plan9fox/sys/man/4/factotum

.TH FACTOTUM 4
.SH NAME
factotum, fgui, userpasswd \- authentication agent
.SH SYNOPSIS
.B auth/factotum
[
.B -DdknpuS
] [
.B -a asaddr
] [
.B -s
.I srvname
] [
.B -m
.I mtpt
]
.PP
.B auth/factotum
.B -g
.IB attribute = value
.B ...
.IB attribute ?
.B ...
.PP
.B auth/fgui
.PP
.B auth/userpasswd
.I fmt
.SH DESCRIPTION
.I Factotum
is a user-level file system that
acts as the authentication agent for a user.
It does so by managing a set of
.IR keys .
A key is a collection of information used to authenticate a particular action.
Stored as a list of
.IB attribute = value
pairs, a key typically contains a user, an authentication domain, a protocol, and
some secret data.
.PP
.I Factotum
presents a two level directory.  The first
level contains a single directory
.BR factotum ,
which in turn contains:
.TF needkey
.TP
.B rpc
each open represents a new private channel to
.I factotum
.TP
.B proto
when read lists the protocols available
.TP
.B confirm
for confiming the use of key
.TP
.B needkey
allows external programs to control the addition of new keys
.TP
.B log
a log of actions
.TP
.B ctl
for maintaining keys; when read, it returns a list of keys.
For secret attributes, only the attribute name follow by a
.L ?
is returned.
.PD
.PP
In any authentication, the caller typically acts as a client
and the callee as a server.  The server determines
the authentication domain, sometimes after a negotiation with
the client.  Authentication always requires the client to
prove its identity to the server.  Under some protocols, the
authentication is mutual.
Proof is accomplished using secret information kept by factotum
in conjunction with a cryptographic protocol.
.PP
.I Factotum
can act in the role of client for any process possessing the
same user id as it.  For select protocols such as
.B p9sk1
and
.B dp9ik
it can also act as a client for other processes provided
its user id may speak for the other process' user id (see
.IR authsrv (6)).
.I Factotum
can act in the role of server for any process.
.PP
.IR Factotum 's
structure is independent of
any particular authentication protocol.
.I Factotum
supports the following protocols:
.TF mschapv2
.TP
.B p9any
a metaprotocol used to negotiate which actual protocol to use.
.TP
.B p9sk1
legacy Plan 9 shared key protocol described in
.IR authsrv (6)'s
``Ticket Service''
and
``P9sk1'' sections.
.TP
.B dp9ik
extended version of
.B p9sk1
that adds password bruteforce resistance and forward secrecy (see
.IR authsrv (6)'s
``Password authenticated key exchange''
and
``Dp9ik''
sections).
.TP
.B p9cr
legacy Plan 9 protocol that can use either
.B p9sk1
keys or SecureID tokens.
.TP
.B apop
the challenge/response protocol used by POP3 mail servers.
.TP
.B cram
the challenge/response protocol also used by POP3 mail servers.
.TP
.B chap
the challenge/response protocols used by PPP and PPTP.
.TP
.B mschap
a proprietary Microsoft challenge/response protocol also used by PPP, PPTP and CIFS.
.TP
.B mschapv2
version two of Microsofts challenge/response protocol used by WPA.
.TP
.B mschap2
Microsofts NTLMv2 challenge/response protocol used by CIFS.
.TP
.B rsa
RSA public key decryption, used by SSH and TLS.
.TP
.B pass
passwords in the clear.
.TP
.B vnc
.IR vnc (1)'s
challenge/response.
.TP
.B wpapsk
WPA passwords for wireless ethernet cards.
.PD
.PP
The options are:
.TP
.B \-a
supplies the address of the authentication server to use.
Without this option, it will attempt to find an authentication server by
querying the connection server, the file
.BR <mtpt>/ndb ,
and finally the network database in
.BR /lib/ndb .
.TP
.B \-m
specifies the mount point to use, by default
.BR /mnt .
.TP
.B \-s
specifies the service name to use.
Without this option,
.I factotum
does not create a service file in
.BR /srv .
.TP
.B \-D
turns on 9P tracing, written to standard error.
.TP
.B \-d
turns on debugging, written to standard error.
.TP
.B \-g
causes the agent to prompt for the key, write it
to the
.B ctl
file, and exit.
The agent will prompt for values for any of the
attributes ending with a question mark
.RB ( ? )
and will append all the supplied
.I attribute = value
pairs.  See the section on key templates below.
.TP
.B \-n
don't look for a secstore.
.TP
.B \-S
indicates that the agent is running on a
CPU server.  On starting, it will attempt to get
.B p9sk1
and
.B dp9ik
keys from NVRAM using
.B readnvram
(see
.IR authsrv (2)),
prompting for anything it needs.
It will never subsequently prompt for a
key that it doesn't have.
This option is typically used by
the kernel at boot time.
.TP
.B \-k
causes the NVRAM to be written.
It is only valid with the
.B \-S
option.
This option is typically used by
the kernel at boot time.
.TP
.B \-u
causes the agent to prompt for user
id and writes it to
.BR /dev/hostowner .
It is mutually exclusive with
.B \-k
and
.BR \-S .
This option is typically used by
the kernel at boot time.
.TP
.B \-p
causes the agent not to mark itself `private'
via 
.IR proc (3),
so that it can be debugged.
It is implied by
.BR \-d .
.PD
.PP
.I Fgui
is a graphic user interface for confirming key usage and
entering new keys.  It hides the window in which it starts
and waits reading requests from
.B confirm
and
.BR needkey .
For each requests, it unhides itself and waits for
user input.
See the sections on key confirmation and key prompting below.
.PP
.I Userpasswd
queries and prints a cleartext user/password pair from factotum
for the
.B proto=pass
key tuple specified in
.IR fmt .
This can be used by shell scripts to do cleartext password
authentication.
.SS "Key Tuples
.PP
A
.I "key tuple
is a space delimited list of 
.IB attribute = value
pairs.  An attribute whose name begins with an exclamation point
.RB ( ! )
does not appear when reading the
.B ctl
file.
The required attributes depend on the authentication protocol.
.PP
.BR Dp9ik ,
.B p9sk1
and
.B p9cr
all require a key with
.BR proto = dp9ik
or
.BR proto = p9sk1 ,
a
.B dom
attribute identifying the authentication domain, a
.B user
name valid in that domain, and either a
.B !password
or
.B !hex
attribute specifying the password or hexadecimal secret
to be used.  Here is an example:
.PP
.EX
    proto=dp9ik dom=9front user=glenda !password=secret
.EE
.PP
.BR Apop ,
.BR cram ,
.BR chap ,
and
.BR mschap ,
require a key with a
.B proto
attribute whose value matches the protocol,
in addition to
.BR server ,
.BR user ,
and
.B !password
attributes; 
e.g.
.PP
.EX
    proto=apop server=mit.edu user=rsc !password=nerdsRus
.EE
Vnc is similar but does not require a
.B user
attribute.
.PP
.B Pass
requires a key with
.B proto=pass
in addition to
.B user
and
.B !password
attributes; e.g.
.PP
.EX
    proto=pass user=tb !password=does.it.matter
.EE
.PP
.B Rsa
requires a key with
.B proto=rsa
in addition to all the hex attributes defining an RSA key:
.BR ek ,
.BR n ,
.BR !p ,
.BR !q ,
.BR !kp ,
.BR !kq ,
.BR !c2 ,
and
.BR !dk .
By convention, programs using the RSA protocol also require a
.B service
attribute set to
.B ssh
or
.BR tls .
.PP
All keys can have additional attributes that act either as comments
or as selectors to distinguish them in the
.IR auth (2)
library calls.
.PP
The factotum owner can use any key stored by factotum.
Any key may have one or more
.B owner
attributes listing the users who can use the key
as though they were the owner.
For example, the TLS and SSH host keys on a server
often have an attribute
.B owner=*
to allow any user (and in particular,
.LR none )
to run the TLS or SSH server-side protocol.
.PP
Any key may have a
.B role
attribute for restricting how it can be used.
If this attribute is missing, the key can be used in any role.
The possible values are:
.TP
.B client
for authenticating outbound calls
.TP
.B server
for authenticating inbound calls
.TP
.B speakfor
for authenticating processes whose
user id does not match
.IR factotum 's.
.PP
If a key has a
.B disabled
attribute (with any value), the key is not used
during any protocols.  Factotum automatically marks
keys with
.B disabled=by.factotum
when they fail during certain authentication
protocols (in particular, the Plan 9 ones).
.PD
.PP
Whenever
.I factotum
runs as a server, it must have
.B dp9ik
or
.B p9sk1
keys in order to communicate with the authentication
server for validating passwords and challenge/responses of
other users.
.SS "Key Templates
Key templates are used by routines that interface to
.I factotum
such as
.B auth_proxy
and
.B auth_challenge
(see
.IR auth (2))
to specify which key and protocol to use for an authentication.
Like a key tuple, a key template is also a list of 
.IB attribute = value
pairs.
It must specify at least the protocol and enough
other attributes to uniquely identify a key, or set of keys, to use.
The keys chosen are those that match all the attributes specified
in the template.  The possible attribute/value formats are:
.TP 1i
.IB attr = val
The attribute
.I attr
must exist in the key and its value must exactly
match
.I val
.TP 1i
.IB attr ?
The attribute
.I attr
must exist in the key but its value doesn't matter.
.TP 1i
.I attr
The attribute
.I attr
must exist in the key with a null value
.PD
.PP
Key templates are also used by factotum to request a key either via
an RPC error or via the
.B needkey
interface.
The possible attribute/value formats are:
.TP 1i
.IB attr = val
This pair must remain unchanged
.TP 1i
.IB attr ?
This attribute needs a value
.TP 1i
.I attr
The pair must remain unchanged
.PD
.SS "Control and Key Management
.PP
A number of messages can be written to the control file.
The messages are:
.TP
.B "key \fIattribute-value-list\fP
add a new key.  This will replace any old key whose
public, i.e. non ! attributes, match.
.TP
.B "delkey \fIattribute-value-list\fP
delete a key whose attributes match those given.
.TP
.B debug
toggle debugging on and off, i.e., the debugging also
turned on by the
.B \-d
option.
.PP
By default when factotum starts it looks for a
.IR secstore (1)
account on $auth for the user and, if one exists,
prompts for a secstore password in order to fetch
the file
.IR factotum ,
which should contain control file commands.
An example would be
.EX
  key dom=x.com proto=p9sk1 user=boyd !hex=26E522ADE2BBB2A229
  key proto=rsa service=ssh size=1024 ek=3B !dk=...
.EE
where the first line sets a password for
challenge/response authentication, strong against dictionary
attack by being a long random string, and the second line
sets a public/private keypair for ssh authentication.
.PD
.SS "Confirming key use
.PP
The 
.B confirm
file provides a connection from
.I factotum
to a confirmation server, normally the program
.IR auth/fgui .
Whenever a key with the
.B confirm
attribute is used, 
.I factotum
requires confirmation of its use.  If no process has
.B confirm
opened, use of the key will be denied.
However, if the file is opened a request can be read from it
with the following format:
.PP
.B confirm
.BI tag= tagno
.I "<key template>
.PP
The reply, written back to
.BR confirm ,
consists of string:
.PP
.BI tag= tagno
.BI answer= xxx
.PP
If
.I xxx
is the string
.B yes
then the use is confirmed and the authentication will proceed.
Otherwise, it fails.
.PP
.B Confirm
is exclusive open and can only be opened by a process with
the same user id as
.IR factotum .
.SS "Prompting for keys
.PP
The 
.B needkey
file provides a connection from
.I factotum
to a key server, normally the program
.IR auth/fgui .
Whenever
.I factotum
needs a new key, it first checks to see if
.B needkey
is opened.  If it isn't, it returns a error to its client.
If the file is opened a request can be read from it
with the following format:
.PP
.B needkey
.BI tag= tagno
.I "<key template>
.PP
It is up to the reader to then query the user for any missing fields,
write the key tuple into the
.B ctl
file, and then reply by writing into the
.B needkey
file the string:
.PP
.BI tag= tagno
.PP
.B Needkey
is exclusive open and can only be opened by a process with
the same user id as
.IR factotum .
.SS "The RPC Protocol
Authentication is performed by
.IP 1)
opening
.BR rpc
.IP 2)
setting up the protocol and key to be used (see the
.B start
RPC below),
.IP 3)
shuttling messages back and forth between
.IR factotum
and the other party (see the
.B read
and
.B write
RPC's) until done
.IP 4)
if successful, reading back an
.I AuthInfo
structure (see
.IR authsrv (2)).
.PP
The RPC protocol is normally embodied by one of the
routines in
.IR auth (2).
We describe it here should anyone want to extend
the library.
.PP
An RPC consists of writing a request message to
.B rpc
followed by reading a reply message back.
RPC's are strictly ordered; requests and replies of
different RPC's cannot be interleaved.
Messages consist of a verb, a single space, and data.
The data format depends on the verb.  The request verbs are:
.TP
.B "start \fIattribute-value-list\fP
start a new authentication.
.I Attribute-value-pair-list
must include a
.B proto
attribute, a
.B role
attribute with value
.B client
or
.BR server ,
and enough other attributes to uniquely identify a key to use.
A
.B start
RPC is required before any others.    The possible replies are:
.RS
.TP
.B ok
start succeeded.
.TP
.B "error \fIstring\fP
where
.I string
is the reason.
.RE
.PD
.TP
.B read
get data from
.I factotum
to send to the other party.  The possible replies are:
.RS
.TP
.B ok
read succeeded, this is zero length message.
.TP
.B "ok \fIdata\fP
read succeeded, the data follows the space and is
unformatted.
.TP
.B "done
authentication has succeeded, no further RPC's are
necessary
.TP
.B "done haveai
authentication has succeeded, an
.B AuthInfo
structure (see
.IR auth (2))
can be retrieved with an
.B authinfo
RPC
.TP
.B "phase \fIstring\fP
its not your turn to read, get some data from
the other party and return it with a write RPC.
.TP
.B "error \fIstring\fP
authentication failed,
.I string
is the reason.
.TP
.B "protocol not started
a
.B start
RPC needs to precede reads and writes
.TP
.B "needkey \fIattribute-value-list\fP
a key matching the argument is needed.  This argument
may be passed as an argument to
.I factotum
.B -g
in order to prompt for a key.  After that, the
authentication may proceed, i.e., the read restarted.
.PD
.RE
.TP
.B "write \fIdata\fP
send data from the other party to
.IR factotum .
The possible replies are:
.RS
.TP
.B "ok
the write succeeded
.TP
.B "needkey \fIattribute-value-list\fP
see above
.TP
.B "toosmall \fIn\fP
the write is too short, get more data from the
other party and retry the write.
.I n
specifies the maximun total number of bytes.
.TP
.B "phase \fIstring\fP
its not your turn to write, get some data from
.I factotum
first.
.TP
.B "done
see above
.TP
.B "done haveai
see above
.RE
.TP
.B authinfo
retrieve the AuthInfo structure.  
The possible replies are:
.RS
.TP
.B "ok \fIdata\fP
.I data
is a marshaled form of the AuthInfo structure.
.TP
.B "error \fIstring\fP
where
.I string
is the reason for the error.
.PD
.RE
.TP
.B attr
retrieve the attributes used in the
.B start
RPC.
The possible replies are:
.RS
.TP
.B "ok \fIattribute-value-list\fP
.TP
.B "error \fIstring\fP
where
.I string
is the reason for the error.
.PD
.RE
.SH SOURCE
.B /sys/src/cmd/auth/factotum
.SH "SEE ALSO"
.IR authsrv (6)