I'm going to try TLS with mutual authentication using openssl.
However, as shown in the output results below, the client can receive a server certificate and output it, but the server has not received the client certificate.
The details of my work are as follows.
- Server and client certificate generation (without certificate signing through CA, just self-signing)
(1) Generating the server key and certificate.
$ openssl genrsa -des3 -out server.key 2048
$ openssl req -new -key server.key -out server.csr
$ cp server.key server.key.origin
$ openssl rsa -in server.key.origin -out server.key
$ openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
(2) Generating the client key and certificate. $ openssl genrsa -des3 -out client.key 2048
$ openssl req -new -key client.key -out client.csr
$ cp client.key client.key.origin
$ openssl rsa -in client.key.origin -out client.key
$ openssl x509 -req -days 365 -in client.csr -signkey client.key -out client.crt
// Server.c
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <memory.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <openssl/rsa.h>
#include <openssl/crypto.h>
#include <openssl/x509.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#define HOME "./"
#define CERTF HOME "server.crt"
#define KEYF HOME "server.key"
#define CHK_NULL(x) if((x) == NULL) exit(1);
#define CHK_ERR(err, s) if((err) == -1) { perror(s); exit(1); }
#define CHK_SSL(err) if((err) == -1) { ERR_print_errors_fp(stderr); exit(2); }
int main(void) {
int err;
int listen_sd;
int sd;
struct sockaddr_in sa_serv;
struct sockaddr_in sa_cli;
size_t client_len;
SSL_CTX *ctx;
SSL *ssl;
X509 *client_cert;
char *str;
char buf[4096];
SSL_METHOD *meth;
SSL_load_error_strings();
SSLeay_add_ssl_algorithms();
meth = TLSv1_2_server_method();
ctx = SSL_CTX_new(meth);
if(!ctx) {
ERR_print_errors_fp(stderr);
exit(2);
}
if(SSL_CTX_use_certificate_file(ctx, CERTF, SSL_FILETYPE_PEM) <= 0) {
ERR_print_errors_fp(stderr);
exit(3);
}
if(SSL_CTX_use_PrivateKey_file(ctx, KEYF, SSL_FILETYPE_PEM) <= 0) {
ERR_print_errors_fp(stderr);
exit(4);
}
if(!SSL_CTX_check_private_key(ctx)) {
fprintf(stderr, "Private key does not match the certificate public keyn");
exit(5);
}
listen_sd = socket(AF_INET, SOCK_STREAM, 0);
CHK_ERR(listen_sd, "socket");
memset(&sa_serv, 0x00, sizeof(sa_serv));
sa_serv.sin_family = AF_INET;
sa_serv.sin_addr.s_addr = INADDR_ANY;
sa_serv.sin_port = htons(1111);
err = bind(listen_sd, (struct sockaddr*)&sa_serv, sizeof(sa_serv));
CHK_ERR(err, "bind");
err = listen(listen_sd, 5);
CHK_ERR(err, "listen");
client_len = sizeof(sa_cli);
sd = accept(listen_sd, (struct sockaddr*)&sa_cli, &client_len);
CHK_ERR(sd, "accept");
close(listen_sd);
ssl = SSL_new(ctx);
CHK_NULL(ssl);
SSL_set_fd(ssl, sd);
// to request client's certificate
SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);
err = SSL_accept(ssl);
CHK_SSL(err);
printf("SSL connection using %s \n", SSL_get_cipher(ssl));
client_cert = SSL_get_peer_certificate(ssl);
if(client_cert != NULL) {
printf("Client certificate: \n");
str = X509_NAME_oneline(X509_get_subject_name(client_cert), 0, 0);
CHK_NULL(str);
printf("\t subject: %s\n", str);
OPENSSL_free(str);
str = X509_NAME_oneline(X509_get_issuer_name(client_cert), 0, 0);
CHK_NULL(str);
printf("\t issuer: %s\n", str);
OPENSSL_free(str);
X509_free(client_cert);
} else {
printf("Client does not have certificate. \n");
}
err = SSL_read(ssl, buf, sizeof(buf)-1);
CHK_SSL(err);
buf[err] = 0x00;
printf("Got %d chars: %s \n", err, buf);
err = SSL_write(ssl, "I hear you/", strlen("I hear you."));
CHK_SSL(err);
close(sd);
SSL_free(ssl);
SSL_CTX_free(ctx);
return(0);
}
// client.c
#include <stdio.h>
#include <memory.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <openssl/crypto.h>
#include <openssl/x509.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#define CHK_NULL(x) if((x) == NULL) exit(1);
#define CHK_ERR(err, s) if((err) == -1) { perror(s); exit(1); }
#define CHK_SSL(err) if((err) == -1) { ERR_print_errors_fp(stderr); exit(2); }
int main(void) {
int err;
int sd;
struct sockaddr_in sa;
SSL_CTX *ctx;
SSL *ssl;
X509 *server_cert;
char *str;
char buf[4096];
SSL_METHOD *meth;
SSL_load_error_strings();
SSLeay_add_ssl_algorithms();
meth = TLSv1_2_client_method();
ctx = SSL_CTX_new(meth);
CHK_NULL(ctx);
if(SSL_CTX_use_certificate_file(ctx, "./client.crt", SSL_FILETYPE_PEM) <= 0) {
ERR_print_errors_fp(stderr);
exit(3);
}
if(SSL_CTX_use_PrivateKey_file(ctx, "./client.key", SSL_FILETYPE_PEM) <= 0) {
ERR_print_errors_fp(stderr);
exit(4);
}
if(!SSL_CTX_check_private_key(ctx)) {
fprintf(stderr, "Private key does not match the certificate public keyn");
exit(5);
}
CHK_SSL(err);
sd = socket(AF_INET, SOCK_STREAM, 0);
CHK_ERR(sd, "socket");
memset(&sa, 0x00, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_addr.s_addr = inet_addr("127.0.0.1");
sa.sin_port = htons(1111);
err = connect(sd, (struct sockaddr*)&sa, sizeof(sa));
CHK_ERR(err, "connect");
ssl = SSL_new(ctx);
CHK_NULL(ssl);
SSL_set_fd(ssl, sd);
err = SSL_connect(ssl);
CHK_NULL(err);
printf("SSL connection using %s \n", SSL_get_cipher(ssl));
server_cert = SSL_get_peer_certificate(ssl);
CHK_NULL(server_cert);
printf("Server certificate: \n");
str = X509_NAME_oneline(X509_get_subject_name(server_cert), 0, 0);
CHK_NULL(str);
printf("\t subject: %s \n", str);
OPENSSL_free(str);
str = X509_NAME_oneline(X509_get_issuer_name(server_cert), 0, 0);
CHK_NULL(str);
printf("\t issuer: %s \n", str);
OPENSSL_free(str);
X509_free(server_cert);
err = SSL_write(ssl, "Hello World!", strlen("Hello World!"));
CHK_SSL(err);
err = SSL_read(ssl, buf, sizeof(buf)-1);
CHK_SSL(err);
buf[err] = 0x0;
printf("Got %d chars: %s \n", err, buf);
SSL_shutdown(ssl);
close(sd);
SSL_free(ssl);
SSL_CTX_free(ctx);
return 0;
}
below is output results.
(1) server
$ ./server
SSL connection using ECDHE-RSA-AES256-GCM-SHA384
Client does not have certificate.
Got 12 chars: Hello World!
(2) client
$ ./client
SSL connection using ECDHE-RSA-AES256-GCM-SHA384
Server certificate:
subject: /C=IN/ST=WB/L=Kolkata/O=TEST-INFO-CLIENTA/OU=IT/CN=clienta.com/[email protected]
issuer: /C=IN/ST=WB/L=Kolkata/O=TEST-INFO-CLIENTA/OU=IT/CN=clienta.com/[email protected]
Got 11 chars: I hear you/
=======================================================
I don't know why the server's output says, "Client does not have certificate."
Although I added "SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL)" in server.c, the server does not receive the client's certificate.
If anyone knows about this, please reply.
openssl req -newkey rsa:2048 -nodes -keyout key.pem -x509 -days 365 -out certificate.pem
is the pattern I prefer – Daniel FarrellSSL_VERIFY_PEER
on the context after creating the SSL object withSSL_new()
so this change in the context is ignored. Either move it before theSSL_new
or make it insteadSSL_set_verify(...)
(NOTSSL_CTX_
). @DanFarrell: 3key-3DES still has 112 bits strength, which is enough and far better than the horribly lame KDF used for OpenSSL 'legacy' files, and one privatekey file will never ever come anywhere near the gigabytes where 64-bit block is a concern. Although OP actually removes the encryption immediately after setting it so it doesn't matter at all. – dave_thompson_085