mod_mime_magic.c

/* 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 Software Foundation 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 Software Foundation.
 *
 * 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 apr_pool_t 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 <ikluft@cisco.com>
 * 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 Software Foundation    July 1997
 *
 */

#include "apr.h"
#include "apr_strings.h"
#include "apr_lib.h"
#define APR_WANT_STRFUNC
#include "apr_want.h"

#if APR_HAVE_UNISTD_H
#include <unistd.h>
#endif

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

/* ### this isn't set by configure? does anybody set this? */
#ifdef HAVE_UTIME_H
#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;             /* suppress 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 *, apr_size_t);
static int is_tar(unsigned char *, apr_size_t);
static int softmagic(request_rec *, unsigned char *, apr_size_t);
static int tryit(request_rec *, unsigned char *, apr_size_t, int);
static int zmagic(request_rec *, unsigned char *, apr_size_t);

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 *, apr_pool_t *p, char *, int);

static int match(request_rec *, unsigned char *, apr_size_t);
static int mget(request_rec *, union VALUETYPE *, unsigned char *,
                struct magic *, apr_size_t);
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 **, apr_size_t);
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 apr_table_t '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 const 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 const struct names {
    const 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 {
    const 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 {
    const 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 AP_MODULE_DECLARE_DATA mime_magic_module;

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

static void *merge_magic_server_config(apr_pool_t *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 *)
                            apr_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, void *dummy, const 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
 */

static const command_rec mime_magic_cmds[] =
{
    AP_INIT_TAKE1("MimeMagicFile", set_magicfile, NULL, RSRC_CONF,
     "Path to MIME Magic file (in file(1) format)"),
    {NULL}
};

/*
 * RSL (result string list) processing routines
 *
 * These collect strings that would have been printed in fragments by file(1)
 * into a list of magic_rsl structures with the strings. When complete,
 * they're concatenated together to become the MIME content and encoding
 * types.
 *
 * return value conventions for these functions: functions which return int:
 * failure = -1, other = result functions which return pointers: failure = 0,
 * other = result
 */

/* allocate a per-request structure and put it in the request record */
static magic_req_rec *magic_set_config(request_rec *r)
{
    magic_req_rec *req_dat = (magic_req_rec *) apr_palloc(r->pool,
                                                      sizeof(magic_req_rec));

    req_dat->head = req_dat->tail = (magic_rsl *) NULL;
    ap_set_module_config(r->request_config, &mime_magic_module, req_dat);
    return req_dat;
}

/* add a string to the result string list for this request */
/* it is the responsibility of the caller to allocate "str" */
static int magic_rsl_add(request_rec *r, const char *str)
{
    magic_req_rec *req_dat = (magic_req_rec *)
                    ap_get_module_config(r->request_config, &mime_magic_module);
    magic_rsl *rsl;

    /* make sure we have a list to put it in */
    if (!req_dat) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, APR_EINVAL, r, APLOGNO(01507)
                    MODNAME ": request config should not be NULL");
        if (!(req_dat = magic_set_config(r))) {
            /* failure */
            return -1;
        }
    }

    /* allocate the list entry */
    rsl = (magic_rsl *) apr_palloc(r->pool, sizeof(magic_rsl));

    /* fill it */
    rsl->str = str;
    rsl->next = (magic_rsl *) NULL;

    /* append to the list */
    if (req_dat->head && req_dat->tail) {
        req_dat->tail->next = rsl;
        req_dat->tail = rsl;
    }
    else {
        req_dat->head = req_dat->tail = rsl;
    }

    /* success */
    return 0;
}

/* RSL hook for puts-type functions */
static int magic_rsl_puts(request_rec *r, const char *str)
{
    return magic_rsl_add(r, str);
}

/* RSL hook for printf-type functions */
static int magic_rsl_printf(request_rec *r, char *str,...)
{
    va_list ap;

    char buf[MAXMIMESTRING];

    /* assemble the string into the buffer */
    va_start(ap, str);
    apr_vsnprintf(buf, sizeof(buf), str, ap);
    va_end(ap);

    /* add the buffer to the list */
    return magic_rsl_add(r, apr_pstrdup(r->pool, buf));
}

/* RSL hook for putchar-type functions */
static int magic_rsl_putchar(request_rec *r, char c)
{
    char str[2];

    /* high overhead for 1 char - just hope they don't do this much */
    str[0] = c;
    str[1] = '\0';
    return magic_rsl_add(r, str);
}

/* allocate and copy a contiguous string from a result string list */
static char *rsl_strdup(request_rec *r, int start_frag, int start_pos, int len)
{
    char *result;       /* return value */
    int cur_frag,       /* current fragment number/counter */
        cur_pos,        /* current position within fragment */
        res_pos;        /* position in result string */
    magic_rsl *frag;    /* list-traversal pointer */
    magic_req_rec *req_dat = (magic_req_rec *)
                    ap_get_module_config(r->request_config, &mime_magic_module);

    /* allocate the result string */
    result = (char *) apr_palloc(r->pool, len + 1);

    /* loop through and collect the string */
    res_pos = 0;
    for (frag = req_dat->head, cur_frag = 0;
         frag->next;
         frag = frag->next, cur_frag++) {
        /* loop to the first fragment */
        if (cur_frag < start_frag)
            continue;

        /* loop through and collect chars */
        for (cur_pos = (cur_frag == start_frag) ? start_pos : 0;
             frag->str[cur_pos];
             cur_pos++) {
            if (cur_frag >= start_frag
                && cur_pos >= start_pos
                && res_pos <= len) {
                result[res_pos++] = frag->str[cur_pos];
                if (res_pos > len) {
                    break;
                }
            }
        }
    }

    /* clean up and return */
    result[res_pos] = 0;
#if MIME_MAGIC_DEBUG
    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(01508)
             MODNAME ": rsl_strdup() %d chars: %s", res_pos - 1, result);
#endif
    return result;
}

/* states for the state-machine algorithm in magic_rsl_to_request() */
typedef enum {
    rsl_leading_space, rsl_type, rsl_subtype, rsl_separator, rsl_encoding
} rsl_states;

/* process the RSL and set the MIME info in the request record */
static int magic_rsl_to_request(request_rec *r)
{
    int cur_frag,         /* current fragment number/counter */
        cur_pos,          /* current position within fragment */
        type_frag,        /* content type starting point: fragment */
        type_pos,         /* content type starting point: position */
        type_len,         /* content type length */
        encoding_frag,    /* content encoding starting point: fragment */
        encoding_pos,     /* content encoding starting point: position */
        encoding_len;     /* content encoding length */

    char *tmp;
    magic_rsl *frag;      /* list-traversal pointer */
    rsl_states state;

    magic_req_rec *req_dat = (magic_req_rec *)
                    ap_get_module_config(r->request_config, &mime_magic_module);

    /* check if we have a result */
    if (!req_dat || !req_dat->head) {
        /* empty - no match, we defer to other Apache modules */
        return DECLINED;
    }

    /* start searching for the type and encoding */
    state = rsl_leading_space;
    type_frag = type_pos = type_len = 0;
    encoding_frag = encoding_pos = encoding_len = 0;
    for (frag = req_dat->head, cur_frag = 0;
         frag && frag->next;
         frag = frag->next, cur_frag++) {
        /* loop through the characters in the fragment */
        for (cur_pos = 0; frag->str[cur_pos]; cur_pos++) {
            if (apr_isspace(frag->str[cur_pos])) {
                /* process whitespace actions for each state */
                if (state == rsl_leading_space) {
                    /* eat whitespace in this state */
                    continue;
                }
                else if (state == rsl_type) {
                    /* whitespace: type has no slash! */
                    return DECLINED;
                }
                else if (state == rsl_subtype) {
                    /* whitespace: end of MIME type */
                    state++;
                    continue;
                }
                else if (state == rsl_separator) {
                    /* eat whitespace in this state */
                    continue;
                }
                else if (state == rsl_encoding) {
                    /* whitespace: end of MIME encoding */
                    /* we're done */
                    frag = req_dat->tail;
                    break;
                }
                else {
                    /* should not be possible */
                    /* abandon malfunctioning module */
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01509)
                                MODNAME ": bad state %d (ws)", state);
                    return DECLINED;
                }
                /* NOTREACHED */
            }
            else if (state == rsl_type &&
                     frag->str[cur_pos] == '/') {
                /* copy the char and go to rsl_subtype state */
                type_len++;
                state++;
            }
            else {
                /* process non-space actions for each state */
                if (state == rsl_leading_space) {
                    /* non-space: begin MIME type */
                    state++;
                    type_frag = cur_frag;
                    type_pos = cur_pos;
                    type_len = 1;
                    continue;
                }
                else if (state == rsl_type ||
                         state == rsl_subtype) {
                    /* non-space: adds to type */
                    type_len++;
                    continue;
                }
                else if (state == rsl_separator) {
                    /* non-space: begin MIME encoding */
                    state++;
                    encoding_frag = cur_frag;
                    encoding_pos = cur_pos;
                    encoding_len = 1;
                    continue;
                }
                else if (state == rsl_encoding) {
                    /* non-space: adds to encoding */
                    encoding_len++;
                    continue;
                }
                else {
                    /* should not be possible */
                    /* abandon malfunctioning module */
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01510)
                                MODNAME ": bad state %d (ns)", state);
                    return DECLINED;
                }
                /* NOTREACHED */
            }
            /* NOTREACHED */
        }
    }

    /* if we ended prior to state rsl_subtype, we had incomplete info */
    if (state != rsl_subtype && state != rsl_separator &&
        state != rsl_encoding) {
        /* defer to other modules */
        return DECLINED;
    }

    /* save the info in the request record */
    tmp = rsl_strdup(r, type_frag, type_pos, type_len);
    /* XXX: this could be done at config time I'm sure... but I'm
     * confused by all this magic_rsl stuff. -djg */
    ap_content_type_tolower(tmp);
    ap_set_content_type(r, tmp);

    if (state == rsl_encoding) {
        tmp = rsl_strdup(r, encoding_frag,
                                         encoding_pos, encoding_len);
        /* XXX: this could be done at config time I'm sure... but I'm
         * confused by all this magic_rsl stuff. -djg */
        ap_str_tolower(tmp);
        r->content_encoding = tmp;
    }

    /* detect memory allocation or other errors */
    if (!r->content_type ||
        (state == rsl_encoding && !r->content_encoding)) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01511)
                      MODNAME ": unexpected state %d; could be caused by bad "
                      "data in magic file",
                      state);
        return HTTP_INTERNAL_SERVER_ERROR;
    }

    /* success! */
    return OK;
}

/*
 * magic_process - process input file r        Apache API request record
 * (formerly called "process" in file command, prefix added for clarity) Opens
 * the file and reads a fixed-size buffer to begin processing the contents.
 */
static int magic_process(request_rec *r)
{
    apr_file_t *fd = NULL;
    unsigned char buf[HOWMANY + 1];  /* one extra for terminating '\0' */
    apr_size_t nbytes = 0;           /* number of bytes read from a datafile */
    int result;

    /*
     * first try judging the file based on its filesystem status
     */
    switch ((result = fsmagic(r, r->filename))) {
    case DONE:
        magic_rsl_putchar(r, '\n');
        return OK;
    case OK:
        break;
    default:
        /* fatal error, bail out */
        return result;
    }

    if (apr_file_open(&fd, r->filename, APR_READ, APR_OS_DEFAULT, r->pool) != APR_SUCCESS) {
        /* We can't open it, but we were able to stat it. */
        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01512)
                    MODNAME ": can't read `%s'", r->filename);
        /* let some other handler decide what the problem is */
        return DECLINED;
    }

    /*
     * try looking at the first HOWMANY bytes
     */
    nbytes = sizeof(buf) - 1;
    if ((result = apr_file_read(fd, (char *) buf, &nbytes)) != APR_SUCCESS) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR, result, r, APLOGNO(01513)
                    MODNAME ": read failed: %s", r->filename);
        return HTTP_INTERNAL_SERVER_ERROR;
    }

    if (nbytes == 0) {
        return DECLINED;
    }
    else {
        buf[nbytes++] = '\0';  /* null-terminate it */
        result = tryit(r, buf, nbytes, 1);
        if (result != OK) {
            return result;
        }
    }

    (void) apr_file_close(fd);
    (void) magic_rsl_putchar(r, '\n');

    return OK;
}


static int tryit(request_rec *r, unsigned char *buf, apr_size_t nb,
                 int checkzmagic)
{
    /*
     * Try compression stuff
     */
    if (checkzmagic == 1) {
        if (zmagic(r, buf, nb) == 1)
            return OK;
    }

    /*
     * try tests in /etc/magic (or surrogate magic file)
     */
    if (softmagic(r, buf, nb) == 1)
        return OK;

    /*
     * try known keywords, check for ascii-ness too.
     */
    if (ascmagic(r, buf, nb) == 1)
        return OK;

    /*
     * abandon hope, all ye who remain here
     */
    return DECLINED;
}

#define    EATAB {while (apr_isspace(*l))  ++l;}

/*
 * apprentice - load configuration from the magic file r
 *  API request record
 */
static int apprentice(server_rec *s, apr_pool_t *p)
{
    apr_file_t *f = NULL;
    apr_status_t result;
    char line[BUFSIZ + 1];
    int errs = 0;
    int lineno;
#if MIME_MAGIC_DEBUG
    int rule = 0;
    struct magic *m, *prevm;
#endif
    magic_server_config_rec *conf = (magic_server_config_rec *)
                    ap_get_module_config(s->module_config, &mime_magic_module);
    const char *fname = ap_server_root_relative(p, conf->magicfile);

    if (!fname) {
        ap_log_error(APLOG_MARK, APLOG_ERR, APR_EBADPATH, s, APLOGNO(01514)
                     MODNAME ": Invalid magic file path %s", conf->magicfile);
        return -1;
    }
    if ((result = apr_file_open(&f, fname, APR_READ | APR_BUFFERED,
                                APR_OS_DEFAULT, p)) != APR_SUCCESS) {
        ap_log_error(APLOG_MARK, APLOG_ERR, result, s, APLOGNO(01515)
                     MODNAME ": can't read magic file %s", fname);
        return -1;
    }

    /* set up the magic list (empty) */
    conf->magic = conf->last = NULL;

    /* parse it */
    for (lineno = 1; apr_file_gets(line, BUFSIZ, f) == APR_SUCCESS; lineno++) {
        int ws_offset;
        char *last = line + strlen(line) - 1; /* guaranteed that len >= 1 since an
                                               * "empty" line contains a '\n'
                                               */

        /* delete newline and any other trailing whitespace */
        while (last >= line
               && apr_isspace(*last)) {
            *last = '\0';
            --last;
        }

        /* skip leading whitespace */
        ws_offset = 0;
        while (line[ws_offset] && apr_isspace(line[ws_offset])) {
            ws_offset++;
        }

        /* skip blank lines */
        if (line[ws_offset] == 0) {
            continue;
        }

        /* comment, do not parse */
        if (line[ws_offset] == '#')
            continue;

#if MIME_MAGIC_DEBUG
        /* if we get here, we're going to use it so count it */
        rule++;
#endif

        /* parse it */
        if (parse(s, p, line + ws_offset, lineno) != 0)
            ++errs;
    }

    (void) apr_file_close(f);

#if MIME_MAGIC_DEBUG
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(01516)
                MODNAME ": apprentice conf=%x file=%s m=%s m->next=%s last=%s",
                conf,
                conf->magicfile ? conf->magicfile : "NULL",
                conf->magic ? "set" : "NULL",
                (conf->magic && conf->magic->next) ? "set" : "NULL",
                conf->last ? "set" : "NULL");
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(01517)
                MODNAME ": apprentice read %d lines, %d rules, %d errors",
                lineno, rule, errs);
#endif

#if MIME_MAGIC_DEBUG
    prevm = 0;
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(01518)