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Really open disk as read only and do not use encrypted_volume_size metadata #252

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Really open disk as read only and do not use encrypted_volume_size metadata #252

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1ca0b38
dis_initialize: Open block device RO if asked with --readonly
benjarobin May 8, 2021
845cf7a
prepare_crypt: Get encrypted_volume_size from disk device size
benjarobin May 8, 2021
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41 changes: 22 additions & 19 deletions src/dislocker.c
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Original file line number Diff line number Diff line change
Expand Up @@ -127,33 +127,36 @@ int dis_initialize(dis_context_t dis_ctx)


/* Open the volume as a (big) normal file */
dis_printf(L_DEBUG, "Trying to open '%s'...\n", dis_ctx->cfg.volume_path);
dis_ctx->fve_fd = dis_open(dis_ctx->cfg.volume_path, O_RDWR|O_LARGEFILE);
if(dis_ctx->fve_fd < 0)

if(dis_is_read_only(dis_ctx) != 0)
{
/* Trying to open it in read-only if O_RDWR doesn't work */
dis_ctx->fve_fd = dis_open(
dis_ctx->cfg.volume_path,
O_RDONLY|O_LARGEFILE
);
dis_printf(L_DEBUG, "Trying to open RO '%s'...\n", dis_ctx->cfg.volume_path);
dis_ctx->fve_fd = dis_open(dis_ctx->cfg.volume_path, O_RDONLY|O_LARGEFILE);
}
else
{
dis_printf(L_DEBUG, "Trying to open RW '%s'...\n", dis_ctx->cfg.volume_path);
dis_ctx->fve_fd = dis_open(dis_ctx->cfg.volume_path, O_RDWR|O_LARGEFILE);

if(dis_ctx->fve_fd < 0)
{
/* Trying to open it in read-only if O_RDWR doesn't work */
dis_ctx->cfg.flags |= DIS_FLAG_READ_ONLY;
dis_printf(
L_CRITICAL,
"Failed to open %s: %s\n",
dis_ctx->cfg.volume_path, strerror(errno)
L_WARNING,
"Failed to open %s for writing. Falling back to read-only.\n",
dis_ctx->cfg.volume_path
);
dis_destroy(dis_ctx);
return DIS_RET_ERROR_FILE_OPEN;

dis_ctx->fve_fd = dis_open(dis_ctx->cfg.volume_path, O_RDONLY|O_LARGEFILE);
}
}

dis_ctx->cfg.flags |= DIS_FLAG_READ_ONLY;
dis_printf(
L_WARNING,
"Failed to open %s for writing. Falling back to read-only.\n",
dis_ctx->cfg.volume_path
);
if(dis_ctx->fve_fd < 0)
{
dis_printf(L_CRITICAL, "Failed to open %s: %s\n", dis_ctx->cfg.volume_path, strerror(errno));
dis_destroy(dis_ctx);
return DIS_RET_ERROR_FILE_OPEN;
}

dis_printf(L_DEBUG, "Opened (fd #%d).\n", dis_ctx->fve_fd);
Expand Down
13 changes: 13 additions & 0 deletions src/inouts/prepare.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,9 @@

#include <errno.h>
#include <pthread.h>
#include <sys/mount.h>
#include <sys/ioctl.h>
#include <stdint.h>

#include "dislocker/inouts/prepare.h"
#include "dislocker/inouts/sectors.h"
Expand Down Expand Up @@ -98,6 +101,7 @@ int init_keys(bitlocker_dataset_t* dataset, datum_key_t* fvek_datum,
int prepare_crypt(dis_context_t dis_ctx)
{
dis_iodata_t* io_data;
uint64_t part_volume_size = UINT64_MAX;

if(!dis_ctx)
return DIS_RET_ERROR_DISLOCKER_INVAL;
Expand All @@ -113,6 +117,15 @@ int prepare_crypt(dis_context_t dis_ctx)
io_data->encrypted_volume_size = dis_metadata_volume_size_from_vbr(dis_ctx->metadata);
io_data->encrypted_volume_size += io_data->sector_size; //The volume size of Vista should include the DBR backup
}

// Do not trust the encrypted volume size in metadata. After shrinking the volume, metadata
// is not updated at least by Windows 10 1909
if (ioctl(dis_ctx->fve_fd, BLKGETSIZE64, &part_volume_size) >= 0)
{
if (part_volume_size < io_data->encrypted_volume_size)
io_data->encrypted_volume_size = part_volume_size;
}

io_data->backup_sectors_addr = dis_metadata_ntfs_sectors_address(io_data->metadata);
io_data->nb_backup_sectors = dis_metadata_backup_sectors_count(io_data->metadata);

Expand Down