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lukemftpd sous FreeBSD
Les serveurs FTP (et notamment Lukemftpd, importé du projet NetBSD dans le projet FreeBSD) affichent spontanément ou à la demande certaines informations sensibles :
# ftp localhost
220 localhost.maison FTP server (lukemftpd 1.2 beta 1) ready.
Name (localhost:root): guest
331 Password required for guest.
Password: ********
230-
FreeBSD 4.7-RELEASE (GENERIC) #0: Tue Oct 8 14:11:51 GMT 2002
Welcome to FreeBSD!
230 User guest logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> syst
215 UNIX Type: L8 Version: lukemftpd 1.2 beta 1
ftp> rstatus
211-localhost.maison FTP server status:
Version: lukemftpd 1.2 beta 1
Connected to localhost.maison (127.0.0.1)
Logged in as guest
TYPE: ASCII, FORM: Nonprint; STRUcture: File; transfer MODE: Stream
No data connection
Data sent: 0 bytes in 0 files
Data received: 0 bytes in 0 files
Total data: 0 bytes in 0 files
Traffic sent: 1830 bytes in 0 transfers
Traffic received: 42 bytes in 0 transfers
Total traffic: 1872 bytes in 0 transfers
Class: real, type: REAL
Check PORT/LPRT commands: enabled
Idle timeout: 900, maximum timeout: 7200
Current connections: 2
Maximum connections: unlimited
Deny bad ftpusers(5) quickly: disabled
Maximum file size: unlimited
MotD file: /etc/motd
Modify commands (CHMOD, DELE, MKD, RMD, RNFR, UMASK): enabled
Upload commands (APPE, STOR, STOU): enabled
Sanitize file names: disabled
PASV/LPSV/EPSV connections: enabled
Rate get limit: disabled
Rate put limit: disabled
Umask: 0027
211 End of status
ftp> bye
221-
Data traffic for this session was 0 bytes in 0 files.
Total traffic for this session was 2664 bytes in 0 transfers.
221 Thank you for using the FTP service on localhost.maison.
|
Une option de lancement permet cependant d'éviter ces fuites d'informations :
# man lukemftpd [...] -V version Use version as the version to advertise in the login banner and in the output of STAT and SYST instead of the default version information. If version is empty or `-' then don't display any version information. [...] |
Cette option peut être ajoutée dans le fichier /etc/inetd.conf :
ftp stream tcp nowait root /usr/libexec/lukemftpd ftpd -l -r -V - |
Quant à l'affichage du "message du jour", il peut être débrayé via une option du fichier de configuration de lukemftpd :
# echo "motd none" >> /etc/ftpd.conf |
Le serveur se comporte alors comme suit :
# ftp localhost
220 localhost.maison FTP server ready.
Name (localhost:root): guest
331 Password required for guest.
Password: ********
230 User guest logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> syst
215 UNIX Type: L8
ftp> rstatus
211-localhost.maison FTP server status:
Version: <suppressed>
Connected to localhost.maison (127.0.0.1)
Logged in as guest
TYPE: ASCII, FORM: Nonprint; STRUcture: File; transfer MODE: Stream
No data connection
Data sent: 0 bytes in 0 files
Data received: 0 bytes in 0 files
Total data: 0 bytes in 0 files
Traffic sent: 501 bytes in 0 transfers
Traffic received: 42 bytes in 0 transfers
Total traffic: 543 bytes in 0 transfers
Class: real, type: REAL
Check PORT/LPRT commands: enabled
Idle timeout: 900, maximum timeout: 7200
Current connections: 1
Maximum connections: unlimited
Deny bad ftpusers(5) quickly: disabled
Maximum file size: unlimited
Modify commands (CHMOD, DELE, MKD, RMD, RNFR, UMASK): enabled
Upload commands (APPE, STOR, STOU): enabled
Sanitize file names: disabled
PASV/LPSV/EPSV connections: enabled
Rate get limit: disabled
Rate put limit: disabled
Umask: 0027
211 End of status
ftp> bye
221-
Data traffic for this session was 0 bytes in 0 files.
Total traffic for this session was 1307 bytes in 0 transfers.
221 Thank you for using the FTP service on localhost.maison.
|
Derniers avertissements
Notez que l'identification du serveur reste toujours possible par le biais de son implémentation du protocole FTP (les verbes de commandes et la structure des réponses associées pouvant être assez caractéristiques).
En particulier, on pourra constater ici la spécificité de la réponse à la commande "rstatus" par rapport à celle du ftpd BSD traditionnel...
Au-delà de ces considérations, essayez d'éviter le protocole FTP chaque fois que possible (par exemple au profit de SFTP), les identifiants et authentifiants utilisés passant en effet en clair sur le réseau...
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