commit d61fc6881a988cec565cd2b987f6ec1236aa8814
author Janos Follath <janos.follath@arm.com> Tue Feb 23 14:42:48 2016 +0000
committer Simon Butcher <simon.butcher@arm.com> Tue Apr 19 09:42:17 2016 +0100
tree 860e7997c419992eaafede8a68595bf60ef2fae5
parent 4dfecabb977ebf24d3cff66e43bc96aa21d2c077

Fix odd bitlength RSA key generation

Fix issue that caused a hang up when generating RSA keys of odd
bitlength.

library/rsa.c

diff --git a/library/rsa.c b/library/rsa.c
index 0cb0e7d..f7ed0be 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -97,7 +97,8 @@
     if( f_rng == NULL || nbits < 128 || exponent < 3 )
         return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
 
-    mpi_init( &P1 ); mpi_init( &Q1 ); mpi_init( &H ); mpi_init( &G );
+    mpi_init( &P1 ); mpi_init( &Q1 );
+    mpi_init( &H ); mpi_init( &G );
 
     /*
      * find primes P and Q with Q < P so that:
@@ -107,14 +108,15 @@
 
     do
     {
-        MPI_CHK( mpi_gen_prime( &ctx->P, ( nbits + 1 ) >> 1, 0,
+       MPI_CHK( mpi_gen_prime( &ctx->P, nbits >> 1, 0,
                                 f_rng, p_rng ) );
 
-        MPI_CHK( mpi_gen_prime( &ctx->Q, ( nbits + 1 ) >> 1, 0,
+        if( nbits % 2 )
+            MPI_CHK( mpi_gen_prime( &ctx->Q, ( nbits >> 1 ) + 1, 0,
                                 f_rng, p_rng ) );
-
-        if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) < 0 )
-            mpi_swap( &ctx->P, &ctx->Q );
+        else
+            MPI_CHK( mpi_gen_prime( &ctx->Q, nbits >> 1, 0,
+                                f_rng, p_rng ) );
 
         if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) == 0 )
             continue;