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KHPH cpan:MLDEVINE last updated on 2020-07-29



Keep Honest People Honest


String Obfuscation, Storage, & Retrieval


This module scrambles a string to help keep it private, but of course the scrambled string is inherently vulnerable to being unscrambled by someone other than the owner.  One might ask, "Why even bother employing a scrambling function?"  The pragmatic answer is that simply masking sensitive data from view can prevent many of the exposure scenarios that exist in the real world.

Consider the egregious case where you need to run a program that absolutely requires you to include a *password* in its command line invocation.

    [email protected]> /usr/local/bin/srvrconn -acct=USER72 -password=pAsSwOrD57! START INSTANCE ABC

If you run it interactively, your shell history will record the entire command line for posterity, including the exposed password.  Then your system backup will make a copy of that, and who knows where that goes and for how long?  If it were executed via a job scheduler, the password could be exposed in multiple places: crontab, logs, email, backups, etc.

You might consider a solution where you put the secret characters in a file and judiciously apply DAC controls to restrict access (chown/chgrp/chmod).  When it's time to use the password, you could read the secret string from the file and insert it where needed.  But **root** would be able to look at your secret with a quick `cat` command, and then your secret wouldn't be a secret anymore.

This module offers you a way to reduce the likelihood of baring your secret information to curious people who are just poking around.  It also aims to reduce the number of surfaces where your private data is openly exposed.  It does not purport to fully protect your private information from prying eyes, but rather to make it opaque to glances.

Think of it like the difference in playing hide-and-go-seek with a 2-year-old versus a 10-year-old: the 10-year-old will stay out of sight and make you work for it.

> ALWAYS ENCRYPT CUSTOMER DATA.  Customer data and other types of sensitive information warrant Fort Knox level security, not a privacy fence.


This module will scramble a string, stash it wherever you specify, then expose it to you whole again when you ask for it.  **root** can’t expose it directly, unless **root** originally stored it.  `su`’ing into the owner’s account from a different account won’t expose it directly either.  It’s not in the direct line of sight by anyone other than the owner.


use KHPH;

my $userid = 'testid';
my KHPH $secret-string .= new(
    :herald('myapp credentials'),
    :prompt($userid ~ ' password'),
    :stash-path('/tmp/myapp/' ~ $userid ~ '/mysecret'),
    :user-exclusive-at('/tmp/myapp/' ~ $userid);
say $secret-string.expose;


Generate a KHPH object

#### :herald?

  * Optional announcement used only when interactively stashing the secret.

#### :prompt?

  * Optional prompt string used only when interactively stashing the secret.

#### :secret?

  * Optionally send the constructor the secret string. No prompting will occur.

#### :stash-path!

  * Specify the path (directories/file) to create or find the stash file.  Always include a subdirectory in the path, as KHPH will `chmod` the directory containing the stash file.

#### :user-exclusive-at?

  * Optionally specify a segment of the :stash-path to exclude all group & other access (0700).

Return the secret as a clear-text Str.

Example I

The `myapp-pass.p6` script will manage the password stash of `myapp`.  Run it interactively one time to stash your secret, then you (not someone else) can run it anytime to expose the secret.

The `myapp-pass.p6` script:

#!/usr/bin/env raku
use KHPH;'/tmp/.myapp/password.khph')).expose.print;

Run ~/myapp-pass.p6 once interactively to stash the secret:

    [email protected]> ~/myapp-pass.p6 && echo
    [1/2] Enter secret> aW3S0m3pA55w0rDI'LlN3VeRr3m3mB3R
    [2/2] Enter secret> aW3S0m3pA55w0rDI'LlN3VeRr3m3mB3R
    [email protected]>

> _Notice how the script dumps the secret when you personally run it?  Have someone else log into the same system, have them run the same script, and see what they get.  Have them `su` to your account and try again.  Have them log in as **root** and give it a go.  Have them `su` from **root** into your account and try.  Have them `sudo su -` into your account and try again._

Then in your application client:

    [email protected]> /usr/bin/dsmadmc -id=MYSELF -password=`~/myapp-pass.p6` QUERY SESSION FORMAT=DETAILED

The password will be inserted into the command line and authentication will succeed.

> __Note__:  _The above example demonstrates a particular application client (familiar to some backup admins) that is more helpful than most, in that it re-writes the process' args after the program launches.  `ps` will only display the string `-password=*******` instead of the actual password string.  Not all application vendors pay attention to such details, so beware -- `ps` could be displaying the secret despite your efforts to protect it._

Example II

The following contrived `acme-connect` script, which connects to a fictitious ACME application, is implemented so that all passwords are stored in a common directory:


Ensure that all users can descend to that directory.  It would be ideal to set 1777 to the last directory in that path.

Different users run the script to connect to instances of the ACME application on multiple hosts.

| OS Login | Application Host  | Application UserId | Application Password  |
| -------- | ----------------- | ------------------ | --------------------- |
| user_a   |    | ACMEUSERX          | pAsSwOrDx             |
| user_b   |    | ACMEUSERY          | pAsSwOrDy             |
| user_c   |    | ACMEUSERZ          | pAsSwOrDz             |

The `acme-connect` script:

#!/opt/bin/env raku
use KHPH;
sub MAIN (
    :$acme-host is required, #= ACME Host
    :$acme-id   is required, #= ACME UserId
    :$start-monthly-batch,   #= Launch monthly batch processing
) {
    my KHPH $passwd .= new(
        :herald('ACME credentials'),
        :prompt($acme-id ~ '@' ~ $acme-host ~ ' password'),
        :stash-path('/var/raku/.credentials/' ~ $*USER ~ '/ACME/' ~ $acme-host ~ '/' ~ $acme-id),
        :user-exclusive-at('/var/raku/.credentials/' ~ $*USER),

#   Assemble the acme-manager command parts
    my @cmd =   '/usr/bin/acme-manager',
                '-serv=' ~ $acme-host,
                '-acct=' ~ $acme-id,
                '-pass=' ~ $passwd.expose;
    if $start-monthly-batch {
        @cmd.push: '-m_end';
    else {
        @cmd.push: '-stat';

#   Run ACME
    run @cmd;   # hope /usr/bin/acme-manager masks the -pass=...

**user_a** runs the `acme-connect` script interactively from the **linux5** server:

[email protected]> acme-connect --acme-id=ACMEUSERX
ACME credentials
[1/2] [email protected] password> pAsSwOrDx
[2/2] [email protected] password> pAsSwOrDx
    ACME Status Report: A-OK
[email protected]> 

Then **user_c** runs the `acme-connect` script from the **linux5** server using their connection information.

The following hierarchy will result on the **linux5** server:

    *         1777    /var/raku/.credentials/
    user_a    0700    /var/raku/.credentials/user_a/
    user_a    0700    /var/raku/.credentials/user_a/ACME/
    user_a    0700    /var/raku/.credentials/user_a/ACME/
    user_a    0600    /var/raku/.credentials/user_a/ACME/
    user_c    0700    /var/raku/.credentials/user_c/
    user_c    0700    /var/raku/.credentials/user_c/ACME/
    user_c    0700    /var/raku/.credentials/user_c/ACME/
    user_c    0600    /var/raku/.credentials/user_c/ACME/

The `acme-connect` script will not prompt the users for their application passwords again when connecting to their application instances with their particular userids.  They will be able to run the `acme-connect` script as above, along with additional switches, in a job scheduler for unattended execution on the **linux5** server.  

Example III

When crafting REST API clients, servers will often issue session tokens for subsequent connections.  These authenticating session tokens remain valid for long intervals of time (hours, days, weeks) and should be protected like passwords.  When stashing a token locally for reuse, minimally use KHPH instead of clear-text so that it isn't easily viewed by passersby.

Usage Recommendation

Since the intent of using this module is to obfuscate, it is recommended to specify a :stash-path that doesn't indicate what's being stored.

This looks innocuous:

    :stash-path($*HOME ~ '/.metrics/' ~ $account ~ '/' ~ $server ~ '/stats')

This wouldn't generate much interest:

    :stash-path('/var/dynaplex/.perf/' ~ $account ~ '/dynaplex.' ~ $server)
    :user-exclusive-at('/var/dynaplex/.perf/' ~ $account)
These misleading paths result in added camouflage, and every little bit helps.


Only developed on Linux.

Mark Devine <[email protected]>