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Description of problem:
usermod -p allowing colon (ie. ':' ) in encrypted password which then breaks /etc/shadow
Version-Release number of selected component (if applicable):
shadow-utils-4.1.4.2-19.el6_6.1.x86_64
How reproducible:
VERY
Steps to Reproduce:
1. Create test user
# useradd test
# passwd test
# grep ^test: /etc/shadow
test:$6$ziMs4I5K$yh6QO6q4siNK8j.CMxCBO.hjF75XlQZzl7I2dXIJqnANNvhMwFtdDY2obXOjGnniPcVTpSazk5REcTKGHVEUb1:16566:0:99999:7:::
2. Modify user password with usermod and include colon
# usermod -p 'sstest:123' test
3. Now see that the ':' was accepted even though it is really a delimiter for the file
# grep ^test: /etc/shadow
test:sstest:123:16566:0:99999:7:::
Actual results:
# grep ^test: /etc/shadow
test:sstest:123:16566:0:99999:7:::
Expected results:
A failure like you get on RHEL 7
# usermod -p 'sstest:123' test
usermod: failure while writing changes to /etc/shadow
Additional info:
If you run the usermod again you start adding duplicate lines:
# usermod -p 'sstest:123' test
# grep ^test: /etc/shadow
test:sstest:123:16566:0:99999:7:::
test:sstest:123:16566:0:99999:7:::
I opened the RHEL 6 verstion of the BZ, and included in the Expected results above is that RHEL 7 already warns of this issue. So not sure this BZ is needed for RHEL 7...
# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.2 (Maipo)
# grep ^test: /etc/shadow
test:$6$iimWa/Hp$h2Vx0aM1WD/Z.khihwBnpRocSLTc8PgVNIwFjRejYpp74JxToLo6IrgaT.1CZDrbw9cYXfLt494aDQsweU6/60:16787:0:99999:7:::
# usermod -p 'sstest:123' test
usermod: failure while writing changes to /etc/shadow
# grep ^test: /etc/shadow
test:$6$iimWa/Hp$h2Vx0aM1WD/Z.khihwBnpRocSLTc8PgVNIwFjRejYpp74JxToLo6IrgaT.1CZDrbw9cYXfLt494aDQsweU6/60:16787:0:99999:7:::
Now with colon removed on RHEL 7 (so seems the colon is cause of failure):
# usermod -p 'sstest123' test
# grep ^test: /etc/shadow
test:sstest123:16787:0:99999:7:::
Hmm, you're right that there is additional check when writing the shadow entry. However the error message is not completely clear so it is better to include the explicit check for ':' which will be in RHEL-6.8.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHBA-2016-2322.html