.h-data
+++ b/conform/data/stdlib.h-data
@@ -149,9 +149,6 @@ function {unsigned short int*} seed48 (unsigned short int[3])
 #if !defined ISO && !defined ISO99 && !defined ISO11 && !defined POSIX && !defined XPG4 && !defined XPG42 && !defined UNIX98
 function int setenv (const char*, const char*, int)
 #endif
-#if !defined ISO && !defined ISO99 && !defined ISO11 && !defined POSIX && !defined POSIX2008
-function void setkey (const char*)
-#endif
 #if !defined ISO && !defined ISO99 && !defined ISO11 && !defined XPG4 && !defined POSIX && !defined POSIX2008
 function {char*} setstate (char*)
 #endif
diff --git a/conform/data/unistd.h-data b/conform/data/unistd.h-data
index ddf4f25132..aa070528e8 100644
--- a/conform/data/unistd.h-data
+++ b/conform/data/unistd.h-data
@@ -437,9 +437,6 @@ function int chroot (const char*)
 function int chown (const char*, uid_t, gid_t)
 function int close (int)
 function size_t confstr (int, char*, size_t)
-#if !defined POSIX && !defined POSIX2008
-function {char*} crypt (const char*, const char*)
-#endif
 #if defined XPG4 || defined XPG42 || defined UNIX98
 function {char*} ctermid (char*)
 function {char*} cuserid (char*)
@@ -449,9 +446,6 @@ allow cuserid
 #endif
 function int dup (int)
 function int dup2 (int, int)
-#if !defined POSIX && !defined POSIX2008
-function void encrypt (char[64], int)
-#endif
 function int execl (const char*, const char*, ...)
 function int execle (const char*, const char*, ...)
 function int execlp (const char*, const char*, ...)
diff --git a/crypt/cert.c b/crypt/cert.c
index 80029e9078..e070ca398d 100644
--- a/crypt/cert.c
+++ b/crypt/cert.c
@@ -10,6 +10,22 @@
 #include <stdlib.h>
 #include "crypt.h"
 
+/* This file tests the deprecated setkey/encrypt interface.  */
+#include <shlib-compat.h>
+#if TEST_COMPAT (libcrypt, GLIBC_2_0, GLIBC_2_28)
+
+#define libcrypt_version_reference(symbol, version) \
+  _libcrypt_version_reference (symbol, VERSION_libcrypt_##version)
+#define _libcrypt_version_reference(symbol, version) \
+  __libcrypt_version_reference (symbol, version)
+#define __libcrypt_version_reference(symbol, version) \
+  __asm__ (".symver " #symbol ", " #symbol "@" #version)
+
+extern void setkey (const char *);
+extern void encrypt (const char *, int);
+libcrypt_version_reference (setkey, GLIBC_2_0);
+libcrypt_version_reference (encrypt, GLIBC_2_0);
+
 int totfails = 0;
 
 int main (int argc, char *argv[]);
@@ -104,3 +120,13 @@ put8 (char *cp)
 	  printf("%02x", t);
 	}
 }
+
+#else /* encrypt and setkey are not available.  */
+
+int
+main (void)
+{
+  return 77; /* UNSUPPORTED */
+}
+
+#endif
diff --git a/crypt/crypt-entry.c b/crypt/crypt-entry.c
index 58691fb384..4e95f74878 100644
--- a/crypt/crypt-entry.c
+++ b/crypt/crypt-entry.c
@@ -35,6 +35,7 @@
 #endif
 
 #include "crypt-private.h"
+#include <shlib-compat.h>
 
 /* Prototypes for local functions.  */
 #ifndef __GNU_LIBRARY__
@@ -176,17 +177,7 @@ crypt (const char *key, const char *salt)
   return __crypt_r (key, salt, &_ufc_foobar);
 }
 
-
-/*
- * To make fcrypt users happy.
- * They don't need to call init_des.
- */
-#ifdef _LIBC
+#if SHLIB_COMPAT (libcrypt, GLIBC_2_0, GLIBC_2_28)
 weak_alias (crypt, fcrypt)
-#else
-char *
-__fcrypt (const char *key, const char *salt)
-{
-  return crypt (key, salt);
-}
+compat_symbol (libcrypt, fcrypt, fcrypt, GLIBC_2_0);
 #endif
diff --git a/crypt/crypt.h b/crypt/crypt.h
index 5da098b715..3cb18de14d 100644
--- a/crypt/crypt.h
+++ b/crypt/crypt.h
@@ -32,16 +32,8 @@ __BEGIN_DECLS
 extern char *crypt (const char *__key, const char *__salt)
      __THROW __nonnull ((1, 2));
 
-/* Setup DES tables according KEY.  */
-extern void setkey (const char *__key) __THROW __nonnull ((1));
-
-/* Encrypt data in BLOCK in place if EDFLAG is zero; otherwise decrypt
-   block in place.  */
-extern void encrypt (char *__glibc_block, int __edflag)
-     __THROW __nonnull ((1));
-
 #ifdef __USE_GNU
-/* Reentrant versions of the functions above.  The additional argument
+/* Reentrant version of 'crypt'.  The additional argument
    points to a structure where the results are placed in.  */
 struct crypt_data
   {
@@ -60,14 +52,6 @@ struct crypt_data
 extern char *crypt_r (const char *__key, const char *__salt,
 		      struct crypt_data * __restrict __data)
      __THROW __nonnull ((1, 2, 3));
-
-extern void setkey_r (const char *__key,
-		      struct crypt_data * __restrict __data)
-     __THROW __nonnull ((1, 2));
-
-extern void encrypt_r (char *__glibc_block, int __edflag,
-		       struct crypt_data * __restrict __data)
-     __THROW __nonnull ((1, 3));
 #endif
 
 __END_DECLS
diff --git a/crypt/crypt_util.c b/crypt/crypt_util.c
index 4958918770..fbfc783751 100644
--- a/crypt/crypt_util.c
+++ b/crypt/crypt_util.c
@@ -34,6 +34,7 @@
 #endif
 
 #include "crypt-private.h"
+#include <shlib-compat.h>
 
 /* Prototypes for local functions.  */
 #ifndef __GNU_LIBRARY__
@@ -150,6 +151,7 @@ static const int sbox[8][4][16]= {
 	}
 };
 
+#if SHLIB_COMPAT (libcrypt, GLIBC_2_0, GLIBC_2_28)
 /*
  * This is the initial
  * permutation matrix
@@ -160,6 +162,7 @@ static const int initial_perm[64] = {
   57, 49, 41, 33, 25, 17,  9,  1, 59, 51, 43, 35, 27, 19, 11, 3,
   61, 53, 45, 37, 29, 21, 13,  5, 63, 55, 47, 39, 31, 23, 15, 7
 };
+#endif
 
 /*
  * This is the final
@@ -785,6 +788,7 @@ _ufc_output_conversion_r (ufc_long v1, ufc_long v2, const char *salt,
   __data->crypt_3_buf[13] = 0;
 }
 
+#if SHLIB_COMPAT (libcrypt, GLIBC_2_0, GLIBC_2_28)
 
 /*
  * UNIX encrypt function. Takes a bitvector
@@ -885,12 +889,14 @@ __encrypt_r (char *__block, int __edflag,
   }
 }
 weak_alias (__encrypt_r, encrypt_r)
+compat_symbol (libcrypt, encrypt_r, encrypt_r, GLIBC_2_0);
 
 void
 encrypt (char *__block, int __edflag)
 {
   __encrypt_r(__block, __edflag, &_ufc_foobar);
 }
+compat_symbol (libcrypt, encrypt, encrypt, GLIBC_2_0);
 
 
 /*
@@ -915,12 +921,15 @@ __setkey_r (const char *__key, struct crypt_data * __restrict __data)
   _ufc_mk_keytab_r((char *) ktab, __data);
 }
 weak_alias (__setkey_r, setkey_r)
+compat_symbol (libcrypt, setkey_r, setkey_r, GLIBC_2_0);
 
 void
 setkey (const char *__key)
 {
   __setkey_r(__key, &_ufc_foobar);
 }
+compat_symbol (libcrypt, setkey, setkey, GLIBC_2_0);
+#endif /* SHLIB_COMPAT (libcrypt, GLIBC_2_0, GLIBC_2_28) */
 
 void
 __b64_from_24bit (char **cp, int *buflen,
diff --git a/manual/conf.texi b/manual/conf.texi
index f1dce4aa44..dbd1d30287 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}
diff --git a/manual/crypt.texi b/manual/crypt.texi
index 99d2d8e092..6bbe2bfdc5 100644
--- a/manual/crypt.texi
+++ b/manual/crypt.texi
@@ -30,21 +30,10 @@ message-digest algorithm that is compatible with modern BSD systems,
 and the other based on the Data Encryption Standard (DES) that is
 compatible with Unix systems.
 
-@vindex AUTH_DES
-@cindex FIPS 140-2
-It also provides support for Secure RPC, and some library functions that
-can be used to perform normal DES encryption.  The @code{AUTH_DES}
-authentication flavor in Secure RPC, as provided by @theglibc{},
-uses DES and does not comply with FIPS 140-2 nor does any other use of DES
-within @theglibc{}.  It is recommended that Secure RPC should not be used
-for systems that need to comply with FIPS 140-2 since all flavors of
-encrypted authentication use normal DES.
-
 @menu
 * Legal Problems::              This software can get you locked up, or worse.
 * getpass::                     Prompting the user for a password.
 * crypt::                       A one-way function for passwords.
-* DES Encryption::              Routines for DES encryption.
 * Unpredictable Bytes::         Randomness for cryptography purposes.
 @end menu
 
@@ -223,196 +212,6 @@ The @code{crypt_r} function is a GNU extension.
 The @code{crypt} and @code{crypt_r} functions are prototyped in the
 header @file{crypt.h}.
 
-@node DES Encryption
-@section DES Encryption
-
-@cindex FIPS 46-3
-The Data Encryption Standard is described in the US Government Federal
-Information Processing Standards (FIPS) 46-3 published by the National
-Institute of Standards and Technology.  The DES has been very thoroughly
-analyzed since it was developed in the late 1970s, and no new
-significant flaws have been found.
-
-However, the DES uses only a 56-bit key (plus 8 parity bits), and a
-machine has been built in 1998 which can search through all possible
-keys in about 6 days, which cost about US$200000; faster searches would
-be possible with more money.  This makes simple DES insecure for most
-purposes, and NIST no longer permits new US government systems
-to use simple DES.
-
-For serious encryption functionality, it is recommended that one of the
-many free encryption libraries be used instead of these routines.
-
-The DES is a reversible operation which takes a 64-bit block and a
-64-bit key, and produces another 64-bit block.  Usually the bits are
-numbered so that the most-significant bit, the first bit, of each block
-is numbered 1.
-
-Under that numbering, every 8th bit of the key (the 8th, 16th, and so
-on) is not used by the encryption algorithm itself.  But the key must
-have odd parity; that is, out of bits 1 through 8, and 9 through 16, and
-so on, there must be an odd number of `1' bits, and this completely
-specifies the unused bits.
-
-@deftypefun void setkey (const char *@var{key})
-@standards{BSD, crypt.h}
-@standards{SVID, crypt.h}
-@safety{@prelim{}@mtunsafe{@mtasurace{:crypt}}@asunsafe{@asucorrupt{} @asulock{}}@acunsafe{@aculock{}}}
-@c The static buffer stores the key, making it fundamentally
-@c thread-unsafe.  The locking issues are only in the initialization
-@c path; cancelling the initialization will leave the lock held, it
-@c would otherwise repeat the initialization on the next call.
-
-The @code{setkey} function sets an internal data structure to be an
-expanded form of @var{key}.  @var{key} is specified as an array of 64
-bits each stored in a @code{char}, the first bit is @code{key[0]} and
-the 64th bit is @code{key[63]}.  The @var{key} should have the correct
-parity.
-@end deftypefun
-
-@deftypefun void encrypt (char *@var{block}, int @var{edflag})
-@standards{BSD, crypt.h}
-@standards{SVID, crypt.h}
-@safety{@prelim{}@mtunsafe{@mtasurace{:crypt}}@asunsafe{@asucorrupt{} @asulock{}}@acunsafe{@aculock{}}}
-@c Same issues as setkey.
-
-The @code{encrypt} function encrypts @var{block} if
-@var{edflag} is 0, otherwise it decrypts @var{block}, using a key
-previously set by @code{setkey}.  The result is
-placed in @var{block}.
-
-Like @code{setkey}, @var{block} is specified as an array of 64 bits each
-stored in a @code{char}, but there are no parity bits in @var{block}.
-@end deftypefun
-
-@deftypefun void setkey_r (const char *@var{key}, {struct crypt_data *} @var{data})
-@deftypefunx void encrypt_r (char *@var{block}, int @var{edflag}, {struct crypt_data *} @var{data})
-@standards{GNU, crypt.h}
-@c setkey_r: @safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{} @asulock{}}@acunsafe{@aculock{}}}
-@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{} @asulock{}}@acunsafe{@aculock{}}}
-
-These are reentrant versions of @code{setkey} and @code{encrypt}.  The
-only difference is the extra parameter, which stores the expanded
-version of @var{key}.  Before calling @code{setkey_r} the first time,
-@code{data->initialized} must be cleared to zero.
-@end deftypefun
-
-The @code{setkey_r} and @code{encrypt_r} functions are GNU extensions.
-@code{setkey}, @code{encrypt}, @code{setkey_r}, and @code{encrypt_r} are
-defined in @file{crypt.h}.
-
-@deftypefun int ecb_crypt (char *@var{key}, char *@var{blocks}, unsigned int @var{len}, unsigned int @var{mode})
-@standards{SUNRPC, rpc/des_crypt.h}
-@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
-
-The function @code{ecb_crypt} encrypts or decrypts one or more blocks
-using DES.  Each block is encrypted independently.
-
-The @var{blocks} and the @var{key} are stored packed in 8-bit bytes, so
-that the first bit of the key is the most-significant bit of
-@code{key[0]} and the 63rd bit of the key is stored as the
-least-significant bit of @code{key[7]}.  The @var{key} should have the
-correct parity.
-
-@var{len} is the number of bytes in @var{blocks}.  It should be a
-multiple of 8 (so that there are a whole number of blocks to encrypt).
-@var{len} is limited to a maximum of @code{DES_MAXDATA} bytes.
-
-The result of the encryption replaces the input in @var{blocks}.
-
-The @var{mode} parameter is the bitwise OR of two of the following:
-
-@vtable @code
-@item DES_ENCRYPT
-@standards{SUNRPC, rpc/des_crypt.h}
-This constant, used in the @var{mode} parameter, specifies that
-@var{blocks} is to be encrypted.
-
-@item DES_DECRYPT
-@standards{SUNRPC, rpc/des_crypt.h}
-This constant, used in the @var{mode} parameter, specifies that
-@var{blocks} is to be decrypted.
-
-@item DES_HW
-@standards{SUNRPC, rpc/des_crypt.h}
-This constant, used in the @var{mode} parameter, asks to use a hardware
-device.  If no hardware device is available, encryption happens anyway,
-but in software.
-
-@item DES_SW
-@standards{SUNRPC, rpc/des_crypt.h}
-This constant, used in the @var{mode} parameter, specifies that no
-hardware device is to be used.
-@end vtable
-
-The result of the function will be one of these values:
-
-@vtable @code
-@item DESERR_NONE
-@standards{SUNRPC, rpc/des_crypt.h}
-The encryption succeeded.
-
-@item DESERR_NOHWDEVICE
-@standards{SUNRPC, rpc/des_crypt.h}
-The encryption succeeded, but there was no hardware device available.
-
-@item DESERR_HWERROR
-@standards{SUNRPC, rpc/des_crypt.h}
-The encryption failed because of a hardware problem.
-
-@item DESERR_BADPARAM
-@standards{SUNRPC, rpc/des_crypt.h}
-The encryption failed because of a bad parameter, for instance @var{len}
-is not a multiple of 8 or @var{len} is larger than @code{DES_MAXDATA}.
-@end vtable
-@end deftypefun
-
-@deftypefun int DES_FAILED (int @var{err})
-@standards{SUNRPC, rpc/des_crypt.h}
-@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
-This macro returns 1 if @var{err} is a `success' result code from
-@code{ecb_crypt} or @code{cbc_crypt}, and 0 otherwise.
-@end deftypefun
-
-@deftypefun int cbc_crypt (char *@var{key}, char *@var{blocks}, unsigned int @var{len}, unsigned int @var{mode}, char *@var{ivec})
-@standards{SUNRPC, rpc/des_crypt.h}
-@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
-
-The function @code{cbc_crypt} encrypts or decrypts one or more blocks
-using DES in Cipher Block Chaining mode.
-
-For encryption in CBC mode, each block is exclusive-ored with @var{ivec}
-before being encrypted, then @var{ivec} is replaced with the result of
-the encryption, then the next block is processed.  Decryption is the
-reverse of this process.
-
-This has the advantage that blocks which are the same before being
-encrypted are very unlikely to be the same after being encrypted, making
-it much harder to detect patterns in the data.
-
-Usually, @var{ivec} is set to 8 random bytes before encryption starts.
-Then the 8 random bytes are transmitted along with the encrypted data
-(without themselves being encrypted), and passed back in as @var{ivec}
-for decryption.  Another possibility is to set @var{ivec} to 8 zeroes
-initially, and have the first block encrypted consist of 8 random
-bytes.
-
-Otherwise, all the parameters are similar to those for @code{ecb_crypt}.
-@end deftypefun
-
-@deftypefun void des_setparity (char *@var{key})
-@standards{SUNRPC, rpc/des_crypt.h}
-@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
-
-The function @code{des_setparity} changes the 64-bit @var{key}, stored
-packed in 8-bit bytes, to have odd parity by altering the low bits of
-each byte.
-@end deftypefun
-
-The @code{ecb_crypt}, @code{cbc_crypt}, and @code{des_setparity}
-functions and their accompanying macros are all defined in the header
-@file{rpc/des_crypt.h}.
-
 @node Unpredictable Bytes
 @section Generating Unpredictable Bytes
 
diff --git a/manual/string.texi b/manual/string.texi
index b07cfb4550..a1c58e58fa 100644
--- a/manual/string.texi
+++ b/manual/string.texi
@@ -36,8 +36,8 @@ too.
 				 for delimiters.
 * Erasing Sensitive Data::      Clearing memory which contains sensitive
                                  data, after it's no longer needed.
-* strfry::                      Function for flash-cooking a string.
-* Trivial Encryption::          Obscuring data.
+* Shuffling Bytes::             Or how to flash-cook a string.
+* Obfuscating Data::            Reversibly obscuring data from casual view.
 * Encode Binary Data::          Encoding and Decoding of Binary Data.
 * Argz and Envz Vectors::       Null-separated string vectors.
 @end menu
@@ -2426,73 +2426,73 @@ functionality under a different name, such as @code{explicit_memset},
 systems it may be in @file{strings.h} instead.
 @end deftypefun
 
-@node strfry
-@section strfry
+
+@node Shuffling Bytes
+@section Shuffling Bytes
 
 The function below addresses the perennial programming quandary: ``How do
 I take good data in string form and painlessly turn it into garbage?''
-This is actually a fairly simple task for C programmers who do not use
-@theglibc{} string functions, but for programs based on @theglibc{},
-the @code{strfry} function is the preferred method for
-destroying string data.
+This is not a difficult thing to code for oneself, but the authors of
+@theglibc{} wish to make it as convenient as possible.
 
-The prototype for this function is in @file{string.h}.
+To @emph{erase} data, use @code{explicit_bzero} (@pxref{Erasing
+Sensitive Data}); to obfuscate it reversibly, use @code{memfrob}
+(@pxref{Obfuscating Data}).
 
 @deftypefun {char *} strfry (char *@var{string})
 @standards{GNU, string.h}
 @safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 @c Calls initstate_r, time, getpid, strlen, and random_r.
 
-@code{strfry} creates a pseudorandom anagram of a string, replacing the
-input with the anagram in place.  For each position in the string,
-@code{strfry} swaps it with a position in the string selected at random
-(from a uniform distribution).  The two positions may be the same.
+@code{strfry} performs an in-place shuffle on @var{string}.  Each
+character is swapped to a position selected at random, within the
+portion of the string starting with the character's original position.
+(This is the Fisher-Yates algorithm for unbiased shuffling.)
+
+Calling @code{strfry} will not disturb any of the random number
+generators that have global state (@pxref{Pseudo-Random Numbers}).
 
 The return value of @code{strfry} is always @var{string}.
 
 @strong{Portability Note:}  This function is unique to @theglibc{}.
-
+It is declared in @file{string.h}.
 @end deftypefun
 
 
-@node Trivial Encryption
-@section Trivial Encryption
-@cindex encryption
-
-
-The @code{memfrob} function converts an array of data to something
-unrecognizable and back again.  It is not encryption in its usual sense
-since it is easy for someone to convert the encrypted data back to clear
-text.  The transformation is analogous to Usenet's ``Rot13'' encryption
-method for obscuring offensive jokes from sensitive eyes and such.
-Unlike Rot13, @code{memfrob} works on arbitrary binary data, not just
-text.
+@node Obfuscating Data
+@section Obfuscating Data
 @cindex Rot13
 
-For true encryption, @xref{Cryptographic Functions}.
+The @code{memfrob} function reversibly obfuscates an array of binary
+data.  This is not true encryption; the obfuscated data still bears a
+clear relationship to the original, and no secret key is required to
+undo the obfuscation.  It is analogous to the ``Rot13'' cipher used on
+Usenet for obscuring offensive jokes, spoilers for works of fiction,
+and so on, but it can be applied to arbitrary binary data.
 
-This function is declared in @file{string.h}.
-@pindex string.h
+Programs that need true encryption---a transformation that completely
+obscures the original and cannot be reversed without knowledge of a
+secret key---should use a dedicated cryptography library, such as
+@uref{https://www.gnu.org/software/libgcrypt/,,libgcrypt}.
+
+Programs that need to @emph{destroy} data should use
+@code{explicit_bzero} (@pxref{Erasing Sensitive Data}), or possibly
+@code{strfry} (@pxref{Shuffling Bytes}).
 
 @deftypefun {void *} memfrob (void *@var{mem}, size_t @var{length})
 @standards{GNU, string.h}
 @safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
 
-@code{memfrob} transforms (frobnicates) each byte of the data structure
-at @var{mem}, which is @var{length} bytes long, by bitwise exclusive
-oring it with binary 00101010.  It does the transformation in place and
-its return value is always @var{mem}.
+The function @code{memfrob} obfuscates @var{length} bytes of data
+beginning at @var{mem}, in place.  Each byte is bitwise xor-ed with
+the binary pattern 00101010 (hexadecimal 0x2A).  The return value is
+always @var{mem}.
 
-Note that @code{memfrob} a second time on the same data structure
-returns it to its original state.
-
-This is a good function for hiding information from someone who doesn't
-want to see it or doesn't want to see it very much.  To really prevent
-people from retrieving the information, use stronger encryption such as
-that described in @xref{Cryptographic Functions}.
+@code{memfrob} a second time on the same data returns it to
+its original state.
 
 @strong{Portability Note:}  This function is unique to @theglibc{}.
-
+It is declared in @file{string.h}.
 @end deftypefun
 
 @node Encode Binary Data
diff --git a/posix/unistd.h b/posix/unistd.h
index 4d149f9945..afb08f5186 100644
--- a/posix/unistd.h
+++ b/posix/unistd.h
@@ -107,9 +107,6 @@ __BEGIN_DECLS
 /* The X/Open Unix extensions are available.  */
 #define _XOPEN_UNIX	1
 
-/* Encryption is present.  */
-#define	_XOPEN_CRYPT	1
-
 /* The enhanced internationalization capabilities according to XPG4.2
    are present.  */
 #define	_XOPEN_ENH_I18N	1
@@ -1118,20 +1115,13 @@ ssize_t copy_file_range (int __infd, __off64_t *__pinoff,
 extern int fdatasync (int __fildes);
 #endif /* Use POSIX199309 */
 
-
-/* XPG4.2 specifies that prototypes for the encryption functions must
-   be defined here.  */
-#ifdef	__USE_XOPEN
+#ifdef __USE_MISC
 /* Encrypt at most 8 characters from KEY using salt to perturb DES.  */
 extern char *crypt (const char *__key, const char *__salt)
      __THROW __nonnull ((1, 2));
+#endif
 
-/* Encrypt data in BLOCK in place if EDFLAG is zero; otherwise decrypt
-   block in place.  */
-extern void encrypt (char *__glibc_block, int __edflag)
-     __THROW __nonnull ((1));
-
-
+#ifdef	__USE_XOPEN
 /* Swab pairs bytes in the first N bytes of the area pointed to by
    FROM and copy the result to TO.  The value of TO must not be in the
    range [FROM - N + 1, FROM - 1].  If N is odd the first byte in FROM
diff --git a/stdlib/stdlib.h b/stdlib/stdlib.h
index 6b1ead31e0..8e23e93557 100644
--- a/stdlib/stdlib.h
+++ b/stdlib/stdlib.h
@@ -958,12 +958,6 @@ extern int getsubopt (char **__restrict __optionp,
 #endif
 
 
-#ifdef __USE_XOPEN
-/* Setup DES tables according KEY.  */
-extern void setkey (const char *__key) __THROW __nonnull ((1));
-#endif
-
-
 /* X/Open pseudo terminal handling.  */
 
 #ifdef __USE_XOPEN2KXSI
diff --git a/sunrpc/Makefile b/sunrpc/Makefile
index 0e2f8d7c9e..85b0b3356a 100644
--- a/sunrpc/Makefile
+++ b/sunrpc/Makefile
@@ -51,7 +51,7 @@ rpcsvc = bootparam_prot.x nlm_prot.x rstat.x \
 headers-sunrpc = $(addprefix rpc/,auth.h auth_unix.h clnt.h pmap_clnt.h \
 				  pmap_prot.h pmap_rmt.h rpc.h rpc_msg.h \
 				  svc.h svc_auth.h types.h xdr.h auth_des.h \
-				  des_crypt.h key_prot.h rpc_des.h) \
+				  key_prot.h) \
 		       $(rpcsvc:%=rpcsvc/%) rpcsvc/bootparam.h
 headers = rpc/netdb.h
 install-others = $(inst_sysconfdir)/rpc
diff --git a/sunrpc/des_crypt.c b/sunrpc/des_crypt.c
index a4d8b2936b..9b4bd2d5dd 100644
--- a/sunrpc/des_crypt.c
+++ b/sunrpc/des_crypt.c
@@ -86,6 +86,9 @@ common_crypt (char *key, char *buf, register unsigned len,
   return desdev == DES_SW ? DESERR_NONE : DESERR_NOHWDEVICE;
 }
 
+/* Note: these cannot be excluded from the build yet, because they are
+   still used internally.  */
+
 /*
  * CBC mode encryption
  */
@@ -102,7 +105,7 @@ cbc_crypt (char *key, char *buf, unsigned int len, unsigned int mode,
   COPY8 (dp.des_ivec, ivec);
   return err;
 }
-libc_hidden_nolink_sunrpc (cbc_crypt, GLIBC_2_1)
+hidden_nolink (cbc_crypt, libc, GLIBC_2_1)
 
 /*
  * ECB mode encryption
@@ -115,4 +118,4 @@ ecb_crypt (char *key, char *buf, unsigned int len, unsigned int mode)
   dp.des_mode = ECB;
   return common_crypt (key, buf, len, mode, &dp);
 }
-libc_hidden_nolink_sunrpc (ecb_crypt, GLIBC_2_1)
+hidden_nolink (ecb_crypt, libc, GLIBC_2_1)
diff --git a/sunrpc/des_soft.c b/sunrpc/des_soft.c
index f884f8f21b..a87de96cc7 100644
--- a/sunrpc/des_soft.c
+++ b/sunrpc/des_soft.c
@@ -71,4 +71,4 @@ des_setparity (char *p)
       p++;
     }
 }
-libc_hidden_nolink_sunrpc (des_setparity, GLIBC_2_1)
+hidden_nolink (des_setparity, libc, GLIBC_2_1)