Add the relevant XKCD to the passwd(1) manual page. It already explains
most of the rationale behind this patch.
Add also reference to makepasswd(1), which is a good way to generate
strong passwords. Personally, I commonly run `makepasswd --chars 64` to
create my passwords, or 32 for passwords I need to type interactively
often.
The strength of a password is an exponential formula, where the base is
the size of the character set, and the exponent is the length of the
password. That already shows why long passwords of just lowercase
letters are better than short Pa$sw0rdZ3. But an even more important
point is that humans, when forced to use symbols in a password, are more
likely to do trivial substitutions on simple passwords, which doesn't
increase strength, and can instead give a false sense of strength, which
is dangerous.
Closes: <https://github.com/shadow-maint/shadow/issues/688>
Link: <https://xkcd.com/936/>
Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Use of these macros, apart from the benefits mentioned in the commit
that adds the macros, has some other good side effects:
- Consistency in getting the size of the object from sizeof(type),
instead of a mix of sizeof(type) sometimes and sizeof(*p) other
times.
- More readable code: no casts, and no sizeof(), so also shorter lines
that we don't need to cut.
- Consistency in using array allocation calls for allocations of arrays
of objects, even when the object size is 1.
Cc: Valentin V. Bartenev <vbartenev@gmail.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
- Every non-const pointer converts automatically to void *.
- Every pointer converts automatically to void *.
- void * converts to any other pointer.
- const void * converts to any other const pointer.
- Integer variables convert to each other.
I changed the declaration of a few variables in order to allow removing
a cast.
However, I didn't attempt to edit casts inside comparisons, since they
are very delicate. I also kept casts in variadic functions, since they
are necessary, and in allocation functions, because I have other plans
for them.
I also changed a few casts to int that are better as ptrdiff_t.
This change has triggered some warnings about const correctness issues,
which have also been fixed in this patch (see for example src/login.c).
Signed-off-by: Alejandro Colomar <alx@kernel.org>
It is Undefined Behavior to declare errno (see NOTES in its manual page).
Instead of using the errno dummy declaration, use one that doesn't need
a comment.
Signed-off-by: Alejandro Colomar <alx@kernel.org>
boolean.
* libmisc/basename.c: Avoid implicit conversion of pointer to
boolean.
* libmisc/basename.c, lib/prototypes.h (Basename): Return a
constant string.
* libmisc/basename.c, libmisc/obscure.c, lib/prototypes.h,
libmisc/xmalloc.c, libmisc/getdate.h, libmisc/system.c,
libmisc/getgr_nam_gid.c, libmisc/failure.c, libmisc/valid.c: Add
splint annotations.
* libmisc/chowndir.c: Avoid memory leak.
* libmisc/chowndir.c: Do not check *printf/*puts return value.
* libmisc/chowntty.c: Avoid implicit conversion between integer
types.
* libmisc/obscure.c: Return a bool when possible instead of int.
* libmisc/shell.c: Do not check *printf/*puts return value.
* libmisc/shell.c: Do not check execle return value.
* libmisc/setupenv.c: Avoid implicit conversion between integer
types.
* libmisc/xmalloc.c: size should not be zero to avoid returning
NULL pointers.
* libmisc/hushed.c: Do not check *printf/*puts return value.
* libmisc/system.c: Avoid implicit conversion of integer to
boolean. safe_system last argument is a boolean.
* libmisc/system.c: Check return value of dup2.
* libmisc/system.c: Do not check *printf/*puts return value.
* libmisc/system.c: Do not check execve return value.
* libmisc/salt.c: Do not check *printf/*puts return value.
* libmisc/loginprompt.c: Do not check gethostname return value.
* libmisc/find_new_gid.c, libmisc/find_new_uid.c: Do not check
gr_rewind/pw_rewind return value.
* libmisc/ttytype.c: Limit the number of parsed characters in the
sscanf format.
* libmisc/ttytype.c: Test if a type was really read.
* libmisc/sub.c: Do not check *printf/*puts return value.
* libmisc/sub.c: Avoid implicit conversion of integer to boolean.
* src/userdel.c: Fix typo in comment.
* src/userdel.c: Avoid implicit conversion of boolean to integer.
* src/userdel.c: safe_system last argument is a boolean.
* src/newusers.c: Avoid implicit conversion of boolean to integer.
* src/newusers.c: Avoid implicit conversion of integer to boolean.
* src/usermod.c: Add brackets.
* src/usermod.c: Avoid implicit conversion of characters or
integers to booleans.
* src/vipw.c: Avoid implicit conversion of integer to boolean.
* src/su.c: Avoid implicit conversion of integer to boolean.
* src/su.c: Add brackets.
* src/useradd.c: Avoid implicit conversion of characters or
integers to booleans.
instead of an int.
* libmisc/obscure.c, libmisc/tz.c, src/passwd.c, lib/encrypt.c,
libmisc/copydir.c, lib/prototypes.h: Add splint annotations.
* libmisc/tz.c: Fix some const issues.
* libmisc/tz.c: Avoid multi-statements lines.
* libmisc/tz.c: Add brackets.
* libmisc/copydir.c: Do not check *printf/*puts return value.
* libmisc/copydir.c: Fail if we cannot set or reset the SELinux
fscreate context.
* libmisc/copydir.c: Use xmalloc instead of malloc.
* libmisc/copydir.c: Do not check lutimes return value
* src/vipw.c: Avoid implicit conversion of integer to boolean.
* src/su.c (iswheel): Return a bool instead of an int.
* src/passwd.c: Remove insert_crypt_passwd(). Use xstrdup instead.
* src/passwd.c: Return constant strings when sufficient.
* src/passwd.c: Do not check *printf/*puts return value.
* src/passwd.c: Avoid implicit conversion of character to boolean.
* src/passwd.c: Do not check sleep return value.
* src/sulogin.c: Do not check *printf/*puts return value.
* lib/encrypt.c: Do not check fprintf return value.
Files with no license use the default 3-clauses BSD license. The copyright
were mostly not recorded; they were updated according to the Changelog.
"Julianne Frances Haugh and contributors" changed to "copyright holders
and contributors".
similar(), and simple() as unused.
* libmisc/loginprompt.c: Tag the `sig' parameter of login_exit()
as unused.
* src/expiry.c: Tag the `sig' parameter of catch_signals() as
unused.
* src/su.c: Tag the `sig' parameter of catch_signals() as unused.
* src/su.c: Add int parameter to the prototype of oldsig().
* src/login.c: Tag the `sig' parameter of alarm_handler() as
unused.
* src/sulogin.c: Tag the `sig' parameter of catch_signals() as
unused.
* libmisc/getdate.y: Tag the `string' parameter of yyerror() as
unused.
* libmisc/getdate.y: The string provided to yyerror() is const.
* libmisc/getdate.y: Fix the prototypes of yylex() and yyerror().
default. Keeping the feature enabled is safe. Disabling it permits
to disable the references to the SHA256 and SHA512 password
encryption algorithms from the usage help and manuals (in addition
to the support for these algorithms in the code).
* libmisc/obscure.c, libmisc/salt.c, src/newusers.c,
src/chpasswd.c, src/chgpasswd.c, src/passwd.c: ENCRYPT_METHOD is
always supported in login.defs. Remove the ENCRYPTMETHOD_SELECT
preprocessor condition.
* libmisc/obscure.c, libmisc/salt.c, src/newusers.c,
src/chpasswd.c, src/chgpasswd.c, src/passwd.c: Disable SHA256 and
SHA512 if USE_SHA_CRYPT is not defined (this corresponds to a
subset of the ENCRYPTMETHOD_SELECT sections).
SHA256, and SHA512 exactly (not only the first 3/6 chars).
* libmisc/salt.c (SHA_salt_rounds): Set rounds to the specified
prefered_rounds value, if specified.
* src/gpasswd.c, libmisc/salt.c: Fix compilation warnings (use
size_t for lengths).
* src/chpasswd.c, src/chgpasswd.c: Add missing parenthesis.
shadow-4.0.18.1-sha256.patch. Thanks to Peter Vrabec. Hardly no changes
except re-indent and changes related to recent modifications (max_salt_len
in crypt_make_salt). Changes in lib/defines.h not applied (definition of
ENCRYPTMETHOD_SELECT). I will add a configure check or flag.
