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Add checksum validation

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This commit is contained in:
shermp
2019-06-09 14:03:37 +12:00
parent 0e877d1ec7
commit 106be5bb00
2 changed files with 46 additions and 1 deletions
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4
minivhd.h
View File

@@ -14,7 +14,9 @@ typedef enum MVHDError {
MVHD_ERR_MEM = -1,
MVHD_ERR_FILE,
MVHD_ERR_NOT_VHD,
MVHD_ERR_TYPE
MVHD_ERR_TYPE,
MVHD_ERR_FOOTER_CHECKSUM,
MVHD_ERR_SPARSE_CHECKSUM
} MVHDError;
typedef struct MVHDMeta {

43
minivhd_manage.c
View File

@@ -10,6 +10,10 @@
static bool mvhd_file_is_vhd(FILE* f);
static void mvhd_read_footer(MVHDMeta* vhdm);
static void mvhd_read_sparse_header(MVHDMeta* vhdm);
static uint32_t mvhd_gen_footer_checksum(MVHDMeta* vhdm);
static uint32_t mvhd_gen_sparse_checksum(MVHDMeta* vhdm);
static bool mvhd_footer_checksum_valid(MVHDMeta* vhdm);
static bool mvhd_sparse_checksum_valid(MVHDMeta* vhdm);
static bool mvhd_file_is_vhd(FILE* f) {
if (f) {
@@ -36,6 +40,37 @@ static void mvhd_read_sparse_header(MVHDMeta* vhdm) {
mvhd_buffer_to_header(&vhdm->sparse, buffer);
}
static uint32_t mvhd_gen_footer_checksum(MVHDMeta* vhdm) {
uint32_t new_chk = 0;
uint32_t orig_chk = vhdm->footer.checksum;
vhdm->footer.checksum = 0;
uint8_t* footer_bytes = (uint8_t*)&vhdm->footer;
for (size_t i = 0; i < sizeof vhdm->footer; i++) {
new_chk += footer_bytes[i];
}
vhdm->footer.checksum = orig_chk;
return ~new_chk;
}
static uint32_t mvhd_gen_sparse_checksum(MVHDMeta* vhdm) {
uint32_t new_chk = 0;
uint32_t orig_chk = vhdm->sparse.checksum;
vhdm->sparse.checksum = 0;
uint8_t* sparse_bytes = (uint8_t*)&vhdm->sparse;
for (size_t i = 0; i < sizeof vhdm->sparse; i++) {
new_chk = sparse_bytes[i];
}
vhdm->sparse.checksum = orig_chk;
return ~new_chk;
}
static bool mvhd_footer_checksum_valid(MVHDMeta* vhdm) {
return vhdm->footer.checksum == mvhd_gen_footer_checksum(vhdm);
}
static bool mvhd_sparse_checksum_valid(MVHDMeta* vhdm) {
return vhdm->sparse.checksum == mvhd_gen_sparse_checksum(vhdm);
}
MVHDMeta* mvhd_open(const char* path, int* err) {
MVHDMeta *vhdm = calloc(sizeof *vhdm, 1);
if (vhdm == NULL) {
@@ -52,8 +87,16 @@ MVHDMeta* mvhd_open(const char* path, int* err) {
goto cleanup_file;
}
mvhd_read_footer(vhdm);
if (!mvhd_footer_checksum_valid(vhdm)) {
*err = MVHD_ERR_FOOTER_CHECKSUM;
goto cleanup_file;
}
if (vhdm->footer.disk_type == MVHD_TYPE_DIFF || vhdm->footer.disk_type == MVHD_TYPE_DYNAMIC) {
mvhd_read_sparse_header(vhdm);
if (!mvhd_sparse_checksum_valid(vhdm)) {
*err = MVHD_ERR_SPARSE_CHECKSUM;
goto cleanup_file;
}
} else if (vhdm->footer.disk_type != MVHD_TYPE_FIXED) {
*err = MVHD_ERR_TYPE;
goto cleanup_file;