Running bash script from PHP halts

Question

EDIT

It seems that I cannot cat /dev/urandom from a PHP script, please keep this in mind while reading the following

/EDIT

I ran into an issue while trying to execute a BASH script from PHP, seems to be halting at generating a rand directory (variable generate) I can see if I change the variable string to something like foo as I did in the commented out portion of the script this executes appropriately.

What is the issue with sghell_exec'ing cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 32 | head -n 1 is this a (possibly) restricted command sequence to user(s) www-data (DEB based system) or httpd (RHEL based system)

The bash script

#!/bin/bash

# INP : co.sh ${website} ${branch} ${hash}

set -x # trace

declare -r hostname='localhost'

# bricks
declare -r generate=$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 32 | head -n 1)

# works
#declare -r generate='foo'

declare -r archive="$1" # git repository name
declare -r branchd="$2" # git repo branch name
declare -r hashmap="$3" # git blob hash (6/~)


# if repository or branch is empty...
if [ '' == "${archive}" ] || [ '' == "${branchd}" ]; then

   [ '' == "${archive}" ] &&  echo -e "ERR: Archive must be defined."
   [ '' == "${branchd}" ] &&  echo -e "ERR: Branch must be defined."

       exit 1 # err fatal
fi

    # clone repository to rand directory
    git clone "git@${hostname}:web-archive/${archive}.git" "/var/www/html/${generate}"
    cd "/var/www/html/${generate}" && git checkout "${branchd}"

    position='HEAD' # pre-warm

    [ '' != "${hashmap}" ] &&
    {
        git reset "${hashmap}" --hard   # move to hash blob
        position="${hashmap}"           # override position
    }

    # encode for push
    json="{'s':'${archive}','b':'${branchd}','h':'${position}','d':'${generate}'}"

echo -e "\nSUCC: ${json}"

The test runner script

#!/usr/bin/php
<?php

$dir=__DIR__; // curr

$site_name='www.foo.com';

$rev_hash='feb2da';

$cmd="$dir/co.sh " . escapeshellarg($site_name) . " 'render' " . escapeshellarg($rev_hash);

echo "running $cmd\n";
$ret = passthru($cmd,$return_status));

trace log

running /{dir_path}/co.sh 'www.foo.com' 'render' 'feb2da'
+ declare -r hostname=localhost
++ cat /dev/urandom
++ fold -w 32
++ head -n 1
++ tr -dc a-zA-Z0-9

Are you running the script in the context of a PHP session? In such case, check part 2 of the answer to this question: stackoverflow.com/questions/13690490/… — Claudi
– Claudi, Commented Dec 3, 2013 at 19:22
@Claudix - that seems pretty Windows-specific. ehime - is the actual bash script failing when you try to run it, or only when run via that test runner? What error(s), if any, do you get? — admdrew
– admdrew, Commented Dec 3, 2013 at 19:24
Honestly keeping the above in mind, I can use openssl rand -base64 36 | tr -dc 'a-zA-Z0-9' just as well without worrying about accessing /dev/urandom — ehime
– ehime, Commented Dec 3, 2013 at 19:55
Haha. Actually, you should answer your own question; totally acceptable to do. — admdrew
– admdrew, Commented Dec 3, 2013 at 20:19

ehime · Accepted Answer · 2013-12-03 20:22:09Z

3

Due to PHP not liking to operate on /dev/urandom the following is an acceptable compromise

openssl rand -base64 36 | tr -dc 'a-zA-Z0-9'

answered Dec 3, 2013 at 20:22

ehime

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1 Comment

ehime Over a year ago

lmao, completely worth the extra bandwidth ;)

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