file/src/funcs.c

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/*
 * Copyright (c) Christos Zoulas 2003.
 * 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 immediately at the beginning of the file, without modification,
 *    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 "file.h"
#include "magic.h"
#include <assert.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#if defined(HAVE_WCHAR_H)
#include <wchar.h>
#endif
#if defined(HAVE_WCTYPE_H)
#include <wctype.h>
#endif

#ifndef lint
FILE_RCSID("@(#)$File: funcs.c,v 1.28 2007/03/01 22:14:54 christos Exp $")
#endif  /* lint */

#ifndef HAVE_VSNPRINTF
int vsnprintf(char *, size_t, const char *, va_list)
        /*@*/;
#endif

/*
 * Like printf, only we print to a buffer and advance it.
 */
protected int
file_printf(struct magic_set *ms, const char *fmt, ...)
{
        va_list ap;
        size_t len, size;
        char *buf;

        va_start(ap, fmt);

        if ((len = vsnprintf(ms->o.ptr, ms->o.left, fmt, ap)) >= ms->o.left) {
                long diff;      /* XXX: really ptrdiff_t */

                va_end(ap);
                size = (ms->o.size - ms->o.left) + len + 1024;
                if ((buf = realloc(ms->o.buf, size)) == NULL) {
                        file_oomem(ms, size);
                        return -1;
                }
                diff = ms->o.ptr - ms->o.buf;
                ms->o.ptr = buf + diff;
                ms->o.buf = buf;
                ms->o.left = size - diff;
                ms->o.size = size;

                va_start(ap, fmt);
                len = vsnprintf(ms->o.ptr, ms->o.left, fmt, ap);
        }
        va_end(ap);
        ms->o.ptr += len;
        ms->o.left -= len;
        return 0;
}

/*
 * error - print best error message possible
 */
/*VARARGS*/
private void
file_error_core(struct magic_set *ms, int error, const char *f, va_list va,
    uint32_t lineno)
        /*@modifies ms @*/
{
        size_t len;
        /* Only the first error is ok */
        if (ms->haderr)
                return;
        len = 0;
        if (lineno != 0) {
                (void)snprintf(ms->o.buf, ms->o.size, "line %u: ", lineno);
                len = strlen(ms->o.buf);
        }
        (void)vsnprintf(ms->o.buf + len, ms->o.size - len, f, va);
        if (error > 0) {
                len = strlen(ms->o.buf);
                (void)snprintf(ms->o.buf + len, ms->o.size - len, " (%s)",
                    strerror(error));
        }
        ms->haderr++;
        ms->error = error;
}

/*VARARGS*/
protected void
file_error(struct magic_set *ms, int error, const char *f, ...)
{
        va_list va;
        va_start(va, f);
        file_error_core(ms, error, f, va, 0);
        va_end(va);
}

/*
 * Print an error with magic line number.
 */
/*VARARGS*/
protected void
file_magerror(struct magic_set *ms, const char *f, ...)
{
        va_list va;
        va_start(va, f);
        file_error_core(ms, 0, f, va, ms->line);
        va_end(va);
}

protected void
file_oomem(struct magic_set *ms, size_t len)
{
        file_error(ms, errno, "cannot allocate %zu bytes", len);
}

protected void
file_badseek(struct magic_set *ms)
{
        file_error(ms, errno, "error seeking");
}

protected void
file_badread(struct magic_set *ms)
{
        file_error(ms, errno, "error reading");
}

#ifndef COMPILE_ONLY
protected int
file_buffer(struct magic_set *ms, int fd, const char *inname, const void *buf,
    size_t nb)
{
    int m;

#ifdef __EMX__
    if ((ms->flags & MAGIC_NO_CHECK_APPTYPE) == 0 && inname) {
        switch (file_os2_apptype(ms, inname, buf, nb)) {
        case -1:
            return -1;
        case 0:
            break;
        default:
            return 1;
        }
    }
#endif

    /* try compression stuff */
    if ((ms->flags & MAGIC_NO_CHECK_COMPRESS) != 0 ||
        (m = file_zmagic(ms, fd, inname, buf, nb)) == 0) {
        /* Check if we have a tar file */
        if ((ms->flags & MAGIC_NO_CHECK_TAR) != 0 ||
            (m = file_is_tar(ms, buf, nb)) == 0) {
            /* try tests in /etc/magic (or surrogate magic file) */
            if ((ms->flags & MAGIC_NO_CHECK_SOFT) != 0 ||
                (m = file_softmagic(ms, buf, nb)) == 0) {
                /* try known keywords, check whether it is ASCII */
                if ((ms->flags & MAGIC_NO_CHECK_ASCII) != 0 ||
                    (m = file_ascmagic(ms, buf, nb)) == 0) {
                    /* abandon hope, all ye who remain here */
                    if (file_printf(ms, ms->flags & MAGIC_MIME ?
                        (nb ? "application/octet-stream" :
                            "application/empty") :
                        (nb ? "data" :
                            "empty")) == -1)
                            return -1;
                    m = 1;
                }
            }
        }
    }
#ifdef BUILTIN_ELF
    if ((ms->flags & MAGIC_NO_CHECK_ELF) == 0 && m == 1 && nb > 5 && fd != -1) {
        /*
         * We matched something in the file, so this *might*
         * be an ELF file, and the file is at least 5 bytes
         * long, so if it's an ELF file it has at least one
         * byte past the ELF magic number - try extracting
         * information from the ELF headers that cannot easily
         * be extracted with rules in the magic file.
         */
        (void)file_tryelf(ms, fd, buf, nb);
    }
#endif
    return m;
}
#endif

protected int
file_reset(struct magic_set *ms)
{
        if (ms->mlist == NULL) {
                file_error(ms, 0, "no magic files loaded");
                return -1;
        }
        ms->o.ptr = ms->o.buf;
        ms->haderr = 0;
        ms->error = -1;
        return 0;
}

#define OCTALIFY(n, o)  \
        /*LINTED*/ \
        (void)(*(n)++ = '\\', \
        *(n)++ = (((uint32_t)*(o) >> 6) & 3) + '0', \
        *(n)++ = (((uint32_t)*(o) >> 3) & 7) + '0', \
        *(n)++ = (((uint32_t)*(o) >> 0) & 7) + '0', \
        (o)++)

protected const char *
file_getbuffer(struct magic_set *ms)
{
        char *pbuf, *op, *np;
        size_t psize, len;

        if (ms->haderr)
                return NULL;

        if (ms->flags & MAGIC_RAW)
                return ms->o.buf;

        len = ms->o.size - ms->o.left;
        /* * 4 is for octal representation, + 1 is for NUL */
        psize = len * 4 + 1;
        assert(psize > len);
        if (ms->o.psize < psize) {
                if ((pbuf = realloc(ms->o.pbuf, psize)) == NULL) {
                        file_oomem(ms, psize);
                        return NULL;
                }
                ms->o.psize = psize;
                ms->o.pbuf = pbuf;
        }

#if defined(HAVE_WCHAR_H) && defined(HAVE_MBRTOWC) && defined(HAVE_WCWIDTH)
        {
                mbstate_t state;
                wchar_t nextchar;
                int mb_conv = 1;
                size_t bytesconsumed;
                char *eop;
                (void)memset(&state, 0, sizeof(mbstate_t));

                np = ms->o.pbuf;
                op = ms->o.buf;
                eop = op + strlen(ms->o.buf);

                while (op < eop) {
                        bytesconsumed = mbrtowc(&nextchar, op,
                            (size_t)(eop - op), &state);
                        if (bytesconsumed == (size_t)(-1) ||
                            bytesconsumed == (size_t)(-2)) {
                                mb_conv = 0;
                                break;
                        }

                        if (iswprint(nextchar)) {
                                (void)memcpy(np, op, bytesconsumed);
                                op += bytesconsumed;
                                np += bytesconsumed;
                        } else {
                                while (bytesconsumed-- > 0)
                                        OCTALIFY(np, op);
        }
                }
                *np = '\0';

                /* Parsing succeeded as a multi-byte sequence */
                if (mb_conv != 0)
                        return ms->o.pbuf;
        }
#endif

        for (np = ms->o.pbuf, op = ms->o.buf; *op; op++) {
                if (isprint((unsigned char)*op)) {
                        *np++ = *op;    
                } else {
                        OCTALIFY(np, op);
                }
        }
        *np = '\0';
        return ms->o.pbuf;
}

/*
 * Yes these wrappers suffer from buffer overflows, but if your OS does not
 * have the real functions, maybe you should consider replacing your OS?
 */
#ifndef HAVE_VSNPRINTF
int
vsnprintf(char *buf, size_t len, const char *fmt, va_list ap)
{
        return vsprintf(buf, fmt, ap);
}
#endif

#ifndef HAVE_SNPRINTF
/*ARGSUSED*/
int
snprintf(char *buf, size_t len, const char *fmt, ...)
{
        int rv;
        va_list ap;
        va_start(ap, fmt);
        rv = vsprintf(buf, fmt, ap);
        va_end(ap);
        return rv;
}
#endif

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