Revert "Remove Diffie-Hellman examples"

This reverts commit bea98b4.

Conflicts:
* programs/Makefile:
  * APPS: the layout of the definition has changed. re-add dh_client
    and dh_server appropriately.

Run scripts/generate_visualc_files.pl to account for the added programs.

Author: gilles-peskine-arm

programs/.gitignore

@@ -9,7 +9,9 @@ hash/hello
 hash/md5sum
 hash/sha1sum
 hash/sha2sum
+pkey/dh_client
 pkey/dh_genprime
+pkey/dh_server
 pkey/ecdsa
 pkey/ecdh_curve25519
 pkey/gen_key

programs/Makefile

@@ -55,7 +55,9 @@ APPS = \
 	aes/crypt_and_hash$(EXEXT) \
 	hash/hello$(EXEXT) \
 	hash/generic_sum$(EXEXT) \
+	pkey/dh_client$(EXEXT) \
 	pkey/dh_genprime$(EXEXT) \
+	pkey/dh_server$(EXEXT) \
 	pkey/ecdh_curve25519$(EXEXT) \
 	pkey/ecdsa$(EXEXT) \
 	pkey/gen_key$(EXEXT) \
@@ -147,10 +149,18 @@ hash/generic_sum$(EXEXT): hash/generic_sum.c $(DEP)
 	echo "  CC    hash/generic_sum.c"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) hash/generic_sum.c $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
 
+pkey/dh_client$(EXEXT): pkey/dh_client.c $(DEP)
+	echo "  CC    pkey/dh_client.c"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/dh_client.c   $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
+
 pkey/dh_genprime$(EXEXT): pkey/dh_genprime.c $(DEP)
 	echo "  CC    pkey/dh_genprime.c"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/dh_genprime.c $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
 
+pkey/dh_server$(EXEXT): pkey/dh_server.c $(DEP)
+	echo "  CC    pkey/dh_server.c"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/dh_server.c   $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@
+
 pkey/ecdh_curve25519$(EXEXT): pkey/ecdh_curve25519.c $(DEP)
 	echo "  CC    pkey/ecdh_curve25519.c"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) pkey/ecdh_curve25519.c   $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@

programs/README.md

@@ -44,6 +44,8 @@ This subdirectory mostly contains sample programs that illustrate specific featu
 
 ### Diffie-Hellman key exchange examples
 
+* [`pkey/dh_client.c`](pkey/dh_client.c), [`pkey/dh_server.c`](pkey/dh_server.c): secure channel demonstrators (client, server). This pair of programs illustrates how to set up a secure channel using RSA for authentication and Diffie-Hellman to generate a shared AES session key.
+
 * [`pkey/ecdh_curve25519.c`](pkey/ecdh_curve25519.c): demonstration of a elliptic curve Diffie-Hellman (ECDH) key agreement.
 
 ### Bignum (`mpi`) usage examples

programs/pkey/CMakeLists.txt

@@ -1,6 +1,12 @@
+add_executable(dh_client dh_client.c)
+target_link_libraries(dh_client mbedtls)
+
 add_executable(dh_genprime dh_genprime.c)
 target_link_libraries(dh_genprime mbedtls)
 
+add_executable(dh_server dh_server.c)
+target_link_libraries(dh_server mbedtls)
+
 add_executable(ecdh_curve25519 ecdh_curve25519.c)
 target_link_libraries(ecdh_curve25519 mbedtls)
 
@@ -52,6 +58,6 @@ target_link_libraries(pk_encrypt mbedtls)
 add_executable(pk_decrypt pk_decrypt.c)
 target_link_libraries(pk_decrypt mbedtls)
 
-install(TARGETS dh_genprime key_app mpi_demo rsa_genkey rsa_sign rsa_verify rsa_encrypt rsa_decrypt pk_encrypt pk_decrypt pk_sign pk_verify gen_key
+install(TARGETS dh_client dh_genprime dh_server key_app mpi_demo rsa_genkey rsa_sign rsa_verify rsa_encrypt rsa_decrypt pk_encrypt pk_decrypt pk_sign pk_verify gen_key
         DESTINATION "bin"
         PERMISSIONS OWNER_READ OWNER_WRITE OWNER_EXECUTE GROUP_READ GROUP_EXECUTE WORLD_READ WORLD_EXECUTE)

programs/pkey/dh_client.c

@@ -0,0 +1,325 @@
+/*
+ *  Diffie-Hellman-Merkle key exchange (client side)
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdio.h>
+#include <stdlib.h>
+#define mbedtls_printf          printf
+#define mbedtls_time_t          time_t
+#define mbedtls_exit            exit
+#define MBEDTLS_EXIT_SUCCESS    EXIT_SUCCESS
+#define MBEDTLS_EXIT_FAILURE    EXIT_FAILURE
+#endif /* MBEDTLS_PLATFORM_C */
+
+#if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
+    defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
+    defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
+    defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C) && \
+    defined(MBEDTLS_SHA1_C)
+#include "mbedtls/net_sockets.h"
+#include "mbedtls/aes.h"
+#include "mbedtls/dhm.h"
+#include "mbedtls/rsa.h"
+#include "mbedtls/sha1.h"
+#include "mbedtls/entropy.h"
+#include "mbedtls/ctr_drbg.h"
+
+#include <stdio.h>
+#include <string.h>
+#endif
+
+#define SERVER_NAME "localhost"
+#define SERVER_PORT "11999"
+
+#if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) ||     \
+    !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) ||  \
+    !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) ||    \
+    !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
+    !defined(MBEDTLS_SHA1_C)
+int main( void )
+{
+    mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
+           "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
+           "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO and/or "
+           "MBEDTLS_CTR_DRBG_C not defined.\n");
+    return( 0 );
+}
+#else
+
+#if defined(MBEDTLS_CHECK_PARAMS)
+#include "mbedtls/platform_util.h"
+void mbedtls_param_failed( const char *failure_condition,
+                           const char *file,
+                           int line )
+{
+    mbedtls_printf( "%s:%i: Input param failed - %s\n",
+                    file, line, failure_condition );
+    mbedtls_exit( MBEDTLS_EXIT_FAILURE );
+}
+#endif
+
+int main( void )
+{
+    FILE *f;
+
+    int ret = 1;
+    int exit_code = MBEDTLS_EXIT_FAILURE;
+    size_t n, buflen;
+    mbedtls_net_context server_fd;
+
+    unsigned char *p, *end;
+    unsigned char buf[2048];
+    unsigned char hash[32];
+    const char *pers = "dh_client";
+
+    mbedtls_entropy_context entropy;
+    mbedtls_ctr_drbg_context ctr_drbg;
+    mbedtls_rsa_context rsa;
+    mbedtls_dhm_context dhm;
+    mbedtls_aes_context aes;
+
+    mbedtls_net_init( &server_fd );
+    mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_SHA256 );
+    mbedtls_dhm_init( &dhm );
+    mbedtls_aes_init( &aes );
+    mbedtls_ctr_drbg_init( &ctr_drbg );
+
+    /*
+     * 1. Setup the RNG
+     */
+    mbedtls_printf( "\n  . Seeding 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,
+                               strlen( pers ) ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
+        goto exit;
+    }
+
+    /*
+     * 2. Read the server's public RSA key
+     */
+    mbedtls_printf( "\n  . Reading public key from rsa_pub.txt" );
+    fflush( stdout );
+
+    if( ( f = fopen( "rsa_pub.txt", "rb" ) ) == NULL )
+    {
+        mbedtls_printf( " failed\n  ! Could not open rsa_pub.txt\n" \
+                "  ! Please run rsa_genkey first\n\n" );
+        goto exit;
+    }
+
+    mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, 0 );
+
+    if( ( ret = mbedtls_mpi_read_file( &rsa.N, 16, f ) ) != 0 ||
+        ( ret = mbedtls_mpi_read_file( &rsa.E, 16, f ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_mpi_read_file returned %d\n\n", ret );
+        fclose( f );
+        goto exit;
+    }
+
+    rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
+
+    fclose( f );
+
+    /*
+     * 3. Initiate the connection
+     */
+    mbedtls_printf( "\n  . Connecting to tcp/%s/%s", SERVER_NAME,
+                                             SERVER_PORT );
+    fflush( stdout );
+
+    if( ( ret = mbedtls_net_connect( &server_fd, SERVER_NAME,
+                                         SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_net_connect returned %d\n\n", ret );
+        goto exit;
+    }
+
+    /*
+     * 4a. First get the buffer length
+     */
+    mbedtls_printf( "\n  . Receiving the server's DH parameters" );
+    fflush( stdout );
+
+    memset( buf, 0, sizeof( buf ) );
+
+    if( ( ret = mbedtls_net_recv( &server_fd, buf, 2 ) ) != 2 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_net_recv returned %d\n\n", ret );
+        goto exit;
+    }
+
+    n = buflen = ( buf[0] << 8 ) | buf[1];
+    if( buflen < 1 || buflen > sizeof( buf ) )
+    {
+        mbedtls_printf( " failed\n  ! Got an invalid buffer length\n\n" );
+        goto exit;
+    }
+
+    /*
+     * 4b. Get the DHM parameters: P, G and Ys = G^Xs mod P
+     */
+    memset( buf, 0, sizeof( buf ) );
+
+    if( ( ret = mbedtls_net_recv( &server_fd, buf, n ) ) != (int) n )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_net_recv returned %d\n\n", ret );
+        goto exit;
+    }
+
+    p = buf, end = buf + buflen;
+
+    if( ( ret = mbedtls_dhm_read_params( &dhm, &p, end ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_dhm_read_params returned %d\n\n", ret );
+        goto exit;
+    }
+
+    if( dhm.len < 64 || dhm.len > 512 )
+    {
+        mbedtls_printf( " failed\n  ! Invalid DHM modulus size\n\n" );
+        goto exit;
+    }
+
+    /*
+     * 5. Check that the server's RSA signature matches
+     *    the SHA-256 hash of (P,G,Ys)
+     */
+    mbedtls_printf( "\n  . Verifying the server's RSA signature" );
+    fflush( stdout );
+
+    p += 2;
+
+    if( ( n = (size_t) ( end - p ) ) != rsa.len )
+    {
+        mbedtls_printf( " failed\n  ! Invalid RSA signature size\n\n" );
+        goto exit;
+    }
+
+    if( ( ret = mbedtls_sha1_ret( buf, (int)( p - 2 - buf ), hash ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_sha1_ret returned %d\n\n", ret );
+        goto exit;
+    }
+
+    if( ( ret = mbedtls_rsa_pkcs1_verify( &rsa, NULL, NULL, MBEDTLS_RSA_PUBLIC,
+                                  MBEDTLS_MD_SHA256, 0, hash, p ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_rsa_pkcs1_verify returned %d\n\n", ret );
+        goto exit;
+    }
+
+    /*
+     * 6. Send our public value: Yc = G ^ Xc mod P
+     */
+    mbedtls_printf( "\n  . Sending own public value to server" );
+    fflush( stdout );
+
+    n = dhm.len;
+    if( ( ret = mbedtls_dhm_make_public( &dhm, (int) dhm.len, buf, n,
+                                 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_dhm_make_public returned %d\n\n", ret );
+        goto exit;
+    }
+
+    if( ( ret = mbedtls_net_send( &server_fd, buf, n ) ) != (int) n )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_net_send returned %d\n\n", ret );
+        goto exit;
+    }
+
+    /*
+     * 7. Derive the shared secret: K = Ys ^ Xc mod P
+     */
+    mbedtls_printf( "\n  . Shared secret: " );
+    fflush( stdout );
+
+    if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
+                                 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
+        goto exit;
+    }
+
+    for( n = 0; n < 16; n++ )
+        mbedtls_printf( "%02x", buf[n] );
+
+    /*
+     * 8. Setup the AES-256 decryption key
+     *
+     * This is an overly simplified example; best practice is
+     * to hash the shared secret with a random value to derive
+     * the keying material for the encryption/decryption keys,
+     * IVs and MACs.
+     */
+    mbedtls_printf( "...\n  . Receiving and decrypting the ciphertext" );
+    fflush( stdout );
+
+    mbedtls_aes_setkey_dec( &aes, buf, 256 );
+
+    memset( buf, 0, sizeof( buf ) );
+
+    if( ( ret = mbedtls_net_recv( &server_fd, buf, 16 ) ) != 16 )
+    {
+        mbedtls_printf( " failed\n  ! mbedtls_net_recv returned %d\n\n", ret );
+        goto exit;
+    }
+
+    mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_DECRYPT, buf, buf );
+    buf[16] = '\0';
+    mbedtls_printf( "\n  . Plaintext is \"%s\"\n\n", (char *) buf );
+
+    exit_code = MBEDTLS_EXIT_SUCCESS;
+
+exit:
+
+    mbedtls_net_free( &server_fd );
+
+    mbedtls_aes_free( &aes );
+    mbedtls_rsa_free( &rsa );
+    mbedtls_dhm_free( &dhm );
+    mbedtls_ctr_drbg_free( &ctr_drbg );
+    mbedtls_entropy_free( &entropy );
+
+#if defined(_WIN32)
+    mbedtls_printf( "  + Press Enter to exit this program.\n" );
+    fflush( stdout ); getchar();
+#endif
+
+    return( exit_code );
+}
+#endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
+          MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
+          MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */