source: bootcd/isolinux/syslinux-6.03/com32/chain/partiter.c @ 26ffad7

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
 *   Copyright 2010 Shao Miller
 *   Copyright 2010-2012 Michal Soltys
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

/*
 * partiter.c
 *
 * Provides disk / partition iteration.
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <zlib.h>
#include <syslinux/disk.h>
#include "partiter.h"
#include "utility.h"

#define ost_is_ext(type) ((type) == 0x05 || (type) == 0x0F || (type) == 0x85)
#define ost_is_nondata(type) (ost_is_ext(type) || (type) == 0x00)
#define sane(s,l) ((s)+(l) > (s))

/* virtual forwards */

static void pi_dtor_(struct part_iter *);
static int  pi_next_(struct part_iter *);
static int  pi_dos_next(struct part_iter *);
static int  pi_gpt_next(struct part_iter *);

/* vtab and types */

static struct itertype types[] = {
   [0] = {
        .dtor = &pi_dtor_,
        .next = &pi_dos_next,
}, [1] = {
        .dtor = &pi_dtor_,
        .next = &pi_gpt_next,
}, [2] = {
        .dtor = &pi_dtor_,
        .next = &pi_next_,
}};

const struct itertype * const typedos = types;
const struct itertype * const typegpt = types+1;
const struct itertype * const typeraw = types+2;

/* pi_dtor_() - common/raw iterator cleanup */
static void pi_dtor_(struct part_iter *iter)
{
    /* syslinux's free is null resilient */
    free(iter->data);
}

/* pi_ctor() - common/raw iterator initialization */
static int pi_ctor(struct part_iter *iter,
        const struct disk_info *di, int flags
)
{
    memcpy(&iter->di, di, sizeof *di);
    iter->flags = flags;
    iter->index0 = -1;
    iter->length = di->lbacnt;

    iter->type = typeraw;
    return 0;
}

/* pi_dos_ctor() - MBR/EBR iterator specific initialization */
static int pi_dos_ctor(struct part_iter *iter,
        const struct disk_info *di, int flags,
        const struct disk_dos_mbr *mbr
)
{
    if (pi_ctor(iter, di, flags))
        return -1;

    if (!(iter->data = malloc(sizeof *mbr))) {
        critm();
        goto bail;
    }

    memcpy(iter->data, mbr, sizeof *mbr);

    iter->dos.bebr_index0 = -1;
    iter->dos.disk_sig = mbr->disk_sig;

    iter->type = typedos;
    return 0;
bail:
    pi_dtor_(iter);
    return -1;
}

/* pi_gpt_ctor() - GPT iterator specific initialization */
static int pi_gpt_ctor(struct part_iter *iter,
        const struct disk_info *di, int flags,
        const struct disk_gpt_header *gpth, const struct disk_gpt_part_entry *gptl
)
{
    uint64_t siz;

    if (pi_ctor(iter, di, flags))
        return -1;

    siz = (uint64_t)gpth->part_count * gpth->part_size;

    if (!(iter->data = malloc((size_t)siz))) {
        critm();
        goto bail;
    }

    memcpy(iter->data, gptl, (size_t)siz);

    iter->gpt.pe_count = (int)gpth->part_count;
    iter->gpt.pe_size = (int)gpth->part_size;
    iter->gpt.ufirst = gpth->lba_first_usable;
    iter->gpt.ulast = gpth->lba_last_usable;

    memcpy(&iter->gpt.disk_guid, &gpth->disk_guid, sizeof gpth->disk_guid);
    memcpy(&iter->gpt.part_guid, &gpth->disk_guid, sizeof gpth->disk_guid);

    iter->type = typegpt;
    return 0;
bail:
    pi_dtor_(iter);
    return -1;
}

/* Logical partition must be sane, meaning:
 * - must be data or empty
 * - must have non-0 start and length
 * - values must not wrap around 32bit
 * - must be inside current EBR frame
 */

static int notsane_logical(const struct part_iter *iter)
{
    const struct disk_dos_part_entry *dp;
    uint32_t end_log;

    dp = ((struct disk_dos_mbr *)iter->data)->table;

    if (!dp[0].ostype)
        return 0;

    if (ost_is_ext(dp[0].ostype)) {
        error("The 1st EBR entry must be data or empty.");
        return -1;
    }

    if (!(iter->flags & PIF_STRICT))
        return 0;

    end_log = dp[0].start_lba + dp[0].length;

    if (!dp[0].start_lba ||
        !dp[0].length ||
        !sane(dp[0].start_lba, dp[0].length) ||
        end_log > iter->dos.nebr_siz) {

        error("Logical partition (in EBR) with invalid offset and/or length.");
        return -1;
    }

    return 0;
}

/* Extended partition must be sane, meaning:
 * - must be extended or empty
 * - must have non-0 start and length
 * - values must not wrap around 32bit
 * - must be inside base EBR frame
 */

static int notsane_extended(const struct part_iter *iter)
{
    const struct disk_dos_part_entry *dp;
    uint32_t end_ebr;

    dp = ((struct disk_dos_mbr *)iter->data)->table;

    if (!dp[1].ostype)
        return 0;

    if (!ost_is_nondata(dp[1].ostype)) {
        error("The 2nd EBR entry must be extended or empty.");
        return -1;
    }

    if (!(iter->flags & PIF_STRICT))
        return 0;

    end_ebr = dp[1].start_lba + dp[1].length;

    if (!dp[1].start_lba ||
        !dp[1].length ||
        !sane(dp[1].start_lba, dp[1].length) ||
        end_ebr > iter->dos.bebr_siz) {

        error("Extended partition (EBR) with invalid offset and/or length.");
        return -1;
    }

    return 0;
}

/* Primary partition must be sane, meaning:
 * - must have non-0 start and length
 * - values must not wrap around 32bit
 */

static int notsane_primary(const struct part_iter *iter)
{
    const struct disk_dos_part_entry *dp;
    dp = ((struct disk_dos_mbr *)iter->data)->table + iter->index0;

    if (!dp->ostype)
        return 0;

    if (!(iter->flags & PIF_STRICT))
        return 0;

    if (!dp->start_lba ||
        !dp->length ||
        !sane(dp->start_lba, dp->length) ||
        ((iter->flags & PIF_STRICTER) && (dp->start_lba + dp->length > iter->di.lbacnt))) {
        error("Primary partition (in MBR) with invalid offset and/or length.");
        return -1;
    }

    return 0;
}

static int notsane_gpt(const struct part_iter *iter)
{
    const struct disk_gpt_part_entry *gp;
    gp = (const struct disk_gpt_part_entry *)
        (iter->data + iter->index0 * iter->gpt.pe_size);

    if (guid_is0(&gp->type))
        return 0;

    if (!(iter->flags & PIF_STRICT))
        return 0;

    if (gp->lba_first < iter->gpt.ufirst ||
        gp->lba_last > iter->gpt.ulast) {
        error("LBA sectors of GPT partition are beyond the range allowed in GPT header.");
        return -1;
    }

    return 0;
}

static int dos_next_mbr(struct part_iter *iter, uint32_t *lba,
                            struct disk_dos_part_entry **_dp)
{
    struct disk_dos_part_entry *dp;

    while (++iter->index0 < 4) {
        dp = ((struct disk_dos_mbr *)iter->data)->table + iter->index0;

        if (notsane_primary(iter)) {
            iter->status = PI_INSANE;
            return -1;
        }

        if (ost_is_ext(dp->ostype)) {
            if (iter->dos.bebr_index0 >= 0) {
                error("More than 1 extended partition.");
                iter->status = PI_INSANE;
                return -1;
            }
            /* record base EBR index */
            iter->dos.bebr_index0 = iter->index0;
        }
        if (!ost_is_nondata(dp->ostype) || (iter->flags & PIF_STEPALL)) {
            *lba = dp->start_lba;
            *_dp = dp;
            break;
        }
    }

    return 0;
}

static int prep_base_ebr(struct part_iter *iter)
{
    struct disk_dos_part_entry *dp;

    if (iter->dos.bebr_index0 < 0)      /* if we don't have base extended partition at all */
        return -1;
    else if (!iter->dos.bebr_lba) { /* if not initialized yet */
        dp = ((struct disk_dos_mbr *)iter->data)->table + iter->dos.bebr_index0;

        iter->dos.bebr_lba = dp->start_lba;
        iter->dos.bebr_siz = dp->length;

        iter->dos.nebr_lba = dp->start_lba;
        iter->dos.nebr_siz = dp->length;

        iter->index0--;
    }
    return 0;
}

static int dos_next_ebr(struct part_iter *iter, uint32_t *lba,
                            struct disk_dos_part_entry **_dp)
{
    struct disk_dos_part_entry *dp;

    if (prep_base_ebr(iter) < 0) {
        iter->status = PI_DONE;
        return -1;
    }

    while (++iter->index0 < 1024 && iter->dos.nebr_lba) {
        free(iter->data);
        if (!(iter->data =
                    disk_read_sectors(&iter->di, iter->dos.nebr_lba, 1))) {
            error("Couldn't load EBR.");
            iter->status = PI_ERRLOAD;
            return -1;
        }

        /* check sanity of loaded data */
        if (notsane_logical(iter) || notsane_extended(iter)) {
            iter->status = PI_INSANE;
            return -1;
        }

        dp = ((struct disk_dos_mbr *)iter->data)->table;

        iter->dos.cebr_lba = iter->dos.nebr_lba;
        iter->dos.cebr_siz = iter->dos.nebr_siz;

        /* setup next frame values */
        if (dp[1].ostype) {
            iter->dos.nebr_lba = iter->dos.bebr_lba + dp[1].start_lba;
            iter->dos.nebr_siz = dp[1].length;
        } else {
            iter->dos.nebr_lba = 0;
            iter->dos.nebr_siz = 0;
        }

        if (!dp[0].ostype)
            iter->dos.logskipcnt++;

        if (dp[0].ostype || (iter->flags & PIF_STEPALL)) {
            *lba = dp[0].start_lba ? iter->dos.cebr_lba + dp[0].start_lba : 0;
            *_dp = dp;
            return 0;
        }
        /*
         * This way it's possible to continue, if some crazy soft left a "hole"
         * - EBR with a valid extended partition without a logical one. In
         * such case, linux will not reserve a number for such hole - so we
         * don't increase index0. If PIF_STEPALL flag is set, we will never
         * reach this place.
         */
    }
    iter->status = PI_DONE;
    return -1;
}

static void gpt_conv_label(struct part_iter *iter)
{
    const struct disk_gpt_part_entry *gp;
    const int16_t *orig_lab;

    gp = (const struct disk_gpt_part_entry *)
        (iter->data + iter->index0 * iter->gpt.pe_size);
    orig_lab = (const int16_t *)gp->name;

    /* caveat: this is very crude conversion */
    for (int i = 0; i < PI_GPTLABSIZE/2; i++) {
        iter->gpt.part_label[i] = (char)orig_lab[i];
    }
    iter->gpt.part_label[PI_GPTLABSIZE/2] = 0;
}

static inline int valid_crc(uint32_t crc, const uint8_t *buf, unsigned int siz)
{
    return crc == crc32(crc32(0, NULL, 0), buf, siz);
}

static int valid_crc_hdr(void *buf)
{
    struct disk_gpt_header *gh = buf;
    uint32_t crc = gh->chksum;
    int valid;

    gh->chksum = 0;
    valid = crc == crc32(crc32(0, NULL, 0), buf, gh->hdr_size);
    gh->chksum = crc;
    return valid;
}

static int pi_next_(struct part_iter *iter)
{
    iter->status = PI_DONE;
    return iter->status;
}

static int pi_dos_next(struct part_iter *iter)
{
    uint32_t abs_lba = 0;
    struct disk_dos_part_entry *dos_part = NULL;

    if (iter->status)
        return iter->status;

    /* look for primary partitions */
    if (iter->index0 < 4 &&
            dos_next_mbr(iter, &abs_lba, &dos_part) < 0)
        return iter->status;

    /* look for logical partitions */
    if (iter->index0 >= 4 &&
            dos_next_ebr(iter, &abs_lba, &dos_part) < 0)
        return iter->status;

    /*
     * note special index handling:
     * in case PIF_STEPALL is set - this makes the index consistent with
     * non-PIF_STEPALL iterators
     */

    if (!dos_part->ostype)
        iter->index = -1;
    else
        iter->index = iter->index0 + 1 - iter->dos.logskipcnt;
    iter->abs_lba = abs_lba;
    iter->length = dos_part->length;
    iter->record = (char *)dos_part;

#ifdef DEBUG
    disk_dos_part_dump(dos_part);
#endif

    return iter->status;
}

static int pi_gpt_next(struct part_iter *iter)
{
    const struct disk_gpt_part_entry *gpt_part = NULL;

    if (iter->status)
        return iter->status;

    while (++iter->index0 < iter->gpt.pe_count) {
        gpt_part = (const struct disk_gpt_part_entry *)
            (iter->data + iter->index0 * iter->gpt.pe_size);

        if (notsane_gpt(iter)) {
            iter->status = PI_INSANE;
            return iter->status;
        }

        if (!guid_is0(&gpt_part->type) || (iter->flags & PIF_STEPALL))
            break;
    }
    /* no more partitions ? */
    if (iter->index0 == iter->gpt.pe_count) {
        iter->status = PI_DONE;
        return iter->status;
    }
    /* gpt_part is guaranteed to be valid here */
    iter->index = iter->index0 + 1;
    iter->abs_lba = gpt_part->lba_first;
    iter->length = gpt_part->lba_last - gpt_part->lba_first + 1;
    iter->record = (char *)gpt_part;
    memcpy(&iter->gpt.part_guid, &gpt_part->uid, sizeof(struct guid));
    gpt_conv_label(iter);

#ifdef DEBUG
    disk_gpt_part_dump(gpt_part);
#endif

    return iter->status;
}

static struct part_iter *pi_alloc(void)
{
    struct part_iter *iter;
    if (!(iter = malloc(sizeof *iter)))
        critm();
    else
        memset(iter, 0, sizeof *iter);
    return iter;
}

/* pi_del() - delete iterator */
void pi_del(struct part_iter **_iter)
{
    if(!_iter || !*_iter)
        return;
    pi_dtor(*_iter);
    free(*_iter);
    *_iter = NULL;
}

static void try_gpt_we(const char *str, int sec)
{
    if (sec)
        error(str);
    else
        warn(str);
}

static struct disk_gpt_header *try_gpt_hdr(const struct disk_info *di, int sec)
{
    const char *desc = sec ? "backup" : "primary";
    uint64_t gpt_cur = sec ? di->lbacnt - 1 : 1;
    struct disk_gpt_header *gpth;
    char errbuf[64];

    gpth = disk_read_sectors(di, gpt_cur, 1);
    if (!gpth) {
        sprintf(errbuf, "Unable to read %s GPT header.", desc);
        try_gpt_we(errbuf, sec);
        return NULL;
    }
    if(!valid_crc_hdr(gpth)) {
        sprintf(errbuf, "Invalid checksum of %s GPT header.", desc);
        try_gpt_we(errbuf, sec);
        free(gpth);
        return NULL;
    }
    return gpth;
}

static struct disk_gpt_part_entry *try_gpt_list(const struct disk_info *di, const struct disk_gpt_header *gpth, int alt)
{
    int pri = gpth->lba_cur < gpth->lba_alt;
    const char *desc = alt ? "alternative" : "main";
    struct disk_gpt_part_entry *gptl;
    char errbuf[64];
    uint64_t gpt_lsiz;      /* size of GPT partition list in bytes */
    uint64_t gpt_lcnt;      /* size of GPT partition in sectors */
    uint64_t gpt_loff;      /* offset to GPT partition list in sectors */

    gpt_lsiz = (uint64_t)gpth->part_size * gpth->part_count;
    gpt_lcnt = (gpt_lsiz + di->bps - 1) / di->bps;
    if (!alt) {
        /* prefer header value for partition table if not asking for alternative */
        gpt_loff = gpth->lba_table;
    } else {
        /* try to read alternative, we have to calculate its position */
        if (!pri)
            gpt_loff = gpth->lba_alt + 1;
        else
            gpt_loff = gpth->lba_alt - gpt_lcnt;
    }

    gptl = disk_read_sectors(di, gpt_loff, gpt_lcnt);
    if (!gptl) {
        sprintf(errbuf, "Unable to read %s GPT partition list.", desc);
        try_gpt_we(errbuf, alt);
        return NULL;
    }
    if (!valid_crc(gpth->table_chksum, (const uint8_t *)gptl, gpt_lsiz)) {
        sprintf(errbuf, "Invalid checksum of %s GPT partition list.", desc);
        try_gpt_we(errbuf, alt);
        free(gptl);
        return NULL;
    }
    return gptl;
}

static int notsane_gpt_hdr(const struct disk_info *di, const struct disk_gpt_header *gpth, int flags)
{
    uint64_t gpt_loff;      /* offset to GPT partition list in sectors */
    uint64_t gpt_lsiz;      /* size of GPT partition list in bytes */
    uint64_t gpt_lcnt;      /* size of GPT partition in sectors */
    uint64_t gpt_sec;       /* secondary gpt header */

    if (!(flags & PIF_STRICT))
        return 0;

    if (gpth->lba_alt < gpth->lba_cur)
        gpt_sec = gpth->lba_cur;
    else
        gpt_sec = gpth->lba_alt;
    gpt_loff = gpth->lba_table;
    gpt_lsiz = (uint64_t)gpth->part_size * gpth->part_count;
    gpt_lcnt = (gpt_lsiz + di->bps - 1) / di->bps;

    /*
     * disk_read_sectors allows reading of max 255 sectors, so we use
     * it as a sanity check base. EFI doesn't specify max (AFAIK).
     */
    if (gpt_loff < 2 || !gpt_lsiz || gpt_lcnt > 255u ||
            gpth->lba_first_usable > gpth->lba_last_usable ||
            !sane(gpt_loff, gpt_lcnt) ||
            (gpt_loff + gpt_lcnt > gpth->lba_first_usable && gpt_loff <= gpth->lba_last_usable) ||
             gpt_loff + gpt_lcnt > gpt_sec ||
            ((flags & PIF_STRICTER) && (gpt_sec >= di->lbacnt)) ||
            gpth->part_size < sizeof(struct disk_gpt_part_entry))
        return -1;

    return 0;
}

/* pi_begin() - validate and and get proper iterator for a disk described by di */
struct part_iter *pi_begin(const struct disk_info *di, int flags)
{
    int isgpt = 0, ret = -1;
    struct part_iter *iter;
    struct disk_dos_mbr *mbr = NULL;
    struct disk_gpt_header *gpth = NULL;
    struct disk_gpt_part_entry *gptl = NULL;

    /* Preallocate iterator */
    if (!(iter = pi_alloc()))
        goto out;

    /* Read MBR */
    if (!(mbr = disk_read_sectors(di, 0, 1))) {
        error("Unable to read the first disk sector.");
        goto out;
    }

    /* Check for MBR magic */
    if (mbr->sig != disk_mbr_sig_magic) {
        warn("No MBR magic, treating disk as raw.");
        /* looks like RAW */
        ret = pi_ctor(iter, di, flags);
        goto out;
    }

    /* Check for GPT protective MBR */
    for (size_t i = 0; i < 4; i++)
        isgpt |= (mbr->table[i].ostype == 0xEE);
    isgpt = isgpt && !(flags & PIF_PREFMBR);

    /* Try to read GPT header */
    if (isgpt) {
        gpth = try_gpt_hdr(di, 0);
        if (!gpth)
            /*
             * this read might fail if bios reports different disk size (different vm/pc)
             * not much we can do here to avoid it
             */
            gpth = try_gpt_hdr(di, 1);
        if (!gpth)
            goto out;
    }

    if (gpth && gpth->rev.uint32 == 0x00010000 &&
            !memcmp(gpth->sig, disk_gpt_sig_magic, sizeof gpth->sig)) {
        /* looks like GPT v1.0 */
#ifdef DEBUG
        dprintf("Looks like a GPT v1.0 disk.\n");
        disk_gpt_header_dump(gpth);
#endif
        if (notsane_gpt_hdr(di, gpth, flags)) {
            error("GPT header values are corrupted.");
            goto out;
        }

        gptl = try_gpt_list(di, gpth, 0);
        if (!gptl)
            gptl = try_gpt_list(di, gpth, 1);
        if (!gptl)
            goto out;

        /* looks like GPT */
        ret = pi_gpt_ctor(iter, di, flags, gpth, gptl);
    } else {
        /* looks like MBR */
        ret = pi_dos_ctor(iter, di, flags, mbr);
    }
out:
    if (ret < 0) {
        free(iter);
        iter = NULL;
    }
    free(mbr);
    free(gpth);
    free(gptl);

    return iter;
}

/* vim: set ts=8 sts=4 sw=4 noet: */