File: ssi.c

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/* ssi - server-side-includes CGI program
**
** Copyright  1995 by Jef Poskanzer <jef@acme.com>.
** All rights reserved.
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions
** are met:
** 1. Redistributions of source code must retain the above copyright
**    notice, this list of conditions and the following disclaimer.
** 2. Redistributions in binary form must reproduce the above copyright
**    notice, this list of conditions and the following disclaimer in the
**    documentation and/or other materials provided with the distribution.
**
** THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
** ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
** SUCH DAMAGE.
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "config.h"
#include "match.h"


#define ST_GROUND 0
#define ST_LESSTHAN 1
#define ST_BANG 2
#define ST_MINUS1 3
#define ST_MINUS2 4


static void read_file( char* vfilename, char* filename, FILE* fp );


static char* argv0;
static char* url;

static char timefmt[100];
static int sizefmt;
#define SF_BYTES 0
#define SF_ABBREV 1
static struct stat sb;


static void
internal_error( char* reason )
    {
    char* title = "500 Internal Error";

    (void) printf( "\
<HTML><HEAD><TITLE>%s</TITLE></HEAD>\n\
<BODY><H2>%s</H2>\n\
Something unusual went wrong during a server-side-includes request:\n\
<BLOCKQUOTE>\n\
%s\n\
</BLOCKQUOTE>\n\
</BODY></HTML>\n", title, title, reason );
    }


static void
not_found( char* filename )
    {
    char* title = "404 Not Found";

    (void) printf( "\
<HTML><HEAD><TITLE>%s</TITLE></HEAD>\n\
<BODY><H2>%s</H2>\n\
The requested server-side-includes filename, %s,\n\
does not seem to exist.\n\
</BODY></HTML>\n", title, title, filename );
    }


static void
not_found2( char* directive, char* tag, char* filename2 )
    {
    char* title = "Not Found";

    (void) printf( "\
<HR><H2>%s</H2>\n\
The filename requested in a %s %s directive, %s,\n\
does not seem to exist.\n\
<HR>\n", title, directive, tag, filename2 );
    }


static void
not_permitted( char* directive, char* tag, char* val )
    {
    char* title = "Not Permitted";

    (void) printf( "\
<HR><H2>%s</H2>\n\
The filename requested in the %s %s=%s directive\n\
may not be fetched.\n\
<HR>\n", title, directive, tag, val );
    }


static void
unknown_directive( char* filename, char* directive )
    {
    char* title = "Unknown Directive";

    (void) printf( "\
<HR><H2>%s</H2>\n\
The requested server-side-includes filename, %s,\n\
tried to use an unknown directive, %s.\n\
<HR>\n", title, filename, directive );
    }


static void
unknown_tag( char* filename, char* directive, char* tag )
    {
    char* title = "Unknown Tag";

    (void) printf( "\
<HR><H2>%s</H2>\n\
The requested server-side-includes filename, %s,\n\
tried to use the directive %s with an unknown tag, %s.\n\
<HR>\n", title, filename, directive, tag );
    }


static void
unknown_value( char* filename, char* directive, char* tag, char* val )
    {
    char* title = "Unknown Value";

    (void) printf( "\
<HR><H2>%s</H2>\n\
The requested server-side-includes filename, %s,\n\
tried to use the directive %s %s with an unknown value, %s.\n\
<HR>\n", title, filename, directive, tag, val );
    }


static int
get_filename( char* vfilename, char* filename, char* directive, char* tag, char* val, char* fn, int fnsize )
    {
    int vl, fl;
    char* cp;

    /* Used for the various commands that accept a file name.
    ** These commands accept two tags:
    **   virtual
    **     Gives a virtual path to a document on the server.
    **   file
    **     Gives a pathname relative to the current directory. ../ cannot
    **     be used in this pathname, nor can absolute paths be used.
    */
    vl = strlen( vfilename );
    fl = strlen( filename );
    if ( strcmp( tag, "virtual" ) == 0 )
	{
	if ( strstr( val, "../" ) != (char*) 0 )
	    {
	    not_permitted( directive, tag, val );
	    return -1;
	    }
	/* Figure out root using difference between vfilename and filename. */
	if ( vl > fl ||
	     strcmp( vfilename, &filename[fl - vl] ) != 0 )
	    return -1;
	if ( fl - vl + strlen( val ) >= fnsize )
	    return -1;
	(void) strncpy( fn, filename, fl - vl );
	(void) strcpy( &fn[fl - vl], val );
	}
    else if ( strcmp( tag, "file" ) == 0 )
	{
	if ( val[0] == '/' || strstr( val, "../" ) != (char*) 0 )
	    {
	    not_permitted( directive, tag, val );
	    return -1;
	    }
	if ( fl + 1 + strlen( val ) >= fnsize )
	    return -1;
	(void) strcpy( fn, filename );
	cp = strrchr( fn, '/' );
	if ( cp == (char*) 0 )
	    {
	    cp = &fn[strlen( fn )];
	    *cp = '/';
	    }
	(void) strcpy( ++cp, val );
	}
    else
	{
	unknown_tag( filename, directive, tag );
	return -1;
	}
    return 0;
    }


static int
check_filename( char* filename )
    {
    static int inited = 0;
    static char* cgi_pattern;
    int fnl;
    char* cp;
    char* dirname;
    char* authname;
    struct stat sb;
    int r;

    if ( ! inited )
	{
	/* Get the cgi pattern. */
	cgi_pattern = getenv( "CGI_PATTERN" );
#ifdef CGI_PATTERN
	if ( cgi_pattern == (char*) 0 )
	    cgi_pattern = CGI_PATTERN;
#endif /* CGI_PATTERN */
	inited = 1;
	}

    /* ../ is not permitted. */
    if ( strstr( filename, "../" ) != (char*) 0 )
	return 0;

#ifdef AUTH_FILE
    /* Ensure that we are not reading a basic auth password file. */
    fnl = strlen(filename);
    if ( strcmp( filename, AUTH_FILE ) == 0 ||
	 ( fnl >= sizeof(AUTH_FILE) &&
	   strcmp( &filename[fnl - sizeof(AUTH_FILE) + 1], AUTH_FILE ) == 0 &&
	   filename[fnl - sizeof(AUTH_FILE)] == '/' ) )
	return 0;

    /* Check for an auth file in the same directory.  We can't do an actual
    ** auth password check here because CGI programs are not given the
    ** authorization header, for security reasons.  So instead we just
    ** prohibit access to all auth-protected files.
    */
    dirname = strdup( filename );
    if ( dirname == (char*) 0 )
	return 0;	/* out of memory */
    cp = strrchr( dirname, '/' );
    if ( cp == (char*) 0 )
	(void) strcpy( dirname, "." );
    else
	*cp = '\0';
    authname = malloc( strlen( dirname ) + 1 + sizeof(AUTH_FILE) );
    if ( authname == (char*) 0 )
	return 0;	/* out of memory */
    (void) sprintf( authname, "%s/%s", dirname, AUTH_FILE );
    r = stat( authname, &sb );
    free( dirname );
    free( authname );
    if ( r == 0 )
	return 0;
#endif /* AUTH_FILE */

    /* Ensure that we are not reading a CGI file. */
    if ( cgi_pattern != (char*) 0 && match( cgi_pattern, filename ) )
	return 0;

    return 1;
    }


static void
show_time( time_t t, int gmt )
    {
    struct tm* tmP;
    char tbuf[500];

    if ( gmt )
	tmP = gmtime( &t );
    else
	tmP = localtime( &t );
    if ( strftime( tbuf, sizeof(tbuf), timefmt, tmP ) > 0 )
	(void) fputs( tbuf, stdout );
    }


static void
show_size( off_t size )
    {
    switch ( sizefmt )
	{
	case SF_BYTES:
	(void) printf( "%ld", (long) size );  /* spec says should have commas */
	break;
	case SF_ABBREV:
	if ( size < 1024 )
	    (void) printf( "%ld", (long) size );
	else if ( size < 1024 )
	    (void) printf( "%ldK", (long) size / 1024L );
	else if ( size < 1024*1024 )
	    (void) printf( "%ldM", (long) size / (1024L*1024L) );
	else
	    (void) printf( "%ldG", (long) size / (1024L*1024L*1024L) );
	break;
	}
    }


static void
do_config( char* vfilename, char* filename, FILE* fp, char* directive, char* tag, char* val )
    {
    /* The config directive controls various aspects of the file parsing.
    ** There are two valid tags:
    **   timefmt
    **     Gives the server a new format to use when providing dates.  This
    **     is a string compatible with the strftime library call.
    **   sizefmt
    **     Determines the formatting to be used when displaying the size of
    **     a file.  Valid choices are bytes, for a formatted byte count
    **     (formatted as 1,234,567), or abbrev for an abbreviated version
    **     displaying the number of kilobytes or megabytes the file occupies.
    */

    if ( strcmp( tag, "timefmt" ) == 0 )
	{
	(void) strncpy( timefmt, val, sizeof(timefmt) - 1 );
	timefmt[sizeof(timefmt) - 1] = '\0';
	}
    else if ( strcmp( tag, "sizefmt" ) == 0 )
	{
	if ( strcmp( val, "bytes" ) == 0 )
	    sizefmt = SF_BYTES;
	else if ( strcmp( val, "abbrev" ) == 0 )
	    sizefmt = SF_ABBREV;
	else
	    unknown_value( filename, directive, tag, val );
	}
    else
	unknown_tag( filename, directive, tag );
    }


static void
do_include( char* vfilename, char* filename, FILE* fp, char* directive, char* tag, char* val )
    {
    char vfilename2[1000];
    char filename2[1000];
    FILE* fp2;

    /* Inserts the text of another document into the parsed document. */

    if ( get_filename(
	     vfilename, filename, directive, tag, val, filename2,
	     sizeof(filename2) ) < 0 )
	return;

    if ( ! check_filename( filename2 ) )
	{
	not_permitted( directive, tag, filename2 );
	return;
	}

    fp2 = fopen( filename2, "r" );
    if ( fp2 == (FILE*) 0 )
	{
	not_found2( directive, tag, filename2 );
	return;
	}

    if ( strcmp( tag, "virtual" ) == 0 )
	{
	if ( strlen( val ) < sizeof( vfilename2 ) )
	    (void) strcpy( vfilename2, val );
	else
	    (void) strcpy( vfilename2, filename2 );  /* same size, has to fit */
	}
    else
	{
	if ( strlen( vfilename ) + 1 + strlen( val ) < sizeof(vfilename2) )
	    {
	    char* cp;
	    (void) strcpy( vfilename2, vfilename );
	    cp = strrchr( vfilename2, '/' );
	    if ( cp == (char*) 0 )
		{
		cp = &vfilename2[strlen( vfilename2 )];
		*cp = '/';
		}
	    (void) strcpy( ++cp, val );
	    }
	else
	    (void) strcpy( vfilename2, filename2 );  /* same size, has to fit */
	}

    read_file( vfilename2, filename2, fp2 );
    (void) fclose( fp2 );
    }


static void
do_echo( char* vfilename, char* filename, FILE* fp, char* directive, char* tag, char* val )
    {
    char* cp;
    time_t t;

    /* Prints the value of one of the include variables.  Any dates are
    ** printed subject to the currently configured timefmt.  The only valid
    ** tag is var, whose value is the name of the variable you wish to echo.
    */

    if ( strcmp( tag, "var" ) != 0 )
	unknown_tag( filename, directive, tag );
    else
	{
	if ( strcmp( val, "DOCUMENT_NAME" ) == 0 )
	    {
	    /* The current filename. */
	    (void) fputs( filename, stdout );
	    }
	else if ( strcmp( val, "DOCUMENT_URI" ) == 0 )
	    {
	    /* The virtual path to this file (such as /~robm/foo.shtml). */
	    (void) fputs( vfilename, stdout );
	    }
	else if ( strcmp( val, "QUERY_STRING_UNESCAPED" ) == 0 )
	    {
	    /* The unescaped version of any search query the client sent. */
	    cp = getenv( "QUERY_STRING" );
	    if ( cp != (char*) 0 )
		(void) fputs( cp, stdout );
	    }
	else if ( strcmp( val, "DATE_LOCAL" ) == 0 )
	    {
	    /* The current date, local time zone. */
	    t = time( (time_t*) 0 );
	    show_time( t, 0 );
	    }
	else if ( strcmp( val, "DATE_GMT" ) == 0 )
	    {
	    /* Same as DATE_LOCAL but in Greenwich mean time. */
	    t = time( (time_t*) 0 );
	    show_time( t, 1 );
	    }
	else if ( strcmp( val, "LAST_MODIFIED" ) == 0 )
	    {
	    /* The last modification date of the current document. */
	    if ( fstat( fileno( fp ), &sb ) >= 0 )
		show_time( sb.st_mtime, 0 );
	    }
	else
	    {
	    /* Try an environment variable. */
	    cp = getenv( val );
	    if ( cp == (char*) 0 )
		unknown_value( filename, directive, tag, val );
	    else
		(void) fputs( cp, stdout );
	    }
	}
    }


static void
do_fsize( char* vfilename, char* filename, FILE* fp, char* directive, char* tag, char* val )
    {
    char filename2[1000];

    /* Prints the size of the specified file. */

    if ( get_filename(
	     vfilename, filename, directive, tag, val, filename2,
	     sizeof(filename2) ) < 0 )
	return;
    if ( stat( filename2, &sb ) < 0 )
	{
	not_found2( directive, tag, filename2 );
	return;
	}
    show_size( sb.st_size );
    }


static void
do_flastmod( char* vfilename, char* filename, FILE* fp, char* directive, char* tag, char* val )
    {
    char filename2[1000];

    /* Prints the last modification date of the specified file. */

    if ( get_filename(
	     vfilename, filename, directive, tag, val, filename2,
	     sizeof(filename2) ) < 0 )
	return;
    if ( stat( filename2, &sb ) < 0 )
	{
	not_found2( directive, tag, filename2 );
	return;
	}
    show_time( sb.st_mtime, 0 );
    }


static void
parse( char* vfilename, char* filename, FILE* fp, char* str )
    {
    char* directive;
    char* cp;
    int ntags;
    char* tags[200];
    int dirn;
#define DI_CONFIG 0
#define DI_INCLUDE 1
#define DI_ECHO 2
#define DI_FSIZE 3
#define DI_FLASTMOD 4
    int i;
    char* val;

    directive = str;
    directive += strspn( directive, " \t\n\r" );

    ntags = 0;
    cp = directive;
    for (;;)
	{
	cp = strpbrk( cp, " \t\n\r\"" );
	if ( cp == (char*) 0 )
	    break;
	if ( *cp == '"' )
	    {
	    cp = strpbrk( cp + 1, "\"" );
	    ++cp;
	    if ( *cp == '\0' )
		break;
	    }
	*cp++ = '\0';
	cp += strspn( cp, " \t\n\r" );
	if ( *cp == '\0' )
	    break;
	if ( ntags < sizeof(tags)/sizeof(*tags) )
	    tags[ntags++] = cp;
	}
    
    if ( strcmp( directive, "config" ) == 0 )
	dirn = DI_CONFIG;
    else if ( strcmp( directive, "include" ) == 0 )
	dirn = DI_INCLUDE;
    else if ( strcmp( directive, "echo" ) == 0 )
	dirn = DI_ECHO;
    else if ( strcmp( directive, "fsize" ) == 0 )
	dirn = DI_FSIZE;
    else if ( strcmp( directive, "flastmod" ) == 0 )
	dirn = DI_FLASTMOD;
    else
	{
	unknown_directive( filename, directive );
	return;
	}

    for ( i = 0; i < ntags; ++i )
	{
	if ( i > 0 )
	    putchar( ' ' );
	val = strchr( tags[i], '=' );
	if ( val == (char*) 0 )
	    val = "";
	else
	    *val++ = '\0';
	if ( *val == '"' && val[strlen( val ) - 1] == '"' )
	    {
	    val[strlen( val ) - 1] = '\0';
	    ++val;
	    }
	switch( dirn )
	    {
	    case DI_CONFIG:
	    do_config( vfilename, filename, fp, directive, tags[i], val );
	    break;
	    case DI_INCLUDE:
	    do_include( vfilename, filename, fp, directive, tags[i], val );
	    break;
	    case DI_ECHO:
	    do_echo( vfilename, filename, fp, directive, tags[i], val );
	    break;
	    case DI_FSIZE:
	    do_fsize( vfilename, filename, fp, directive, tags[i], val );
	    break;
	    case DI_FLASTMOD:
	    do_flastmod( vfilename, filename, fp, directive, tags[i], val );
	    break;
	    }
	}
    }


static void
slurp( char* vfilename, char* filename, FILE* fp )
    {
    char buf[1000];
    int i;
    int state;
    int ich;

    /* Now slurp in the rest of the comment from the input file. */
    i = 0;
    state = ST_GROUND;
    while ( ( ich = getc( fp ) ) != EOF )
	{
	switch ( state )
	    {
	    case ST_GROUND:
	    if ( ich == '-' )
		state = ST_MINUS1;
	    break;
	    case ST_MINUS1:
	    if ( ich == '-' )
		state = ST_MINUS2;
	    else
		state = ST_GROUND;
	    break;
	    case ST_MINUS2:
	    if ( ich == '>' )
		{
		buf[i - 2] = '\0';
		parse( vfilename, filename, fp, buf );
		return;
		}
	    else if ( ich != '-' )
		state = ST_GROUND;
	    break;
	    }
	if ( i < sizeof(buf) - 1 )
	    buf[i++] = (char) ich;
	}
    }


static void
read_file( char* vfilename, char* filename, FILE* fp )
    {
    int ich;
    int state;

    /* Copy it to output, while running a state-machine to look for
    ** SSI directives.
    */
    state = ST_GROUND;
    while ( ( ich = getc( fp ) ) != EOF )
	{
	switch ( state )
	    {
	    case ST_GROUND:
	    if ( ich == '<' )
		{ state = ST_LESSTHAN; continue; }
	    break;
	    case ST_LESSTHAN:
	    if ( ich == '!' )
		{ state = ST_BANG; continue; }
	    else
		{ state = ST_GROUND; putchar( '<' ); }
	    break;
	    case ST_BANG:
	    if ( ich == '-' )
		{ state = ST_MINUS1; continue; }
	    else
		{ state = ST_GROUND; (void) fputs ( "<!", stdout ); }
	    break;
	    case ST_MINUS1:
	    if ( ich == '-' )
		{ state = ST_MINUS2; continue; }
	    else
		{ state = ST_GROUND; (void) fputs ( "<!-", stdout ); }
	    break;
	    case ST_MINUS2:
	    if ( ich == '#' )
		{
		slurp( vfilename, filename, fp );
		state = ST_GROUND;
		continue;
		}
	    else
		{ state = ST_GROUND; (void) fputs ( "<!--", stdout ); }
	    break;
	    }
	putchar( (char) ich );
	}
    }


int
main( int argc, char** argv )
    {
    char* script_name;
    char* path_info;
    char* path_translated;
    FILE* fp;

    argv0 = argv[0];

    /* Default formats. */
    (void) strcpy( timefmt, "%a %b %e %T %Z %Y" );
    sizefmt = SF_BYTES;

    /* The MIME type has to be text/html. */
    (void) fputs( "Content-type: text/html\n\n", stdout );

    /* Get the name that we were run as. */
    script_name = getenv( "SCRIPT_NAME" );
    if ( script_name == (char*) 0 )
	{
	internal_error( "Couldn't get SCRIPT_NAME environment variable." );
	exit( 1 );
	}

    /* Append the PATH_INFO, if any, to get the full URL. */
    path_info = getenv( "PATH_INFO" );
    if ( path_info == (char*) 0 )
	{
	internal_error( "Couldn't get PATH_INFO environment variable." );
	exit( 1 );
	}
    url = (char*) malloc( strlen( script_name ) + strlen( path_info ) + 1 );
    if ( url == (char*) 0 )
	{
	internal_error( "Out of memory." );
	exit( 1 );
	}
    (void) sprintf( url, "%s%s", script_name, path_info );

    /* Get the name of the file to parse. */
    path_translated = getenv( "PATH_TRANSLATED" );
    if ( path_translated == (char*) 0 )
	{
	internal_error( "Couldn't get PATH_TRANSLATED environment variable." );
	exit( 1 );
	}

    if ( ! check_filename( path_translated ) )
	{
	not_permitted( "initial", "PATH_TRANSLATED", path_translated );
	exit( 1 );
	}

    /* Open it. */
    fp = fopen( path_translated, "r" );
    if ( fp == (FILE*) 0 )
	{
	not_found( path_translated );
	exit( 1 );
	}

    /* Read and handle the file. */
    read_file( path_info, path_translated, fp );

    (void) fclose( fp );
    exit( 0 );
    }