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Restore P>Q in RSA key generation (#558)

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The PKCS#1 standard says nothing about the relation between P and Q
but many libraries guarantee P>Q and mbed TLS did so too in earlier
versions.

This commit restores this behaviour.
This commit is contained in:
Janos Follath 2016-09-21 13:18:12 +01:00 committed by Simon Butcher
parent f6e3b9e8b2
commit ef44178474
4 changed files with 11 additions and 11 deletions
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1
ChangeLog
View File

@ -40,6 +40,7 @@ Bugfix
by inestlerode. #559. by inestlerode. #559.
* Fix documentation and implementation missmatch for function arguments of * Fix documentation and implementation missmatch for function arguments of
mbedtls_gcm_finish(). Found by cmiatpaar. #602 mbedtls_gcm_finish(). Found by cmiatpaar. #602
* Guarantee that P>Q at RSA key generation. #558
Changes Changes
* Extended test coverage of special cases, and added new timing test suite. * Extended test coverage of special cases, and added new timing test suite.

18
library/rsa.c
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@ -102,7 +102,10 @@ int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx,
if( f_rng == NULL || nbits < 128 || exponent < 3 ) if( f_rng == NULL || nbits < 128 || exponent < 3 )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA ); return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
mbedtls_mpi_init( &P1 ); mbedtls_mpi_init( &Q1 ); if( nbits % 2 )
return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
mbedtls_mpi_init( &P1 ); mbedtls_mpi_init( &Q1 );
mbedtls_mpi_init( &H ); mbedtls_mpi_init( &G ); mbedtls_mpi_init( &H ); mbedtls_mpi_init( &G );
/* /*
@ -116,16 +119,8 @@ int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx,
MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->P, nbits >> 1, 0, MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->P, nbits >> 1, 0,
f_rng, p_rng ) ); f_rng, p_rng ) );
if( nbits % 2 ) MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, nbits >> 1, 0,
{
MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, ( nbits >> 1 ) + 1, 0,
f_rng, p_rng ) ); f_rng, p_rng ) );
}
else
{
MBEDTLS_MPI_CHK( mbedtls_mpi_gen_prime( &ctx->Q, nbits >> 1, 0,
f_rng, p_rng ) );
}
if( mbedtls_mpi_cmp_mpi( &ctx->P, &ctx->Q ) == 0 ) if( mbedtls_mpi_cmp_mpi( &ctx->P, &ctx->Q ) == 0 )
continue; continue;
@ -134,6 +129,9 @@ int mbedtls_rsa_gen_key( mbedtls_rsa_context *ctx,
if( mbedtls_mpi_bitlen( &ctx->N ) != nbits ) if( mbedtls_mpi_bitlen( &ctx->N ) != nbits )
continue; continue;
if( mbedtls_mpi_cmp_mpi( &ctx->P, &ctx->Q ) < 0 )
mbedtls_mpi_swap( &ctx->P, &ctx->Q );
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &P1, &ctx->P, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &P1, &ctx->P, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &Q1, &ctx->Q, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &Q1, &ctx->Q, 1 ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &H, &P1, &Q1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &H, &P1, &Q1 ) );

2
tests/suites/test_suite_rsa.data
View File

@ -361,7 +361,7 @@ RSA Generate Key - 2048 bit key
mbedtls_rsa_gen_key:2048:3:0 mbedtls_rsa_gen_key:2048:3:0
RSA Generate Key - 1025 bit key RSA Generate Key - 1025 bit key
mbedtls_rsa_gen_key:1025:3:0 mbedtls_rsa_gen_key:1025:3:MBEDTLS_ERR_RSA_BAD_INPUT_DATA
RSA PKCS1 Encrypt Bad RNG RSA PKCS1 Encrypt Bad RNG
depends_on:MBEDTLS_PKCS1_V15 depends_on:MBEDTLS_PKCS1_V15

1
tests/suites/test_suite_rsa.function
View File

@ -678,6 +678,7 @@ void mbedtls_rsa_gen_key( int nrbits, int exponent, int result)
if( result == 0 ) if( result == 0 )
{ {
TEST_ASSERT( mbedtls_rsa_check_privkey( &ctx ) == 0 ); TEST_ASSERT( mbedtls_rsa_check_privkey( &ctx ) == 0 );
TEST_ASSERT( mbedtls_mpi_cmp_mpi( &ctx.P, &ctx.Q ) > 0 );
} }
exit: exit: