ext/ftp: cryptic error on servers that don't support TLS session resumption on data connection
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- Langage dominant
- C
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- Merge moyen
- 2 j 13 h
- PR mergées (30 j)
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Description
Description
The following code:
<?php
$conn_id = ftp_ssl_connect($url);
$login_result = ftp_login($conn_id, $un, $pw);
ftp_set_option($conn_id, FTP_USEPASVADDRESS, false);
ftp_pasv($conn_id, true);
if (!$login_result) {
die("can't login\n");
}
else{
echo "logged in success\n";
$buff = ftp_nlist($conn_id,'outbound');
var_dump($buff);
}
Resulted in this output:
logged in success
Warning: ftp_nlist: data_accept: failed to retrieve the existing SSL session
But I expected this output instead:
logged in success
[nlist output]
TLS session resumption on the data connection is required for it to be secure. GH-12851 fixed that. However, some servers don't seem to support TLS session resumption. In this case, PHP seems to fail with a cryptic-to-the-user error message. However, other FTP clients like i.e. FileZilla will prompt the user with a message like:
This server does not support TLS session resumption on the data connection.
TLS session resumption on the data connection is an important security feature to protect against data connection stealing attacks.
If you continue, transferred files may be intercepted or their contents replaced by an attacker.
I don't know if we want to support opting out of the behaviour (and certainly not continue insecurely silently), but we should definitely provide a better warning here, so users know what's wrong and what to blame.
A user reached out to me for support because this was "working" in PHP 8.1 (insecurely. probably) but stopped working when they upgraded to PHP 8.5, and thought it was a PHP issue. They did try it under 8.2.12 (last version XAMPP shipped) and that worked, and that was prior to when that PR was merged. I'm asking the user to bisect 8.2.13 vs. 8.2.14 to confirm.
As for the problematic FTP server in question, it seems to be Axway SecureTransport as installed by a large logistics company. A little hard to test for ourselves, and a little hard to get them to fix it. I don't know if we can force i.e. vsftpd to disallow session resumption to test it.
PHP Version
PHP 8.5.9
Operating System
Windows Server 2019
Guide de contribution
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Par où commencer
- Lisez l'issue en entier, puis le guide de contribution du projet.
- Signalez en commentaire que vous la prenez — cela évite que deux personnes fassent le même travail.
- Forkez le dépôt et travaillez sur une branche.
- Ouvrez une pull request qui référence le numéro de l'issue.
Piste de recherche
Commencez dans ext/ftp, au niveau du chemin de connexion de données de ftp_nlist et de l’échec de data_accept qui signale l’erreur de session TLS. Reproduisez le problème avec l’exemple PHP 8.5.9 et examinez comment l’avertissement est formé ; le travail est terminé lorsque les utilisateurs reçoivent une explication claire indiquant que la reprise de session TLS n’est pas prise en charge, sans continuer silencieusement de manière non sécurisée.
Rédigé par le modèle d'indexation à partir du texte de l'issue.
Évaluation
- Stack technique
- c
- Domaine
- networking, security
- Type d'issue
- Bug
- Difficulté
- 4/5
- Temps estimé
- 3-5 jours
- Activité
- Active
- Clarté
- Plutôt claire
- Accessibilité débutants
- 52/100