file/src/readelf.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"

#ifdef BUILTIN_ELF
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "readelf.h"

#ifndef lint
FILE_RCSID("@(#)$File: readelf.c,v 1.63 2007/01/16 14:56:45 ljt Exp $")
#endif

#ifdef  ELFCORE
private int dophn_core(struct magic_set *ms, int class, int swap, int fd,
    off_t off, int num, size_t size, off_t fsize, int *flags)
        /*@modifies ms, *flags @*/;
#endif
private int dophn_exec(struct magic_set *ms, int class, int swap, int fd,
    off_t off, int num, size_t size, off_t fsize, int *flags, int sh_num)
        /*@modifies ms, *flags @*/;
private int doshn(struct magic_set *ms, int class, int swap, int fd, off_t off,
    int num, size_t size, int *flags)
        /*@modifies ms, *flags @*/;
private size_t donote(struct magic_set *ms, unsigned char *nbuf, size_t offset,
    size_t size, int class, int swap, size_t align, int *flags)
        /*@modifies ms, *flags @*/;

#define ELF_ALIGN(a)    ((((a) + align - 1) / align) * align)

#define isquote(c) (strchr("'\"`", (c)) != NULL)

private uint16_t getu16(int, uint16_t)
        /*@*/;
private uint32_t getu32(int, uint32_t)
        /*@*/;
private uint64_t getu64(int, uint64_t)
        /*@*/;

private uint16_t
getu16(int swap, uint16_t value)
{
        union {
                uint16_t ui;
                char c[2];
        } retval, tmpval;

        if (swap) {
                tmpval.ui = value;

                retval.c[0] = tmpval.c[1];
                retval.c[1] = tmpval.c[0];
                
                return retval.ui;
        } else
                return value;
}

private uint32_t
getu32(int swap, uint32_t value)
{
        union {
                uint32_t ui;
                char c[4];
        } retval, tmpval;

        if (swap) {
                tmpval.ui = value;

                retval.c[0] = tmpval.c[3];
                retval.c[1] = tmpval.c[2];
                retval.c[2] = tmpval.c[1];
                retval.c[3] = tmpval.c[0];
                
                return retval.ui;
        } else
                return value;
}

private uint64_t
getu64(int swap, uint64_t value)
{
        union {
                uint64_t ui;
                char c[8];
        } retval, tmpval;

        if (swap) {
                tmpval.ui = value;

                retval.c[0] = tmpval.c[7];
                retval.c[1] = tmpval.c[6];
                retval.c[2] = tmpval.c[5];
                retval.c[3] = tmpval.c[4];
                retval.c[4] = tmpval.c[3];
                retval.c[5] = tmpval.c[2];
                retval.c[6] = tmpval.c[1];
                retval.c[7] = tmpval.c[0];
                
                return retval.ui;
        } else
                return value;
}

#ifdef USE_ARRAY_FOR_64BIT_TYPES
# define elf_getu64(swap, array) \
        ((swap ? ((uint64_t)getu32(swap, array[0])) << 32 : getu32(swap, array[0])) + \
         (swap ? getu32(swap, array[1]) : ((uint64_t)getu32(swap, array[1]) << 32)))
#else
# define elf_getu64(swap, value) getu64(swap, value)
#endif

#define xsh_addr        (class == ELFCLASS32            \
                         ? (void *) &sh32               \
                         : (void *) &sh64)
#define xsh_sizeof      (class == ELFCLASS32            \
                         ? sizeof sh32                  \
                         : sizeof sh64)
#define xsh_size        (class == ELFCLASS32            \
                         ? getu32(swap, sh32.sh_size)   \
                         : getu64(swap, sh64.sh_size))
#define xsh_offset      (class == ELFCLASS32            \
                         ? getu32(swap, sh32.sh_offset) \
                         : getu64(swap, sh64.sh_offset))
#define xsh_type        (class == ELFCLASS32            \
                         ? getu32(swap, sh32.sh_type)   \
                         : getu32(swap, sh64.sh_type))
#define xph_addr        (class == ELFCLASS32            \
                         ? (void *) &ph32               \
                         : (void *) &ph64)
#define xph_sizeof      (class == ELFCLASS32            \
                         ? sizeof ph32                  \
                         : sizeof ph64)
#define xph_type        (class == ELFCLASS32            \
                         ? getu32(swap, ph32.p_type)    \
                         : getu32(swap, ph64.p_type))
#define xph_offset      (off_t)(class == ELFCLASS32     \
                         ? getu32(swap, ph32.p_offset)  \
                         : getu64(swap, ph64.p_offset))
#define xph_align       (size_t)((class == ELFCLASS32   \
                         ? (off_t) (ph32.p_align ?      \
                            getu32(swap, ph32.p_align) : 4) \
                         : (off_t) (ph64.p_align ?      \
                            getu64(swap, ph64.p_align) : 4)))
#define xph_filesz      (size_t)((class == ELFCLASS32   \
                         ? getu32(swap, ph32.p_filesz)  \
                         : getu64(swap, ph64.p_filesz)))
#define xnh_addr        (class == ELFCLASS32            \
                         ? (void *) &nh32               \
                         : (void *) &nh64)
#define xph_memsz       (size_t)((class == ELFCLASS32   \
                         ? getu32(swap, ph32.p_memsz)   \
                         : getu64(swap, ph64.p_memsz)))
#define xnh_sizeof      (class == ELFCLASS32            \
                         ? sizeof nh32                  \
                         : sizeof nh64)
#define xnh_type        (class == ELFCLASS32            \
                         ? getu32(swap, nh32.n_type)    \
                         : getu32(swap, nh64.n_type))
#define xnh_namesz      (class == ELFCLASS32            \
                         ? getu32(swap, nh32.n_namesz)  \
                         : getu32(swap, nh64.n_namesz))
#define xnh_descsz      (class == ELFCLASS32            \
                         ? getu32(swap, nh32.n_descsz)  \
                         : getu32(swap, nh64.n_descsz))
#define prpsoffsets(i)  (class == ELFCLASS32            \
                         ? prpsoffsets32[i]             \
                         : prpsoffsets64[i])

#ifdef ELFCORE
/*@unchecked@*/ /*@observer@*/
size_t  prpsoffsets32[] = {
        8,              /* FreeBSD */
        28,             /* Linux 2.0.36 (short name) */
        44,             /* Linux (path name) */
        84,             /* SunOS 5.x */
};

/*@unchecked@*/ /*@observer@*/
size_t  prpsoffsets64[] = {
        16,             /* FreeBSD, 64-bit */
        40,             /* Linux (tested on core from 2.4.x, short name) */
        56,             /* Linux (path name) */
       120,             /* SunOS 5.x, 64-bit */
};

#define NOFFSETS32      (sizeof prpsoffsets32 / sizeof prpsoffsets32[0])
#define NOFFSETS64      (sizeof prpsoffsets64 / sizeof prpsoffsets64[0])

#define NOFFSETS        (class == ELFCLASS32 ? NOFFSETS32 : NOFFSETS64)

/*
 * Look through the program headers of an executable image, searching
 * for a PT_NOTE section of type NT_PRPSINFO, with a name "CORE" or
 * "FreeBSD"; if one is found, try looking in various places in its
 * contents for a 16-character string containing only printable
 * characters - if found, that string should be the name of the program
 * that dropped core.  Note: right after that 16-character string is,
 * at least in SunOS 5.x (and possibly other SVR4-flavored systems) and
 * Linux, a longer string (80 characters, in 5.x, probably other
 * SVR4-flavored systems, and Linux) containing the start of the
 * command line for that program.
 *
 * The signal number probably appears in a section of type NT_PRSTATUS,
 * but that's also rather OS-dependent, in ways that are harder to
 * dissect with heuristics, so I'm not bothering with the signal number.
 * (I suppose the signal number could be of interest in situations where
 * you don't have the binary of the program that dropped core; if you
 * *do* have that binary, the debugger will probably tell you what
 * signal it was.)
 */

#define OS_STYLE_SVR4           0
#define OS_STYLE_FREEBSD        1
#define OS_STYLE_NETBSD         2

/*@unchecked@*/ /*@observer@*/
private const char *os_style_names[] = {
        "SVR4",
        "FreeBSD",
        "NetBSD",
};

#define FLAGS_DID_CORE          1
#define FLAGS_DID_NOTE          2

private int
dophn_core(struct magic_set *ms, int class, int swap, int fd, off_t off,
    int num, size_t size, off_t fsize, int *flags)
{
        Elf32_Phdr ph32;
        Elf64_Phdr ph64;
        size_t offset;
        unsigned char nbuf[BUFSIZ];
        ssize_t bufsize;
        off_t savedoffset;
        struct stat st;

        if (fstat(fd, &st) < 0) {
                file_badread(ms);
                return -1;
        }

        if (size != xph_sizeof) {
                if (file_printf(ms, ", corrupted program header size") == -1)
                        return -1;
                return 0;
        }

        /*
         * Loop through all the program headers.
         */
        for ( ; num; num--) {
                if ((savedoffset = lseek(fd, off, SEEK_SET)) == (off_t)-1) {
                        file_badseek(ms);
                        return -1;
                }
                if (read(fd, xph_addr, xph_sizeof) == -1) {
                        file_badread(ms);
                        return -1;
                }
                if (xph_offset > fsize) {
                        if (lseek(fd, savedoffset, SEEK_SET) == (off_t)-1) {
                                file_badseek(ms);
                                return -1;
                        }
                        continue;
                }

                off += size;
                if (xph_type != PT_NOTE)
                        continue;

                /*
                 * This is a PT_NOTE section; loop through all the notes
                 * in the section.
                 */
                if (lseek(fd, xph_offset, SEEK_SET) == (off_t)-1) {
                        file_badseek(ms);
                        return -1;
                }
                bufsize = read(fd, nbuf,
                    ((xph_filesz < sizeof(nbuf)) ? xph_filesz : sizeof(nbuf)));
                if (bufsize == -1) {
                        file_badread(ms);
                        return -1;
                }
                offset = 0;
                for (;;) {
                        if (offset >= (size_t)bufsize)
                                /*@innerbreak@*/ break;
                        offset = donote(ms, nbuf, offset, (size_t)bufsize,
                            class, swap, 4, flags);
                        if (offset == 0)
                                /*@innerbreak@*/ break;

                }
        }
        return 0;
}
#endif

private size_t
donote(struct magic_set *ms, unsigned char *nbuf, size_t offset, size_t size,
    int class, int swap, size_t align, int *flags)
{
        Elf32_Nhdr nh32;
        Elf64_Nhdr nh64;
        size_t noff, doff;
#ifdef ELFCORE
        int os_style = -1;
#endif
        uint32_t namesz, descsz;

        (void)memcpy(xnh_addr, &nbuf[offset], xnh_sizeof);
        offset += xnh_sizeof;

        namesz = xnh_namesz;
        descsz = xnh_descsz;
        if ((namesz == 0) && (descsz == 0)) {
                /*
                 * We're out of note headers.
                 */
                return (offset >= size) ? offset : size;
        }

        if (namesz & 0x80000000) {
            (void)file_printf(ms, ", bad note name size 0x%lx",
                (unsigned long)namesz);
            return offset;
        }

        if (descsz & 0x80000000) {
            (void)file_printf(ms, ", bad note description size 0x%lx",
                (unsigned long)descsz);
            return offset;
        }


        noff = offset;
        doff = ELF_ALIGN(offset + namesz);

        if (offset + namesz > size) {
                /*
                 * We're past the end of the buffer.
                 */
                return doff;
        }

        offset = ELF_ALIGN(doff + descsz);
        if (doff + descsz > size) {
                /*
                 * We're past the end of the buffer.
                 */
                return (offset >= size) ? offset : size;
        }

        if (*flags & FLAGS_DID_NOTE)
                goto core;

        if (namesz == 4 && strcmp((char *)&nbuf[noff], "GNU") == 0 &&
            xnh_type == NT_GNU_VERSION && descsz == 16) {
                uint32_t desc[4];
                (void)memcpy(desc, &nbuf[doff], sizeof(desc));

                if (file_printf(ms, ", for GNU/") == -1)
                        return size;
                switch (getu32(swap, desc[0])) {
                case GNU_OS_LINUX:
                        if (file_printf(ms, "Linux") == -1)
                                return size;
                        break;
                case GNU_OS_HURD:
                        if (file_printf(ms, "Hurd") == -1)
                                return size;
                        break;
                case GNU_OS_SOLARIS:
                        if (file_printf(ms, "Solaris") == -1)
                                return size;
                        break;
                default:
                        if (file_printf(ms, "<unknown>") == -1)
                                return size; 
                }
                if (file_printf(ms, " %d.%d.%d", getu32(swap, desc[1]),
                    getu32(swap, desc[2]), getu32(swap, desc[3])) == -1)
                        return size;
                *flags |= FLAGS_DID_NOTE;
                return size;
        }

        if (namesz == 7 && strcmp((char *)&nbuf[noff], "NetBSD") == 0 &&
            xnh_type == NT_NETBSD_VERSION && descsz == 4) {
                uint32_t desc;
                (void)memcpy(&desc, &nbuf[doff], sizeof(desc));
                desc = getu32(swap, desc);

                if (file_printf(ms, ", for NetBSD") == -1)
                        return size;
                /*
                 * The version number used to be stuck as 199905, and was thus
                 * basically content-free.  Newer versions of NetBSD have fixed
                 * this and now use the encoding of __NetBSD_Version__:
                 *
                 *      MMmmrrpp00
                 *
                 * M = major version
                 * m = minor version
                 * r = release ["",A-Z,Z[A-Z] but numeric]
                 * p = patchlevel
                 */
                if (desc > 100000000U) {
                        uint32_t ver_patch = (desc / 100) % 100;
                        uint32_t ver_rel = (desc / 10000) % 100;
                        uint32_t ver_min = (desc / 1000000) % 100;
                        uint32_t ver_maj = desc / 100000000;

                        if (file_printf(ms, " %u.%u", ver_maj, ver_min) == -1)
                                return size;
                        if (ver_rel == 0 && ver_patch != 0) {
                                if (file_printf(ms, ".%u", ver_patch) == -1)
                                        return size;
                        } else if (ver_rel != 0) {
                                while (ver_rel > 26) {
                                        if (file_printf(ms, "Z") == -1)
                                                return size;
                                        ver_rel -= 26;
                                }
                                if (file_printf(ms, "%c", 'A' + ver_rel - 1)
                                    == -1)
                                        return size;
                        }
                }
                *flags |= FLAGS_DID_NOTE;
                return size;
        }

        if (namesz == 8 && strcmp((char *)&nbuf[noff], "FreeBSD") == 0 &&
            xnh_type == NT_FREEBSD_VERSION && descsz == 4) {
                uint32_t desc;
                (void)memcpy(&desc, &nbuf[doff], sizeof(desc));
                desc = getu32(swap, desc);
                if (file_printf(ms, ", for FreeBSD") == -1)
                        return size;

                /*
                 * Contents is __FreeBSD_version, whose relation to OS
                 * versions is defined by a huge table in the Porter's
                 * Handbook.  This is the general scheme:
                 * 
                 * Releases:
                 *      Mmp000 (before 4.10)
                 *      Mmi0p0 (before 5.0)
                 *      Mmm0p0
                 * 
                 * Development branches:
                 *      Mmpxxx (before 4.6)
                 *      Mmp1xx (before 4.10)
                 *      Mmi1xx (before 5.0)
                 *      M000xx (pre-M.0)
                 *      Mmm1xx
                 * 
                 * M = major version
                 * m = minor version
                 * i = minor version increment (491000 -> 4.10)
                 * p = patchlevel
                 * x = revision
                 * 
                 * The first release of FreeBSD to use ELF by default
                 * was version 3.0.
                 */
                if (desc == 460002) {
                        if (file_printf(ms, " 4.6.2") == -1)
                                return size;
                } else if (desc < 460100) {
                        if (file_printf(ms, " %d.%d", desc / 100000,
                            desc / 10000 % 10) == -1)
                                return size;
                        if (desc / 1000 % 10 > 0)
                                if (file_printf(ms, ".%d", desc / 1000 % 10)
                                    == -1)
                                        return size;
                        if ((desc % 1000 > 0) || (desc % 100000 == 0))
                                if (file_printf(ms, " (%d)", desc) == -1)
                                        return size;
                } else if (desc < 500000) {
                        if (file_printf(ms, " %d.%d", desc / 100000,
                            desc / 10000 % 10 + desc / 1000 % 10) == -1)
                                return size;
                        if (desc / 100 % 10 > 0) {
                                if (file_printf(ms, " (%d)", desc) == -1)
                                        return size;
                        } else if (desc / 10 % 10 > 0) {
                                if (file_printf(ms, ".%d", desc / 10 % 10)
                                    == -1)
                                        return size;
                        }
                } else {
                        if (file_printf(ms, " %d.%d", desc / 100000,
                            desc / 1000 % 100) == -1)
                                return size;
                        if ((desc / 100 % 10 > 0) ||
                            (desc % 100000 / 100 == 0)) {
                                if (file_printf(ms, " (%d)", desc) == -1)
                                        return size;
                        } else if (desc / 10 % 10 > 0) {
                                if (file_printf(ms, ".%d", desc / 10 % 10)
                                    == -1)
                                        return size;
                        }
                }
                *flags |= FLAGS_DID_NOTE;
                return size;
        }

        if (namesz == 8 && strcmp((char *)&nbuf[noff], "OpenBSD") == 0 &&
            xnh_type == NT_OPENBSD_VERSION && descsz == 4) {
                if (file_printf(ms, ", for OpenBSD") == -1)
                        return size;
                /* Content of note is always 0 */
                *flags |= FLAGS_DID_NOTE;
                return size;
        }

        if (namesz == 10 && strcmp((char *)&nbuf[noff], "DragonFly") == 0 &&
            xnh_type == NT_DRAGONFLY_VERSION && descsz == 4) {
                uint32_t desc;
                if (file_printf(ms, ", for DragonFly") == -1)
                        return size;
                (void)memcpy(&desc, &nbuf[doff], sizeof(desc));
                desc = getu32(swap, desc);
                if (file_printf(ms, " %d.%d.%d", desc / 100000,
                    desc / 10000 % 10, desc % 10000) == -1)
                        return size;
                *flags |= FLAGS_DID_NOTE;
                return size;
        }

core:
        /*
         * Sigh.  The 2.0.36 kernel in Debian 2.1, at
         * least, doesn't correctly implement name
         * sections, in core dumps, as specified by
         * the "Program Linking" section of "UNIX(R) System
         * V Release 4 Programmer's Guide: ANSI C and
         * Programming Support Tools", because my copy
         * clearly says "The first 'namesz' bytes in 'name'
         * contain a *null-terminated* [emphasis mine]
         * character representation of the entry's owner
         * or originator", but the 2.0.36 kernel code
         * doesn't include the terminating null in the
         * name....
         */
        if ((namesz == 4 && strncmp((char *)&nbuf[noff], "CORE", 4) == 0) ||
            (namesz == 5 && strcmp((char *)&nbuf[noff], "CORE") == 0)) {
                os_style = OS_STYLE_SVR4;
        } 

        if ((namesz == 8 && strcmp((char *)&nbuf[noff], "FreeBSD") == 0)) {
                os_style = OS_STYLE_FREEBSD;
        }

        if ((namesz >= 11 && strncmp((char *)&nbuf[noff], "NetBSD-CORE", 11)
            == 0)) {
                os_style = OS_STYLE_NETBSD;
        }

#ifdef ELFCORE
        if ((*flags & FLAGS_DID_CORE) != 0)
                return size;

        if (os_style != -1) {
                if (file_printf(ms, ", %s-style", os_style_names[os_style])
                    == -1)
                                return size;
        }

        switch (os_style) {
        case OS_STYLE_NETBSD:
                if (xnh_type == NT_NETBSD_CORE_PROCINFO) {
                        uint32_t signo;
                        /*
                         * Extract the program name.  It is at
                         * offset 0x7c, and is up to 32-bytes,
                         * including the terminating NUL.
                         */
                        if (file_printf(ms, ", from '%.31s'",
                            &nbuf[doff + 0x7c]) == -1)
                                return size;
                        
                        /*
                         * Extract the signal number.  It is at
                         * offset 0x08.
                         */
                        (void)memcpy(&signo, &nbuf[doff + 0x08],
                            sizeof(signo));
                        if (file_printf(ms, " (signal %u)",
                            getu32(swap, signo)) == -1)
                                return size;
                        return size;
                }
                break;

        default:
                if (xnh_type == NT_PRPSINFO) {
                        size_t i, j;
                        unsigned char c;
                        /*
                         * Extract the program name.  We assume
                         * it to be 16 characters (that's what it
                         * is in SunOS 5.x and Linux).
                         *
                         * Unfortunately, it's at a different offset
                         * in varous OSes, so try multiple offsets.
                         * If the characters aren't all printable,
                         * reject it.
                         */
                        for (i = 0; i < NOFFSETS; i++) {
                                size_t reloffset = prpsoffsets(i);
                                size_t noffset = doff + reloffset;
                                for (j = 0; j < 16; j++, noffset++,
                                    reloffset++) {
                                        /*
                                         * Make sure we're not past
                                         * the end of the buffer; if
                                         * we are, just give up.
                                         */
                                        if (noffset >= size)
                                                goto tryanother;

                                        /*
                                         * Make sure we're not past
                                         * the end of the contents;
                                         * if we are, this obviously
                                         * isn't the right offset.
                                         */
                                        if (reloffset >= descsz)
                                                goto tryanother;

                                        c = nbuf[noffset];
                                        if (c == '\0') {
                                                /*
                                                 * A '\0' at the
                                                 * beginning is
                                                 * obviously wrong.
                                                 * Any other '\0'
                                                 * means we're done.
                                                 */
                                                if (j == 0)
                                                        goto tryanother;
                                                else
                                                        /*@innerbreak@*/ break;
                                        } else {
                                                /*
                                                 * A nonprintable
                                                 * character is also
                                                 * wrong.
                                                 */
                                                if (!isprint(c) || isquote(c))
                                                        goto tryanother;
                                        }
                                }
                                /*
                                 * Well, that worked.
                                 */
                                if (file_printf(ms, ", from '%.16s'",
                                    &nbuf[doff + prpsoffsets(i)]) == -1)
                                        return size;
                                return size;

                        tryanother:
                                ;
                        }
                }
                break;
        }
#endif
        *flags |= FLAGS_DID_CORE;
        return offset;
}

private int
doshn(struct magic_set *ms, int class, int swap, int fd, off_t off, int num,
    size_t size, int *flags)
{
        Elf32_Shdr sh32;
        Elf64_Shdr sh64;
        int stripped = 1;
        void *nbuf;
        off_t noff;

        if (size != xsh_sizeof) {
                if (file_printf(ms, ", corrupted section header size") == -1)
                        return -1;
                return 0;
        }

        if (lseek(fd, off, SEEK_SET) == (off_t)-1) {
                file_badseek(ms);
                return -1;
        }

        for ( ; num; num--) {
                if (read(fd, xsh_addr, xsh_sizeof) == -1) {
                        file_badread(ms);
                        return -1;
                }
                switch (xsh_type) {
                case SHT_SYMTAB:
#if 0
                case SHT_DYNSYM:
#endif
                        stripped = 0;
                        /*@switchbreak@*/ break;
                case SHT_NOTE:
                        if ((off = lseek(fd, (off_t)0, SEEK_CUR)) ==
                            (off_t)-1) {
                                file_badread(ms);
                                return -1;
                        }
                        if ((nbuf = malloc((size_t)xsh_size)) == NULL) {
                                file_error(ms, errno, "Cannot allocate memory"
                                    " for note");
                                return -1;
                        }
                        if ((noff = lseek(fd, (off_t)xsh_offset, SEEK_SET)) ==
                            (off_t)-1) {
                                file_badread(ms);
                                free(nbuf);
                                return -1;
                        }
                        if (read(fd, nbuf, (size_t)xsh_size) !=
                            (ssize_t)xsh_size) {
                                free(nbuf);
                                file_badread(ms);
                                return -1;
                        }

                        noff = 0;
                        for (;;) {
                                if (noff >= (size_t)xsh_size)
                                        /*@innerbreak@*/ break;
                                noff = donote(ms, nbuf, (size_t)noff,
                                    (size_t)xsh_size, class, swap, 4,
                                    flags);
                                if (noff == 0)
                                        /*@innerbreak@*/ break;
                        }
                        if ((lseek(fd, off, SEEK_SET)) == (off_t)-1) {
                                free(nbuf);
                                file_badread(ms);
                                return -1;
                        }
                        free(nbuf);
                        /*@switchbreak@*/ break;
                }
        }
        if (file_printf(ms, ", %sstripped", stripped ? "" : "not ") == -1)
                return -1;
        return 0;
}

/*
 * Look through the program headers of an executable image, searching
 * for a PT_INTERP section; if one is found, it's dynamically linked,
 * otherwise it's statically linked.
 */
private int
dophn_exec(struct magic_set *ms, int class, int swap, int fd, off_t off,
    int num, size_t size, off_t fsize, int *flags, int sh_num)
{
        Elf32_Phdr ph32;
        Elf64_Phdr ph64;
        const char *linking_style = "statically";
        const char *shared_libraries = "";
        unsigned char nbuf[BUFSIZ];
        int bufsize;
        size_t offset, align;
        off_t savedoffset = (off_t)-1;
        struct stat st;

        if (fstat(fd, &st) < 0) {
                file_badread(ms);
                return -1;
        }

        if (size != xph_sizeof) {
                if (file_printf(ms, ", corrupted program header size") == -1)
                    return -1;
                return 0;
        }
        if (lseek(fd, off, SEEK_SET) == (off_t)-1) {
                file_badseek(ms);
                return -1;
        }

        for ( ; num; num--) {
                if (read(fd, xph_addr, xph_sizeof) == -1) {
                        file_badread(ms);
                        return -1;
                }
                if (xph_offset > st.st_size && savedoffset != (off_t)-1) {
                        if (lseek(fd, savedoffset, SEEK_SET) == (off_t)-1) {
                                file_badseek(ms);
                                return -1;
                        }
                        continue;
                }

                if ((savedoffset = lseek(fd, (off_t)0, SEEK_CUR)) == (off_t)-1) {
                        file_badseek(ms);
                        return -1;
                }

                if (xph_offset > fsize) {
                        if (lseek(fd, savedoffset, SEEK_SET) == (off_t)-1) {
                                file_badseek(ms);
                                return -1;
                        }
                        continue;
                }

                switch (xph_type) {
                case PT_DYNAMIC:
                        linking_style = "dynamically";
                        /*@switchbreak@*/ break;
                case PT_INTERP:
                        shared_libraries = " (uses shared libs)";
                        /*@switchbreak@*/ break;
                case PT_NOTE:
                        if ((align = xph_align) & 0x80000000) {
                                if (file_printf(ms, 
                                    ", invalid note alignment 0x%lx",
                                    (unsigned long)align) == -1)
                                        return -1;
                                align = 4;
                        }
                        /* If we have a section header table, handle note
                           sections just in doshn.  Handling them also here
                           means that for executables we print the note content
                           twice and, more importantly, don't handle
                           strip -o created debuginfo files correctly.
                           They have PT_NOTE header, but the actual note
                           content is not present in the debuginfo file,
                           only in the original stripped executable or library.
                           The corresponding .note.* section is SHT_NOBITS
                           rather than SHT_NOTE, so doshn will not look
                           at it.  */
                        if (sh_num)
                                /*@switchbreak@*/ break;
                        /*
                         * This is a PT_NOTE section; loop through all the notes
                         * in the section.
                         */
                        if (lseek(fd, xph_offset, SEEK_SET)
                            == (off_t)-1) {
                                file_badseek(ms);
                                return -1;
                        }
                        bufsize = read(fd, nbuf, ((xph_filesz < sizeof(nbuf)) ?
                            xph_filesz : sizeof(nbuf)));
                        if (bufsize == -1) {
                                file_badread(ms);
                                return -1;
                        }
                        offset = 0;
                        for (;;) {
                                if (offset >= (size_t)bufsize)
                                        /*@innerbreak@*/ break;
                                offset = donote(ms, nbuf, offset,
                                    (size_t)bufsize, class, swap, align,
                                    flags);
                                if (offset == 0)
                                        /*@innerbreak@*/ break;
                        }
                        if (lseek(fd, savedoffset, SEEK_SET) == (off_t)-1) {
                                file_badseek(ms);
                                return -1;
                        }
                        /*@switchbreak@*/ break;
                }
        }
        if (file_printf(ms, ", %s linked%s", linking_style, shared_libraries)
            == -1)
            return -1;
        return 0;
}


protected int
file_tryelf(struct magic_set *ms, int fd, const unsigned char *buf,
    size_t nbytes)
{
        union {
                int32_t l;
                char c[sizeof (int32_t)];
        } u;
        int class;
        int swap;
        struct stat st;
        off_t fsize;
        int flags = 0;

        /*
         * If we cannot seek, it must be a pipe, socket or fifo.
         */
        if((lseek(fd, (off_t)0, SEEK_SET) == (off_t)-1) && (errno == ESPIPE))
                fd = file_pipe2file(ms, fd, buf, nbytes);

        if (fstat(fd, &st) == -1) {
                file_badread(ms);
                return -1;
        }
        fsize = st.st_size;

        /*
         * ELF executables have multiple section headers in arbitrary
         * file locations and thus file(1) cannot determine it from easily.
         * Instead we traverse thru all section headers until a symbol table
         * one is found or else the binary is stripped.
         */
        if (buf[EI_MAG0] != ELFMAG0
            || (buf[EI_MAG1] != ELFMAG1 && buf[EI_MAG1] != OLFMAG1)
            || buf[EI_MAG2] != ELFMAG2 || buf[EI_MAG3] != ELFMAG3)
            return 0;


        class = buf[EI_CLASS];

        if (class == ELFCLASS32) {
                Elf32_Ehdr elfhdr;
                if (nbytes <= sizeof (Elf32_Ehdr))
                        return 0;


                u.l = 1;
                (void) memcpy(&elfhdr, buf, sizeof elfhdr);
                swap = (u.c[sizeof(int32_t) - 1] + 1) != elfhdr.e_ident[EI_DATA];

                if (getu16(swap, elfhdr.e_type) == ET_CORE) {
#ifdef ELFCORE
                        if (dophn_core(ms, class, swap, fd,
                            (off_t)getu32(swap, elfhdr.e_phoff),
                            getu16(swap, elfhdr.e_phnum), 
                            (size_t)getu16(swap, elfhdr.e_phentsize),
                            fsize, &flags) == -1)
                                return -1;
#else
                        ;
#endif
                } else {
                        if (getu16(swap, elfhdr.e_type) == ET_EXEC) {
                                if (dophn_exec(ms, class, swap,
                                    fd, (off_t)getu32(swap, elfhdr.e_phoff),
                                    getu16(swap, elfhdr.e_phnum), 
                                    (size_t)getu16(swap, elfhdr.e_phentsize),
                                    fsize, &flags,
                    getu16(swap, elfhdr.e_shnum))
                                    == -1)
                                        return -1;
                        }
                        if (doshn(ms, class, swap, fd,
                            (off_t)getu32(swap, elfhdr.e_shoff),
                            getu16(swap, elfhdr.e_shnum),
                            (size_t)getu16(swap, elfhdr.e_shentsize),
                            &flags) == -1)
                                return -1;
                }
                return 1;
        }

        if (class == ELFCLASS64) {
                Elf64_Ehdr elfhdr;
                if (nbytes <= sizeof (Elf64_Ehdr))
                        return 0;


                u.l = 1;
                (void) memcpy(&elfhdr, buf, sizeof elfhdr);
                swap = (u.c[sizeof(int32_t) - 1] + 1) != elfhdr.e_ident[EI_DATA];

                if (getu16(swap, elfhdr.e_type) == ET_CORE) {
#ifdef ELFCORE
                        if (dophn_core(ms, class, swap, fd,
                            (off_t)elf_getu64(swap, elfhdr.e_phoff),
                            getu16(swap, elfhdr.e_phnum), 
                            (size_t)getu16(swap, elfhdr.e_phentsize),
                            fsize, &flags) == -1)
                                return -1;
#else
                        ;
#endif
                } else {
                        if (getu16(swap, elfhdr.e_type) == ET_EXEC) {
                                if (dophn_exec(ms, class, swap, fd,
                                    (off_t)elf_getu64(swap, elfhdr.e_phoff),
                                    getu16(swap, elfhdr.e_phnum), 
                                    (size_t)getu16(swap, elfhdr.e_phentsize),
                                    fsize, &flags,
                    getu16(swap, elfhdr.e_shnum)) == -1)
                                        return -1;
                        }
                        if (doshn(ms, class, swap, fd,
                            (off_t)elf_getu64(swap, elfhdr.e_shoff),
                            getu16(swap, elfhdr.e_shnum),
                            (size_t)getu16(swap, elfhdr.e_shentsize), &flags)
                            == -1)
                                return -1;
                }
                return 1;
        }
        return 0;
}
#endif

---