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Merge pull request #4430 from gilles-peskine-arm/dhm_min_bitlen-bits

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Backport 2.x: Enforce dhm_min_bitlen exactly
This commit is contained in:
Gilles Peskine
2021-04-29 14:55:36 +02:00
committed by GitHub
parent e0427c777f e8a2fc8461
commit 4ad0967125
6 changed files with 87 additions and 2 deletions
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6
library/ssl_cli.c
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@ -2610,6 +2610,7 @@ static int ssl_parse_server_dh_params( mbedtls_ssl_context *ssl,
unsigned char *end )
{
int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
size_t dhm_actual_bitlen;
/*
* Ephemeral DH parameters:
@ -2627,10 +2628,11 @@ static int ssl_parse_server_dh_params( mbedtls_ssl_context *ssl,
return( ret );
}
if( ssl->handshake->dhm_ctx.len * 8 < ssl->conf->dhm_min_bitlen )
dhm_actual_bitlen = mbedtls_mpi_bitlen( &ssl->handshake->dhm_ctx.P );
if( dhm_actual_bitlen < ssl->conf->dhm_min_bitlen )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "DHM prime too short: %" MBEDTLS_PRINTF_SIZET " < %u",
ssl->handshake->dhm_ctx.len * 8,
dhm_actual_bitlen,
ssl->conf->dhm_min_bitlen ) );
return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_KEY_EXCHANGE );
}