NAME

authopen — open file with authorization

SYNOPSIS

DESCRIPTION

authopen provides authorization-based file opening services. In its simplest form, authopen verifies that it is allowed to open filename (using an appropriate sys.openfile.* authorization right) and then writes the file to stdout. If -w is specified, authopen will read from stdin and write to the file.

authopen is designed to be used both from the command line and programmatically. The -stdoutpipe flag allows a parent process to receive an open file descriptor pointing to the file in question.

Before opening filename, authopen will make an authorization request for a right of the form:

sys.openfile.[readonly|readwrite|readwritecreate]./fully/qualified/path ‘.readonly’ rights only allow for read-only file descriptors. ‘.readwrite’ rights allow for read/write file descriptors. ‘.readwritecreate’ rights allow for read/write descriptors and the creation of new files.

The -extauth option can be used to provide an AuthorizationRef constructed by the client. This generally prevents authopen from presenting an authorization dialog containing its own name.

OPTIONS

-stdoutpipe

specifies that STDOUT_FILENO has been dup2()'d onto a pipe to a parent process and that an open file descriptor to filename (with the appropriate access mode) should be sent back across it using the SCM_RIGHTS extension to sendmsg(2) rather than having the file itself written to or read from stdin / stdout.

-extauth

specifies that authopen should read one AuthorizationExternalForm structure from stdin, convert it to an AuthorizationRef, and attempt to use it to authorize the open(2) operation. The authorization should refer to the sys.apenfile right corresponding to the requested operation. The authorization data will be read before any additional data supplied on stdin, and will not be included in data written with -w.

-w

instructs authopen to open filename read/write and truncate it. If -stdoutpipe has not been specified, authopen will then copy stdin to filename until stdin is closed.

-a

append to filename rather than truncating it (truncating is the default).

-c

create the file if it doesn't exist. -m requires -c.

-m mode

specify the mode bits if a file is created.

-o flags

numerically specify the flags that should be passed to open(2).

-x

require that the file being created not exist.

EXAMPLES

To replace /etc/hostconfig (assuming sys.openfile.readwrite./etc/hostconfig or better can be obtained):

ERRORS

authopen will fail if an appropriate sys.openfile.readonly.*, sys.openfile.readwrite.*, or sys.openfile.readwritecreate.* right cannot be obtained or if the named path does not exist.

BUGS

authopen should support prefix path authentication such that the right sys.openfile.*./dev/ could give access to all /dev entries and sys.openfile.*./dev/disk1 could give access to all disk1-related /dev entries.

authopen should use getopt(3).

LOCATION

/usr/libexec/authopen

SEE ALSO

open(2), Security/Authorization.h, realpath(3), recvmsg(2).

W. Richard Stevens, Passing File Descriptors, Advanced Programming in the Tn UNIX Environment.

HISTORY

authopen appeared in Mac OS X 10.1 to assist with the manipulation of disk devices.