From bdcb39616d1f036cf9fae6cc1eba596779e09669 Mon Sep 17 00:00:00 2001 From: Gilles Peskine Date: Thu, 4 Jun 2020 20:55:15 +0200 Subject: [PATCH] Revert "Shut up a clang-analyzer warning" This reverts commit 2cc69fffcf431085f18f4e59c3c5188297f97b87. A check was added in mpi_montmul because clang-analyzer warned about a possibly null pointer. However this was a false positive. Recent versions of clang-analyzer no longer emit a warning (3.6 does, 6 doesn't). Incidentally, the size check was wrong: mpi_montmul needs T->n >= 2 * (N->n + 1), not just T->n >= N->n + 1. Given that this is an internal function which is only used from one public function and in a tightly controlled way, remove both the null check (which is of low value to begin with) and the size check (which would be slightly more valuable, but was wrong anyway). This allows the function not to need to return an error, which makes the source code a little easier to read and makes the object code a little smaller. Signed-off-by: Gilles Peskine --- library/bignum.c | 33 ++++++++++++++------------------- 1 file changed, 14 insertions(+), 19 deletions(-) diff --git a/library/bignum.c b/library/bignum.c index 8d2ad9584..7d1843029 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -1892,15 +1892,12 @@ static void mpi_montg_init( mbedtls_mpi_uint *mm, const mbedtls_mpi *N ) /* * Montgomery multiplication: A = A * B * R^-1 mod N (HAC 14.36) */ -static int mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi *N, mbedtls_mpi_uint mm, +static void mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi *N, mbedtls_mpi_uint mm, const mbedtls_mpi *T ) { size_t i, n, m; mbedtls_mpi_uint u0, u1, *d; - if( T->n < N->n + 1 || T->p == NULL ) - return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA ); - memset( T->p, 0, T->n * ciL ); d = T->p; @@ -1928,15 +1925,13 @@ static int mpi_montmul( mbedtls_mpi *A, const mbedtls_mpi *B, const mbedtls_mpi else /* prevent timing attacks */ mpi_sub_hlp( n, A->p, T->p ); - - return( 0 ); } /* * Montgomery reduction: A = A * R^-1 mod N */ -static int mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, - mbedtls_mpi_uint mm, const mbedtls_mpi *T ) +static void mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, + mbedtls_mpi_uint mm, const mbedtls_mpi *T ) { mbedtls_mpi_uint z = 1; mbedtls_mpi U; @@ -1944,7 +1939,7 @@ static int mpi_montred( mbedtls_mpi *A, const mbedtls_mpi *N, U.n = U.s = (int) z; U.p = &z; - return( mpi_montmul( A, &U, N, mm, T ) ); + mpi_montmul( A, &U, N, mm, T ); } /* @@ -2030,13 +2025,13 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, else MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &W[1], A ) ); - MBEDTLS_MPI_CHK( mpi_montmul( &W[1], &RR, N, mm, &T ) ); + mpi_montmul( &W[1], &RR, N, mm, &T ); /* * X = R^2 * R^-1 mod N = R mod N */ MBEDTLS_MPI_CHK( mbedtls_mpi_copy( X, &RR ) ); - MBEDTLS_MPI_CHK( mpi_montred( X, N, mm, &T ) ); + mpi_montred( X, N, mm, &T ); if( wsize > 1 ) { @@ -2049,7 +2044,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &W[j], &W[1] ) ); for( i = 0; i < wsize - 1; i++ ) - MBEDTLS_MPI_CHK( mpi_montmul( &W[j], &W[j], N, mm, &T ) ); + mpi_montmul( &W[j], &W[j], N, mm, &T ); /* * W[i] = W[i - 1] * W[1] @@ -2059,7 +2054,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, MBEDTLS_MPI_CHK( mbedtls_mpi_grow( &W[i], N->n + 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &W[i], &W[i - 1] ) ); - MBEDTLS_MPI_CHK( mpi_montmul( &W[i], &W[1], N, mm, &T ) ); + mpi_montmul( &W[i], &W[1], N, mm, &T ); } } @@ -2096,7 +2091,7 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, /* * out of window, square X */ - MBEDTLS_MPI_CHK( mpi_montmul( X, X, N, mm, &T ) ); + mpi_montmul( X, X, N, mm, &T ); continue; } @@ -2114,12 +2109,12 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, * X = X^wsize R^-1 mod N */ for( i = 0; i < wsize; i++ ) - MBEDTLS_MPI_CHK( mpi_montmul( X, X, N, mm, &T ) ); + mpi_montmul( X, X, N, mm, &T ); /* * X = X * W[wbits] R^-1 mod N */ - MBEDTLS_MPI_CHK( mpi_montmul( X, &W[wbits], N, mm, &T ) ); + mpi_montmul( X, &W[wbits], N, mm, &T ); state--; nbits = 0; @@ -2132,18 +2127,18 @@ int mbedtls_mpi_exp_mod( mbedtls_mpi *X, const mbedtls_mpi *A, */ for( i = 0; i < nbits; i++ ) { - MBEDTLS_MPI_CHK( mpi_montmul( X, X, N, mm, &T ) ); + mpi_montmul( X, X, N, mm, &T ); wbits <<= 1; if( ( wbits & ( one << wsize ) ) != 0 ) - MBEDTLS_MPI_CHK( mpi_montmul( X, &W[1], N, mm, &T ) ); + mpi_montmul( X, &W[1], N, mm, &T ); } /* * X = A^E * R * R^-1 mod N = A^E mod N */ - MBEDTLS_MPI_CHK( mpi_montred( X, N, mm, &T ) ); + mpi_montred( X, N, mm, &T ); if( neg && E->n != 0 && ( E->p[0] & 1 ) != 0 ) {