mod_mime_magic.c

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/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * mod_mime_magic: MIME type lookup via file magic numbers
 * Copyright (c) 1996-1997 Cisco Systems, Inc.
 *
 * This software was submitted by Cisco Systems to the Apache Group in July
 * 1997.  Future revisions and derivatives of this source code must
 * acknowledge Cisco Systems as the original contributor of this module.
 * All other licensing and usage conditions are those of the Apache Group.
 *
 * Some of this code is derived from the free version of the file command
 * originally posted to comp.sources.unix.  Copyright info for that program
 * is included below as required.
 * ---------------------------------------------------------------------------
 * - Copyright (c) Ian F. Darwin, 1987. Written by Ian F. Darwin.
 *
 * This software is not subject to any license of the American Telephone and
 * Telegraph Company or of the Regents of the University of California.
 *
 * Permission is granted to anyone to use this software for any purpose on any
 * computer system, and to alter it and redistribute it freely, subject to
 * the following restrictions:
 *
 * 1. The author is not responsible for the consequences of use of this
 * software, no matter how awful, even if they arise from flaws in it.
 *
 * 2. The origin of this software must not be misrepresented, either by
 * explicit claim or by omission.  Since few users ever read sources, credits
 * must appear in the documentation.
 *
 * 3. Altered versions must be plainly marked as such, and must not be
 * misrepresented as being the original software.  Since few users ever read
 * sources, credits must appear in the documentation.
 *
 * 4. This notice may not be removed or altered.
 * -------------------------------------------------------------------------
 *
 * For compliance with Mr Darwin's terms: this has been very significantly
 * modified from the free "file" command.
 * - all-in-one file for compilation convenience when moving from one
 *   version of Apache to the next.
 * - Memory allocation is done through the Apache API's pool structure.
 * - All functions have had necessary Apache API request or server
 *   structures passed to them where necessary to call other Apache API
 *   routines.  (i.e. usually for logging, files, or memory allocation in
 *   itself or a called function.)
 * - struct magic has been converted from an array to a single-ended linked
 *   list because it only grows one record at a time, it's only accessed
 *   sequentially, and the Apache API has no equivalent of realloc().
 * - Functions have been changed to get their parameters from the server
 *   configuration instead of globals.  (It should be reentrant now but has
 *   not been tested in a threaded environment.)
 * - Places where it used to print results to stdout now saves them in a
 *   list where they're used to set the MIME type in the Apache request
 *   record.
 * - Command-line flags have been removed since they will never be used here.
 *
 * Ian Kluft <[e-mail]>
 * Engineering Information Framework
 * Central Engineering
 * Cisco Systems, Inc.
 * San Jose, CA, USA
 *
 * Initial installation          July/August 1996
 * Misc bug fixes                May 1997
 * Submission to Apache Group    July 1997
 *
 */

#include "httpd.h"
#include "http_config.h"
#include "http_request.h"
#include "http_core.h"
#include "http_log.h"
#include "http_protocol.h"

#ifndef WIN32
#include <utime.h>
#endif

/*
 * data structures and related constants
 */

#define MODNAME        "mod_mime_magic"
#define MIME_MAGIC_DEBUG        0

#define MIME_BINARY_UNKNOWN    "application/octet-stream"
#define MIME_TEXT_UNKNOWN    "text/plain"

#define MAXMIMESTRING        256

/* HOWMANY must be at least 4096 to make gzip -dcq work */
#define HOWMANY	4096
/* SMALL_HOWMANY limits how much work we do to figure out text files */
#define SMALL_HOWMANY 1024
#define MAXDESC    50		/* max leng of text description */
#define MAXstring 64		/* max leng of "string" types */

struct magic {
    struct magic *next;		/* link to next entry */
    int lineno;			/* line number from magic file */

    short flag;
#define INDIR    1		/* if '>(...)' appears,  */
#define    UNSIGNED 2		/* comparison is unsigned */
    short cont_level;		/* level of ">" */
    struct {
	char type;		/* byte short long */
	long offset;		/* offset from indirection */
    } in;
    long offset;		/* offset to magic number */
    unsigned char reln;		/* relation (0=eq, '>'=gt, etc) */
    char type;			/* int, short, long or string. */
    char vallen;		/* length of string value, if any */
#define BYTE    1
#define SHORT    2
#define LONG    4
#define STRING    5
#define DATE    6
#define BESHORT    7
#define BELONG    8
#define BEDATE    9
#define LESHORT    10
#define LELONG    11
#define LEDATE    12
    union VALUETYPE {
	unsigned char b;
	unsigned short h;
	unsigned long l;
	char s[MAXstring];
	unsigned char hs[2];	/* 2 bytes of a fixed-endian "short" */
	unsigned char hl[4];	/* 2 bytes of a fixed-endian "long" */
    } value;			/* either number or string */
    unsigned long mask;		/* mask before comparison with value */
    char nospflag;		/* supress space character */

    /* NOTE: this string is suspected of overrunning - find it! */
    char desc[MAXDESC];		/* description */
};

/*
 * data structures for tar file recognition
 * --------------------------------------------------------------------------
 * Header file for public domain tar (tape archive) program.
 *
 * @(#)tar.h 1.20 86/10/29    Public Domain. Created 25 August 1985 by John
 * Gilmore, ihnp4!hoptoad!gnu.
 *
 * Header block on tape.
 *
 * I'm going to use traditional DP naming conventions here. A "block" is a big
 * chunk of stuff that we do I/O on. A "record" is a piece of info that we
 * care about. Typically many "record"s fit into a "block".
 */
#define RECORDSIZE    512
#define NAMSIZ    100
#define TUNMLEN    32
#define TGNMLEN    32

union record {
    char charptr[RECORDSIZE];
    struct header {
	char name[NAMSIZ];
	char mode[8];
	char uid[8];
	char gid[8];
	char size[12];
	char mtime[12];
	char chksum[8];
	char linkflag;
	char linkname[NAMSIZ];
	char magic[8];
	char uname[TUNMLEN];
	char gname[TGNMLEN];
	char devmajor[8];
	char devminor[8];
    } header;
};

/* The magic field is filled with this if uname and gname are valid. */
#define    TMAGIC        "ustar  "	/* 7 chars and a null */

/*
 * file-function prototypes
 */
static int ascmagic(request_rec *, unsigned char *, int);
static int is_tar(unsigned char *, int);
static int softmagic(request_rec *, unsigned char *, int);
static void tryit(request_rec *, unsigned char *, int, int);
static int zmagic(request_rec *, unsigned char *, int);

static int getvalue(server_rec *, struct magic *, char **);
static int hextoint(int);
static char *getstr(server_rec *, char *, char *, int, int *);
static int parse(server_rec *, pool *p, char *, int);

static int match(request_rec *, unsigned char *, int);
static int mget(request_rec *, union VALUETYPE *, unsigned char *,
		struct magic *, int);
static int mcheck(request_rec *, union VALUETYPE *, struct magic *);
static void mprint(request_rec *, union VALUETYPE *, struct magic *);

static int uncompress(request_rec *, int, 
		      unsigned char **, int);
static long from_oct(int, char *);
static int fsmagic(request_rec *r, const char *fn);

/*
 * includes for ASCII substring recognition formerly "names.h" in file
 * command
 *
 * Original notes: names and types used by ascmagic in file(1). These tokens are
 * here because they can appear anywhere in the first HOWMANY bytes, while
 * tokens in /etc/magic must appear at fixed offsets into the file. Don't
 * make HOWMANY too high unless you have a very fast CPU.
 */

/* these types are used to index the table 'types': keep em in sync! */
/* HTML inserted in first because this is a web server module now */
#define L_HTML    0		/* HTML */
#define L_C       1		/* first and foremost on UNIX */
#define L_FORT    2		/* the oldest one */
#define L_MAKE    3		/* Makefiles */
#define L_PLI     4		/* PL/1 */
#define L_MACH    5		/* some kinda assembler */
#define L_ENG     6		/* English */
#define L_PAS     7		/* Pascal */
#define L_MAIL    8		/* Electronic mail */
#define L_NEWS    9		/* Usenet Netnews */

static char *types[] =
{
    "text/html",		/* HTML */
    "text/plain",		/* "c program text", */
    "text/plain",		/* "fortran program text", */
    "text/plain",		/* "make commands text", */
    "text/plain",		/* "pl/1 program text", */
    "text/plain",		/* "assembler program text", */
    "text/plain",		/* "English text", */
    "text/plain",		/* "pascal program text", */
    "message/rfc822",		/* "mail text", */
    "message/news",		/* "news text", */
    "application/binary",	/* "can't happen error on names.h/types", */
    0
};

static struct names {
    char *name;
    short type;
} names[] = {

    /* These must be sorted by eye for optimal hit rate */
    /* Add to this list only after substantial meditation */
    {
	"<html>", L_HTML
    },
    {
	"<HTML>", L_HTML
    },
    {
	"<head>", L_HTML
    },
    {
	"<HEAD>", L_HTML
    },
    {
	"<title>", L_HTML
    },
    {
	"<TITLE>", L_HTML
    },
    {
	"<h1>", L_HTML
    },
    {
	"<H1>", L_HTML
    },
    {
	"<!--", L_HTML
    },
    {
	"<!DOCTYPE HTML", L_HTML
    },
    {
	"/*", L_C
    },				/* must precede "The", "the", etc. */
    {
	"#include", L_C
    },
    {
	"char", L_C
    },
    {
	"The", L_ENG
    },
    {
	"the", L_ENG
    },
    {
	"double", L_C
    },
    {
	"extern", L_C
    },
    {
	"float", L_C
    },
    {
	"real", L_C
    },
    {
	"struct", L_C
    },
    {
	"union", L_C
    },
    {
	"CFLAGS", L_MAKE
    },
    {
	"LDFLAGS", L_MAKE
    },
    {
	"all:", L_MAKE
    },
    {
	".PRECIOUS", L_MAKE
    },
    /*
     * Too many files of text have these words in them.  Find another way to
     * recognize Fortrash.
     */
#ifdef    NOTDEF
    {
	"subroutine", L_FORT
    },
    {
	"function", L_FORT
    },
    {
	"block", L_FORT
    },
    {
	"common", L_FORT
    },
    {
	"dimension", L_FORT
    },
    {
	"integer", L_FORT
    },
    {
	"data", L_FORT
    },
#endif /* NOTDEF */
    {
	".ascii", L_MACH
    },
    {
	".asciiz", L_MACH
    },
    {
	".byte", L_MACH
    },
    {
	".even", L_MACH
    },
    {
	".globl", L_MACH
    },
    {
	"clr", L_MACH
    },
    {
	"(input,", L_PAS
    },
    {
	"dcl", L_PLI
    },
    {
	"Received:", L_MAIL
    },
    {
	">From", L_MAIL
    },
    {
	"Return-Path:", L_MAIL
    },
    {
	"Cc:", L_MAIL
    },
    {
	"Newsgroups:", L_NEWS
    },
    {
	"Path:", L_NEWS
    },
    {
	"Organization:", L_NEWS
    },
    {
	NULL, 0
    }
};

#define NNAMES ((sizeof(names)/sizeof(struct names)) - 1)

/*
 * Result String List (RSL)
 *
 * The file(1) command prints its output.  Instead, we store the various
 * "printed" strings in a list (allocating memory as we go) and concatenate
 * them at the end when we finally know how much space they'll need.
 */

typedef struct magic_rsl_s {
    char *str;			/* string, possibly a fragment */
    struct magic_rsl_s *next;	/* pointer to next fragment */
} magic_rsl;

/*
 * Apache module configuration structures
 */

/* per-server info */
typedef struct {
    char *magicfile;		/* where magic be found */
    struct magic *magic;	/* head of magic config list */
    struct magic *last;
} magic_server_config_rec;

/* per-request info */
typedef struct {
    magic_rsl *head;		/* result string list */
    magic_rsl *tail;
    unsigned suf_recursion;	/* recursion depth in suffix check */
} magic_req_rec;

/*
 * configuration functions - called by Apache API routines
 */

module MODULE_VAR_EXPORT mime_magic_module;

static void *create_magic_server_config(pool *p, server_rec *d)
{
    /* allocate the config - use pcalloc because it needs to be zeroed */
    return ap_pcalloc(p, sizeof(magic_server_config_rec));
}

static void *merge_magic_server_config(pool *p, void *basev, void *addv)
{
    magic_server_config_rec *base = (magic_server_config_rec *) basev;
    magic_server_config_rec *add = (magic_server_config_rec *) addv;
    magic_server_config_rec *new = (magic_server_config_rec *)
			    ap_palloc(p, sizeof(magic_server_config_rec));

    new->magicfile = add->magicfile ? add->magicfile : base->magicfile;
    new->magic = NULL;
    new->last = NULL;
    return new;
}

static const char *set_magicfile(cmd_parms *cmd, char *d, char *arg)
{
    magic_server_config_rec *conf = (magic_server_config_rec *)
    ap_get_module_config(cmd->server->module_config,
		      &mime_magic_module);

    if (!conf) {
	return MODNAME ": server structure not allocated";
    }
    conf->magicfile = arg;
    return NULL;
}

/*
 * configuration file commands - exported to Apache API
 */