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Test Your Knowledge in Computers #268
Difficulty: Easy
In 1936, Turing published his paper 'On Computable Numbers, with an Application to the Entscheidungsproblem'. In this paper, Turing reformulated Kurt Godel's 1931 results on the limits of proof and computation, replacing Godel's universal arithmetic-based formal language with the formal and simple hypothetical devices that became known as Turing machines.
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nfssec(5) [bsd man page]

nfssec(5)																 nfssec(5)

NAME
nfssec - overview of NFS security modes The mount_nfs(1M) and share_nfs(1M) commands each provide a way to specify the security mode to be used on an NFS file system through the sec=mode option. mode can be sys, dh, krb5, krb5i, krb5p, or none. These security modes can also be added to the automount maps. Note that mount_nfs(1M) and automount(1M) do not support sec=none at this time. mount_nfs(1M) allows you to specify a single security mode; share_nfs(1M) allows you to specify multiple modes (or none). With multiple modes, an NFS client can choose any of the modes in the list. The sec=mode option on the share_nfs(1M) command line establishes the security mode of NFS servers. If the NFS connection uses the NFS Ver- sion 3 protocol, the NFS clients must query the server for the appropriate mode to use. If the NFS connection uses the NFS Version 2 proto- col, then the NFS client uses the default security mode, which is currently sys. NFS clients may force the use of a specific security mode by specifying the sec=mode option on the command line. However, if the file system on the server is not shared with that security mode, the client may be denied access. If the NFS client wants to authenticate the NFS server using a particular (stronger) security mode, the client wants to specify the secu- rity mode to be used, even if the connection uses the NFS Version 3 protocol. This guarantees that an attacker masquerading as the server does not compromise the client. The NFS security modes are described below. Of these, the krb5, krb5i, krb5p modes use the Kerberos V5 protocol for authenticating and pro- tecting the shared filesystems. Before these can be used, the system must be configured to be part of a Kerberos realm. See SEAM(5). sys Use AUTH_SYS authentication. The user's UNIX user-id and group-ids are passed in the clear on the network, unauthenticated by the NFS server. This is the simplest security method and requires no additional administration. It is the default used by Solaris NFS Version 2 clients and Solaris NFS servers. dh Use a Diffie-Hellman public key system (AUTH_DES, which is referred to as AUTH_DH in the forthcoming Internet RFC). krb5 Use Kerberos V5 protocol to authenticate users before granting access to the shared filesystem. krb5i Use Kerberos V5 authentication with integrity checking (checksums) to verify that the data has not been tampered with. krb5p User Kerberos V5 authentication, integrity checksums, and privacy protection (encryption) on the shared filesystem. This provides the most secure filesystem sharing, as all traffic is encrypted. It should be noted that performance might suffer on some systems when using krb5p, depending on the computational intensity of the encryption algorithm and the amount of data being transferred. none Use null authentication (AUTH_NONE). NFS clients using AUTH_NONE have no identity and are mapped to the anonymous user nobody by NFS servers. A client using a security mode other than the one with which a Solaris NFS server shares the file system has its security mode mapped to AUTH_NONE. In this case, if the file system is shared with sec=none, users from the client are mapped to the anonymous user. The NFS security mode none is supported by share_nfs(1M), but not by mount_nfs(1M) or automount(1M). /etc/nfssec.conf NFS security service configuration file See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | |Availability |SUNWnfscr | +-----------------------------+-----------------------------+ automount(1M), mount_nfs(1M), share_nfs(1M), rpc_clnt_auth(3NSL), secure_rpc(3NSL), nfssec.conf(4), attributes(5) /etc/nfssec.conf lists the NFS security services. Do not edit this file. It is not intended to be user-configurable. 13 Apr 2005 nfssec(5)

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