command.c File Reference

Client authentication and server commands. More...

#include <netinet/in.h>
#include <sys/socket.h>
#include <regex.h>
#include <signal.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <lopsub.h>
#include "para.h"
#include "error.h"
#include "lsu.h"
#include "crypt.h"
#include "sideband.h"
#include "command.h"
#include "string.h"
#include "afh.h"
#include "net.h"
#include "server.h"
#include "list.h"
#include "sched.h"
#include "send.h"
#include "vss.h"
#include "daemon.h"
#include "fd.h"
#include "ipc.h"
#include "server_cmd.lsg.h"
#include "user_list.h"
#include "version.h"

Macros
#define	SERVER_CMD_AUX_INFO(_arg)   _arg,
#define	SERVER_CMD_AUX_INFO(_arg)   #_arg,
#define	MAX_COMMAND_LEN   32768
	Commands including options must be shorter than this. More...
#define	EMPTY_STATUS_ITEMS
	These status items are cleared if no audio file is currently open. More...
#define	ITEM(x)   "0004 %02x:\n"
#define	ITEM(x)   , (unsigned) SI_ ## x
#define	ITEM(x)   "%s:\n"
#define	ITEM(x)   ,status_item_list[SI_ ## x]
#define	HANDSHAKE_BUFSIZE   4096

Functions
int	send_afs_status (struct command_context *cc, int parser_friendly)
	Get the current afs status items from the afs process and send it. More...
int	send_sb (struct stream_cipher_context *scc, void *buf, size_t numbytes, int band, bool dont_free)
	Send a sideband packet through a blocking file descriptor. More...
__printf_3_4 int	send_sb_va (struct stream_cipher_context *scc, int band, const char *fmt,...)
	Create a variable sized buffer and send it as a sideband packet. More...
int	send_strerror (struct command_context *cc, int err)
	Send an error message to a client. More...
int	send_errctx (struct command_context *cc, char *errctx)
	Send an error context to a client,. More...
int	recv_sb (struct stream_cipher_context *scc, enum sb_designator expected_band, size_t max_size, struct iovec *result)
	Receive a sideband packet from a blocking file descriptor. More...
int	handle_connect (int fd)
	Perform user authentication and execute a command. More...

Variables
int	mmd_mutex
	The mutex protecting the shared memory area containing the mmd struct. More...
struct misc_meta_data *	mmd
	Pointer to shared memory area for communication between para_server and its children. More...
const struct server_cmd_user_data	lsg_server_cmd_com_sender_user_data = { .handler = com_sender }
const struct server_cmd_user_data	lsg_server_cmd_com_si_user_data = { .handler = com_si }
const struct server_cmd_user_data	lsg_server_cmd_com_version_user_data = { .handler = com_version }
const struct server_cmd_user_data	lsg_server_cmd_com_stat_user_data = { .handler = com_stat }
const struct server_cmd_user_data	lsg_server_cmd_com_help_user_data = { .handler = com_help }
const struct server_cmd_user_data	lsg_server_cmd_com_hup_user_data = { .handler = com_hup }
const struct server_cmd_user_data	lsg_server_cmd_com_ll_user_data = { .handler = com_ll }
const struct server_cmd_user_data	lsg_server_cmd_com_term_user_data = { .handler = com_term }
const struct server_cmd_user_data	lsg_server_cmd_com_play_user_data = { .handler = com_play }
const struct server_cmd_user_data	lsg_server_cmd_com_stop_user_data = { .handler = com_stop }
const struct server_cmd_user_data	lsg_server_cmd_com_pause_user_data = { .handler = com_pause }
const struct server_cmd_user_data	lsg_server_cmd_com_next_user_data = { .handler = com_next }
const struct server_cmd_user_data	lsg_server_cmd_com_nomore_user_data = { .handler = com_nomore }
const struct server_cmd_user_data	lsg_server_cmd_com_ff_user_data = { .handler = com_ff }
const struct server_cmd_user_data	lsg_server_cmd_com_jmp_user_data = { .handler = com_jmp }

Detailed Description

Client authentication and server commands.

Macro Definition Documentation

SERVER_CMD_AUX_INFO [1/2]

#define SERVER_CMD_AUX_INFO

(

_arg

)

_arg,

SERVER_CMD_AUX_INFO [2/2]

#define SERVER_CMD_AUX_INFO

(

_arg

)

#_arg,

MAX_COMMAND_LEN

#define MAX_COMMAND_LEN   32768

Commands including options must be shorter than this.

EMPTY_STATUS_ITEMS

#define EMPTY_STATUS_ITEMS

These status items are cleared if no audio file is currently open.

ITEM [1/4]

#define ITEM

(

x

)

"0004 %02x:\n"

ITEM [2/4]

#define ITEM

(

x

)

, (unsigned) SI_ ## x

ITEM [3/4]

#define ITEM

(

x

)

"%s:\n"

ITEM [4/4]

#define ITEM

(

x

)

,status_item_list[SI_ ## x]

HANDSHAKE_BUFSIZE

#define HANDSHAKE_BUFSIZE   4096

Function Documentation

send_afs_status()

int send_afs_status	(	struct command_context *	cc,
		int	parser_friendly
	)

Get the current afs status items from the afs process and send it.

Parameters

cc	The command context, used e.g. for data encryption.
parser_friendly	Whether parser-friendly output format should be used.

As the contents of the afs status items change in time and the command handler only has a COW version created at fork time, it can not send up-to-date afs status items directly. Therefore the usual callback mechanism is used to pass the status items from the afs process to the command handler via a shared memory area and a pipe.

Returns

The return value of the underlying call to send_callback_request().

References send_callback_request().

send_sb()

int send_sb	(	struct stream_cipher_context *	scc,
		void *	buf,
		size_t	numbytes,
		int	band,
		bool	dont_free
	)

Send a sideband packet through a blocking file descriptor.

Parameters

scc	fd and crypto keys.
buf	The buffer to send.
numbytes	The size of buf.
band	The sideband designator of this packet.
dont_free	If true, never deallocate buf.

The nonblock flag must be disabled for the file descriptor given by scc.

Stream cipher encryption is automatically activated if necessary via the sideband transformation, depending on the value of band.

Returns

Standard.

See also

send_sb_va().

References sb_buffer::band, stream_cipher_context::fd, sb_buffer::iov, sb_free(), sb_get_send_buffers(), sb_new_send(), sb_sent(), SBB_INIT, SBD_PROCEED, sc_trafo(), stream_cipher_context::send, and xwritev().

Referenced by send_sb_va().

send_sb_va()

__printf_3_4 int send_sb_va	(	struct stream_cipher_context *	scc,
		int	band,
		const char *	fmt,
			...
	)

Create a variable sized buffer and send it as a sideband packet.

Parameters

scc	Passed to send_sb.
band	See send_sb.
fmt	The format string.

Returns

The return value of the underlying call to send_sb.

References sb_buffer::band, send_sb(), and xvasprintf().

Referenced by send_errctx(), and send_strerror().

send_strerror()

int send_strerror	(	struct command_context *	cc,
		int	err
	)

Send an error message to a client.

Parameters

cc	Client info.
err	The (positive) error code.

Returns

The return value of the underlying call to send_sb_va().

References para_strerror(), SBD_ERROR_LOG, command_context::scc, and send_sb_va().

send_errctx()

int send_errctx	(	struct command_context *	cc,
		char *	errctx
	)

Send an error context to a client,.

Parameters

cc	Client info.
errctx	The error context string.

Returns

The return value of the underlying call to send_sb_va().

This function frees the error context string after it was sent.

References SBD_ERROR_LOG, command_context::scc, and send_sb_va().

recv_sb()

int recv_sb	(	struct stream_cipher_context *	scc,
		enum sb_designator	expected_band,
		size_t	max_size,
		struct iovec *	result
	)

Receive a sideband packet from a blocking file descriptor.

Parameters

scc	fd and crypto keys.
expected_band	The expected band designator.
max_size	Passed to sb_new_recv().
result	Body of the sideband packet is returned here.

If expected_band is not SBD_ANY, the band designator of the received sideband packet is compared to expected_band and a mismatch is considered an error.

Returns

Standard.

References sb_buffer::band, stream_cipher_context::fd, sb_buffer::iov, stream_cipher_context::recv, recv_bin_buffer(), sb_free(), sb_get_recv_buffer(), sb_new_recv(), sb_received(), SBD_ANY, SBD_PROCEED, and sc_trafo().

handle_connect()

int handle_connect

(

int

fd

)

Perform user authentication and execute a command.

Parameters

fd	The file descriptor to send output to.

Whenever para_server accepts an incoming tcp connection on the port it listens on, it forks and the resulting child calls this function.

An RSA-based challenge/response is used to authenticate the peer. If the authentication succeeds, a random session key is generated and sent back to the peer, encrypted with its RSA public key. From this point on, all transfers are encrypted with this session key using a stream cipher.

Next it is checked if the peer supplied a valid server command or a command for the audio file selector. If yes, and if the user has sufficient permissions to execute this command, the function calls the corresponding command handler which performs argument checking and further processing.

To cope with DOS attacks, a timer is set up right after the fork. If the connection was still not authenticated when the timeout expires, the child process is terminated.

Returns

Standard.

See also

alarm(2), openssl.c, crypt.h.

References alloc(), APC_CHALLENGE_SIZE, stream_cipher_context::fd, HANDSHAKE_BUFSIZE, HASH2_SIZE, command_context::scc, SESSION_KEY_LEN, and command_context::u.

Variable Documentation

mmd_mutex

int mmd_mutex

extern

The mutex protecting the shared memory area containing the mmd struct.

mmd

struct misc_meta_data* mmd

extern

Pointer to shared memory area for communication between para_server and its children.

Exported to vss.c, command.c and to afs.

lsg_server_cmd_com_sender_user_data

const struct server_cmd_user_data lsg_server_cmd_com_sender_user_data = { .handler = com_sender }

lsg_server_cmd_com_si_user_data

const struct server_cmd_user_data lsg_server_cmd_com_si_user_data = { .handler = com_si }

lsg_server_cmd_com_version_user_data

const struct server_cmd_user_data lsg_server_cmd_com_version_user_data = { .handler = com_version }

lsg_server_cmd_com_stat_user_data

const struct server_cmd_user_data lsg_server_cmd_com_stat_user_data = { .handler = com_stat }

lsg_server_cmd_com_help_user_data

const struct server_cmd_user_data lsg_server_cmd_com_help_user_data = { .handler = com_help }

lsg_server_cmd_com_hup_user_data

const struct server_cmd_user_data lsg_server_cmd_com_hup_user_data = { .handler = com_hup }

lsg_server_cmd_com_ll_user_data

const struct server_cmd_user_data lsg_server_cmd_com_ll_user_data = { .handler = com_ll }

lsg_server_cmd_com_term_user_data

const struct server_cmd_user_data lsg_server_cmd_com_term_user_data = { .handler = com_term }

lsg_server_cmd_com_play_user_data

const struct server_cmd_user_data lsg_server_cmd_com_play_user_data = { .handler = com_play }

lsg_server_cmd_com_stop_user_data

const struct server_cmd_user_data lsg_server_cmd_com_stop_user_data = { .handler = com_stop }

lsg_server_cmd_com_pause_user_data

const struct server_cmd_user_data lsg_server_cmd_com_pause_user_data = { .handler = com_pause }

lsg_server_cmd_com_next_user_data

const struct server_cmd_user_data lsg_server_cmd_com_next_user_data = { .handler = com_next }

lsg_server_cmd_com_nomore_user_data

const struct server_cmd_user_data lsg_server_cmd_com_nomore_user_data = { .handler = com_nomore }

lsg_server_cmd_com_ff_user_data

const struct server_cmd_user_data lsg_server_cmd_com_ff_user_data = { .handler = com_ff }

lsg_server_cmd_com_jmp_user_data

const struct server_cmd_user_data lsg_server_cmd_com_jmp_user_data = { .handler = com_jmp }