From d99f8b28978e47e77c013a36136f3576af87baf0 Mon Sep 17 00:00:00 2001 From: Thomas Daubney Date: Wed, 18 May 2022 15:13:31 +0100 Subject: [PATCH] Rewrite x25519 example program Rewrite x25519 example program to fix fatal bug and show current best practices with the ECDH API. Signed-off-by: Thomas Daubney --- programs/pkey/ecdh_curve25519.c | 132 ++++++++++++++------------------ 1 file changed, 59 insertions(+), 73 deletions(-) diff --git a/programs/pkey/ecdh_curve25519.c b/programs/pkey/ecdh_curve25519.c index 67f136360c5e..65b206a24769 100644 --- a/programs/pkey/ecdh_curve25519.c +++ b/programs/pkey/ecdh_curve25519.c @@ -34,12 +34,12 @@ #define MBEDTLS_EXIT_FAILURE EXIT_FAILURE #endif /* MBEDTLS_PLATFORM_C */ -#if !defined(MBEDTLS_ECDH_C) || !defined(MBEDTLS_ECDH_LEGACY_CONTEXT) || \ +#if !defined(MBEDTLS_ECDH_C) || \ !defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED) || \ !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C) int main( void ) { - mbedtls_printf( "MBEDTLS_ECDH_C and/or MBEDTLS_ECDH_LEGACY_CONTEXT and/or " + mbedtls_printf( "MBEDTLS_ECDH_C and/or " "MBEDTLS_ECP_DP_CURVE25519_ENABLED and/or " "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C " "not defined\n" ); @@ -51,6 +51,8 @@ int main( void ) #include "mbedtls/ctr_drbg.h" #include "mbedtls/ecdh.h" +#include + int main( int argc, char *argv[] ) { @@ -59,8 +61,15 @@ int main( int argc, char *argv[] ) mbedtls_ecdh_context ctx_cli, ctx_srv; mbedtls_entropy_context entropy; mbedtls_ctr_drbg_context ctr_drbg; - unsigned char cli_to_srv[32], srv_to_cli[32]; + unsigned char cli_to_srv[36], srv_to_cli[33]; const char pers[] = "ecdh"; + + size_t srv_olen; + size_t cli_olen; + unsigned char secret_cli[32] = { 0 }; + unsigned char secret_srv[32] = { 0 }; + const unsigned char *p_cli_to_srv = cli_to_srv; + ((void) argc); ((void) argv); @@ -71,15 +80,17 @@ int main( int argc, char *argv[] ) /* * Initialize random number generation */ - mbedtls_printf( " . Seeding the random number generator..." ); + mbedtls_printf( " . Seed the random number generator..." ); fflush( stdout ); mbedtls_entropy_init( &entropy ); - if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy, - (const unsigned char *) pers, - sizeof pers ) ) != 0 ) + if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, + &entropy, + (const unsigned char *) pers, + sizeof pers ) ) != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", + ret ); goto exit; } @@ -88,28 +99,23 @@ int main( int argc, char *argv[] ) /* * Client: initialize context and generate keypair */ - mbedtls_printf( " . Setting up client context..." ); + mbedtls_printf( " . Set up client context, generate EC key pair..." ); fflush( stdout ); - ret = mbedtls_ecp_group_load( &ctx_cli.grp, MBEDTLS_ECP_DP_CURVE25519 ); - if( ret != 0 ) - { - mbedtls_printf( " failed\n ! mbedtls_ecp_group_load returned %d\n", ret ); - goto exit; - } - - ret = mbedtls_ecdh_gen_public( &ctx_cli.grp, &ctx_cli.d, &ctx_cli.Q, - mbedtls_ctr_drbg_random, &ctr_drbg ); + ret = mbedtls_ecdh_setup( &ctx_cli, MBEDTLS_ECP_DP_CURVE25519 ); if( ret != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_ecdh_gen_public returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ecdh_setup returned %d\n", ret ); goto exit; } - ret = mbedtls_mpi_write_binary( &ctx_cli.Q.X, cli_to_srv, 32 ); + ret = mbedtls_ecdh_make_params( &ctx_cli, &cli_olen, cli_to_srv, + sizeof( cli_to_srv ), + mbedtls_ctr_drbg_random, &ctr_drbg ); if( ret != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_mpi_write_binary returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ecdh_make_params returned %d\n", + ret ); goto exit; } @@ -118,90 +124,70 @@ int main( int argc, char *argv[] ) /* * Server: initialize context and generate keypair */ - mbedtls_printf( " . Setting up server context..." ); + mbedtls_printf( " . Server: read params, generate public key..." ); fflush( stdout ); - ret = mbedtls_ecp_group_load( &ctx_srv.grp, MBEDTLS_ECP_DP_CURVE25519 ); + ret = mbedtls_ecdh_read_params( &ctx_srv, &p_cli_to_srv, + p_cli_to_srv + sizeof( cli_to_srv ) ); if( ret != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_ecp_group_load returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ecdh_read_params returned %d\n", + ret ); goto exit; } - ret = mbedtls_ecdh_gen_public( &ctx_srv.grp, &ctx_srv.d, &ctx_srv.Q, - mbedtls_ctr_drbg_random, &ctr_drbg ); + ret = mbedtls_ecdh_make_public( &ctx_srv, &srv_olen, srv_to_cli, + sizeof( srv_to_cli ), + mbedtls_ctr_drbg_random, &ctr_drbg ); if( ret != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_ecdh_gen_public returned %d\n", ret ); - goto exit; - } - - ret = mbedtls_mpi_write_binary( &ctx_srv.Q.X, srv_to_cli, 32 ); - if( ret != 0 ) - { - mbedtls_printf( " failed\n ! mbedtls_mpi_write_binary returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ecdh_make_public returned %d\n", + ret ); goto exit; } mbedtls_printf( " ok\n" ); /* - * Server: read peer's key and generate shared secret + * Client: read public key */ - mbedtls_printf( " . Server reading client key and computing secret..." ); + mbedtls_printf( " . Client: read public key..." ); fflush( stdout ); - ret = mbedtls_mpi_lset( &ctx_srv.Qp.Z, 1 ); + ret = mbedtls_ecdh_read_public( &ctx_cli, srv_to_cli, + sizeof( srv_to_cli ) ); if( ret != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_mpi_lset returned %d\n", ret ); - goto exit; - } - - ret = mbedtls_mpi_read_binary( &ctx_srv.Qp.X, cli_to_srv, 32 ); - if( ret != 0 ) - { - mbedtls_printf( " failed\n ! mbedtls_mpi_read_binary returned %d\n", ret ); - goto exit; - } - - ret = mbedtls_ecdh_compute_shared( &ctx_srv.grp, &ctx_srv.z, - &ctx_srv.Qp, &ctx_srv.d, - mbedtls_ctr_drbg_random, &ctr_drbg ); - if( ret != 0 ) - { - mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ecdh_read_public returned %d\n", + ret ); goto exit; } mbedtls_printf( " ok\n" ); /* - * Client: read peer's key and generate shared secret + * Calculate secrets */ - mbedtls_printf( " . Client reading server key and computing secret..." ); + mbedtls_printf( " . Calculate secrets..." ); fflush( stdout ); - ret = mbedtls_mpi_lset( &ctx_cli.Qp.Z, 1 ); + ret = mbedtls_ecdh_calc_secret( &ctx_cli, &cli_olen, secret_cli, + sizeof( secret_cli ), + mbedtls_ctr_drbg_random, &ctr_drbg ); if( ret != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_mpi_lset returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ecdh_calc_secret returned %d\n", + ret ); goto exit; } - ret = mbedtls_mpi_read_binary( &ctx_cli.Qp.X, srv_to_cli, 32 ); + ret = mbedtls_ecdh_calc_secret( &ctx_srv, &srv_olen, secret_srv, + sizeof( secret_srv ), + mbedtls_ctr_drbg_random, &ctr_drbg ); if( ret != 0 ) { - mbedtls_printf( " failed\n ! mbedtls_mpi_read_binary returned %d\n", ret ); - goto exit; - } - - ret = mbedtls_ecdh_compute_shared( &ctx_cli.grp, &ctx_cli.z, - &ctx_cli.Qp, &ctx_cli.d, - mbedtls_ctr_drbg_random, &ctr_drbg ); - if( ret != 0 ) - { - mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret ); + mbedtls_printf( " failed\n ! mbedtls_ecdh_calc_secret returned %d\n", + ret ); goto exit; } @@ -210,13 +196,13 @@ int main( int argc, char *argv[] ) /* * Verification: are the computed secrets equal? */ - mbedtls_printf( " . Checking if both computed secrets are equal..." ); + mbedtls_printf( " . Check if both calculated secrets are equal..." ); fflush( stdout ); - ret = mbedtls_mpi_cmp_mpi( &ctx_cli.z, &ctx_srv.z ); - if( ret != 0 ) + ret = memcmp( secret_srv, secret_cli, srv_olen ); + if( ret != 0 || ( cli_olen != srv_olen ) ) { - mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret ); + mbedtls_printf( " failed\n ! Shared secrets not equal.\n" ); goto exit; }