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login.defs: warn about weak choices

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According to crypt(5), MD5 and DES should not be used for new
hashes. Also the default number of SHA rounds chosen by libc is orders
of magnitude too low for modern hardware. Let's warn the users about
weak choices.

Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
This commit is contained in:
Topi Miettinen 2020-04-10 14:09:55 +03:00
parent 125a5dc309
commit 69301dfa24
No known key found for this signature in database
GPG Key ID: 87E1A51C590B0577
3 changed files with 7 additions and 2 deletions
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4
etc/login.defs
View File

@ -327,6 +327,7 @@ CHFN_RESTRICT rwh
# If set to SHA512, SHA512-based algorithm will be used for encrypting password
# If set to BCRYPT, BCRYPT-based algorithm will be used for encrypting password
# If set to DES, DES-based algorithm will be used for encrypting password (default)
# MD5 and DES should not be used for new hashes, see crypt(5) for recommendations.
# Overrides the MD5_CRYPT_ENAB option
#
# Note: If you use PAM, it is recommended to use a value consistent with
@ -342,7 +343,8 @@ CHFN_RESTRICT rwh
# However, more CPU resources will be needed to authenticate users if
# this value is increased.
#
# If not specified, the libc will choose the default number of rounds (5000).
# If not specified, the libc will choose the default number of rounds (5000),
# which is orders of magnitude too low for modern hardware.
# The values must be within the 1000-999999999 range.
# If only one of the MIN or MAX values is set, then this value will be used.
# If MIN > MAX, the highest value will be used.

3
man/login.defs.d/ENCRYPT_METHOD.xml
View File

@ -39,6 +39,9 @@
<replaceable>MD5</replaceable><phrase condition="sha_crypt">,
<replaceable>SHA256</replaceable>,
<replaceable>SHA512</replaceable></phrase>.
MD5 and DES should not be used for new hashes, see
<refentrytitle>crypt</refentrytitle><manvolnum>5</manvolnum>
for recommendations.
</para>
<para>
Note: this parameter overrides the <option>MD5_CRYPT_ENAB</option>

2
man/login.defs.d/SHA_CRYPT_MIN_ROUNDS.xml
View File

@ -44,7 +44,7 @@
</para>
<para>
If not specified, the libc will choose the default number of rounds
(5000).
(5000), which is orders of magnitude too low for modern hardware.
</para>
<para>
The values must be inside the 1000-999,999,999 range.