Provided by: dacs_1.4.38a-2build1_amd64 
NAME
dacspasswd - manage DACS accounts
SYNOPSIS
dacspasswd [dacsoptions[1]] [-p password] [-pf file] [-simple] [-vfs vfs_uri]
[op-spec] [--] [username]
DESCRIPTION
This program is part of the DACS suite.
The dacspasswd command manages accounts that are used by the local_passwd_authenticate[2]
and local_simple_authenticate[3], authentication modules. This utility serves a similar
purpose for these authentication modules that Apache's htpasswd(1)[4] command does for its
mod_auth_basic[5] and mod_authn_dbm[6] modules.
Apart from their use by local_passwd_authenticate and local_simple_authenticate, these
accounts are completely separate from any other accounts and passwords.
Note
Only lowercase usernames are permitted for these accounts.
The command allows arbitrary data to be associated with each account. This "private" data
is opaque to DACS and is not used by DACS. Custom, account-specific information can be
stored, retrieved, and deleted. Data that is not printable text must be encoded. The
information is automatically deleted when its account is removed. Using this feature,
account administration programs might be developed to store:
• the last time a password was changed;
• hashes of previous password values (so that they are not reused);
• a note that the account's password must be changed;
• a password reminder question and answer;
• information for mutual authentication, such as a small image provided by the user that
is displayed at login time;
• an encrypted representation of the password for recovery purposes (when absolutely
necessary)
• several security questions (with answers), one of which might be selected at random
and presented to the user at login time; or
• user preferences.
Or instead, a pointer to any of this sort of information might be stored. There is no size
limit for the data, but if relatively large amounts of data are being stored for a large
number of accounts, the storage type should be chosen with care to ensure reasonable
performance.
Passwords are accessed using the DACS virtual filestore through the passwds or simple item
types. Each record in the file is keyed on the username. The information associated with
each key consists of several fields separated by a "|" character, and includes a digest
algorithm identifier, salt, the computed digest, and optional application data.
Use dacsauth(1)[7] to validate (test) a password.
Security
The password digest algorithm used depends on the PASSWORD_DIGEST[8] directive in
effect. The PASSWORD_SALT_PREFIX[9] directive is also used.
Apart from using an authentication method stronger than one based on passwords,
current best practice is to use a key derivation function like scrypt rather than a
cryptographic digest for the PASSWORD_DIGEST[8]. While in general doing so will
provide additional protection if an attacker obtains the password file, it will not
help if users are allowed to choose weak passwords.
Plaintext passwords are not stored by dacspasswd. This makes it more difficult for an
attacker that gains access to the password file to discover plaintext passwords, but
also means that forgotten passwords cannot be recovered (except by exhaustive search,
which ought to be impractical).
The salted hash of the password is stored, assuming salting has not been disabled,
rather than the hash of the password itself. This makes a stolen password file more
difficult for an attacker to use (see rainbow tables[10]).
Only a DACS administrator should be able to successfully run this program from the
command line. Because DACS keys and configuration files, including the file used to
store passwords, must be restricted to an administrator, this will normally be the
case, but a careful administrator will set file permissions to deny access to all
other users. An ordinary user is able to change his own password using the
dacs_passwd(8)[11] web service.
Tip
Even if the password file is stored as a plain text file, it is probably best to
modify it only through this program or dacs_passwd. Corrupting a password file entry
may prevent signing on to the corresponding account or even all accounts that require
the password file.
It is good administrative practice to store accounts with passwords separately from
those without.
This program is also available as a DACS web service, dacs_passwd(8)[11].
OPTIONS
By default, the program will prompt for a new password if one is required by the selected
operation.
The dacspasswd command recognizes these command line flags:
-p password
Specify the password.
Security
A password given on the command line may be visible to other users on the same
system.
-pdd
Delete the private data associated with username.
-pdg
Get the private data associated with username and print it to the standard output.
-pds string
Set (or replace) string as private data associated with username.
-pdsf file
Set (or replace) the private data associated with username, reading it from file. If
file is "-", then the data is read from the standard input. This flag and -pf cannot
both be used to read from the standard input.
-pf file
Read the password to use from file. If file is "-", then the password is read from the
standard input without prompting. This flag and -pdsf cannot both be used to read from
the standard input.
-simple
Use the simple item type expected by local_simple_authenticate instead of the default.
The program will not prompt for passwords because these accounts do not use them.
-vfs vfs_uri
Add vfs_uri as a VFS[12] configuration directive. By specifying the item type passwds,
a location for the password file can be given, overriding any configuration file
value. This is particularly useful in conjunction with dacsauth(1)[7].
op-spec
The following operations are recognized. The -enable, -disable, -pdd, -pds, and -pdsf
are the only operations that can be combined with another operation (for example, you
can disable an account and set its private data at the same time).
-a
-add
Add username to the password file. The entry must not already exist. By default,
the user will be prompted for the password, which must be retyped for
confirmation. This is the default operation.
-d
-del
-delete
Delete username from the password file.
-dis
-disable
Disable the account for username so that authentication modules will not accept
any password. If used with -a, -s, or -u, the account will also be disabled. The
username may subsequently be enabled.
-en
-ena
-enable
Re-enable the account for username, which is currently disabled. The
authentication modules will once again accept the password. If used with -a, -s,
or -u, the account will also be enabled.
-g
-get
Get the digest string for username and print it to the standard output. A script
can validate a password by passing this digest string to password()[13] along with
the password obtained from the user.
-l
-list
-long
-longlist
List username if it appears in the password file. If no username is provided, list
all usernames. A disabled account is indicated by a '*' (which is not a valid
character in a username). The -long and -longlist variants display additional
detail about each entry, such as the digest algorithm used.
-s
-set
Set or reset the password for username, which must already exist in the password
file. The enabled/disabled status is preserved unless overridden by a flag.
-regen
-regenerate
Read the current password file (item type passwds) and copy it to the item type
newpasswds. This will normally create an exact copy, but if there are applicable
formatting changes, they are automatically applied to the input; that is, if the
format of the input file is older than the format preferred by the current version
of DACS, it will be updated in the output file to the extent possible. The output
file should be carefully examined and tested before being used.
-test test-op
Test an entry for one of several attributes and report the outcome through the
program's exit status. The test-op is one of the following keywords or abbreviated
keywords:
• enabled, ena, en
Return an exit status of 0 if an account for username exists and is enabled,
or 1 if it does not exist or is disabled.
• exists, ex
Return an exit status of 0 if an account for username exists, or 1 if it does
not exist.
• data
Return an exit status of 0 if an account for username exists and has private
data, or 1 if it does not exist or does not have private data. If an entry's
private data is the empty string, it is considered to have private data.
• disabled, dis
Return an exit status of 0 if an account for username exists and is disabled,
or 1 if it does not exist or is enabled.
-u
-up
-update
Add username to the password file or update an existing entry for username. By
default, the user will be prompted for the password, which must be retyped for
confirmation. If the entry exists, the enabled/disabled status is preserved unless
overridden by a flag.
--
This flag signals the end of the flag arguments; a username may follow, possibly
beginning with a "-" character.
Since only the administrator is allowed to use this command, no restrictions are imposed
on the length or quality of the passwords that the administrator supplies; a warning
message will be emitted, however, if the password is considered to be weak based on the
PASSWORD_CONSTRAINTS[14] directive that is configured.
EXAMPLES
To list all of the accounts configured for the jurisdiction named EXAMPLE:
% dacspasswd -uj EXAMPLE -list
auggie
bobo*
booboo
jj
Note that the account for username bobo has been disabled.
To re-enable bobo's account:
% dacspasswd -uj EXAMPLE -ena bobo
To test if bobo's account is enabled:
% dacspasswd -uj EXAMPLE -test ena bobo
% echo $status
0
To test if there are accounts for usernames booboo and bob:
% dacspasswd -uj EXAMPLE -test exists booboo
% echo $status
0
% dacspasswd -uj EXAMPLE -test exists bob
% echo $status
1
To reset the password for username bobo interactively:
% dacspasswd -uj EXAMPLE -set bobo
New password for bobo?
Re-type new password for bobo?
Note that the password text is not displayed.
To reset the password for username bobo using the program's standard input:
% echo $newpasswd | dacspasswd -uj EXAMPLE -set -pf - bobo
To create a new, disabled account for username bob and store the private data "On
vacation":
% dacspasswd -uj EXAMPLE -add -pf ./pwfile -dis -pds "On vacation" bob
The password is read from the file ./pwfile.
To get the private data for username bob:
% set x=`dacspasswd -uj EXAMPLE -pdg bob`
% echo "$x"
On vacation
To regenerate the current password file:
% dacspasswd -uj EXAMPLE -q -vfs "[newpasswds]dacs-kwv-fs:/usr/local/dacs/tmp/newpasswd?field_sep=:" -regen
DIAGNOSTICS
The program exits 0 if everything was fine, and non-zero otherwise. A "false" outcome from
the -test operation is reflected by an exit status of 1. An error condition is indicated
by an exit status of 2.
BUGS
That password information is not represented externally as an XML document tends to haunt
your humble narrator. The password file format is subject to change.
SEE ALSO
dacs_passwd(8)[11], dacsauth(1)[7], dacs_authenticate(8)[15], dacs_admin(8)[16],
dacs.conf(5)[17]
AUTHOR
Distributed Systems Software (www.dss.ca[18])
COPYING
Copyright2003-2016 Distributed Systems Software. See the LICENSE[19] file that accompanies
the distribution for licensing information.
NOTES
1. dacsoptions
http://dacs.dss.ca/man/dacs.1.html#dacsoptions
2. local_passwd_authenticate
http://dacs.dss.ca/man/dacs_authenticate.8.html#local_passwd_authenticate
3. local_simple_authenticate
http://dacs.dss.ca/man/dacs_authenticate.8.html#local_simple_authenticate
4. htpasswd(1)
http://httpd.apache.org/docs/2.2/programs/htpasswd.html
5. mod_auth_basic
http://httpd.apache.org/docs-2.4/mod/mod_auth_basic.html
6. mod_authn_dbm
http://httpd.apache.org/docs-2.4/mod/mod_authn_dbm.html
7. dacsauth(1)
http://dacs.dss.ca/man/dacsauth.1.html
8. PASSWORD_DIGEST
http://dacs.dss.ca/man/dacs.conf.5.html#PASSWORD_DIGEST
9. PASSWORD_SALT_PREFIX
http://dacs.dss.ca/man/dacs.conf.5.html#PASSWORD_SALT_PREFIX
10. rainbow tables
http://en.wikipedia.org/wiki/Rainbow_table
11. dacs_passwd(8)
http://dacs.dss.ca/man/dacs_passwd.8.html
12. VFS
http://dacs.dss.ca/man/dacs.conf.5.html#VFS
13. password()
http://dacs.dss.ca/man/dacs.exprs.5.html#password
14. PASSWORD_CONSTRAINTS
http://dacs.dss.ca/man/dacs.conf.5.html#PASSWORD_CONSTRAINTS
15. dacs_authenticate(8)
http://dacs.dss.ca/man/dacs_authenticate.8.html
16. dacs_admin(8)
http://dacs.dss.ca/man/dacs_admin.8.html
17. dacs.conf(5)
http://dacs.dss.ca/man/dacs.conf.5.html
18. www.dss.ca
http://www.dss.ca
19. LICENSE
http://dacs.dss.ca/man/../misc/LICENSE