From 4eac1dbb5f70a652d31847eec7c28d245f36cdbb Mon Sep 17 00:00:00 2001 From: Martin Sehnoutka Date: Thu, 17 Nov 2016 10:48:28 +0100 Subject: [PATCH 21/59] Introduce support for DHE based cipher suites. --- parseconf.c | 1 + ssl.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- tunables.c | 5 +++- tunables.h | 1 + vsftpd.conf.5 | 6 ++++ 5 files changed, 104 insertions(+), 2 deletions(-) diff --git a/parseconf.c b/parseconf.c index 3e0dba4..38e3182 100644 --- a/parseconf.c +++ b/parseconf.c @@ -176,6 +176,7 @@ parseconf_str_array[] = { "email_password_file", &tunable_email_password_file }, { "rsa_cert_file", &tunable_rsa_cert_file }, { "dsa_cert_file", &tunable_dsa_cert_file }, + { "dh_param_file", &tunable_dh_param_file }, { "ssl_ciphers", &tunable_ssl_ciphers }, { "rsa_private_key_file", &tunable_rsa_private_key_file }, { "dsa_private_key_file", &tunable_dsa_private_key_file }, diff --git a/ssl.c b/ssl.c index c362983..22b69b3 100644 --- a/ssl.c +++ b/ssl.c @@ -28,6 +28,8 @@ #include #include #include +#include +#include #include #include @@ -38,6 +40,7 @@ static void setup_bio_callbacks(); static long bio_callback( BIO* p_bio, int oper, const char* p_arg, int argi, long argl, long retval); static int ssl_verify_callback(int verify_ok, X509_STORE_CTX* p_ctx); +static DH *ssl_tmp_dh_callback(SSL *ssl, int is_export, int keylength); static int ssl_cert_digest( SSL* p_ssl, struct vsf_session* p_sess, struct mystr* p_str); static void maybe_log_shutdown_state(struct vsf_session* p_sess); @@ -51,6 +54,60 @@ static int ssl_read_common(struct vsf_session* p_sess, static int ssl_inited; static struct mystr debug_str; + +// Grab prime number from OpenSSL; +// (get_rfc*) for all available primes. +// wraps selection of comparable algorithm strength +#if !defined(match_dh_bits) + #define match_dh_bits(keylen) \ + keylen >= 8191 ? 8192 : \ + keylen >= 6143 ? 6144 : \ + keylen >= 4095 ? 4096 : \ + keylen >= 3071 ? 3072 : \ + keylen >= 2047 ? 2048 : \ + keylen >= 1535 ? 1536 : \ + keylen >= 1023 ? 1024 : 768 +#endif + +#if !defined(DH_get_prime) + BIGNUM * + DH_get_prime(int bits) + { + switch (bits) { + case 768: return get_rfc2409_prime_768(NULL); + case 1024: return get_rfc2409_prime_1024(NULL); + case 1536: return get_rfc3526_prime_1536(NULL); + case 2048: return get_rfc3526_prime_2048(NULL); + case 3072: return get_rfc3526_prime_3072(NULL); + case 4096: return get_rfc3526_prime_4096(NULL); + case 6144: return get_rfc3526_prime_6144(NULL); + case 8192: return get_rfc3526_prime_8192(NULL); + // shouldn't happen when used match_dh_bits; strict compiler + default: return NULL; + } +} +#endif + +#if !defined(DH_get_dh) + // Grab DH parameters + DH * + DH_get_dh(int size) + { + DH *dh = DH_new(); + if (!dh) { + return NULL; + } + dh->p = DH_get_prime(match_dh_bits(size)); + BN_dec2bn(&dh->g, "2"); + if (!dh->p || !dh->g) + { + DH_free(dh); + return NULL; + } + return dh; + } +#endif + void ssl_init(struct vsf_session* p_sess) { @@ -65,7 +122,7 @@ ssl_init(struct vsf_session* p_sess) { die("SSL: could not allocate SSL context"); } - options = SSL_OP_ALL; + options = SSL_OP_ALL | SSL_OP_SINGLE_DH_USE; if (!tunable_sslv2) { options |= SSL_OP_NO_SSLv2; @@ -111,6 +168,25 @@ ssl_init(struct vsf_session* p_sess) die("SSL: cannot load DSA private key"); } } + if (tunable_dh_param_file) + { + BIO *bio; + DH *dhparams = NULL; + if ((bio = BIO_new_file(tunable_dh_param_file, "r")) == NULL) + { + die("SSL: cannot load custom DH params"); + } + else + { + dhparams = PEM_read_bio_DHparams(bio, NULL, NULL, NULL); + BIO_free(bio); + + if (!SSL_CTX_set_tmp_dh(p_ctx, dhparams)) + { + die("SSL: setting custom DH params failed"); + } + } + } if (tunable_ssl_ciphers && SSL_CTX_set_cipher_list(p_ctx, tunable_ssl_ciphers) != 1) { @@ -165,6 +241,9 @@ ssl_init(struct vsf_session* p_sess) /* Ensure cached session doesn't expire */ SSL_CTX_set_timeout(p_ctx, INT_MAX); } + + SSL_CTX_set_tmp_dh_callback(p_ctx, ssl_tmp_dh_callback); + p_sess->p_ssl_ctx = p_ctx; ssl_inited = 1; } @@ -702,6 +781,18 @@ ssl_verify_callback(int verify_ok, X509_STORE_CTX* p_ctx) return 1; } +#define UNUSED(x) ( (void)(x) ) + +static DH * +ssl_tmp_dh_callback(SSL *ssl, int is_export, int keylength) +{ + // strict compiler bypassing + UNUSED(ssl); + UNUSED(is_export); + + return DH_get_dh(keylength); +} + void ssl_add_entropy(struct vsf_session* p_sess) { diff --git a/tunables.c b/tunables.c index c737465..1ea7227 100644 --- a/tunables.c +++ b/tunables.c @@ -140,6 +140,7 @@ const char* tunable_user_sub_token; const char* tunable_email_password_file; const char* tunable_rsa_cert_file; const char* tunable_dsa_cert_file; +const char* tunable_dh_param_file; const char* tunable_ssl_ciphers; const char* tunable_rsa_private_key_file; const char* tunable_dsa_private_key_file; @@ -288,7 +289,9 @@ tunables_load_defaults() install_str_setting("/usr/share/ssl/certs/vsftpd.pem", &tunable_rsa_cert_file); install_str_setting(0, &tunable_dsa_cert_file); - install_str_setting("ECDHE-RSA-AES256-GCM-SHA384", &tunable_ssl_ciphers); + install_str_setting(0, &tunable_dh_param_file); + install_str_setting("AES128-SHA:DES-CBC3-SHA:DHE-RSA-AES256-SHA", + &tunable_ssl_ciphers); install_str_setting(0, &tunable_rsa_private_key_file); install_str_setting(0, &tunable_dsa_private_key_file); install_str_setting(0, &tunable_ca_certs_file); diff --git a/tunables.h b/tunables.h index 9553038..3995472 100644 --- a/tunables.h +++ b/tunables.h @@ -142,6 +142,7 @@ extern const char* tunable_user_sub_token; extern const char* tunable_email_password_file; extern const char* tunable_rsa_cert_file; extern const char* tunable_dsa_cert_file; +extern const char* tunable_dh_param_file; extern const char* tunable_ssl_ciphers; extern const char* tunable_rsa_private_key_file; extern const char* tunable_dsa_private_key_file; diff --git a/vsftpd.conf.5 b/vsftpd.conf.5 index fb6324e..ff94eca 100644 --- a/vsftpd.conf.5 +++ b/vsftpd.conf.5 @@ -893,6 +893,12 @@ to be in the same file as the certificate. Default: (none) .TP +.B dh_param_file +This option specifies the location of the custom parameters used for +ephemeral Diffie-Hellman key exchange in SSL. + +Default: (none - use built in parameters appropriate for certificate key size) +.TP .B email_password_file This option can be used to provide an alternate file for usage by the .BR secure_email_list_enable -- 2.14.4