2 files changed, 56 insertions, 0 deletions

diff --git a/include/linux/mpi.h b/include/linux/mpi.h
index d02cca6cc8ce..5af1b81def49 100644
--- a/include/linux/mpi.h
+++ b/include/linux/mpi.h
@@ -76,6 +76,7 @@ void mpi_swap(MPI a, MPI b);
 
 /*-- mpicoder.c --*/
 MPI do_encode_md(const void *sha_buffer, unsigned nbits);
+MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes);
 MPI mpi_read_from_buffer(const void *buffer, unsigned *ret_nread);
 int mpi_fromstr(MPI val, const char *str);
 u32 mpi_get_keyid(MPI a, u32 *keyid);
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index f0fa65995800..3962b7f7fe3f 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -18,10 +18,65 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 
+#include <linux/bitops.h>
+#include <asm-generic/bitops/count_zeros.h>
 #include "mpi-internal.h"
 
 #define MAX_EXTERN_MPI_BITS 16384
 
+/**
+ * mpi_read_raw_data - Read a raw byte stream as a positive integer
+ * @xbuffer: The data to read
+ * @nbytes: The amount of data to read
+ */
+MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
+{
+        const uint8_t *buffer = xbuffer;
+        int i, j;
+        unsigned nbits, nlimbs;
+        mpi_limb_t a;
+        MPI val = NULL;
+
+        while (nbytes >= 0 && buffer[0] == 0) {
+                buffer++;
+                nbytes--;
+        }
+
+        nbits = nbytes * 8;
+        if (nbits > MAX_EXTERN_MPI_BITS) {
+                pr_info("MPI: mpi too large (%u bits)\n", nbits);
+                return NULL;
+        }
+        if (nbytes > 0)
+                nbits -= count_leading_zeros(buffer[0]);
+        else
+                nbits = 0;
+
+        nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+        val = mpi_alloc(nlimbs);
+        if (!val)
+                return NULL;
+        val->nbits = nbits;
+        val->sign = 0;
+        val->nlimbs = nlimbs;
+
+        if (nbytes > 0) {
+                i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
+                i %= BYTES_PER_MPI_LIMB;
+                for (j = nlimbs; j > 0; j--) {
+                        a = 0;
+                        for (; i < BYTES_PER_MPI_LIMB; i++) {
+                                a <<= 8;
+                                a |= *buffer++;
+                        }
+                        i = 0;
+                        val->d[j - 1] = a;
+                }
+        }
+        return val;
+}
+EXPORT_SYMBOL_GPL(mpi_read_raw_data);
+
 MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
 {
         const uint8_t *buffer = xbuffer;