Verify VBR checksum on mount.

git-svn-id: http://exfat.googlecode.com/svn/trunk@184 60bc1c72-a15a-11de-b98f-4500b42dc123

diff --git a/libexfat/mount.c b/libexfat/mount.c
index 26afdba..ae7e098 100644 (file)
--- a/libexfat/mount.c
+++ b/libexfat/mount.c
@@ -94,6 +94,29 @@ static void parse_options(struct exfat* ef, const char* options)
        ef->noatime = match_option(options, "noatime");
 }
 
+static int verify_vbr_checksum(void* block, off_t block_size, int fd)
+{
+       uint32_t vbr_checksum;
+       int i;
+
+       exfat_read_raw(block, block_size, 0, fd);
+       vbr_checksum = exfat_vbr_start_checksum(block, block_size);
+       for (i = 1; i < 11; i++)
+       {
+               exfat_read_raw(block, block_size, i * block_size, fd);
+               vbr_checksum = exfat_vbr_add_checksum(block, block_size, vbr_checksum);
+       }
+       exfat_read_raw(block, block_size, i * block_size, fd);
+       for (i = 0; i < block_size / sizeof(vbr_checksum); i++)
+               if (((const uint32_t*) block)[i] != vbr_checksum)
+               {
+                       exfat_error("invalid VBR checksum 0x%x (expected 0x%x)",
+                                       ((const uint32_t*) block)[i], vbr_checksum);
+                       return 1;
+               }
+       return 0;
+}
+
 int exfat_mount(struct exfat* ef, const char* spec, const char* options)
 {
        int rc;
@@ -160,6 +183,14 @@ int exfat_mount(struct exfat* ef, const char* spec, const char* options)
                exfat_error("failed to allocate zero block");
                return -ENOMEM;
        }
+       /* use zero_block as a temporary buffer for VBR checksum verification */
+       if (verify_vbr_checksum(ef->zero_block, BLOCK_SIZE(*ef->sb), ef->fd) != 0)
+       {
+               free(ef->zero_block);
+               close(ef->fd);
+               free(ef->sb);
+               return -EIO;
+       }
        memset(ef->zero_block, 0, BLOCK_SIZE(*ef->sb));
 
        ef->root = malloc(sizeof(struct exfat_node));