* Exim - an Internet mail transport agent *
*************************************************/
-/* Copyright (c) University of Cambridge 1995 - 2009 */
+/* Copyright (c) University of Cambridge 1995 - 2012 */
/* See the file NOTICE for conditions of use and distribution. */
/* This module provides the TLS (aka SSL) support for Exim using the OpenSSL
#define EXIM_OCSP_MAX_AGE (-1L)
#endif
+#if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
+#define EXIM_HAVE_OPENSSL_TLSEXT
+#endif
+
/* Structure for collecting random data for seeding. */
typedef struct randstuff {
static const uschar *sid_ctx = US"exim";
static SSL_CTX *ctx = NULL;
+#ifdef EXIM_HAVE_OPENSSL_TLSEXT
static SSL_CTX *ctx_sni = NULL;
+#endif
static SSL *ssl = NULL;
static char ssl_errstring[256];
setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional);
/* Callbacks */
+#ifdef EXIM_HAVE_OPENSSL_TLSEXT
static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg);
+#endif
#ifdef EXPERIMENTAL_OCSP
static int tls_stapling_cb(SSL *s, void *arg);
#endif
/* If dhparam is set, expand it, and load up the parameters for DH encryption.
Arguments:
- dhparam DH parameter file
+ dhparam DH parameter file or fixed parameter identity string
host connected host, if client; NULL if server
Returns: TRUE if OK (nothing to set up, or setup worked)
*/
static BOOL
-init_dh(uschar *dhparam, host_item *host)
+init_dh(SSL_CTX *sctx, uschar *dhparam, host_item *host)
{
-BOOL yield = TRUE;
BIO *bio;
DH *dh;
uschar *dhexpanded;
+const char *pem;
if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded))
return FALSE;
-if (dhexpanded == NULL) return TRUE;
-
-if ((bio = BIO_new_file(CS dhexpanded, "r")) == NULL)
+if (dhexpanded == NULL || *dhexpanded == '\0')
{
- tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
- host, (uschar *)strerror(errno));
- yield = FALSE;
+ bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1);
}
-else
+else if (dhexpanded[0] == '/')
{
- if ((dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL)) == NULL)
+ bio = BIO_new_file(CS dhexpanded, "r");
+ if (bio == NULL)
{
tls_error(string_sprintf("could not read dhparams file %s", dhexpanded),
- host, NULL);
- yield = FALSE;
+ host, US strerror(errno));
+ return FALSE;
}
- else
+ }
+else
+ {
+ if (Ustrcmp(dhexpanded, "none") == 0)
{
- SSL_CTX_set_tmp_dh(ctx, dh);
- DEBUG(D_tls)
- debug_printf("Diffie-Hellman initialized from %s with %d-bit key\n",
- dhexpanded, 8*DH_size(dh));
- DH_free(dh);
+ DEBUG(D_tls) debug_printf("Requested no DH parameters.\n");
+ return TRUE;
}
+
+ pem = std_dh_prime_named(dhexpanded);
+ if (!pem)
+ {
+ tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded),
+ host, US strerror(errno));
+ return FALSE;
+ }
+ bio = BIO_new_mem_buf(CS pem, -1);
+ }
+
+dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL);
+if (dh == NULL)
+ {
BIO_free(bio);
+ tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded),
+ host, NULL);
+ return FALSE;
+ }
+
+/* Even if it is larger, we silently return success rather than cause things
+ * to fail out, so that a too-large DH will not knock out all TLS; it's a
+ * debatable choice. */
+if ((8*DH_size(dh)) > tls_dh_max_bits)
+ {
+ DEBUG(D_tls)
+ debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d",
+ 8*DH_size(dh), tls_dh_max_bits);
+ }
+else
+ {
+ SSL_CTX_set_tmp_dh(sctx, dh);
+ DEBUG(D_tls)
+ debug_printf("Diffie-Hellman initialized from %s with %d-bit prime\n",
+ dhexpanded ? dhexpanded : US"default", 8*DH_size(dh));
}
-return yield;
+DH_free(dh);
+BIO_free(bio);
+
+return TRUE;
}
Returns: SSL_TLSEXT_ERR_{OK,ALERT_WARNING,ALERT_FATAL,NOACK}
*/
+#ifdef EXIM_HAVE_OPENSSL_TLSEXT
static int
tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg)
{
rc = tls_expand_session_files(ctx_sni, cbinfo);
if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
+rc = init_dh(ctx_sni, cbinfo->dhparam, NULL);
+if (rc != OK) return SSL_TLSEXT_ERR_NOACK;
+
DEBUG(D_tls) debug_printf("Switching SSL context.\n");
SSL_set_SSL_CTX(s, ctx_sni);
return SSL_TLSEXT_ERR_OK;
}
+#endif /* EXIM_HAVE_OPENSSL_TLSEXT */
/* Initialize with DH parameters if supplied */
-if (!init_dh(dhparam, host)) return DEFER;
+if (!init_dh(ctx, dhparam, host)) return DEFER;
/* Set up certificate and key (and perhaps OCSP info) */
if (rc != OK) return rc;
/* If we need to handle SNI, do so */
-#if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
+#ifdef EXIM_HAVE_OPENSSL_TLSEXT
if (host == NULL)
{
#ifdef EXPERIMENTAL_OCSP
tls_sni = NULL;
else
{
+#ifdef EXIM_HAVE_OPENSSL_TLSEXT
DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tls_sni);
SSL_set_tlsext_host_name(ssl, tls_sni);
+#else
+ DEBUG(D_tls)
+ debug_printf("OpenSSL at build-time lacked SNI support, ignoring \"%s\"\n",
+ tls_sni);
+#endif
}
}
+/*************************************************
+* Let tls_require_ciphers be checked at startup *
+*************************************************/
+
+/* The tls_require_ciphers option, if set, must be something which the
+library can parse.
+
+Returns: NULL on success, or error message
+*/
+
+uschar *
+tls_validate_require_cipher(void)
+{
+SSL_CTX *ctx;
+uschar *s, *expciphers, *err;
+
+/* this duplicates from tls_init(), we need a better "init just global
+state, for no specific purpose" singleton function of our own */
+
+SSL_load_error_strings();
+OpenSSL_add_ssl_algorithms();
+#if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256)
+/* SHA256 is becoming ever more popular. This makes sure it gets added to the
+list of available digests. */
+EVP_add_digest(EVP_sha256());
+#endif
+
+if (!(tls_require_ciphers && *tls_require_ciphers))
+ return NULL;
+
+if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers))
+ return US"failed to expand tls_require_ciphers";
+
+if (!(expciphers && *expciphers))
+ return NULL;
+
+/* normalisation ripped from above */
+s = expciphers;
+while (*s != 0) { if (*s == '_') *s = '-'; s++; }
+
+err = NULL;
+
+ctx = SSL_CTX_new(SSLv23_server_method());
+if (!ctx)
+ {
+ ERR_error_string(ERR_get_error(), ssl_errstring);
+ return string_sprintf("SSL_CTX_new() failed: %s", ssl_errstring);
+ }
+
+DEBUG(D_tls)
+ debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers);
+
+if (!SSL_CTX_set_cipher_list(ctx, CS expciphers))
+ {
+ ERR_error_string(ERR_get_error(), ssl_errstring);
+ err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed", expciphers);
+ }
+
+SSL_CTX_free(ctx);
+
+return err;
+}
+
+
+
+
/*************************************************
* Report the library versions. *
*************************************************/
git://git.exim.org / exim.git / blobdiff