mtree/commoncrypto.c

   1 #include <dispatch/dispatch.h>
   2 #include <os/assumes.h>
   3 #include <errno.h>
   4 #include <fcntl.h>
   5
   6 #include "commoncrypto.h"
   7
   8 /* Generic version of libmd's *_File() functions. */
   9 char *
  10 Digest_File(CCDigestAlg algorithm, const char *filename, char *buf)
  11 {
  12         static const char hex[] = "0123456789abcdef";
  13         int fd;
  14         __block CCDigestCtx ctx;
  15         dispatch_queue_t queue;
  16         dispatch_semaphore_t sema;
  17         dispatch_io_t io;
  18         __block int s_error = 0;
  19         uint8_t digest[32]; // SHA256 is the biggest
  20         size_t i, length;
  21
  22         /* dispatch_io_create_with_path requires an absolute path */
  23         fd = open(filename, O_RDONLY);
  24         if (fd < 0) {
  25                 return NULL;
  26         }
  27
  28         (void)fcntl(fd, F_NOCACHE, 1);
  29
  30         (void)os_assumes_zero(CCDigestInit(algorithm, &ctx));
  31
  32         queue = dispatch_queue_create("com.apple.mtree.io", NULL);
  33         os_assert(queue);
  34         sema = dispatch_semaphore_create(0);
  35         os_assert(sema);
  36
  37         io = dispatch_io_create(DISPATCH_IO_STREAM, fd, queue, ^(int error) {
  38                 if (error != 0) {
  39                         s_error = error;
  40                 }
  41                 (void)close(fd);
  42                 (void)dispatch_semaphore_signal(sema);
  43         });
  44         os_assert(io);
  45         dispatch_io_read(io, 0, SIZE_MAX, queue, ^(__unused bool done, dispatch_data_t data, int error) {
  46                 if (data != NULL) {
  47                         (void)dispatch_data_apply(data, ^(__unused dispatch_data_t region, __unused size_t offset, const void *buffer, size_t size) {
  48                                 (void)os_assumes_zero(CCDigestUpdate(&ctx, buffer, size));
  49                                 return (bool)true;
  50                         });
  51                 }
  52
  53                 if (error != 0) {
  54                         s_error = error;
  55                 }
  56         });
  57         dispatch_release(io); // it will close on its own
  58
  59         (void)dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
  60
  61         dispatch_release(queue);
  62         dispatch_release(sema);
  63
  64         if (s_error != 0) {
  65                 errno = s_error;
  66                 return NULL;
  67         }
  68
  69         /* Finalize and convert to hex. */
  70         (void)os_assumes_zero(CCDigestFinal(&ctx, digest));
  71         length = CCDigestOutputSize(&ctx);
  72         os_assert(length <= sizeof(digest));
  73         for (i = 0; i < length; i++) {
  74                 buf[i+i] = hex[digest[i] >> 4];
  75                 buf[i+i+1] = hex[digest[i] & 0x0f];
  76         }
  77         buf[i+i] = '\0';
  78
  79         return buf;
  80 }