assuan-handler.c
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assuan-handler.c
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	/* assuan-handler.c - dispatch commands
	* Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
	*
	* This file is part of Assuan.
	*
	* Assuan is free software; you can redistribute it and/or modify it
	* under the terms of the GNU Lesser General Public License as
	* published by the Free Software Foundation; either version 2.1 of
	* the License, or (at your option) any later version.
	*
	* Assuan is distributed in the hope that it will be useful, but
	* WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with this program; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
	* USA.
	*/

	#include <config.h>
	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>
	#include <errno.h>

	#include "assuan-defs.h"



	#define spacep(p) ((p) == ' ' \|\| (p) == '\t')
	#define digitp(a) ((a) >= '0' && (a) <= '9')

	static int my_strcasecmp (const char a, const char b);



	static int
	dummy_handler (ASSUAN_CONTEXT ctx, char *line)
	{
	return set_error (ctx, Server_Fault, "no handler registered");
	}


	static int
	std_handler_nop (ASSUAN_CONTEXT ctx, char *line)
	{
	return 0; /* okay */
	}

	static int
	std_handler_cancel (ASSUAN_CONTEXT ctx, char *line)
	{
	if (ctx->cancel_notify_fnc)
	ctx->cancel_notify_fnc (ctx);
	return set_error (ctx, Not_Implemented, NULL);
	}

	static int
	std_handler_option (ASSUAN_CONTEXT ctx, char *line)
	{
	char key, value, *p;

	for (key=line; spacep (key); key++)
	;
	if (!*key)
	return set_error (ctx, Syntax_Error, "argument required");
	if (*key == '=')
	return set_error (ctx, Syntax_Error, "no option name given");
	for (value=key; value && !spacep (value) && value != '='; value++)
	;
	if (*value)
	{
	if (spacep (value))
	value++ = 0; / terminate key */
	for (; spacep (value); value++)
	;
	if (*value == '=')
	{
	value++ = 0; / terminate key */
	for (; spacep (value); value++)
	;
	if (!*value)
	return set_error (ctx, Syntax_Error, "option argument expected");
	}
	if (*value)
	{
	for (p = value + strlen(value) - 1; p > value && spacep (p); p--)
	;
	if (p > value)
	++p = 0; / strip trailing spaces */
	}
	}

	if (*key == '-' && key[1] == '-' && key[2])
	key += 2; /* the double dashes are optional */
	if (*key == '-')
	return set_error (ctx, Syntax_Error,
	"option should not begin with one dash");

	if (ctx->option_handler_fnc)
	return ctx->option_handler_fnc (ctx, key, value);
	return 0;
	}

	static int
	std_handler_bye (ASSUAN_CONTEXT ctx, char *line)
	{
	if (ctx->bye_notify_fnc)
	ctx->bye_notify_fnc (ctx);
	assuan_close_input_fd (ctx);
	assuan_close_output_fd (ctx);
	return -1; /* pretty simple :-) */
	}

	static int
	std_handler_auth (ASSUAN_CONTEXT ctx, char *line)
	{
	return set_error (ctx, Not_Implemented, NULL);
	}

	static int
	std_handler_reset (ASSUAN_CONTEXT ctx, char *line)
	{
	if (ctx->reset_notify_fnc)
	ctx->reset_notify_fnc (ctx);
	assuan_close_input_fd (ctx);
	assuan_close_output_fd (ctx);
	return 0;
	}

	static int
	std_handler_end (ASSUAN_CONTEXT ctx, char *line)
	{
	return set_error (ctx, Not_Implemented, NULL);
	}

	assuan_error_t
	assuan_command_parse_fd (ASSUAN_CONTEXT ctx, char line, int rfd)
	{
	char *endp;

	if (strncmp (line, "FD", 2) != 0 \|\| (line[2] != '=' && line[2] != '\0'))
	return set_error (ctx, Syntax_Error, "FD[=<n>] expected");
	line += 2;
	if (*line == '=')
	{
	line ++;
	if (!digitp (*line))
	return set_error (ctx, Syntax_Error, "number required");
	*rfd = strtoul (line, &endp, 10);
	/* remove that argument so that a notify handler won't see it */
	memset (line, ' ', endp? (endp-line):strlen(line));

	if (*rfd == ctx->inbound.fd)
	return set_error (ctx, Parameter_Conflict, "fd same as inbound fd");
	if (*rfd == ctx->outbound.fd)
	return set_error (ctx, Parameter_Conflict, "fd same as outbound fd");
	return 0;
	}
	else
	/* Our peer has sent the file descriptor. */
	return assuan_receivefd (ctx, rfd);
	}

	/* Format is INPUT FD=<n> */
	static int
	std_handler_input (ASSUAN_CONTEXT ctx, char *line)
	{
	int rc, fd;

	rc = assuan_command_parse_fd (ctx, line, &fd);
	if (rc)
	return rc;
	ctx->input_fd = fd;
	if (ctx->input_notify_fnc)
	ctx->input_notify_fnc (ctx, line);
	return 0;
	}

	/* Format is OUTPUT FD=<n> */
	static int
	std_handler_output (ASSUAN_CONTEXT ctx, char *line)
	{
	int rc, fd;

	rc = assuan_command_parse_fd (ctx, line, &fd);
	if (rc)
	return rc;
	ctx->output_fd = fd;
	if (ctx->output_notify_fnc)
	ctx->output_notify_fnc (ctx, line);
	return 0;
	}





	/* This is a table with the standard commands and handler for them.
	The table is used to initialize a new context and associate strings
	with default handlers */
	static struct {
	const char *name;
	int (handler)(ASSUAN_CONTEXT, char line);
	int always; /* always initialize this command */
	} std_cmd_table[] = {
	{ "NOP", std_handler_nop, 1 },
	{ "CANCEL", std_handler_cancel, 1 },
	{ "OPTION", std_handler_option, 1 },
	{ "BYE", std_handler_bye, 1 },
	{ "AUTH", std_handler_auth, 1 },
	{ "RESET", std_handler_reset, 1 },
	{ "END", std_handler_end, 1 },

	{ "INPUT", std_handler_input },
	{ "OUTPUT", std_handler_output },
	{ "OPTION", std_handler_option, 1 },
	{ NULL }
	};


	/**
	* assuan_register_command:
	* @ctx: the server context
	* @cmd_name: A string with the command name
	* @handler: The handler function to be called or NULL to use a default
	* handler.
	*
	* Register a handler to be used for a given command. Note that
	* several default handlers are already regsitered with a new context.
	* This function however allows to override them.
	*
	* Return value: 0 on success or an error code
	**/
	int
	assuan_register_command (ASSUAN_CONTEXT ctx,
	const char *cmd_name,
	int (handler)(ASSUAN_CONTEXT, char ))
	{
	int i;
	const char *s;

	if (cmd_name && !*cmd_name)
	cmd_name = NULL;

	if (!cmd_name)
	return ASSUAN_Invalid_Value;

	if (!handler)
	{ /* find a default handler. */
	for (i=0; (s=std_cmd_table[i].name) && strcmp (cmd_name, s); i++)
	;
	if (!s)
	{ /* Try again but case insensitive. */
	for (i=0; (s=std_cmd_table[i].name)
	&& my_strcasecmp (cmd_name, s); i++)
	;
	}
	if (s)
	handler = std_cmd_table[i].handler;
	if (!handler)
	handler = dummy_handler; /* Last resort is the dummy handler. */
	}

	if (!ctx->cmdtbl)
	{
	ctx->cmdtbl_size = 50;
	ctx->cmdtbl = xtrycalloc ( ctx->cmdtbl_size, sizeof *ctx->cmdtbl);
	if (!ctx->cmdtbl)
	return ASSUAN_Out_Of_Core;
	ctx->cmdtbl_used = 0;
	}
	else if (ctx->cmdtbl_used >= ctx->cmdtbl_size)
	{
	struct cmdtbl_s *x;

	x = xtryrealloc ( ctx->cmdtbl, (ctx->cmdtbl_size+10) * sizeof *x);
	if (!x)
	return ASSUAN_Out_Of_Core;
	ctx->cmdtbl = x;
	ctx->cmdtbl_size += 50;
	}

	ctx->cmdtbl[ctx->cmdtbl_used].name = cmd_name;
	ctx->cmdtbl[ctx->cmdtbl_used].handler = handler;
	ctx->cmdtbl_used++;
	return 0;
	}

	int
	assuan_register_bye_notify (ASSUAN_CONTEXT ctx, void (*fnc)(ASSUAN_CONTEXT))
	{
	if (!ctx)
	return ASSUAN_Invalid_Value;
	ctx->bye_notify_fnc = fnc;
	return 0;
	}

	int
	assuan_register_reset_notify (ASSUAN_CONTEXT ctx, void (*fnc)(ASSUAN_CONTEXT))
	{
	if (!ctx)
	return ASSUAN_Invalid_Value;
	ctx->reset_notify_fnc = fnc;
	return 0;
	}

	int
	assuan_register_cancel_notify (ASSUAN_CONTEXT ctx, void (*fnc)(ASSUAN_CONTEXT))
	{
	if (!ctx)
	return ASSUAN_Invalid_Value;
	ctx->cancel_notify_fnc = fnc;
	return 0;
	}

	int
	assuan_register_option_handler (ASSUAN_CONTEXT ctx,
	int (*fnc)(ASSUAN_CONTEXT,
	const char, const char))
	{
	if (!ctx)
	return ASSUAN_Invalid_Value;
	ctx->option_handler_fnc = fnc;
	return 0;
	}

	int
	assuan_register_input_notify (ASSUAN_CONTEXT ctx,
	void (fnc)(ASSUAN_CONTEXT, const char ))
	{
	if (!ctx)
	return ASSUAN_Invalid_Value;
	ctx->input_notify_fnc = fnc;
	return 0;
	}

	int
	assuan_register_output_notify (ASSUAN_CONTEXT ctx,
	void (fnc)(ASSUAN_CONTEXT, const char ))
	{
	if (!ctx)
	return ASSUAN_Invalid_Value;
	ctx->output_notify_fnc = fnc;
	return 0;
	}


	/* Helper to register the standards commands */
	int
	_assuan_register_std_commands (ASSUAN_CONTEXT ctx)
	{
	int i, rc;

	for (i=0; std_cmd_table[i].name; i++)
	{
	if (std_cmd_table[i].always)
	{
	rc = assuan_register_command (ctx, std_cmd_table[i].name, NULL);
	if (rc)
	return rc;
	}
	}
	return 0;
	}



	/* Process the special data lines. The "D " has already been removed
	from the line. As all handlers this function may modify the line. */
	static int
	handle_data_line (ASSUAN_CONTEXT ctx, char *line, int linelen)
	{
	return set_error (ctx, Not_Implemented, NULL);
	}

	/* like ascii_strcasecmp but assume that B is already uppercase */
	static int
	my_strcasecmp (const char a, const char b)
	{
	if (a == b)
	return 0;

	for (; a && b; a++, b++)
	{
	if (((a >= 'a' && a <= 'z')? (a&~0x20):a) != *b)
	break;
	}
	return a == b? 0 : (((a >= 'a' && a <= 'z')? (a&~0x20):a) - *b);
	}

	/* Parse the line, break out the command, find it in the command
	table, remove leading and white spaces from the arguments, call the
	handler with the argument line and return the error */
	static int
	dispatch_command (ASSUAN_CONTEXT ctx, char *line, int linelen)
	{
	char *p;
	const char *s;
	int shift, i;

	if (line == 'D' && line[1] == ' ') / divert to special handler */
	return handle_data_line (ctx, line+2, linelen-2);

	for (p=line; p && p != ' ' && *p != '\t'; p++)
	;
	if (p==line)
	return set_error (ctx, Invalid_Command, "leading white-space");
	if (*p)
	{ /* Skip over leading WS after the keyword */
	*p++ = 0;
	while ( p == ' ' \|\| p == '\t')
	p++;
	}
	shift = p - line;

	for (i=0; (s=ctx->cmdtbl[i].name); i++)
	{
	if (!strcmp (line, s))
	break;
	}
	if (!s)
	{ /* and try case insensitive */
	for (i=0; (s=ctx->cmdtbl[i].name); i++)
	{
	if (!my_strcasecmp (line, s))
	break;
	}
	}
	if (!s)
	return set_error (ctx, Unknown_Command, NULL);
	line += shift;
	linelen -= shift;

	/* fprintf (stderr, "DBG-assuan: processing %s `%s'\n", s, line); */
	return ctx->cmdtbl[i].handler (ctx, line);
	}




	static int
	process_request (ASSUAN_CONTEXT ctx)
	{
	int rc;

	if (ctx->in_inquire)
	return ASSUAN_Nested_Commands;

	rc = _assuan_read_line (ctx);
	if (rc)
	return rc;
	if (*ctx->inbound.line == '#' \|\| !ctx->inbound.linelen)
	return 0; /* comment line - ignore */

	ctx->outbound.data.error = 0;
	ctx->outbound.data.linelen = 0;
	/* dispatch command and return reply */
	rc = dispatch_command (ctx, ctx->inbound.line, ctx->inbound.linelen);
	/* check from data write errors */
	if (ctx->outbound.data.fp)
	{ /* Flush the data lines */
	fclose (ctx->outbound.data.fp);
	ctx->outbound.data.fp = NULL;
	if (!rc && ctx->outbound.data.error)
	rc = ctx->outbound.data.error;
	}
	else /* flush any data send w/o using the data fp */
	{
	assuan_send_data (ctx, NULL, 0);
	if (!rc && ctx->outbound.data.error)
	rc = ctx->outbound.data.error;
	}
	/* Error handling */
	if (!rc)
	{
	rc = assuan_write_line (ctx, ctx->okay_line? ctx->okay_line : "OK");
	}
	else if (rc == -1)
	{ /* No error checking because the peer may have already disconnect */
	assuan_write_line (ctx, "OK closing connection");
	ctx->finish_handler (ctx);
	}
	else
	{
	char errline[300];

	if (rc < 100)
	sprintf (errline, "ERR %d server fault (%.50s)",
	ASSUAN_Server_Fault, assuan_strerror (rc));
	else
	{
	const char *text = ctx->err_no == rc? ctx->err_str:NULL;

	#if defined(__GNUC__) && defined(__ELF__)
	/* If we have weak symbol support we try to use the error
	strings from libgpg-error without creating a dependency.
	They are used for debugging purposes only, so there is no
	problem if they are not available. We need to make sure
	that we are using elf because only this guarantees that
	weak symbol support is available in case GNU ld is not
	used. */
	unsigned int source, code;

	int gpg_strerror_r (unsigned int err, char *buf, size_t buflen)
	__attribute__ ((weak));

	const char *gpg_strsource (unsigned int err)
	__attribute__ ((weak));

	source = ((rc >> 24) & 0xff);
	code = (rc & 0x00ffffff);
	if (source && gpg_strsource && gpg_strerror_r)
	{
	/* Assume this is an libgpg-error. */
	char ebuf[50];

	gpg_strerror_r (rc, ebuf, sizeof ebuf );
	sprintf (errline, "ERR %d %.50s <%.30s>%s%.100s",
	rc,
	ebuf,
	gpg_strsource (rc),
	text? " - ":"", text?text:"");
	}
	else
	#endif /* __GNUC__ && __ELF__ */
	sprintf (errline, "ERR %d %.50s%s%.100s",
	rc, assuan_strerror (rc), text? " - ":"", text?text:"");
	}
	rc = assuan_write_line (ctx, errline);
	}

	ctx->confidential = 0;
	if (ctx->okay_line)
	{
	xfree (ctx->okay_line);
	ctx->okay_line = NULL;
	}
	return rc;
	}

	/**
	* assuan_process:
	* @ctx: assuan context
	*
	* This function is used to handle the assuan protocol after a
	* connection has been established using assuan_accept(). This is the
	* main protocol handler.
	*
	* Return value: 0 on success or an error code if the assuan operation
	* failed. Note, that no error is returned for operational errors.
	**/
	int
	assuan_process (ASSUAN_CONTEXT ctx)
	{
	int rc;

	do {
	rc = process_request (ctx);
	} while (!rc);

	if (rc == -1)
	rc = 0;

	return rc;
	}


	/**
	* assuan_process_next:
	* @ctx: Assuan context
	*
	* Same as assuan_process() but the user has to provide the outer
	* loop. He should loop as long as the return code is zero and stop
	* otherwise; -1 is regular end.
	*
	* See also: assuan_get_active_fds()
	* Return value: -1 for end of server, 0 on success or an error code
	**/
	int
	assuan_process_next (ASSUAN_CONTEXT ctx)
	{
	return process_request (ctx);
	}


	/**
	* assuan_get_active_fds:
	* @ctx: Assuan context
	* @what: 0 for read fds, 1 for write fds
	* @fdarray: Caller supplied array to store the FDs
	* @fdarraysize: size of that array
	*
	* Return all active filedescriptors for the given context. This
	* function can be used to select on the fds and call
	* assuan_process_next() if there is an active one. The first fd in
	* the array is the one used for the command connection.
	*
	* Note, that write FDs are not yet supported.
	*
	* Return value: number of FDs active and put into @fdarray or -1 on
	* error which is most likely a too small fdarray.
	**/
	int
	assuan_get_active_fds (ASSUAN_CONTEXT ctx, int what,
	int *fdarray, int fdarraysize)
	{
	int n = 0;

	if (!ctx \|\| fdarraysize < 2 \|\| what < 0 \|\| what > 1)
	return -1;

	if (!what)
	{
	if (ctx->inbound.fd != -1)
	fdarray[n++] = ctx->inbound.fd;
	}
	else
	{
	if (ctx->outbound.fd != -1)
	fdarray[n++] = ctx->outbound.fd;
	if (ctx->outbound.data.fp)
	fdarray[n++] = fileno (ctx->outbound.data.fp);
	}

	return n;
	}

	/* Return a FP to be used for data output. The FILE pointer is valid
	until the end of a handler. So a close is not needed. Assuan does
	all the buffering needed to insert the status line as well as the
	required line wappping and quoting for data lines.

	We use GNU's custom streams here. There should be an alternative
	implementaion for systems w/o a glibc, a simple implementation
	could use a child process */
	FILE *
	assuan_get_data_fp (ASSUAN_CONTEXT ctx)
	{
	#if defined (HAVE_FOPENCOOKIE) \|\| defined (HAVE_FUNOPEN)
	if (ctx->outbound.data.fp)
	return ctx->outbound.data.fp;


	ctx->outbound.data.fp = funopen (ctx, 0,
	_assuan_cookie_write_data,
	0, _assuan_cookie_write_flush);
	ctx->outbound.data.error = 0;
	return ctx->outbound.data.fp;
	#else
	errno = ENOSYS;
	return NULL;
	#endif
	}


	/* Set the text used for the next OK reponse. This string is
	automatically reset to NULL after the next command. */
	assuan_error_t
	assuan_set_okay_line (ASSUAN_CONTEXT ctx, const char *line)
	{
	if (!ctx)
	return ASSUAN_Invalid_Value;
	if (!line)
	{
	xfree (ctx->okay_line);
	ctx->okay_line = NULL;
	}
	else
	{
	/* FIXME: we need to use gcry_is_secure() to test whether
	we should allocate the entire line in secure memory */
	char *buf = xtrymalloc (3+strlen(line)+1);
	if (!buf)
	return ASSUAN_Out_Of_Core;
	strcpy (buf, "OK ");
	strcpy (buf+3, line);
	xfree (ctx->okay_line);
	ctx->okay_line = buf;
	}
	return 0;
	}



	assuan_error_t
	assuan_write_status (ASSUAN_CONTEXT ctx, const char keyword, const char text)
	{
	char buffer[256];
	char *helpbuf;
	size_t n;
	assuan_error_t ae;

	if ( !ctx \|\| !keyword)
	return ASSUAN_Invalid_Value;
	if (!text)
	text = "";

	n = 2 + strlen (keyword) + 1 + strlen (text) + 1;
	if (n < sizeof (buffer))
	{
	strcpy (buffer, "S ");
	strcat (buffer, keyword);
	if (*text)
	{
	strcat (buffer, " ");
	strcat (buffer, text);
	}
	ae = assuan_write_line (ctx, buffer);
	}
	else if ( (helpbuf = xtrymalloc (n)) )
	{
	strcpy (helpbuf, "S ");
	strcat (helpbuf, keyword);
	if (*text)
	{
	strcat (helpbuf, " ");
	strcat (helpbuf, text);
	}
	ae = assuan_write_line (ctx, helpbuf);
	xfree (helpbuf);
	}
	else
	ae = 0;
	return ae;
	}

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