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Abort modular inversion when modulus is one.

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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.
This commit is contained in:
Hanno Becker 2017-04-18 15:49:39 +01:00
parent a4af1c47d2
commit 4bcb4914c5
3 changed files with 6 additions and 3 deletions
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4
include/mbedtls/bignum.h
View File

@ -665,8 +665,8 @@ int mbedtls_mpi_gcd( mbedtls_mpi *G, const mbedtls_mpi *A, const mbedtls_mpi *B
*
* \return 0 if successful,
* MBEDTLS_ERR_MPI_ALLOC_FAILED if memory allocation failed,
* MBEDTLS_ERR_MPI_BAD_INPUT_DATA if N is negative or nil
MBEDTLS_ERR_MPI_NOT_ACCEPTABLE if A has no inverse mod N
* MBEDTLS_ERR_MPI_BAD_INPUT_DATA if N is <= 1,
MBEDTLS_ERR_MPI_NOT_ACCEPTABLE if A has no inverse mod N.
*/
int mbedtls_mpi_inv_mod( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi *N );

2
library/bignum.c
View File

@ -1893,7 +1893,7 @@ int mbedtls_mpi_inv_mod( mbedtls_mpi *X, const mbedtls_mpi *A, const mbedtls_mpi
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 );

3
tests/suites/test_suite_mpi.data
View File

@ -550,6 +550,9 @@ mbedtls_mpi_inv_mod:10:"3":10:"-11":10:"4":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
Base test mbedtls_mpi_inv_mod #4
mbedtls_mpi_inv_mod:10:"2":10:"4":10:"0":MBEDTLS_ERR_MPI_NOT_ACCEPTABLE
Base test mbedtls_mpi_inv_mod #5
mbedtls_mpi_inv_mod:10:"3":10:"1":10:"0":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
Test mbedtls_mpi_inv_mod #1
mbedtls_mpi_inv_mod:16:"aa4df5cb14b4c31237f98bd1faf527c283c2d0f3eec89718664ba33f9762907c":16:"fffbbd660b94412ae61ead9c2906a344116e316a256fd387874c6c675b1d587d":16:"8d6a5c1d7adeae3e94b9bcd2c47e0d46e778bc8804a2cc25c02d775dc3d05b0c":0