lib/libradius/libradius.3

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.\" Copyright 2009 Alexander Motin <mav@FreeBSD.org>.
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.Dd August 5, 2009
.Dt LIBRADIUS 3
.Os
.Sh NAME
.Nm libradius
.Nd RADIUS client/server library
.Sh SYNOPSIS
.In radlib.h
.Ft "struct rad_handle *"
.Fn rad_acct_open "void"
.Ft int
.Fn rad_add_server "struct rad_handle *h" "const char *host" "int port" "const char *secret" "int timeout" "int max_tries"
.Ft "struct rad_handle *"
.Fn rad_auth_open "void"
.Ft void
.Fn rad_close "struct rad_handle *h"
.Ft int
.Fn rad_config "struct rad_handle *h" "const char *file"
.Ft int
.Fn rad_continue_send_request "struct rad_handle *h" "int selected" "int *fd" "struct timeval *tv"
.Ft int
.Fn rad_create_request "struct rad_handle *h" "int code"
.Ft int
.Fn rad_create_response "struct rad_handle *h" "int code"
.Ft "struct in_addr"
.Fn rad_cvt_addr "const void *data"
.Ft u_int32_t
.Fn rad_cvt_int "const void *data"
.Ft char *
.Fn rad_cvt_string "const void *data" "size_t len"
.Ft int
.Fn rad_get_attr "struct rad_handle *h" "const void **data" "size_t *len"
.Ft int
.Fn rad_get_vendor_attr "u_int32_t *vendor" "const void **data" "size_t *len"
.Ft int
.Fn rad_init_send_request "struct rad_handle *h" "int *fd" "struct timeval *tv"
.Ft int
.Fn rad_put_addr "struct rad_handle *h" "int type" "struct in_addr addr"
.Ft int
.Fn rad_put_attr "struct rad_handle *h" "int type" "const void *data" "size_t len"
.Ft int
.Fn rad_put_int "struct rad_handle *h" "int type" "u_int32_t value"
.Ft int
.Fn rad_put_string "struct rad_handle *h" "int type" "const char *str"
.Ft int
.Fn rad_put_message_authentic "struct rad_handle *h"
.Ft int
.Fn rad_put_vendor_addr "struct rad_handle *h" "int vendor" "int type" "struct in_addr addr"
.Ft int
.Fn rad_put_vendor_attr "struct rad_handle *h" "int vendor" "int type" "const void *data" "size_t len"
.Ft int
.Fn rad_put_vendor_int "struct rad_handle *h" "int vendor" "int type" "u_int32_t value"
.Ft int
.Fn rad_put_vendor_string "struct rad_handle *h" "int vendor" "int type" "const char *str"
.Ft ssize_t
.Fn rad_request_authenticator "struct rad_handle *h" "char *buf" "size_t len"
.Ft int
.Fn rad_receive_request "struct rad_handle *h"
.Ft int
.Fn rad_send_request "struct rad_handle *h"
.Ft int
.Fn rad_send_response "struct rad_handle *h"
.Ft "struct rad_handle *"
.Fn rad_server_open "int fd"
.Ft "const char *"
.Fn rad_server_secret "struct rad_handle *h"
.Ft u_char *
.Fn rad_demangle "struct rad_handle *h" "const void *mangled" "size_t mlen"
.Ft u_char *
.Fn rad_demangle_mppe_key "struct rad_handle *h" "const void *mangled" "size_t mlen" "size_t *len"
.Ft "const char *"
.Fn rad_strerror "struct rad_handle *h"
.Sh DESCRIPTION
The
.Nm
library implements the Remote Authentication Dial In User Service (RADIUS).
RADIUS, defined in RFCs 2865 and 2866,
allows clients to perform authentication and accounting by means of
network requests to remote servers.
.Ss Initialization
To use the library, an application must first call
.Fn rad_auth_open
,
.Fn rad_acct_open
or
.Fn rad_server_open
to obtain a
.Vt "struct rad_handle *" ,
which provides the context for subsequent operations.
The former function is used for RADIUS authentication and the
latter is used for RADIUS accounting.
Calls to
.Fn rad_auth_open
,
.Fn rad_acct_open
and
.Fn rad_server_open
always succeed unless insufficient virtual memory is available.
If
the necessary memory cannot be allocated, the functions return
.Dv NULL .
For compatibility with earlier versions of this library,
.Fn rad_open
is provided as a synonym for
.Fn rad_auth_open .
.Pp
Before issuing any RADIUS requests, the library must be made aware
of the servers it can contact.
The easiest way to configure the
library is to call
.Fn rad_config .
.Fn rad_config
causes the library to read a configuration file whose format is
described in
.Xr radius.conf 5 .
The pathname of the configuration file is passed as the
.Fa file
argument to
.Fn rad_config .
This argument may also be given as
.Dv NULL ,
in which case the standard configuration file
.Pa /etc/radius.conf
is used.
.Fn rad_config
returns 0 on success, or \-1 if an error occurs.
.Pp
The library can also be configured programmatically by calls to
.Fn rad_add_server .
The
.Fa host
parameter specifies the server host, either as a fully qualified
domain name or as a dotted-quad IP address in text form.
The
.Fa port
parameter specifies the UDP port to contact on the server.
If
.Fa port
is given as 0, the library looks up the
.Ql radius/udp
or
.Ql radacct/udp
service in the network
.Xr services 5
database, and uses the port found
there.
If no entry is found, the library uses the standard RADIUS
ports, 1812 for authentication and 1813 for accounting.
The shared secret for the server host is passed to the
.Fa secret
parameter.
It may be any
.Dv NUL Ns -terminated
string of bytes.
The RADIUS protocol
ignores all but the leading 128 bytes of the shared secret.
The timeout for receiving replies from the server is passed to the
.Fa timeout
parameter, in units of seconds.
The maximum number of repeated
requests to make before giving up is passed into the
.Fa max_tries
parameter.
.Fn rad_add_server
returns 0 on success, or \-1 if an error occurs.
.Pp
.Fn rad_add_server
may be called multiple times, and it may be used together with
.Fn rad_config .
At most 10 servers may be specified.
When multiple servers are given, they are tried in round-robin
fashion until a valid response is received, or until each server's
.Fa max_tries
limit has been reached.
.Ss Creating a RADIUS Request
A RADIUS request consists of a code specifying the kind of request,
and zero or more attributes which provide additional information.
To
begin constructing a new request, call
.Fn rad_create_request .
In addition to the usual
.Vt "struct rad_handle *" ,
this function takes a
.Fa code
parameter which specifies the type of the request.
Most often this
will be
.Dv RAD_ACCESS_REQUEST .
.Fn rad_create_request
returns 0 on success, or \-1 on if an error occurs.
.Pp
After the request has been created with
.Fn rad_create_request ,
attributes can be attached to it.
This is done through calls to
.Fn rad_put_addr ,
.Fn rad_put_int ,
and
.Fn rad_put_string .
Each accepts a
.Fa type
parameter identifying the attribute, and a value which may be
an Internet address, an integer, or a
.Dv NUL Ns -terminated
string,
respectively.
Alternatively,
.Fn rad_put_vendor_addr ,
.Fn rad_put_vendor_int
or
.Fn rad_put_vendor_string
may be used to specify vendor specific attributes.
Vendor specific
definitions may be found in
.In radlib_vs.h
.Pp
The library also provides a function
.Fn rad_put_attr
which can be used to supply a raw, uninterpreted attribute.
The
.Fa data
argument points to an array of bytes, and the
.Fa len
argument specifies its length.
.Pp
It is possible adding the Message-Authenticator to the request.
This is an HMAC-MD5 hash of the entire Access-Request packet (see RFC 3579).
This attribute must be present in any packet that includes an EAP-Message
attribute.
It can be added by using the
.Fn rad_put_message_authentic
function.
The
.Nm
library
calculates the HMAC-MD5 hash implicitly before sending the request.
If the Message-Authenticator was found inside the response packet,
then the packet is silently dropped, if the validation failed.
In order to get this feature, the library should be compiled with
OpenSSL support.
.Pp
The
.Fn rad_put_X
functions return 0 on success, or \-1 if an error occurs.
.Ss Sending the Request and Receiving the Response
After the RADIUS request has been constructed, it is sent either by means of
.Fn rad_send_request
or by a combination of calls to
.Fn rad_init_send_request
and
.Fn rad_continue_send_request .
.Pp
The
.Fn rad_send_request
function sends the request and waits for a valid reply,
retrying the defined servers in round-robin fashion as necessary.
If a valid response is received,
.Fn rad_send_request
returns the RADIUS code which specifies the type of the response.
This will typically be
.Dv RAD_ACCESS_ACCEPT ,
.Dv RAD_ACCESS_REJECT ,
or
.Dv RAD_ACCESS_CHALLENGE .
If no valid response is received,
.Fn rad_send_request
returns \-1.
.Pp
As an alternative, if you do not wish to block waiting for a response,
.Fn rad_init_send_request
and
.Fn rad_continue_send_request
may be used instead.
If a reply is received from the RADIUS server or a
timeout occurs, these functions return a value as described for
.Fn rad_send_request .
Otherwise, a value of zero is returned and the values pointed to by
.Fa fd
and
.Fa tv
are set to the descriptor and timeout that should be passed to
.Xr select 2 .
.Pp
.Fn rad_init_send_request
must be called first, followed by repeated calls to
.Fn rad_continue_send_request
as long as a return value of zero is given.
Between each call, the application should call
.Xr select 2 ,
passing
.Fa *fd
as a read descriptor and timing out after the interval specified by
.Fa tv .
When
.Xr select 2
returns,
.Fn rad_continue_send_request
should be called with
.Fa selected
set to a non-zero value if
.Xr select 2
indicated that the descriptor is readable.
.Pp
Like RADIUS requests, each response may contain zero or more
attributes.
After a response has been received successfully by
.Fn rad_send_request
or
.Fn rad_continue_send_request ,
its attributes can be extracted one by one using
.Fn rad_get_attr .
Each time
.Fn rad_get_attr
is called, it gets the next attribute from the current response, and
stores a pointer to the data and the length of the data via the
reference parameters
.Fa data
and
.Fa len ,
respectively.
Note that the data resides in the response itself,
and must not be modified.
A successful call to
.Fn rad_get_attr
returns the RADIUS attribute type.
If no more attributes remain in the current response,
.Fn rad_get_attr
returns 0.
If an error such as a malformed attribute is detected, \-1 is
returned.
.Pp
If
.Fn rad_get_attr
returns
.Dv RAD_VENDOR_SPECIFIC ,
.Fn rad_get_vendor_attr
may be called to determine the vendor.
The vendor specific RADIUS attribute type is returned.
The reference parameters
.Fa data
and
.Fa len
(as returned from
.Fn rad_get_attr )
are passed to
.Fn rad_get_vendor_attr ,
and are adjusted to point to the vendor specific attribute data.
.Pp
The common types of attributes can be decoded using
.Fn rad_cvt_addr ,
.Fn rad_cvt_int ,
and
.Fn rad_cvt_string .
These functions accept a pointer to the attribute data, which should
have been obtained using
.Fn rad_get_attr
and optionally
.Fn rad_get_vendor_attr .
In the case of
.Fn rad_cvt_string ,
the length
.Fa len
must also be given.
These functions interpret the attribute as an
Internet address, an integer, or a string, respectively, and return
its value.
.Fn rad_cvt_string
returns its value as a
.Dv NUL Ns -terminated
string in dynamically
allocated memory.
The application should free the string using
.Xr free 3
when it is no longer needed.
.Pp
If insufficient virtual memory is available,
.Fn rad_cvt_string
returns
.Dv NULL .
.Fn rad_cvt_addr
and
.Fn rad_cvt_int
cannot fail.
.Pp
The
.Fn rad_request_authenticator
function may be used to obtain the Request-Authenticator attribute value
associated with the current RADIUS server according to the supplied
rad_handle.
The target buffer
.Fa buf
of length
.Fa len
must be supplied and should be at least 16 bytes.
The return value is the number of bytes written to
.Fa buf
or \-1 to indicate that
.Fa len
was not large enough.
.Pp
The
.Fn rad_server_secret
returns the secret shared with the current RADIUS server according to the
supplied rad_handle.
.Pp
The
.Fn rad_demangle
function demangles attributes containing passwords and MS-CHAPv1 MPPE-Keys.
The return value is
.Dv NULL
on failure, or the plaintext attribute.
This value should be freed using
.Xr free 3
when it is no longer needed.
.Pp
The
.Fn rad_demangle_mppe_key
function demangles the send- and recv-keys when using MPPE (see RFC 2548).
The return value is
.Dv NULL
on failure, or the plaintext attribute.
This value should be freed using
.Xr free 3
when it is no longer needed.
.Ss Obtaining Error Messages
Those functions which accept a
.Vt "struct rad_handle *"
argument record an error message if they fail.
The error message
can be retrieved by calling
.Fn rad_strerror .
The message text is overwritten on each new error for the given
.Vt "struct rad_handle *" .
Thus the message must be copied if it is to be preserved through
subsequent library calls using the same handle.
.Ss Cleanup
To free the resources used by the RADIUS library, call
.Fn rad_close .
.Ss Server operation
Server mode operates much alike to client mode, except packet send and receive
steps are swapped. To operate as server you should obtain server context with
.Fn rad_server_open
function, passing opened and bound UDP socket file descriptor as argument.
You should define allowed clients and their secrets using
.Fn rad_add_server
function. port, timeout and max_tries arguments are ignored in server mode.
You should call
.Fn rad_receive_request
function to receive request from client. If you do not want to block on socket
read, you are free to use any poll(), select() or non-blocking sockets for
the socket.
Received request can be parsed with same parsing functions as for client.
To respond to the request you should call
.Fn rad_create_response
and fill response content with same packet writing functions as for client.
When packet is ready, it should be sent with
.Fn rad_send_response
.Sh RETURN VALUES
The following functions return a non-negative value on success.
If
they detect an error, they return \-1 and record an error message
which can be retrieved using
.Fn rad_strerror .
.Pp
.Bl -item -offset indent -compact
.It
.Fn rad_add_server
.It
.Fn rad_config
.It
.Fn rad_create_request
.It
.Fn rad_create_response
.It
.Fn rad_get_attr
.It
.Fn rad_put_addr
.It
.Fn rad_put_attr
.It
.Fn rad_put_int
.It
.Fn rad_put_string
.It
.Fn rad_put_message_authentic
.It
.Fn rad_init_send_request
.It
.Fn rad_continue_send_request
.It
.Fn rad_send_request
.It
.Fn rad_send_response
.El
.Pp
The following functions return a
.No non- Ns Dv NULL
pointer on success.
If they are unable to allocate sufficient
virtual memory, they return
.Dv NULL ,
without recording an error message.
.Pp
.Bl -item -offset indent -compact
.It
.Fn rad_acct_open
.It
.Fn rad_auth_open
.It
.Fn rad_server_open
.It
.Fn rad_cvt_string
.El
.Pp
The following functions return a
.No non- Ns Dv NULL
pointer on success.
If they fail, they return
.Dv NULL ,
with recording an error message.
.Pp
.Bl -item -offset indent -compact
.It
.Fn rad_demangle
.It
.Fn rad_demangle_mppe_key
.El
.Sh FILES
.Bl -tag -width indent
.It Pa /etc/radius.conf
.El
.Sh SEE ALSO
.Xr radius.conf 5
.Rs
.%A "C. Rigney, et al"
.%T "Remote Authentication Dial In User Service (RADIUS)"
.%O "RFC 2865"
.Re
.Rs
.%A "C. Rigney"
.%T "RADIUS Accounting"
.%O "RFC 2866"
.Re
.Rs
.%A G. Zorn
.%T "Microsoft Vendor-specific RADIUS attributes"
.%O RFC 2548
.Re
.Rs
.%A C. Rigney, et al
.%T "RADIUS extensions"
.%O RFC 2869
.Re
.Sh AUTHORS
.An -nosplit
This software was originally written by
.An John Polstra ,
and donated to the
.Fx
project by Juniper Networks, Inc.
.An Oleg Semyonov
subsequently added the ability to perform RADIUS
accounting.
Later additions and changes by
.An Michael Bretterklieber .
Server mode support was added by
.An Alexander Motin .