applets.c

这是一个SIGMA方案的PMP播放器的UCLINUX程序,可播放DVD,VCD,CD MP3...有很好的参考价值.

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) tons of folks.  Tracking down who wrote what
 * isn't something I'm going to worry about...  If you wrote something
 * here, please feel free to acknowledge your work.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Based in part on code from sash, Copyright (c) 1999 by David I. Bell 
 * Permission has been granted to redistribute this code under the GPL.
 *
 */

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "busybox.h"

#undef APPLET
#undef APPLET_NOUSAGE
#undef PROTOTYPES
#include "applets.h"

struct BB_applet *applet_using;

/* The -1 arises because of the {0,NULL,0,-1} entry above. */
const size_t NUM_APPLETS = (sizeof (applets) / sizeof (struct BB_applet) - 1);


#ifdef CONFIG_FEATURE_SUID

static void check_suid ( struct BB_applet *app );

#ifdef CONFIG_FEATURE_SUID_CONFIG

#include <sys/stat.h>
#include <ctype.h>
#include "pwd_.h"
#include "grp_.h"

static int parse_config_file ( void );

static int config_ok;

#define CONFIG_FILE "/etc/busybox.conf"

// applets [] is const, so we have to define this "override" structure
struct BB_suid_config {
	struct BB_applet *m_applet;

	uid_t  m_uid;
	gid_t  m_gid;
	mode_t m_mode;
	
	struct BB_suid_config *m_next;
};

static struct BB_suid_config *suid_config;

#endif // CONFIG_FEATURE_SUID_CONFIG

#endif // CONFIG_FEATURE_SUID



extern void show_usage(void)
{
	const char *format_string;
	const char *usage_string = usage_messages;
	int i;

	for (i = applet_using - applets; i > 0; ) {
		if (!*usage_string++) {
			--i;
		}
	}
	format_string = "%s\n\nUsage: %s %s\n\n";
	if(*usage_string == 0)
		format_string = "%s\n\nNo help available.\n\n";
	fprintf(stderr, format_string,
			full_version, applet_using->name, usage_string);
	exit(EXIT_FAILURE);
}

static int applet_name_compare(const void *x, const void *y)
{
	const char *name = x;
	const struct BB_applet *applet = y;

	return strcmp(name, applet->name);
}

extern const size_t NUM_APPLETS;

struct BB_applet *find_applet_by_name(const char *name)
{
	struct BB_applet *app;
	
	app = bsearch(name, applets, NUM_APPLETS, sizeof(struct BB_applet),
			applet_name_compare);
	if(app==NULL)
		fprintf(stderr,"BB: Applet \"%s\" not found\n",name);
	return app;
}

void run_applet_by_name(const char *name, int argc, char **argv)
{
	static int recurse_level = 0;
	extern int been_there_done_that; /* From busybox.c */

#ifdef CONFIG_FEATURE_SUID_CONFIG
	if ( recurse_level == 0 )
		config_ok = parse_config_file ( );
#endif

	recurse_level++;
	/* Do a binary search to find the applet entry given the name. */
	if ((applet_using = find_applet_by_name(name)) != NULL) {
		applet_name = applet_using->name;
		if (argv[1] && strcmp(argv[1], "--help") == 0) {
			if (strcmp(applet_using->name, "busybox")==0) {
				if(argv[2])
				  applet_using = find_applet_by_name(argv[2]);
				 else
				  applet_using = NULL;
			}
			if(applet_using)
				show_usage();
			been_there_done_that=1;
			busybox_main(0, NULL);
		}
#ifdef CONFIG_FEATURE_SUID
		check_suid ( applet_using );
#endif
			
		exit((*(applet_using->main)) (argc, argv));
	}
	/* Just in case they have renamed busybox - Check argv[1] */
	if (recurse_level == 1) {
		run_applet_by_name("busybox", argc, argv);
	}
	recurse_level--;
}


#ifdef CONFIG_FEATURE_SUID

#ifdef CONFIG_FEATURE_SUID_CONFIG

// check if u is member of group g
static int ingroup ( uid_t u, gid_t g )
{
	struct group *grp = getgrgid ( g );
	
	if ( grp ) {
		char **mem;
		
		for ( mem = grp-> gr_mem; *mem; mem++ ) {
			struct passwd *pwd = getpwnam ( *mem );
		
			if ( pwd && ( pwd-> pw_uid == u ))
				return 1;
		}
	}
	return 0;
}

#endif


void check_suid ( struct BB_applet *applet )
{
	uid_t ruid = getuid ( ); // real [ug]id
	uid_t rgid = getgid ( );
			
#ifdef CONFIG_FEATURE_SUID_CONFIG
	if ( config_ok ) {
		struct BB_suid_config *sct;
		
		for ( sct = suid_config; sct; sct = sct-> m_next ) {
			if ( sct-> m_applet == applet )
				break;
		}		
		if ( sct ) {
			mode_t m = sct-> m_mode;
			
			if ( sct-> m_uid == ruid ) // same uid
				m >>= 6;
			else if (( sct-> m_gid == rgid ) || ingroup ( ruid, sct-> m_gid )) // same group / in group
				m >>= 3;

			if (!( m & S_IXOTH ))   // is x bit not set ?
				error_msg_and_die ( "You have no permission to run this applet!" );
		
			if (( sct-> m_mode & ( S_ISGID | S_IXGRP )) == ( S_ISGID | S_IXGRP )) { // *both* have to be set for sgid
				if ( setegid ( sct-> m_gid ))
					error_msg_and_die ( "BusyBox binary has insufficient rights to set proper GID for applet!" );
			}
			else
				setgid ( rgid ); // no sgid -> drop
				
			if ( sct-> m_mode & S_ISUID ) {
				if ( seteuid ( sct-> m_uid ))
					error_msg_and_die ( "BusyBox binary has insufficient rights to set proper UID for applet!" );
			}	
			else
				setuid ( ruid ); // no suid -> drop
		}
		else { // default: drop all priviledges
			setgid ( rgid );
			setuid ( ruid );
		}
		return;
	}
	else {
		static int onetime = 0;
		
		if ( !onetime ) {
			onetime = 1;
			fprintf ( stderr, "Using fallback suid method\n" );
		}
	}
#endif

	if ( applet-> need_suid == _BB_SUID_ALWAYS ) {
		if ( geteuid ( ) != 0 ) 
			error_msg_and_die ( "This applet requires root priviledges!" );
	} 
	else if ( applet-> need_suid == _BB_SUID_NEVER ) {
		setgid ( rgid ); // drop all priviledges
		setuid ( ruid );
	}	
}

#ifdef CONFIG_FEATURE_SUID_CONFIG


#define parse_error(x)	{ err=x; goto pe_label; }


int parse_config_file ( void )
{
	struct stat st;
	char *err = 0;
	FILE *f = 0;
	int lc = 0;

	suid_config = 0;
	
	// is there a config file ?
	if ( stat ( CONFIG_FILE, &st ) == 0 ) {
		// is it owned by root with no write perm. for group and others ?
		if ( S_ISREG( st. st_mode ) && ( st. st_uid == 0 )	&& (!( st. st_mode & ( S_IWGRP | S_IWOTH )))) {
			// that's ok .. then try to open it
			f = fopen ( CONFIG_FILE, "r" );

			if ( f ) {
				char buffer [256];
				int section = 0;
				
				while ( fgets ( buffer, sizeof( buffer ) - 1, f )) {
					char c = buffer [0];
					char *p;
				
					lc++;
					
					p = strchr ( buffer, '#' );
					if ( p )
						*p = 0;
					p = buffer + xstrlen ( buffer );
					while (( p > buffer ) && isspace ( *--p ))
						*p = 0;		
						
					if ( p == buffer )
						continue;					
				
					if ( c == '[' ) {
						p = strchr ( buffer, ']' );
						
						if ( !p || ( p == ( buffer + 1 )))  // no matching ] or empty []
							parse_error ( "malformed section header" );

						*p = 0;
						
						if ( strcasecmp ( buffer + 1, "SUID" ) == 0 )
							section = 1;
						else
							section = -1; // unknown section - just skip
					}
					else if ( section ) {
						switch ( section ) {
							case 1: { // SUID
								int l;
								struct BB_applet *applet;

								p = strchr ( buffer, '=' ); // <key>[::space::]*=[::space::]*<value>
								
								if ( !p || ( p == ( buffer + 1 ))) // no = or key is empty
									parse_error ( "malformed keyword" );
								
								l = p - buffer;
								while ( isspace ( buffer [--l] )) { } // skip whitespace
								
								buffer [l+1] = 0;
								
								if (( applet = find_applet_by_name ( buffer ))) {
									struct BB_suid_config *sct = xmalloc ( sizeof( struct BB_suid_config ));
									
									sct-> m_applet = applet;
									sct-> m_next = suid_config;
									suid_config = sct;
									
									while ( isspace ( *++p )) { } // skip whitespace
												
									sct-> m_mode = 0;			
									
									switch ( *p++ ) {
										case 'S': sct-> m_mode |= S_ISUID; break;
										case 's': sct-> m_mode |= S_ISUID; // no break
										case 'x': sct-> m_mode |= S_IXUSR; break;
										case '-': break;
										default : parse_error ( "invalid user mode" );
									}
										
									switch ( *p++ ) {
										case 's': sct-> m_mode |= S_ISGID; // no break
										case 'x': sct-> m_mode |= S_IXGRP; break;
										case 'S': break;
										case '-': break;
										default : parse_error ( "invalid group mode" );
									}
										
									switch ( *p ) {
										case 't': 
										case 'x': sct-> m_mode |= S_IXOTH; break;
										case 'T':
										case '-': break;
										default : parse_error ( "invalid other mode" );
									}
										
									while ( isspace ( *++p )) { } // skip whitespace
									
									if ( isdigit ( *p )) {
										sct-> m_uid = strtol ( p, &p, 10 );
										if ( *p++ != '.' )
											parse_error ( "parsing <uid>.<gid>" );										
									}
									else {
										struct passwd *pwd;
										char *p2 = strchr ( p, '.' );
										
										if ( !p2 ) 
											parse_error ( "parsing <uid>.<gid>" );										
	
										*p2 = 0;
										pwd = getpwnam ( p );
						
										if ( !pwd ) 
											parse_error ( "invalid user name" );
										
										sct-> m_uid = pwd-> pw_uid;
										p = p2 + 1;
									}		
									if ( isdigit ( *p )) 
										sct-> m_gid = strtol ( p, &p, 10 );
									else {
										struct group *grp = getgrnam ( p );
						
										if ( !grp ) 
											parse_error ( "invalid group name" );
										
										sct-> m_gid = grp-> gr_gid;
									}																		
								}
								break;
							}
							default: // unknown - skip
								break;
						}					
					}
					else
						parse_error ( "keyword not within section" );
				}				
				fclose ( f );
			}
		}
	}
	return 1;
	
pe_label:	
	fprintf ( stderr, "Parse error in %s, line %d: %s\n", CONFIG_FILE, lc, err );

	if ( f )
		fclose ( f );
	return 0;
}

#endif

#endif

/* END CODE */
/*
Local Variables:
c-file-style: "linux"
c-basic-offset: 4
tab-width: 4
End:
*/