[PATCH v3 01/14] mpi: Introduce mpi_key_length()

[Roberto Sassu]

From: Roberto Sassu <roberto.sa...@huawei.com>

Introduce the new function to get the number of bits and bytes from an MPI.

Signed-off-by: Roberto Sassu <roberto.sa...@huawei.com>
Signed-off-by: David Howells <dhowe...@redhat.com>
---
 include/linux/mpi.h       |  2 ++
 lib/crypto/mpi/mpicoder.c | 33 ++++++++++++++++++++++++++-------
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/include/linux/mpi.h b/include/linux/mpi.h
index eb0d1c1db208..a7dd4c9d8120 100644
--- a/include/linux/mpi.h
+++ b/include/linux/mpi.h
@@ -90,6 +90,8 @@ enum gcry_mpi_format {
 };
 
 MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes);
+int mpi_key_length(const void *xbuffer, unsigned int ret_nread,
+                  unsigned int *nbits_arg, unsigned int *nbytes_arg);
 MPI mpi_read_from_buffer(const void *buffer, unsigned *ret_nread);
 int mpi_fromstr(MPI val, const char *str);
 MPI mpi_scanval(const char *string);
diff --git a/lib/crypto/mpi/mpicoder.c b/lib/crypto/mpi/mpicoder.c
index 3cb6bd148fa9..92447a1c8bf9 100644
--- a/lib/crypto/mpi/mpicoder.c
+++ b/lib/crypto/mpi/mpicoder.c
@@ -79,22 +79,41 @@ MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
 }
 EXPORT_SYMBOL_GPL(mpi_read_raw_data);
 
-MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
+int mpi_key_length(const void *xbuffer, unsigned int ret_nread,
+                  unsigned int *nbits_arg, unsigned int *nbytes_arg)
 {
        const uint8_t *buffer = xbuffer;
-       unsigned int nbits, nbytes;
-       MPI val;
+       unsigned int nbits;
 
-       if (*ret_nread < 2)
-               return ERR_PTR(-EINVAL);
+       if (ret_nread < 2)
+               return -EINVAL;
        nbits = buffer[0] << 8 | buffer[1];
 
        if (nbits > MAX_EXTERN_MPI_BITS) {
                pr_info("MPI: mpi too large (%u bits)\n", nbits);
-               return ERR_PTR(-EINVAL);
+               return -EINVAL;
        }
 
-       nbytes = DIV_ROUND_UP(nbits, 8);
+       if (nbits_arg)
+               *nbits_arg = nbits;
+       if (nbytes_arg)
+               *nbytes_arg = DIV_ROUND_UP(nbits, 8);
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_key_length);
+
+MPI mpi_read_from_buffer(const void *xbuffer, unsigned int *ret_nread)
+{
+       const uint8_t *buffer = xbuffer;
+       unsigned int nbytes;
+       MPI val;
+       int ret;
+
+       ret = mpi_key_length(xbuffer, *ret_nread, NULL, &nbytes);
+       if (ret < 0)
+               return ERR_PTR(ret);
+
        if (nbytes + 2 > *ret_nread) {
                pr_info("MPI: mpi larger than buffer nbytes=%u ret_nread=%u\n",
                                nbytes, *ret_nread);
-- 
2.34.1