commit 4bcb4914c520a7ddbb8f361f2b58ef83237e0f69
author Hanno Becker <hanno.becker@arm.com> Tue Apr 18 15:49:39 2017 +0100
committer Hanno Becker <hanno.becker@arm.com> Mon May 08 14:47:04 2017 +0100
tree de35675aca434e45f5ea7cb7dc3b7f674ed3ac3f
parent a4af1c47d2d9bf4cb62f8df2f12ebe2ed7fbde89

Abort modular inversion when modulus is one.

The modular inversion function hangs when provided with the modulus 1. This commit refuses this modulus with a BAD_INPUT error code. It also adds a test for this case.

library/bignum.c

diff --git a/library/bignum.c b/library/bignum.c
index efc1a51..8df2510 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1893,7 +1893,7 @@
     int ret;
     mbedtls_mpi G, TA, TU, U1, U2, TB, TV, V1, V2;
 
-    if( mbedtls_mpi_cmp_int( N, 0 ) <= 0 )
+    if( mbedtls_mpi_cmp_int( N, 1 ) <= 0 )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
 
     mbedtls_mpi_init( &TA ); mbedtls_mpi_init( &TU ); mbedtls_mpi_init( &U1 ); mbedtls_mpi_init( &U2 );