.\"     Title: cifs.upcall
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets v1.74.0 <http://docbook.sf.net/>
.\"      Date: 06/18/2010
.\"    Manual: System Administration tools
.\"    Source: Samba 3.5
.\"  Language: English
.\"
.TH "CIFS\&.UPCALL" "8" "06/18/2010" "Samba 3\&.5" "System Administration tools"
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.SH "Name"
cifs.upcall \- Userspace upcall helper for Common Internet File System (CIFS)
.SH "Synopsis"
.fam C
.HP \w'\ 'u
\FCcifs\&.upcall\F[] [\-\-trust\-dns|\-t] [\-\-version|\-v] {keyid}
.fam
.SH "DESCRIPTION"
.PP
This tool is part of the
\fBsamba\fR(7)
suite\&.
.PP
cifs\&.upcall is a userspace helper program for the linux CIFS client filesystem\&. There are a number of activities that the kernel cannot easily do itself\&. This program is a callout program that does these things for the kernel and then returns the result\&.
.PP
cifs\&.upcall is generally intended to be run when the kernel calls request\-key(8)
for a particular key type\&. While it can be run directly from the command\-line, it\'s not generally intended to be run that way\&.
.SH "OPTIONS"
.PP
\-c
.RS 4
This option is deprecated and is currently ignored\&.
.RE
.PP
\-\-trust\-dns|\-t
.RS 4
With krb5 upcalls, the name used as the host portion of the service principal defaults to the hostname portion of the UNC\&. This option allows the upcall program to reverse resolve the network address of the server in order to get the hostname\&.
.sp
This is less secure than not trusting DNS\&. When using this option, it\'s possible that an attacker could get control of DNS and trick the client into mounting a different server altogether\&. It\'s preferable to instead add server principals to the KDC for every possible hostname, but this option exists for cases where that isn\'t possible\&. The default is to not trust reverse hostname lookups in this fashion\&.
.RE
.PP
\-\-version|\-v
.RS 4
Print version number and exit\&.
.RE
.SH "CONFIGURATION FOR KEYCTL"
.PP
cifs\&.upcall is designed to be called from the kernel via the request\-key callout program\&. This requires that request\-key be told where and how to call this program\&. The current cifs\&.upcall program handles two different key types:
.PP
cifs\&.spnego
.RS 4
This keytype is for retrieving kerberos session keys
.RE
.PP
dns_resolver
.RS 4
This key type is for resolving hostnames into IP addresses
.RE
.PP
To make this program useful for CIFS, you\'ll need to set up entries for them in request\-key\&.conf(5)\&. Here\'s an example of an entry for each key type:
.sp
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#OPERATION  TYPE           D C PROGRAM ARG1 ARG2\&.\&.\&.
#=========  =============  = = ================================
create      cifs\&.spnego    * * /usr/local/sbin/cifs\&.upcall %k
create      dns_resolver   * * /usr/local/sbin/cifs\&.upcall %k
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.PP
See
\fBrequest-key.conf5\fR()
for more info on each field\&.
.SH "SEE ALSO"
.PP

\fBrequest-key.conf\fR(5),
\fBmount.cifs\fR(8)
.SH "AUTHOR"
.PP
Igor Mammedov wrote the cifs\&.upcall program\&.
.PP
Jeff Layton authored this manpage\&.
.PP
The maintainer of the Linux CIFS VFS is Steve French\&.
.PP
The
Linux CIFS Mailing list
is the preferred place to ask questions regarding these programs\&.