This patch adds the GRND_INSECURE constant from Linux 5.6 to glibc's
sys/random.h. This is also added to the documentation. The constant
acts as a no-op for the Hurd implementation (as that doesn't check
whether the flags are known), which is semantically fine, while older
Linux kernels reject unknown flags with an EINVAL error.
Tested for x86_64.
This is a major rewrite of the description of 'crypt', 'getentropy',
and 'getrandom'.
A few highlights of the content changes:
- Throughout the manual, public headers, and user-visible messages,
I replaced the term "password" with "passphrase", the term
"password database" with "user database", and the term
"encrypt(ion)" with "(one-way) hashing" whenever it was applied to
passphrases. I didn't bother making this change in internal code
or tests. The use of the term "password" in ruserpass.c survives,
because that refers to a keyword in netrc files, but it is adjusted
to make this clearer.
There is a note in crypt.texi explaining that they were
traditionally called passwords but single words are not good enough
anymore, and a note in users.texi explaining that actual passphrase
hashes are found in a "shadow" database nowadays.
- There is a new short introduction to the "Cryptographic Functions"
section, explaining how we do not intend to be a general-purpose
cryptography library, and cautioning that there _are_, or have
been, legal restrictions on the use of cryptography in many
countries, without getting into any kind of detail that we can't
promise to keep up to date.
- I added more detail about what a "one-way function" is, and why
they are used to obscure passphrases for storage. I removed the
paragraph saying that systems not connected to a network need no
user authentication, because that's a pretty rare situation
nowadays. (It still says "sometimes it is necessary" to
authenticate the user, though.)
- I added documentation for all of the hash functions that glibc
actually supports, but not for the additional hash functions
supported by libxcrypt. If we're going to keep this manual section
around after the transition is more advanced, it would probably
make sense to add them then.
- There is much more detailed discussion of how to generate a salt,
and the failure behavior for crypt is documented. (Returning an
invalid hash on failure is what libxcrypt does; Solar Designer's
notes say that this was done "for compatibility with old programs
that assume crypt can never fail".)
- As far as I can tell, the header 'crypt.h' is entirely a GNU
invention, and never existed on any other Unix lineage. The
function 'crypt', however, was in Issue 1 of the SVID and is now
in the XSI component of POSIX. I tried to make all of the
@standards annotations consistent with this, but I'm not sure I got
them perfectly right.
- The genpass.c example has been improved to use getentropy instead
of the current time to generate the salt, and to use a SHA-256 hash
instead of MD5. It uses more random bytes than is strictly
necessary because I didn't want to complicate the code with proper
base64 encoding.
- The testpass.c example has three hardwired hashes now, to
demonstrate that different one-way functions produce different
hashes for the same input. It also demonstrates how DES hashing
only pays attention to the first eight characters of the input.
- There is new text explaining in more detail how a CSPRNG differs
from a regular random number generator, and how
getentropy/getrandom are not exactly a CSPRNG. I tried not to make
specific falsifiable claims here. I also tried to make the
blocking/cancellation/error behavior of both getentropy and
getrandom clearer.
In preparation for a major revision of the documentation for
crypt(_r), getentropy, and getrandom, reorganize crypt.texi. This
patch does not change any text; it only deletes and moves text.
The description of 'getpass' moves to terminal.texi, since all it does
is read a password from the controlling terminal with echo disabled.
The "Legal Problems" section of crypt.texi is dropped, and the
introductory text is shifted down to the "Encrypting Passwords"
section; the next patch will add some new introductory text.
Also, it is no longer true that crypt.texi's top @node needs to have
no pointers. That was a vestige of crypt/ being an add-on. (makeinfo
itself doesn't need @node pointers anymore, but the scripts that
assemble the libc manual's topmost node rely on each chapter-level
node having them.)
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.
The Summary is now generated from @standards, and syntax-checking is
performed. If invalid @standards syntax is detected, summary.pl will
fail, reporting all errors. Failure and error reporting is disabled
for now, however, since much of the manual is still incomplete
wrt. header and standards annotations.
Note that the sorting order of the Summary has changed; summary.pl
respects the locale, like summary.awk did, but the use of LC_ALL=C is
introduced in the Makefile. Other notable deviations are improved
detection of the annotated elements' names, which are used for
sorting, and improved detection of the @node used to reference into
the manual. The most noticeable difference in the rendered Summary is
that entries may now contain multiple lines, one for each header and
standard combination.
summary.pl accepts a `--help' option, which details the expected
syntax of @standards. If errors are reported, the user is directed to
this feature for further information.
* manual/Makefile: Generate summary.texi with summary.pl.
Force use of the C locale. Update Perl dependency comment.
* manual/header.texi: Update reference to summary.awk.
* manual/macros.texi: Refer authors to `summary.pl --help'.
* manual/summary.awk: Remove file.
* manual/summary.pl: New file. Generate summary.texi, and
check for @standards-related syntax errors.
* manual/argp.texi: Convert header and standards @comments to
@standards.
* manual/arith.texi: Likewise.
* manual/charset.texi: Likewise.
* manual/conf.texi: Likewise.
* manual/creature.texi: Likewise.
* manual/crypt.texi: Likewise.
* manual/ctype.texi: Likewise.
* manual/debug.texi: Likewise.
* manual/errno.texi: Likewise.
* manual/filesys.texi: Likewise.
* manual/getopt.texi: Likewise.
* manual/job.texi: Likewise.
* manual/lang.texi: Likewise.
* manual/llio.texi: Likewise.
* manual/locale.texi: Likewise.
* manual/math.texi: Likewise.
* manual/memory.texi: Likewise.
* manual/message.texi: Likewise.
* manual/pattern.texi: Likewise.
* manual/pipe.texi: Likewise.
* manual/process.texi: Likewise.
* manual/resource.texi: Likewise.
* manual/search.texi: Likewise.
* manual/setjmp.texi: Likewise.
* manual/signal.texi: Likewise.
* manual/socket.texi: Likewise.
* manual/startup.texi: Likewise.
* manual/stdio.texi: Likewise.
* manual/string.texi: Likewise.
* manual/sysinfo.texi: Likewise.
* manual/syslog.texi: Likewise.
* manual/terminal.texi: Likewise.
* manual/threads.texi: Likewise.
* manual/time.texi: Likewise.
* manual/users.texi: Likewise.
This commit handles exceptional cases of invalid syntax for the
@standards conversion script.
* manual/crypt.texi: Move a comment out of an @*x list.
* manual/filesys.texi: Refactor some comments, one of which
looks like a standard. Fix incorrectly separated standards.
* manual/locale.texi: Invert an annotation.
* manual/resource.texi: Fix incorrectly separated standards.
* manual/time.texi: Refactor a @vtable that obscures an
annotation.
* manual/users.texi: Refactor multiple headers to occupy a
single @comment.
The Secure RPC implementation in glibc uses DES encryption
during authentication of the user. This use of DES means
that anyone using Sun RPC will likely not be compliant
with FIPS 140-2 which forbids the use of DES.
One solution to the compliance issue is to disable AUTH_DES
and AUTH_KERB, both use DES, when in FIPS compliance mode.
This is not a good idea because it disables all of the even
mildly secure methods of authentication allowing only plain
text methods.
Instead we leave AUTH_DES and AUTH_KERB enabled in FIPS
compliance mode and document the compliance issue in the
manual. FIPS allows this, that is to say that if you can't
fix it you must document the non-compliance.
This commit adds documentation to that effect in the
"DES encryption and password handling" section of the
manual.
