# 2049 - Pentesting NFS Service
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## **Basic Information** It is a client/server system that allows users to access files across a network and treat them as if they resided in a local file directory. It has the same purpose as SMB but it cannot talk to SMB. The NFS protocol has **no mechanism for authentication** or **authorization**. The authorization is taken from the available information of the file system where the server is responsible for translating the **user information** supplied by the **client** to that of the **file system** and converting the corresponding authorization information as correctly as possible into the syntax required by UNIX. The most common **authentication is via UNIX `UID`/`GID` and `group memberships`**, which is why this syntax is most likely to be applied to the NFS protocol. One problem is that the **client** and **server** do **not necessarily** have to have the **same mappings of UID/GID** to users and groups. No further checks can be made on the part of the server. This is why NFS should **only** be used with this authentication method in **trusted networks**. **Default port**: 2049/TCP/UDP (except version 4, it just needs TCP or UDP). ``` 2049/tcp open nfs 2-3 (RPC #100003 ``` ### Versions (From [https://academy.hackthebox.com/module/112/section/1068](https://academy.hackthebox.com/module/112/section/1068)) | **Version** | **Features** | | ----------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `NFSv2` | It is **older** but is supported by many systems and was initially operated entirely over UDP. | | `NFSv3` | It has more features, including variable file size and better error reporting, but is not fully compatible with NFSv2 clients. | | `NFSv4` | It includes Kerberos, works through firewalls and on the Internet, **no longer requires portmappers**, supports ACLs, applies state-based operations, and provides performance improvements and high **security**. It is also the first version to have a stateful protocol. | ## Enumeration ### Useful nmap scripts ```bash nfs-ls #List NFS exports and check permissions nfs-showmount #Like showmount -e nfs-statfs #Disk statistics and info from NFS share ``` ### Useful metasploit modules ```bash scanner/nfs/nfsmount #Scan NFS mounts and list permissions ``` ### Mounting To know **which folder** has the server **available** to mount you an ask it using: ```bash showmount -e ``` Then mount it using: ```bash mount -t nfs [-o vers=2] : -o nolock ``` You should specify to **use version 2** because it doesn't have **any** **authentication** or **authorization**. **Example:** ```bash mkdir /mnt/new_back mount -t nfs [-o vers=2] 10.12.0.150:/backup /mnt/new_back -o nolock ``` ## Permissions If you mount a folder which contains **files or folders only accesible by some user** (by **UID**). You can **create** **locally** a user with that **UID** and using that **user** you will be able to **access** the file/folder. ## NSFShell To easily list, mount and change UID and GID to have access to files you can use [nfsshell](https://github.com/NetDirect/nfsshell). [Nice NFSShell tutorial.](https://www.pentestpartners.com/security-blog/using-nfsshell-to-compromise-older-environments/) ## Config files ``` /etc/exports /etc/lib/nfs/etab ``` ### Dangerous settings (From [https://academy.hackthebox.com/module/112/section/1068](https://academy.hackthebox.com/module/112/section/1068)) | **Option** | **Description** | | ---------------- | -------------------------------------------------------------------------------------------------------------------- | | `rw` | Read and write permissions. | | `insecure` | Ports above 1024 will be used. | | `nohide` | If another file system was mounted below an exported directory, this directory is exported by its own exports entry. | | `no_root_squash` | All files created by root are kept with the UID/GID 0. | | `no_all_squash` | | ## Privilege Escalation using NFS misconfigurations [NFS no\_root\_squash and no\_all\_squash privilege escalation](../linux-hardening/privilege-escalation/nfs-no\_root\_squash-misconfiguration-pe.md) ## HackTricks Automatic Commands ``` Protocol_Name: NFS #Protocol Abbreviation if there is one. Port_Number: 2049 #Comma separated if there is more than one. Protocol_Description: Network File System #Protocol Abbreviation Spelled out Entry_1: Name: Notes Description: Notes for NFS Note: | It is a client/server system that allows users to access files across a network and treat them as if they resided in a local file directory. #apt install nfs-common showmount 10.10.10.180 ~or~showmount -e 10.10.10.180 should show you available shares (example /home) mount -t nfs -o ver=2 10.10.10.180:/home /mnt/ cd /mnt nano into /etc/passwd and change the uid (probably 1000 or 1001) to match the owner of the files if you are not able to get in https://book.hacktricks.xyz/pentesting/nfs-service-pentesting Entry_2: Name: Nmap Description: Nmap with NFS Scripts Command: nmap --script=nfs-ls.nse,nfs-showmount.nse,nfs-statfs.nse -p 2049 {IP} ```
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