diff options
Diffstat (limited to 'src/tls-openssl.c')
| -rw-r--r-- | src/tls-openssl.c | 3366 |
1 files changed, 3366 insertions, 0 deletions
diff --git a/src/tls-openssl.c b/src/tls-openssl.c new file mode 100644 index 0000000..8f4cf4d --- /dev/null +++ b/src/tls-openssl.c @@ -0,0 +1,3366 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ + +/* Copyright (c) University of Cambridge 1995 - 2018 */ +/* See the file NOTICE for conditions of use and distribution. */ + +/* Portions Copyright (c) The OpenSSL Project 1999 */ + +/* This module provides the TLS (aka SSL) support for Exim using the OpenSSL +library. It is #included into the tls.c file when that library is used. The +code herein is based on a patch that was originally contributed by Steve +Haslam. It was adapted from stunnel, a GPL program by Michal Trojnara. + +No cryptographic code is included in Exim. All this module does is to call +functions from the OpenSSL library. */ + + +/* Heading stuff */ + +#include <openssl/lhash.h> +#include <openssl/ssl.h> +#include <openssl/err.h> +#include <openssl/rand.h> +#ifndef OPENSSL_NO_ECDH +# include <openssl/ec.h> +#endif +#ifndef DISABLE_OCSP +# include <openssl/ocsp.h> +#endif +#ifdef SUPPORT_DANE +# include "danessl.h" +#endif + + +#ifndef DISABLE_OCSP +# define EXIM_OCSP_SKEW_SECONDS (300L) +# define EXIM_OCSP_MAX_AGE (-1L) +#endif + +#if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT) +# define EXIM_HAVE_OPENSSL_TLSEXT +#endif +#if OPENSSL_VERSION_NUMBER >= 0x00908000L +# define EXIM_HAVE_RSA_GENKEY_EX +#endif +#if OPENSSL_VERSION_NUMBER >= 0x10100000L +# define EXIM_HAVE_OCSP_RESP_COUNT +#else +# define EXIM_HAVE_EPHEM_RSA_KEX +# define EXIM_HAVE_RAND_PSEUDO +#endif +#if (OPENSSL_VERSION_NUMBER >= 0x0090800fL) && !defined(OPENSSL_NO_SHA256) +# define EXIM_HAVE_SHA256 +#endif + +/* + * X509_check_host provides sane certificate hostname checking, but was added + * to OpenSSL late, after other projects forked off the code-base. So in + * addition to guarding against the base version number, beware that LibreSSL + * does not (at this time) support this function. + * + * If LibreSSL gains a different API, perhaps via libtls, then we'll probably + * opt to disentangle and ask a LibreSSL user to provide glue for a third + * crypto provider for libtls instead of continuing to tie the OpenSSL glue + * into even twistier knots. If LibreSSL gains the same API, we can just + * change this guard and punt the issue for a while longer. + */ +#ifndef LIBRESSL_VERSION_NUMBER +# if OPENSSL_VERSION_NUMBER >= 0x010100000L +# define EXIM_HAVE_OPENSSL_CHECKHOST +# define EXIM_HAVE_OPENSSL_DH_BITS +# define EXIM_HAVE_OPENSSL_TLS_METHOD +# else +# define EXIM_NEED_OPENSSL_INIT +# endif +# if OPENSSL_VERSION_NUMBER >= 0x010000000L \ + && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L +# define EXIM_HAVE_OPENSSL_CHECKHOST +# endif +#endif + +#if !defined(LIBRESSL_VERSION_NUMBER) \ + || LIBRESSL_VERSION_NUMBER >= 0x20010000L +# if !defined(OPENSSL_NO_ECDH) +# if OPENSSL_VERSION_NUMBER >= 0x0090800fL +# define EXIM_HAVE_ECDH +# endif +# if OPENSSL_VERSION_NUMBER >= 0x10002000L +# define EXIM_HAVE_OPENSSL_EC_NIST2NID +# endif +# endif +#endif + +#if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP) +# warning "OpenSSL library version too old; define DISABLE_OCSP in Makefile" +# define DISABLE_OCSP +#endif + +#ifdef EXIM_HAVE_OPENSSL_CHECKHOST +# include <openssl/x509v3.h> +#endif + +/************************************************* +* OpenSSL option parse * +*************************************************/ + +typedef struct exim_openssl_option { + uschar *name; + long value; +} exim_openssl_option; +/* We could use a macro to expand, but we need the ifdef and not all the +options document which version they were introduced in. Policylet: include +all options unless explicitly for DTLS, let the administrator choose which +to apply. + +This list is current as of: + ==> 1.0.1b <== +Plus SSL_OP_SAFARI_ECDHE_ECDSA_BUG from 2013-June patch/discussion on openssl-dev +Plus SSL_OP_NO_TLSv1_3 for 1.1.2-dev +*/ +static exim_openssl_option exim_openssl_options[] = { +/* KEEP SORTED ALPHABETICALLY! */ +#ifdef SSL_OP_ALL + { US"all", SSL_OP_ALL }, +#endif +#ifdef SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION + { US"allow_unsafe_legacy_renegotiation", SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION }, +#endif +#ifdef SSL_OP_CIPHER_SERVER_PREFERENCE + { US"cipher_server_preference", SSL_OP_CIPHER_SERVER_PREFERENCE }, +#endif +#ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS + { US"dont_insert_empty_fragments", SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS }, +#endif +#ifdef SSL_OP_EPHEMERAL_RSA + { US"ephemeral_rsa", SSL_OP_EPHEMERAL_RSA }, +#endif +#ifdef SSL_OP_LEGACY_SERVER_CONNECT + { US"legacy_server_connect", SSL_OP_LEGACY_SERVER_CONNECT }, +#endif +#ifdef SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER + { US"microsoft_big_sslv3_buffer", SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER }, +#endif +#ifdef SSL_OP_MICROSOFT_SESS_ID_BUG + { US"microsoft_sess_id_bug", SSL_OP_MICROSOFT_SESS_ID_BUG }, +#endif +#ifdef SSL_OP_MSIE_SSLV2_RSA_PADDING + { US"msie_sslv2_rsa_padding", SSL_OP_MSIE_SSLV2_RSA_PADDING }, +#endif +#ifdef SSL_OP_NETSCAPE_CHALLENGE_BUG + { US"netscape_challenge_bug", SSL_OP_NETSCAPE_CHALLENGE_BUG }, +#endif +#ifdef SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG + { US"netscape_reuse_cipher_change_bug", SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG }, +#endif +#ifdef SSL_OP_NO_COMPRESSION + { US"no_compression", SSL_OP_NO_COMPRESSION }, +#endif +#ifdef SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION + { US"no_session_resumption_on_renegotiation", SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION }, +#endif +#ifdef SSL_OP_NO_SSLv2 + { US"no_sslv2", SSL_OP_NO_SSLv2 }, +#endif +#ifdef SSL_OP_NO_SSLv3 + { US"no_sslv3", SSL_OP_NO_SSLv3 }, +#endif +#ifdef SSL_OP_NO_TICKET + { US"no_ticket", SSL_OP_NO_TICKET }, +#endif +#ifdef SSL_OP_NO_TLSv1 + { US"no_tlsv1", SSL_OP_NO_TLSv1 }, +#endif +#ifdef SSL_OP_NO_TLSv1_1 +#if SSL_OP_NO_TLSv1_1 == 0x00000400L + /* Error in chosen value in 1.0.1a; see first item in CHANGES for 1.0.1b */ +#warning OpenSSL 1.0.1a uses a bad value for SSL_OP_NO_TLSv1_1, ignoring +#else + { US"no_tlsv1_1", SSL_OP_NO_TLSv1_1 }, +#endif +#endif +#ifdef SSL_OP_NO_TLSv1_2 + { US"no_tlsv1_2", SSL_OP_NO_TLSv1_2 }, +#endif +#ifdef SSL_OP_NO_TLSv1_3 + { US"no_tlsv1_3", SSL_OP_NO_TLSv1_3 }, +#endif +#ifdef SSL_OP_SAFARI_ECDHE_ECDSA_BUG + { US"safari_ecdhe_ecdsa_bug", SSL_OP_SAFARI_ECDHE_ECDSA_BUG }, +#endif +#ifdef SSL_OP_SINGLE_DH_USE + { US"single_dh_use", SSL_OP_SINGLE_DH_USE }, +#endif +#ifdef SSL_OP_SINGLE_ECDH_USE + { US"single_ecdh_use", SSL_OP_SINGLE_ECDH_USE }, +#endif +#ifdef SSL_OP_SSLEAY_080_CLIENT_DH_BUG + { US"ssleay_080_client_dh_bug", SSL_OP_SSLEAY_080_CLIENT_DH_BUG }, +#endif +#ifdef SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG + { US"sslref2_reuse_cert_type_bug", SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG }, +#endif +#ifdef SSL_OP_TLS_BLOCK_PADDING_BUG + { US"tls_block_padding_bug", SSL_OP_TLS_BLOCK_PADDING_BUG }, +#endif +#ifdef SSL_OP_TLS_D5_BUG + { US"tls_d5_bug", SSL_OP_TLS_D5_BUG }, +#endif +#ifdef SSL_OP_TLS_ROLLBACK_BUG + { US"tls_rollback_bug", SSL_OP_TLS_ROLLBACK_BUG }, +#endif +}; + +#ifndef MACRO_PREDEF +static int exim_openssl_options_size = nelem(exim_openssl_options); +#endif + +#ifdef MACRO_PREDEF +void +options_tls(void) +{ +struct exim_openssl_option * o; +uschar buf[64]; + +for (o = exim_openssl_options; + o < exim_openssl_options + nelem(exim_openssl_options); o++) + { + /* Trailing X is workaround for problem with _OPT_OPENSSL_NO_TLSV1 + being a ".ifdef _OPT_OPENSSL_NO_TLSV1_3" match */ + + spf(buf, sizeof(buf), US"_OPT_OPENSSL_%T_X", o->name); + builtin_macro_create(buf); + } +} +#else + +/******************************************************************************/ + +/* Structure for collecting random data for seeding. */ + +typedef struct randstuff { + struct timeval tv; + pid_t p; +} randstuff; + +/* Local static variables */ + +static BOOL client_verify_callback_called = FALSE; +static BOOL server_verify_callback_called = FALSE; +static const uschar *sid_ctx = US"exim"; + +/* We have three different contexts to care about. + +Simple case: client, `client_ctx` + As a client, we can be doing a callout or cut-through delivery while receiving + a message. So we have a client context, which should have options initialised + from the SMTP Transport. We may also concurrently want to make TLS connections + to utility daemons, so client-contexts are allocated and passed around in call + args rather than using a gobal. + +Server: + There are two cases: with and without ServerNameIndication from the client. + Given TLS SNI, we can be using different keys, certs and various other + configuration settings, because they're re-expanded with $tls_sni set. This + allows vhosting with TLS. This SNI is sent in the handshake. + A client might not send SNI, so we need a fallback, and an initial setup too. + So as a server, we start out using `server_ctx`. + If SNI is sent by the client, then we as server, mid-negotiation, try to clone + `server_sni` from `server_ctx` and then initialise settings by re-expanding + configuration. +*/ + +typedef struct { + SSL_CTX * ctx; + SSL * ssl; +} exim_openssl_client_tls_ctx; + +static SSL_CTX *server_ctx = NULL; +static SSL *server_ssl = NULL; + +#ifdef EXIM_HAVE_OPENSSL_TLSEXT +static SSL_CTX *server_sni = NULL; +#endif + +static char ssl_errstring[256]; + +static int ssl_session_timeout = 200; +static BOOL client_verify_optional = FALSE; +static BOOL server_verify_optional = FALSE; + +static BOOL reexpand_tls_files_for_sni = FALSE; + + +typedef struct tls_ext_ctx_cb { + uschar *certificate; + uschar *privatekey; + BOOL is_server; +#ifndef DISABLE_OCSP + STACK_OF(X509) *verify_stack; /* chain for verifying the proof */ + union { + struct { + uschar *file; + uschar *file_expanded; + OCSP_RESPONSE *response; + } server; + struct { + X509_STORE *verify_store; /* non-null if status requested */ + BOOL verify_required; + } client; + } u_ocsp; +#endif + uschar *dhparam; + /* these are cached from first expand */ + uschar *server_cipher_list; + /* only passed down to tls_error: */ + host_item *host; + const uschar * verify_cert_hostnames; +#ifndef DISABLE_EVENT + uschar * event_action; +#endif +} tls_ext_ctx_cb; + +/* should figure out a cleanup of API to handle state preserved per +implementation, for various reasons, which can be void * in the APIs. +For now, we hack around it. */ +tls_ext_ctx_cb *client_static_cbinfo = NULL; +tls_ext_ctx_cb *server_static_cbinfo = NULL; + +static int +setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, + int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr ); + +/* Callbacks */ +#ifdef EXIM_HAVE_OPENSSL_TLSEXT +static int tls_servername_cb(SSL *s, int *ad ARG_UNUSED, void *arg); +#endif +#ifndef DISABLE_OCSP +static int tls_server_stapling_cb(SSL *s, void *arg); +#endif + + +/************************************************* +* Handle TLS error * +*************************************************/ + +/* Called from lots of places when errors occur before actually starting to do +the TLS handshake, that is, while the session is still in clear. Always returns +DEFER for a server and FAIL for a client so that most calls can use "return +tls_error(...)" to do this processing and then give an appropriate return. A +single function is used for both server and client, because it is called from +some shared functions. + +Argument: + prefix text to include in the logged error + host NULL if setting up a server; + the connected host if setting up a client + msg error message or NULL if we should ask OpenSSL + errstr pointer to output error message + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_error(uschar * prefix, const host_item * host, uschar * msg, uschar ** errstr) +{ +if (!msg) + { + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + msg = US ssl_errstring; + } + +msg = string_sprintf("(%s): %s", prefix, msg); +DEBUG(D_tls) debug_printf("TLS error '%s'\n", msg); +if (errstr) *errstr = msg; +return host ? FAIL : DEFER; +} + + + +/************************************************* +* Callback to generate RSA key * +*************************************************/ + +/* +Arguments: + s SSL connection (not used) + export not used + keylength keylength + +Returns: pointer to generated key +*/ + +static RSA * +rsa_callback(SSL *s, int export, int keylength) +{ +RSA *rsa_key; +#ifdef EXIM_HAVE_RSA_GENKEY_EX +BIGNUM *bn = BN_new(); +#endif + +export = export; /* Shut picky compilers up */ +DEBUG(D_tls) debug_printf("Generating %d bit RSA key...\n", keylength); + +#ifdef EXIM_HAVE_RSA_GENKEY_EX +if ( !BN_set_word(bn, (unsigned long)RSA_F4) + || !(rsa_key = RSA_new()) + || !RSA_generate_key_ex(rsa_key, keylength, bn, NULL) + ) +#else +if (!(rsa_key = RSA_generate_key(keylength, RSA_F4, NULL, NULL))) +#endif + + { + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + log_write(0, LOG_MAIN|LOG_PANIC, "TLS error (RSA_generate_key): %s", + ssl_errstring); + return NULL; + } +return rsa_key; +} + + + +/* Extreme debug +#ifndef DISABLE_OCSP +void +x509_store_dump_cert_s_names(X509_STORE * store) +{ +STACK_OF(X509_OBJECT) * roots= store->objs; +int i; +static uschar name[256]; + +for(i= 0; i<sk_X509_OBJECT_num(roots); i++) + { + X509_OBJECT * tmp_obj= sk_X509_OBJECT_value(roots, i); + if(tmp_obj->type == X509_LU_X509) + { + X509_NAME * sn = X509_get_subject_name(tmp_obj->data.x509); + if (X509_NAME_oneline(sn, CS name, sizeof(name))) + { + name[sizeof(name)-1] = '\0'; + debug_printf(" %s\n", name); + } + } + } +} +#endif +*/ + + +#ifndef DISABLE_EVENT +static int +verify_event(tls_support * tlsp, X509 * cert, int depth, const uschar * dn, + BOOL *calledp, const BOOL *optionalp, const uschar * what) +{ +uschar * ev; +uschar * yield; +X509 * old_cert; + +ev = tlsp == &tls_out ? client_static_cbinfo->event_action : event_action; +if (ev) + { + DEBUG(D_tls) debug_printf("verify_event: %s %d\n", what, depth); + old_cert = tlsp->peercert; + tlsp->peercert = X509_dup(cert); + /* NB we do not bother setting peerdn */ + if ((yield = event_raise(ev, US"tls:cert", string_sprintf("%d", depth)))) + { + log_write(0, LOG_MAIN, "[%s] %s verify denied by event-action: " + "depth=%d cert=%s: %s", + tlsp == &tls_out ? deliver_host_address : sender_host_address, + what, depth, dn, yield); + *calledp = TRUE; + if (!*optionalp) + { + if (old_cert) tlsp->peercert = old_cert; /* restore 1st failing cert */ + return 1; /* reject (leaving peercert set) */ + } + DEBUG(D_tls) debug_printf("Event-action verify failure overridden " + "(host in tls_try_verify_hosts)\n"); + } + X509_free(tlsp->peercert); + tlsp->peercert = old_cert; + } +return 0; +} +#endif + +/************************************************* +* Callback for verification * +*************************************************/ + +/* The SSL library does certificate verification if set up to do so. This +callback has the current yes/no state is in "state". If verification succeeded, +we set the certificate-verified flag. If verification failed, what happens +depends on whether the client is required to present a verifiable certificate +or not. + +If verification is optional, we change the state to yes, but still log the +verification error. For some reason (it really would help to have proper +documentation of OpenSSL), this callback function then gets called again, this +time with state = 1. We must take care not to set the private verified flag on +the second time through. + +Note: this function is not called if the client fails to present a certificate +when asked. We get here only if a certificate has been received. Handling of +optional verification for this case is done when requesting SSL to verify, by +setting SSL_VERIFY_FAIL_IF_NO_PEER_CERT in the non-optional case. + +May be called multiple times for different issues with a certificate, even +for a given "depth" in the certificate chain. + +Arguments: + preverify_ok current yes/no state as 1/0 + x509ctx certificate information. + tlsp per-direction (client vs. server) support data + calledp has-been-called flag + optionalp verification-is-optional flag + +Returns: 0 if verification should fail, otherwise 1 +*/ + +static int +verify_callback(int preverify_ok, X509_STORE_CTX * x509ctx, + tls_support * tlsp, BOOL * calledp, BOOL * optionalp) +{ +X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx); +int depth = X509_STORE_CTX_get_error_depth(x509ctx); +uschar dn[256]; + +if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn))) + { + DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); + log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error", + tlsp == &tls_out ? deliver_host_address : sender_host_address); + return 0; + } +dn[sizeof(dn)-1] = '\0'; + +if (preverify_ok == 0) + { + uschar * extra = verify_mode ? string_sprintf(" (during %c-verify for [%s])", + *verify_mode, sender_host_address) + : US""; + log_write(0, LOG_MAIN, "[%s] SSL verify error%s: depth=%d error=%s cert=%s", + tlsp == &tls_out ? deliver_host_address : sender_host_address, + extra, depth, + X509_verify_cert_error_string(X509_STORE_CTX_get_error(x509ctx)), dn); + *calledp = TRUE; + if (!*optionalp) + { + if (!tlsp->peercert) + tlsp->peercert = X509_dup(cert); /* record failing cert */ + return 0; /* reject */ + } + DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " + "tls_try_verify_hosts)\n"); + } + +else if (depth != 0) + { + DEBUG(D_tls) debug_printf("SSL verify ok: depth=%d SN=%s\n", depth, dn); +#ifndef DISABLE_OCSP + if (tlsp == &tls_out && client_static_cbinfo->u_ocsp.client.verify_store) + { /* client, wanting stapling */ + /* Add the server cert's signing chain as the one + for the verification of the OCSP stapled information. */ + + if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store, + cert)) + ERR_clear_error(); + sk_X509_push(client_static_cbinfo->verify_stack, cert); + } +#endif +#ifndef DISABLE_EVENT + if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL")) + return 0; /* reject, with peercert set */ +#endif + } +else + { + const uschar * verify_cert_hostnames; + + if ( tlsp == &tls_out + && ((verify_cert_hostnames = client_static_cbinfo->verify_cert_hostnames))) + /* client, wanting hostname check */ + { + +#ifdef EXIM_HAVE_OPENSSL_CHECKHOST +# ifndef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS +# define X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS 0 +# endif +# ifndef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS +# define X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS 0 +# endif + int sep = 0; + const uschar * list = verify_cert_hostnames; + uschar * name; + int rc; + while ((name = string_nextinlist(&list, &sep, NULL, 0))) + if ((rc = X509_check_host(cert, CCS name, 0, + X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS + | X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS, + NULL))) + { + if (rc < 0) + { + log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error", + tlsp == &tls_out ? deliver_host_address : sender_host_address); + name = NULL; + } + break; + } + if (!name) +#else + if (!tls_is_name_for_cert(verify_cert_hostnames, cert)) +#endif + { + uschar * extra = verify_mode + ? string_sprintf(" (during %c-verify for [%s])", + *verify_mode, sender_host_address) + : US""; + log_write(0, LOG_MAIN, + "[%s] SSL verify error%s: certificate name mismatch: DN=\"%s\" H=\"%s\"", + tlsp == &tls_out ? deliver_host_address : sender_host_address, + extra, dn, verify_cert_hostnames); + *calledp = TRUE; + if (!*optionalp) + { + if (!tlsp->peercert) + tlsp->peercert = X509_dup(cert); /* record failing cert */ + return 0; /* reject */ + } + DEBUG(D_tls) debug_printf("SSL verify failure overridden (host in " + "tls_try_verify_hosts)\n"); + } + } + +#ifndef DISABLE_EVENT + if (verify_event(tlsp, cert, depth, dn, calledp, optionalp, US"SSL")) + return 0; /* reject, with peercert set */ +#endif + + DEBUG(D_tls) debug_printf("SSL%s verify ok: depth=0 SN=%s\n", + *calledp ? "" : " authenticated", dn); + if (!*calledp) tlsp->certificate_verified = TRUE; + *calledp = TRUE; + } + +return 1; /* accept, at least for this level */ +} + +static int +verify_callback_client(int preverify_ok, X509_STORE_CTX *x509ctx) +{ +return verify_callback(preverify_ok, x509ctx, &tls_out, + &client_verify_callback_called, &client_verify_optional); +} + +static int +verify_callback_server(int preverify_ok, X509_STORE_CTX *x509ctx) +{ +return verify_callback(preverify_ok, x509ctx, &tls_in, + &server_verify_callback_called, &server_verify_optional); +} + + +#ifdef SUPPORT_DANE + +/* This gets called *by* the dane library verify callback, which interposes +itself. +*/ +static int +verify_callback_client_dane(int preverify_ok, X509_STORE_CTX * x509ctx) +{ +X509 * cert = X509_STORE_CTX_get_current_cert(x509ctx); +uschar dn[256]; +int depth = X509_STORE_CTX_get_error_depth(x509ctx); +#ifndef DISABLE_EVENT +BOOL dummy_called, optional = FALSE; +#endif + +if (!X509_NAME_oneline(X509_get_subject_name(cert), CS dn, sizeof(dn))) + { + DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); + log_write(0, LOG_MAIN, "[%s] SSL verify error: internal error", + deliver_host_address); + return 0; + } +dn[sizeof(dn)-1] = '\0'; + +DEBUG(D_tls) debug_printf("verify_callback_client_dane: %s depth %d %s\n", + preverify_ok ? "ok":"BAD", depth, dn); + +#ifndef DISABLE_EVENT + if (verify_event(&tls_out, cert, depth, dn, + &dummy_called, &optional, US"DANE")) + return 0; /* reject, with peercert set */ +#endif + +if (preverify_ok == 1) + { + tls_out.dane_verified = tls_out.certificate_verified = TRUE; +#ifndef DISABLE_OCSP + if (client_static_cbinfo->u_ocsp.client.verify_store) + { /* client, wanting stapling */ + /* Add the server cert's signing chain as the one + for the verification of the OCSP stapled information. */ + + if (!X509_STORE_add_cert(client_static_cbinfo->u_ocsp.client.verify_store, + cert)) + ERR_clear_error(); + sk_X509_push(client_static_cbinfo->verify_stack, cert); + } +#endif + } +else + { + int err = X509_STORE_CTX_get_error(x509ctx); + DEBUG(D_tls) + debug_printf(" - err %d '%s'\n", err, X509_verify_cert_error_string(err)); + if (err == X509_V_ERR_APPLICATION_VERIFICATION) + preverify_ok = 1; + } +return preverify_ok; +} + +#endif /*SUPPORT_DANE*/ + + +/************************************************* +* Information callback * +*************************************************/ + +/* The SSL library functions call this from time to time to indicate what they +are doing. We copy the string to the debugging output when TLS debugging has +been requested. + +Arguments: + s the SSL connection + where + ret + +Returns: nothing +*/ + +static void +info_callback(SSL *s, int where, int ret) +{ +DEBUG(D_tls) + { + const uschar * str; + + if (where & SSL_ST_CONNECT) + str = US"SSL_connect"; + else if (where & SSL_ST_ACCEPT) + str = US"SSL_accept"; + else + str = US"SSL info (undefined)"; + + if (where & SSL_CB_LOOP) + debug_printf("%s: %s\n", str, SSL_state_string_long(s)); + else if (where & SSL_CB_ALERT) + debug_printf("SSL3 alert %s:%s:%s\n", + str = where & SSL_CB_READ ? US"read" : US"write", + SSL_alert_type_string_long(ret), SSL_alert_desc_string_long(ret)); + else if (where & SSL_CB_EXIT) + if (ret == 0) + debug_printf("%s: failed in %s\n", str, SSL_state_string_long(s)); + else if (ret < 0) + debug_printf("%s: error in %s\n", str, SSL_state_string_long(s)); + else if (where & SSL_CB_HANDSHAKE_START) + debug_printf("%s: hshake start: %s\n", str, SSL_state_string_long(s)); + else if (where & SSL_CB_HANDSHAKE_DONE) + debug_printf("%s: hshake done: %s\n", str, SSL_state_string_long(s)); + } +} + + + +/************************************************* +* Initialize for DH * +*************************************************/ + +/* If dhparam is set, expand it, and load up the parameters for DH encryption. + +Arguments: + sctx The current SSL CTX (inbound or outbound) + dhparam DH parameter file or fixed parameter identity string + host connected host, if client; NULL if server + errstr error string pointer + +Returns: TRUE if OK (nothing to set up, or setup worked) +*/ + +static BOOL +init_dh(SSL_CTX *sctx, uschar *dhparam, const host_item *host, uschar ** errstr) +{ +BIO *bio; +DH *dh; +uschar *dhexpanded; +const char *pem; +int dh_bitsize; + +if (!expand_check(dhparam, US"tls_dhparam", &dhexpanded, errstr)) + return FALSE; + +if (!dhexpanded || !*dhexpanded) + bio = BIO_new_mem_buf(CS std_dh_prime_default(), -1); +else if (dhexpanded[0] == '/') + { + if (!(bio = BIO_new_file(CS dhexpanded, "r"))) + { + tls_error(string_sprintf("could not read dhparams file %s", dhexpanded), + host, US strerror(errno), errstr); + return FALSE; + } + } +else + { + if (Ustrcmp(dhexpanded, "none") == 0) + { + DEBUG(D_tls) debug_printf("Requested no DH parameters.\n"); + return TRUE; + } + + if (!(pem = std_dh_prime_named(dhexpanded))) + { + tls_error(string_sprintf("Unknown standard DH prime \"%s\"", dhexpanded), + host, US strerror(errno), errstr); + return FALSE; + } + bio = BIO_new_mem_buf(CS pem, -1); + } + +if (!(dh = PEM_read_bio_DHparams(bio, NULL, NULL, NULL))) + { + BIO_free(bio); + tls_error(string_sprintf("Could not read tls_dhparams \"%s\"", dhexpanded), + host, NULL, errstr); + return FALSE; + } + +/* note: our default limit of 2236 is not a multiple of 8; the limit comes from + * an NSS limit, and the GnuTLS APIs handle bit-sizes fine, so we went with + * 2236. But older OpenSSL can only report in bytes (octets), not bits. + * If someone wants to dance at the edge, then they can raise the limit or use + * current libraries. */ +#ifdef EXIM_HAVE_OPENSSL_DH_BITS +/* Added in commit 26c79d5641d; `git describe --contains` says OpenSSL_1_1_0-pre1~1022 + * This predates OpenSSL_1_1_0 (before a, b, ...) so is in all 1.1.0 */ +dh_bitsize = DH_bits(dh); +#else +dh_bitsize = 8 * DH_size(dh); +#endif + +/* 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 (dh_bitsize > tls_dh_max_bits) + { + DEBUG(D_tls) + debug_printf("dhparams file %d bits, is > tls_dh_max_bits limit of %d\n", + dh_bitsize, 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", dh_bitsize); + } + +DH_free(dh); +BIO_free(bio); + +return TRUE; +} + + + + +/************************************************* +* Initialize for ECDH * +*************************************************/ + +/* Load parameters for ECDH encryption. + +For now, we stick to NIST P-256 because: it's simple and easy to configure; +it avoids any patent issues that might bite redistributors; despite events in +the news and concerns over curve choices, we're not cryptographers, we're not +pretending to be, and this is "good enough" to be better than no support, +protecting against most adversaries. Given another year or two, there might +be sufficient clarity about a "right" way forward to let us make an informed +decision, instead of a knee-jerk reaction. + +Longer-term, we should look at supporting both various named curves and +external files generated with "openssl ecparam", much as we do for init_dh(). +We should also support "none" as a value, to explicitly avoid initialisation. + +Patches welcome. + +Arguments: + sctx The current SSL CTX (inbound or outbound) + host connected host, if client; NULL if server + errstr error string pointer + +Returns: TRUE if OK (nothing to set up, or setup worked) +*/ + +static BOOL +init_ecdh(SSL_CTX * sctx, host_item * host, uschar ** errstr) +{ +#ifdef OPENSSL_NO_ECDH +return TRUE; +#else + +EC_KEY * ecdh; +uschar * exp_curve; +int nid; +BOOL rv; + +if (host) /* No ECDH setup for clients, only for servers */ + return TRUE; + +# ifndef EXIM_HAVE_ECDH +DEBUG(D_tls) + debug_printf("No OpenSSL API to define ECDH parameters, skipping\n"); +return TRUE; +# else + +if (!expand_check(tls_eccurve, US"tls_eccurve", &exp_curve, errstr)) + return FALSE; +if (!exp_curve || !*exp_curve) + return TRUE; + +/* "auto" needs to be handled carefully. + * OpenSSL < 1.0.2: we do not select anything, but fallback to prime256v1 + * OpenSSL < 1.1.0: we have to call SSL_CTX_set_ecdh_auto + * (openssl/ssl.h defines SSL_CTRL_SET_ECDH_AUTO) + * OpenSSL >= 1.1.0: we do not set anything, the libray does autoselection + * https://github.com/openssl/openssl/commit/fe6ef2472db933f01b59cad82aa925736935984b + */ +if (Ustrcmp(exp_curve, "auto") == 0) + { +#if OPENSSL_VERSION_NUMBER < 0x10002000L + DEBUG(D_tls) debug_printf( + "ECDH OpenSSL < 1.0.2: temp key parameter settings: overriding \"auto\" with \"prime256v1\"\n"); + exp_curve = US"prime256v1"; +#else +# if defined SSL_CTRL_SET_ECDH_AUTO + DEBUG(D_tls) debug_printf( + "ECDH OpenSSL 1.0.2+ temp key parameter settings: autoselection\n"); + SSL_CTX_set_ecdh_auto(sctx, 1); + return TRUE; +# else + DEBUG(D_tls) debug_printf( + "ECDH OpenSSL 1.1.0+ temp key parameter settings: default selection\n"); + return TRUE; +# endif +#endif + } + +DEBUG(D_tls) debug_printf("ECDH: curve '%s'\n", exp_curve); +if ( (nid = OBJ_sn2nid (CCS exp_curve)) == NID_undef +# ifdef EXIM_HAVE_OPENSSL_EC_NIST2NID + && (nid = EC_curve_nist2nid(CCS exp_curve)) == NID_undef +# endif + ) + { + tls_error(string_sprintf("Unknown curve name tls_eccurve '%s'", exp_curve), + host, NULL, errstr); + return FALSE; + } + +if (!(ecdh = EC_KEY_new_by_curve_name(nid))) + { + tls_error(US"Unable to create ec curve", host, NULL, errstr); + return FALSE; + } + +/* The "tmp" in the name here refers to setting a temporary key +not to the stability of the interface. */ + +if ((rv = SSL_CTX_set_tmp_ecdh(sctx, ecdh) == 0)) + tls_error(string_sprintf("Error enabling '%s' curve", exp_curve), host, NULL, errstr); +else + DEBUG(D_tls) debug_printf("ECDH: enabled '%s' curve\n", exp_curve); + +EC_KEY_free(ecdh); +return !rv; + +# endif /*EXIM_HAVE_ECDH*/ +#endif /*OPENSSL_NO_ECDH*/ +} + + + + +#ifndef DISABLE_OCSP +/************************************************* +* Load OCSP information into state * +*************************************************/ +/* Called to load the server OCSP response from the given file into memory, once +caller has determined this is needed. Checks validity. Debugs a message +if invalid. + +ASSUMES: single response, for single cert. + +Arguments: + sctx the SSL_CTX* to update + cbinfo various parts of session state + expanded the filename putatively holding an OCSP response + +*/ + +static void +ocsp_load_response(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, const uschar *expanded) +{ +BIO * bio; +OCSP_RESPONSE * resp; +OCSP_BASICRESP * basic_response; +OCSP_SINGLERESP * single_response; +ASN1_GENERALIZEDTIME * rev, * thisupd, * nextupd; +STACK_OF(X509) * sk; +unsigned long verify_flags; +int status, reason, i; + +cbinfo->u_ocsp.server.file_expanded = string_copy(expanded); +if (cbinfo->u_ocsp.server.response) + { + OCSP_RESPONSE_free(cbinfo->u_ocsp.server.response); + cbinfo->u_ocsp.server.response = NULL; + } + +if (!(bio = BIO_new_file(CS cbinfo->u_ocsp.server.file_expanded, "rb"))) + { + DEBUG(D_tls) debug_printf("Failed to open OCSP response file \"%s\"\n", + cbinfo->u_ocsp.server.file_expanded); + return; + } + +resp = d2i_OCSP_RESPONSE_bio(bio, NULL); +BIO_free(bio); +if (!resp) + { + DEBUG(D_tls) debug_printf("Error reading OCSP response.\n"); + return; + } + +if ((status = OCSP_response_status(resp)) != OCSP_RESPONSE_STATUS_SUCCESSFUL) + { + DEBUG(D_tls) debug_printf("OCSP response not valid: %s (%d)\n", + OCSP_response_status_str(status), status); + goto bad; + } + +if (!(basic_response = OCSP_response_get1_basic(resp))) + { + DEBUG(D_tls) + debug_printf("OCSP response parse error: unable to extract basic response.\n"); + goto bad; + } + +sk = cbinfo->verify_stack; +verify_flags = OCSP_NOVERIFY; /* check sigs, but not purpose */ + +/* May need to expose ability to adjust those flags? +OCSP_NOSIGS OCSP_NOVERIFY OCSP_NOCHAIN OCSP_NOCHECKS OCSP_NOEXPLICIT +OCSP_TRUSTOTHER OCSP_NOINTERN */ + +/* This does a full verify on the OCSP proof before we load it for serving +up; possibly overkill - just date-checks might be nice enough. + +OCSP_basic_verify takes a "store" arg, but does not +use it for the chain verification, which is all we do +when OCSP_NOVERIFY is set. The content from the wire +"basic_response" and a cert-stack "sk" are all that is used. + +We have a stack, loaded in setup_certs() if tls_verify_certificates +was a file (not a directory, or "system"). It is unfortunate we +cannot used the connection context store, as that would neatly +handle the "system" case too, but there seems to be no library +function for getting a stack from a store. +[ In OpenSSL 1.1 - ? X509_STORE_CTX_get0_chain(ctx) ? ] +We do not free the stack since it could be needed a second time for +SNI handling. + +Separately we might try to replace using OCSP_basic_verify() - which seems to not +be a public interface into the OpenSSL library (there's no manual entry) - +But what with? We also use OCSP_basic_verify in the client stapling callback. +And there we NEED it; we must verify that status... unless the +library does it for us anyway? */ + +if ((i = OCSP_basic_verify(basic_response, sk, NULL, verify_flags)) < 0) + { + DEBUG(D_tls) + { + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + debug_printf("OCSP response verify failure: %s\n", US ssl_errstring); + } + goto bad; + } + +/* Here's the simplifying assumption: there's only one response, for the +one certificate we use, and nothing for anything else in a chain. If this +proves false, we need to extract a cert id from our issued cert +(tls_certificate) and use that for OCSP_resp_find_status() (which finds the +right cert in the stack and then calls OCSP_single_get0_status()). + +I'm hoping to avoid reworking a bunch more of how we handle state here. */ + +if (!(single_response = OCSP_resp_get0(basic_response, 0))) + { + DEBUG(D_tls) + debug_printf("Unable to get first response from OCSP basic response.\n"); + goto bad; + } + +status = OCSP_single_get0_status(single_response, &reason, &rev, &thisupd, &nextupd); +if (status != V_OCSP_CERTSTATUS_GOOD) + { + DEBUG(D_tls) debug_printf("OCSP response bad cert status: %s (%d) %s (%d)\n", + OCSP_cert_status_str(status), status, + OCSP_crl_reason_str(reason), reason); + goto bad; + } + +if (!OCSP_check_validity(thisupd, nextupd, EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE)) + { + DEBUG(D_tls) debug_printf("OCSP status invalid times.\n"); + goto bad; + } + +supply_response: + cbinfo->u_ocsp.server.response = resp; /*XXX stack?*/ +return; + +bad: + if (f.running_in_test_harness) + { + extern char ** environ; + uschar ** p; + if (environ) for (p = USS environ; *p; p++) + if (Ustrncmp(*p, "EXIM_TESTHARNESS_DISABLE_OCSPVALIDITYCHECK", 42) == 0) + { + DEBUG(D_tls) debug_printf("Supplying known bad OCSP response\n"); + goto supply_response; + } + } +return; +} +#endif /*!DISABLE_OCSP*/ + + + + +/* Create and install a selfsigned certificate, for use in server mode */ + +static int +tls_install_selfsign(SSL_CTX * sctx, uschar ** errstr) +{ +X509 * x509 = NULL; +EVP_PKEY * pkey; +RSA * rsa; +X509_NAME * name; +uschar * where; + +where = US"allocating pkey"; +if (!(pkey = EVP_PKEY_new())) + goto err; + +where = US"allocating cert"; +if (!(x509 = X509_new())) + goto err; + +where = US"generating pkey"; +if (!(rsa = rsa_callback(NULL, 0, 2048))) + goto err; + +where = US"assigning pkey"; +if (!EVP_PKEY_assign_RSA(pkey, rsa)) + goto err; + +X509_set_version(x509, 2); /* N+1 - version 3 */ +ASN1_INTEGER_set(X509_get_serialNumber(x509), 1); +X509_gmtime_adj(X509_get_notBefore(x509), 0); +X509_gmtime_adj(X509_get_notAfter(x509), (long)60 * 60); /* 1 hour */ +X509_set_pubkey(x509, pkey); + +name = X509_get_subject_name(x509); +X509_NAME_add_entry_by_txt(name, "C", + MBSTRING_ASC, CUS "UK", -1, -1, 0); +X509_NAME_add_entry_by_txt(name, "O", + MBSTRING_ASC, CUS "Exim Developers", -1, -1, 0); +X509_NAME_add_entry_by_txt(name, "CN", + MBSTRING_ASC, CUS smtp_active_hostname, -1, -1, 0); +X509_set_issuer_name(x509, name); + +where = US"signing cert"; +if (!X509_sign(x509, pkey, EVP_md5())) + goto err; + +where = US"installing selfsign cert"; +if (!SSL_CTX_use_certificate(sctx, x509)) + goto err; + +where = US"installing selfsign key"; +if (!SSL_CTX_use_PrivateKey(sctx, pkey)) + goto err; + +return OK; + +err: + (void) tls_error(where, NULL, NULL, errstr); + if (x509) X509_free(x509); + if (pkey) EVP_PKEY_free(pkey); + return DEFER; +} + + + + +static int +tls_add_certfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file, + uschar ** errstr) +{ +DEBUG(D_tls) debug_printf("tls_certificate file %s\n", file); +if (!SSL_CTX_use_certificate_chain_file(sctx, CS file)) + return tls_error(string_sprintf( + "SSL_CTX_use_certificate_chain_file file=%s", file), + cbinfo->host, NULL, errstr); +return 0; +} + +static int +tls_add_pkeyfile(SSL_CTX * sctx, tls_ext_ctx_cb * cbinfo, uschar * file, + uschar ** errstr) +{ +DEBUG(D_tls) debug_printf("tls_privatekey file %s\n", file); +if (!SSL_CTX_use_PrivateKey_file(sctx, CS file, SSL_FILETYPE_PEM)) + return tls_error(string_sprintf( + "SSL_CTX_use_PrivateKey_file file=%s", file), cbinfo->host, NULL, errstr); +return 0; +} + + +/************************************************* +* Expand key and cert file specs * +*************************************************/ + +/* Called once during tls_init and possibly again during TLS setup, for a +new context, if Server Name Indication was used and tls_sni was seen in +the certificate string. + +Arguments: + sctx the SSL_CTX* to update + cbinfo various parts of session state + errstr error string pointer + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_expand_session_files(SSL_CTX *sctx, tls_ext_ctx_cb *cbinfo, + uschar ** errstr) +{ +uschar *expanded; + +if (!cbinfo->certificate) + { + if (!cbinfo->is_server) /* client */ + return OK; + /* server */ + if (tls_install_selfsign(sctx, errstr) != OK) + return DEFER; + } +else + { + int err; + + if (Ustrstr(cbinfo->certificate, US"tls_sni") || + Ustrstr(cbinfo->certificate, US"tls_in_sni") || + Ustrstr(cbinfo->certificate, US"tls_out_sni") + ) + reexpand_tls_files_for_sni = TRUE; + + if (!expand_check(cbinfo->certificate, US"tls_certificate", &expanded, errstr)) + return DEFER; + + if (expanded) + if (cbinfo->is_server) + { + const uschar * file_list = expanded; + int sep = 0; + uschar * file; + + while (file = string_nextinlist(&file_list, &sep, NULL, 0)) + if ((err = tls_add_certfile(sctx, cbinfo, file, errstr))) + return err; + } + else /* would there ever be a need for multiple client certs? */ + if ((err = tls_add_certfile(sctx, cbinfo, expanded, errstr))) + return err; + + if ( cbinfo->privatekey + && !expand_check(cbinfo->privatekey, US"tls_privatekey", &expanded, errstr)) + return DEFER; + + /* If expansion was forced to fail, key_expanded will be NULL. If the result + of the expansion is an empty string, ignore it also, and assume the private + key is in the same file as the certificate. */ + + if (expanded && *expanded) + if (cbinfo->is_server) + { + const uschar * file_list = expanded; + int sep = 0; + uschar * file; + + while (file = string_nextinlist(&file_list, &sep, NULL, 0)) + if ((err = tls_add_pkeyfile(sctx, cbinfo, file, errstr))) + return err; + } + else /* would there ever be a need for multiple client certs? */ + if ((err = tls_add_pkeyfile(sctx, cbinfo, expanded, errstr))) + return err; + } + +#ifndef DISABLE_OCSP +if (cbinfo->is_server && cbinfo->u_ocsp.server.file) + { + /*XXX stack*/ + if (!expand_check(cbinfo->u_ocsp.server.file, US"tls_ocsp_file", &expanded, errstr)) + return DEFER; + + if (expanded && *expanded) + { + DEBUG(D_tls) debug_printf("tls_ocsp_file %s\n", expanded); + if ( cbinfo->u_ocsp.server.file_expanded + && (Ustrcmp(expanded, cbinfo->u_ocsp.server.file_expanded) == 0)) + { + DEBUG(D_tls) debug_printf(" - value unchanged, using existing values\n"); + } + else + ocsp_load_response(sctx, cbinfo, expanded); + } + } +#endif + +return OK; +} + + + + +/************************************************* +* Callback to handle SNI * +*************************************************/ + +/* Called when acting as server during the TLS session setup if a Server Name +Indication extension was sent by the client. + +API documentation is OpenSSL s_server.c implementation. + +Arguments: + s SSL* of the current session + ad unknown (part of OpenSSL API) (unused) + arg Callback of "our" registered data + +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) +{ +const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name); +tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg; +int rc; +int old_pool = store_pool; +uschar * dummy_errstr; + +if (!servername) + return SSL_TLSEXT_ERR_OK; + +DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", servername, + reexpand_tls_files_for_sni ? "" : " (unused for certificate selection)"); + +/* Make the extension value available for expansion */ +store_pool = POOL_PERM; +tls_in.sni = string_copy(US servername); +store_pool = old_pool; + +if (!reexpand_tls_files_for_sni) + return SSL_TLSEXT_ERR_OK; + +/* Can't find an SSL_CTX_clone() or equivalent, so we do it manually; +not confident that memcpy wouldn't break some internal reference counting. +Especially since there's a references struct member, which would be off. */ + +#ifdef EXIM_HAVE_OPENSSL_TLS_METHOD +if (!(server_sni = SSL_CTX_new(TLS_server_method()))) +#else +if (!(server_sni = SSL_CTX_new(SSLv23_server_method()))) +#endif + { + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + DEBUG(D_tls) debug_printf("SSL_CTX_new() failed: %s\n", ssl_errstring); + goto bad; + } + +/* Not sure how many of these are actually needed, since SSL object +already exists. Might even need this selfsame callback, for reneg? */ + +SSL_CTX_set_info_callback(server_sni, SSL_CTX_get_info_callback(server_ctx)); +SSL_CTX_set_mode(server_sni, SSL_CTX_get_mode(server_ctx)); +SSL_CTX_set_options(server_sni, SSL_CTX_get_options(server_ctx)); +SSL_CTX_set_timeout(server_sni, SSL_CTX_get_timeout(server_ctx)); +SSL_CTX_set_tlsext_servername_callback(server_sni, tls_servername_cb); +SSL_CTX_set_tlsext_servername_arg(server_sni, cbinfo); + +if ( !init_dh(server_sni, cbinfo->dhparam, NULL, &dummy_errstr) + || !init_ecdh(server_sni, NULL, &dummy_errstr) + ) + goto bad; + +if ( cbinfo->server_cipher_list + && !SSL_CTX_set_cipher_list(server_sni, CS cbinfo->server_cipher_list)) + goto bad; + +#ifndef DISABLE_OCSP +if (cbinfo->u_ocsp.server.file) + { + SSL_CTX_set_tlsext_status_cb(server_sni, tls_server_stapling_cb); + SSL_CTX_set_tlsext_status_arg(server_sni, cbinfo); + } +#endif + +if ((rc = setup_certs(server_sni, tls_verify_certificates, tls_crl, NULL, FALSE, + verify_callback_server, &dummy_errstr)) != OK) + goto bad; + +/* do this after setup_certs, because this can require the certs for verifying +OCSP information. */ +if ((rc = tls_expand_session_files(server_sni, cbinfo, &dummy_errstr)) != OK) + goto bad; + +DEBUG(D_tls) debug_printf("Switching SSL context.\n"); +SSL_set_SSL_CTX(s, server_sni); +return SSL_TLSEXT_ERR_OK; + +bad: return SSL_TLSEXT_ERR_ALERT_FATAL; +} +#endif /* EXIM_HAVE_OPENSSL_TLSEXT */ + + + + +#ifndef DISABLE_OCSP + +/************************************************* +* Callback to handle OCSP Stapling * +*************************************************/ + +/* Called when acting as server during the TLS session setup if the client +requests OCSP information with a Certificate Status Request. + +Documentation via openssl s_server.c and the Apache patch from the OpenSSL +project. + +*/ + +static int +tls_server_stapling_cb(SSL *s, void *arg) +{ +const tls_ext_ctx_cb *cbinfo = (tls_ext_ctx_cb *) arg; +uschar *response_der; /*XXX blob */ +int response_der_len; + +/*XXX stack: use SSL_get_certificate() to see which cert; from that work +out which ocsp blob to send. Unfortunately, SSL_get_certificate is known +buggy in current OpenSSL; it returns the last cert loaded always rather than +the one actually presented. So we can't support a stack of OCSP proofs at +this time. */ + +DEBUG(D_tls) + debug_printf("Received TLS status request (OCSP stapling); %s response\n", + cbinfo->u_ocsp.server.response ? "have" : "lack"); + +tls_in.ocsp = OCSP_NOT_RESP; +if (!cbinfo->u_ocsp.server.response) + return SSL_TLSEXT_ERR_NOACK; + +response_der = NULL; +response_der_len = i2d_OCSP_RESPONSE(cbinfo->u_ocsp.server.response, /*XXX stack*/ + &response_der); +if (response_der_len <= 0) + return SSL_TLSEXT_ERR_NOACK; + +SSL_set_tlsext_status_ocsp_resp(server_ssl, response_der, response_der_len); +tls_in.ocsp = OCSP_VFIED; +return SSL_TLSEXT_ERR_OK; +} + + +static void +time_print(BIO * bp, const char * str, ASN1_GENERALIZEDTIME * time) +{ +BIO_printf(bp, "\t%s: ", str); +ASN1_GENERALIZEDTIME_print(bp, time); +BIO_puts(bp, "\n"); +} + +static int +tls_client_stapling_cb(SSL *s, void *arg) +{ +tls_ext_ctx_cb * cbinfo = arg; +const unsigned char * p; +int len; +OCSP_RESPONSE * rsp; +OCSP_BASICRESP * bs; +int i; + +DEBUG(D_tls) debug_printf("Received TLS status response (OCSP stapling):"); +len = SSL_get_tlsext_status_ocsp_resp(s, &p); +if(!p) + { + /* Expect this when we requested ocsp but got none */ + if (cbinfo->u_ocsp.client.verify_required && LOGGING(tls_cipher)) + log_write(0, LOG_MAIN, "Received TLS status callback, null content"); + else + DEBUG(D_tls) debug_printf(" null\n"); + return cbinfo->u_ocsp.client.verify_required ? 0 : 1; + } + +if(!(rsp = d2i_OCSP_RESPONSE(NULL, &p, len))) + { + tls_out.ocsp = OCSP_FAILED; + if (LOGGING(tls_cipher)) + log_write(0, LOG_MAIN, "Received TLS cert status response, parse error"); + else + DEBUG(D_tls) debug_printf(" parse error\n"); + return 0; + } + +if(!(bs = OCSP_response_get1_basic(rsp))) + { + tls_out.ocsp = OCSP_FAILED; + if (LOGGING(tls_cipher)) + log_write(0, LOG_MAIN, "Received TLS cert status response, error parsing response"); + else + DEBUG(D_tls) debug_printf(" error parsing response\n"); + OCSP_RESPONSE_free(rsp); + return 0; + } + +/* We'd check the nonce here if we'd put one in the request. */ +/* However that would defeat cacheability on the server so we don't. */ + +/* This section of code reworked from OpenSSL apps source; + The OpenSSL Project retains copyright: + Copyright (c) 1999 The OpenSSL Project. All rights reserved. +*/ + { + BIO * bp = NULL; + int status, reason; + ASN1_GENERALIZEDTIME *rev, *thisupd, *nextupd; + + DEBUG(D_tls) bp = BIO_new_fp(debug_file, BIO_NOCLOSE); + + /*OCSP_RESPONSE_print(bp, rsp, 0); extreme debug: stapling content */ + + /* Use the chain that verified the server cert to verify the stapled info */ + /* DEBUG(D_tls) x509_store_dump_cert_s_names(cbinfo->u_ocsp.client.verify_store); */ + + if ((i = OCSP_basic_verify(bs, cbinfo->verify_stack, + cbinfo->u_ocsp.client.verify_store, 0)) <= 0) + { + tls_out.ocsp = OCSP_FAILED; + if (LOGGING(tls_cipher)) log_write(0, LOG_MAIN, + "Received TLS cert status response, itself unverifiable: %s", + ERR_reason_error_string(ERR_peek_error())); + BIO_printf(bp, "OCSP response verify failure\n"); + ERR_print_errors(bp); + OCSP_RESPONSE_print(bp, rsp, 0); + goto failed; + } + + BIO_printf(bp, "OCSP response well-formed and signed OK\n"); + + /*XXX So we have a good stapled OCSP status. How do we know + it is for the cert of interest? OpenSSL 1.1.0 has a routine + OCSP_resp_find_status() which matches on a cert id, which presumably + we should use. Making an id needs OCSP_cert_id_new(), which takes + issuerName, issuerKey, serialNumber. Are they all in the cert? + + For now, carry on blindly accepting the resp. */ + + { + OCSP_SINGLERESP * single; + +#ifdef EXIM_HAVE_OCSP_RESP_COUNT + if (OCSP_resp_count(bs) != 1) +#else + STACK_OF(OCSP_SINGLERESP) * sresp = bs->tbsResponseData->responses; + if (sk_OCSP_SINGLERESP_num(sresp) != 1) +#endif + { + tls_out.ocsp = OCSP_FAILED; + log_write(0, LOG_MAIN, "OCSP stapling " + "with multiple responses not handled"); + goto failed; + } + single = OCSP_resp_get0(bs, 0); + status = OCSP_single_get0_status(single, &reason, &rev, + &thisupd, &nextupd); + } + + DEBUG(D_tls) time_print(bp, "This OCSP Update", thisupd); + DEBUG(D_tls) if(nextupd) time_print(bp, "Next OCSP Update", nextupd); + if (!OCSP_check_validity(thisupd, nextupd, + EXIM_OCSP_SKEW_SECONDS, EXIM_OCSP_MAX_AGE)) + { + tls_out.ocsp = OCSP_FAILED; + DEBUG(D_tls) ERR_print_errors(bp); + log_write(0, LOG_MAIN, "Server OSCP dates invalid"); + } + else + { + DEBUG(D_tls) BIO_printf(bp, "Certificate status: %s\n", + OCSP_cert_status_str(status)); + switch(status) + { + case V_OCSP_CERTSTATUS_GOOD: + tls_out.ocsp = OCSP_VFIED; + i = 1; + goto good; + case V_OCSP_CERTSTATUS_REVOKED: + tls_out.ocsp = OCSP_FAILED; + log_write(0, LOG_MAIN, "Server certificate revoked%s%s", + reason != -1 ? "; reason: " : "", + reason != -1 ? OCSP_crl_reason_str(reason) : ""); + DEBUG(D_tls) time_print(bp, "Revocation Time", rev); + break; + default: + tls_out.ocsp = OCSP_FAILED; + log_write(0, LOG_MAIN, + "Server certificate status unknown, in OCSP stapling"); + break; + } + } + failed: + i = cbinfo->u_ocsp.client.verify_required ? 0 : 1; + good: + BIO_free(bp); + } + +OCSP_RESPONSE_free(rsp); +return i; +} +#endif /*!DISABLE_OCSP*/ + + +/************************************************* +* Initialize for TLS * +*************************************************/ + +/* Called from both server and client code, to do preliminary initialization +of the library. We allocate and return a context structure. + +Arguments: + ctxp returned SSL context + host connected host, if client; NULL if server + dhparam DH parameter file + certificate certificate file + privatekey private key + ocsp_file file of stapling info (server); flag for require ocsp (client) + addr address if client; NULL if server (for some randomness) + cbp place to put allocated callback context + errstr error string pointer + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_init(SSL_CTX **ctxp, host_item *host, uschar *dhparam, uschar *certificate, + uschar *privatekey, +#ifndef DISABLE_OCSP + uschar *ocsp_file, /*XXX stack, in server*/ +#endif + address_item *addr, tls_ext_ctx_cb ** cbp, uschar ** errstr) +{ +SSL_CTX * ctx; +long init_options; +int rc; +tls_ext_ctx_cb * cbinfo; + +cbinfo = store_malloc(sizeof(tls_ext_ctx_cb)); +cbinfo->certificate = certificate; +cbinfo->privatekey = privatekey; +cbinfo->is_server = host==NULL; +#ifndef DISABLE_OCSP +cbinfo->verify_stack = NULL; +if (!host) + { + cbinfo->u_ocsp.server.file = ocsp_file; + cbinfo->u_ocsp.server.file_expanded = NULL; + cbinfo->u_ocsp.server.response = NULL; + } +else + cbinfo->u_ocsp.client.verify_store = NULL; +#endif +cbinfo->dhparam = dhparam; +cbinfo->server_cipher_list = NULL; +cbinfo->host = host; +#ifndef DISABLE_EVENT +cbinfo->event_action = NULL; +#endif + +#ifdef EXIM_NEED_OPENSSL_INIT +SSL_load_error_strings(); /* basic set up */ +OpenSSL_add_ssl_algorithms(); +#endif + +#ifdef EXIM_HAVE_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 + +/* Create a context. +The OpenSSL docs in 1.0.1b have not been updated to clarify TLS variant +negotiation in the different methods; as far as I can tell, the only +*_{server,client}_method which allows negotiation is SSLv23, which exists even +when OpenSSL is built without SSLv2 support. +By disabling with openssl_options, we can let admins re-enable with the +existing knob. */ + +#ifdef EXIM_HAVE_OPENSSL_TLS_METHOD +if (!(ctx = SSL_CTX_new(host ? TLS_client_method() : TLS_server_method()))) +#else +if (!(ctx = SSL_CTX_new(host ? SSLv23_client_method() : SSLv23_server_method()))) +#endif + return tls_error(US"SSL_CTX_new", host, NULL, errstr); + +/* It turns out that we need to seed the random number generator this early in +order to get the full complement of ciphers to work. It took me roughly a day +of work to discover this by experiment. + +On systems that have /dev/urandom, SSL may automatically seed itself from +there. Otherwise, we have to make something up as best we can. Double check +afterwards. */ + +if (!RAND_status()) + { + randstuff r; + gettimeofday(&r.tv, NULL); + r.p = getpid(); + + RAND_seed(US (&r), sizeof(r)); + RAND_seed(US big_buffer, big_buffer_size); + if (addr != NULL) RAND_seed(US addr, sizeof(addr)); + + if (!RAND_status()) + return tls_error(US"RAND_status", host, + US"unable to seed random number generator", errstr); + } + +/* Set up the information callback, which outputs if debugging is at a suitable +level. */ + +DEBUG(D_tls) SSL_CTX_set_info_callback(ctx, (void (*)())info_callback); + +/* Automatically re-try reads/writes after renegotiation. */ +(void) SSL_CTX_set_mode(ctx, SSL_MODE_AUTO_RETRY); + +/* Apply administrator-supplied work-arounds. +Historically we applied just one requested option, +SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS, but when bug 994 requested a second, we +moved to an administrator-controlled list of options to specify and +grandfathered in the first one as the default value for "openssl_options". + +No OpenSSL version number checks: the options we accept depend upon the +availability of the option value macros from OpenSSL. */ + +if (!tls_openssl_options_parse(openssl_options, &init_options)) + return tls_error(US"openssl_options parsing failed", host, NULL, errstr); + +if (init_options) + { + DEBUG(D_tls) debug_printf("setting SSL CTX options: %#lx\n", init_options); + if (!(SSL_CTX_set_options(ctx, init_options))) + return tls_error(string_sprintf( + "SSL_CTX_set_option(%#lx)", init_options), host, NULL, errstr); + } +else + DEBUG(D_tls) debug_printf("no SSL CTX options to set\n"); + +/* We'd like to disable session cache unconditionally, but foolish Outlook +Express clients then give up the first TLS connection and make a second one +(which works). Only when there is an IMAP service on the same machine. +Presumably OE is trying to use the cache for A on B. Leave it enabled for +now, until we work out a decent way of presenting control to the config. It +will never be used because we use a new context every time. */ +#ifdef notdef +(void) SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_OFF); +#endif + +/* Initialize with DH parameters if supplied */ +/* Initialize ECDH temp key parameter selection */ + +if ( !init_dh(ctx, dhparam, host, errstr) + || !init_ecdh(ctx, host, errstr) + ) + return DEFER; + +/* Set up certificate and key (and perhaps OCSP info) */ + +if ((rc = tls_expand_session_files(ctx, cbinfo, errstr)) != OK) + return rc; + +/* If we need to handle SNI or OCSP, do so */ + +#ifdef EXIM_HAVE_OPENSSL_TLSEXT +# ifndef DISABLE_OCSP + if (!(cbinfo->verify_stack = sk_X509_new_null())) + { + DEBUG(D_tls) debug_printf("failed to create stack for stapling verify\n"); + return FAIL; + } +# endif + +if (!host) /* server */ + { +# ifndef DISABLE_OCSP + /* We check u_ocsp.server.file, not server.response, because we care about if + the option exists, not what the current expansion might be, as SNI might + change the certificate and OCSP file in use between now and the time the + callback is invoked. */ + if (cbinfo->u_ocsp.server.file) + { + SSL_CTX_set_tlsext_status_cb(ctx, tls_server_stapling_cb); + SSL_CTX_set_tlsext_status_arg(ctx, cbinfo); + } +# endif + /* We always do this, so that $tls_sni is available even if not used in + tls_certificate */ + SSL_CTX_set_tlsext_servername_callback(ctx, tls_servername_cb); + SSL_CTX_set_tlsext_servername_arg(ctx, cbinfo); + } +# ifndef DISABLE_OCSP +else /* client */ + if(ocsp_file) /* wanting stapling */ + { + if (!(cbinfo->u_ocsp.client.verify_store = X509_STORE_new())) + { + DEBUG(D_tls) debug_printf("failed to create store for stapling verify\n"); + return FAIL; + } + SSL_CTX_set_tlsext_status_cb(ctx, tls_client_stapling_cb); + SSL_CTX_set_tlsext_status_arg(ctx, cbinfo); + } +# endif +#endif + +cbinfo->verify_cert_hostnames = NULL; + +#ifdef EXIM_HAVE_EPHEM_RSA_KEX +/* Set up the RSA callback */ +SSL_CTX_set_tmp_rsa_callback(ctx, rsa_callback); +#endif + +/* Finally, set the timeout, and we are done */ + +SSL_CTX_set_timeout(ctx, ssl_session_timeout); +DEBUG(D_tls) debug_printf("Initialized TLS\n"); + +*cbp = cbinfo; +*ctxp = ctx; + +return OK; +} + + + + +/************************************************* +* Get name of cipher in use * +*************************************************/ + +/* +Argument: pointer to an SSL structure for the connection + buffer to use for answer + size of buffer + pointer to number of bits for cipher +Returns: nothing +*/ + +static void +construct_cipher_name(SSL *ssl, uschar *cipherbuf, int bsize, int *bits) +{ +/* With OpenSSL 1.0.0a, 'c' needs to be const but the documentation doesn't +yet reflect that. It should be a safe change anyway, even 0.9.8 versions have +the accessor functions use const in the prototype. */ + +const uschar * ver = CUS SSL_get_version(ssl); +const SSL_CIPHER * c = (const SSL_CIPHER *) SSL_get_current_cipher(ssl); + +SSL_CIPHER_get_bits(c, bits); + +string_format(cipherbuf, bsize, "%s:%s:%u", ver, + SSL_CIPHER_get_name(c), *bits); + +DEBUG(D_tls) debug_printf("Cipher: %s\n", cipherbuf); +} + + +static void +peer_cert(SSL * ssl, tls_support * tlsp, uschar * peerdn, unsigned siz) +{ +/*XXX we might consider a list-of-certs variable for the cert chain. +SSL_get_peer_cert_chain(SSL*). We'd need a new variable type and support +in list-handling functions, also consider the difference between the entire +chain and the elements sent by the peer. */ + +tlsp->peerdn = NULL; + +/* Will have already noted peercert on a verify fail; possibly not the leaf */ +if (!tlsp->peercert) + tlsp->peercert = SSL_get_peer_certificate(ssl); +/* Beware anonymous ciphers which lead to server_cert being NULL */ +if (tlsp->peercert) + if (!X509_NAME_oneline(X509_get_subject_name(tlsp->peercert), CS peerdn, siz)) + { DEBUG(D_tls) debug_printf("X509_NAME_oneline() error\n"); } + else + { + peerdn[siz-1] = '\0'; + tlsp->peerdn = peerdn; /*XXX a static buffer... */ + } +} + + + + + +/************************************************* +* Set up for verifying certificates * +*************************************************/ + +#ifndef DISABLE_OCSP +/* Load certs from file, return TRUE on success */ + +static BOOL +chain_from_pem_file(const uschar * file, STACK_OF(X509) * verify_stack) +{ +BIO * bp; +X509 * x; + +while (sk_X509_num(verify_stack) > 0) + X509_free(sk_X509_pop(verify_stack)); + +if (!(bp = BIO_new_file(CS file, "r"))) return FALSE; +while ((x = PEM_read_bio_X509(bp, NULL, 0, NULL))) + sk_X509_push(verify_stack, x); +BIO_free(bp); +return TRUE; +} +#endif + + + +/* Called by both client and server startup; on the server possibly +repeated after a Server Name Indication. + +Arguments: + sctx SSL_CTX* to initialise + certs certs file or NULL + crl CRL file or NULL + host NULL in a server; the remote host in a client + optional TRUE if called from a server for a host in tls_try_verify_hosts; + otherwise passed as FALSE + cert_vfy_cb Callback function for certificate verification + errstr error string pointer + +Returns: OK/DEFER/FAIL +*/ + +static int +setup_certs(SSL_CTX *sctx, uschar *certs, uschar *crl, host_item *host, BOOL optional, + int (*cert_vfy_cb)(int, X509_STORE_CTX *), uschar ** errstr) +{ +uschar *expcerts, *expcrl; + +if (!expand_check(certs, US"tls_verify_certificates", &expcerts, errstr)) + return DEFER; +DEBUG(D_tls) debug_printf("tls_verify_certificates: %s\n", expcerts); + +if (expcerts && *expcerts) + { + /* Tell the library to use its compiled-in location for the system default + CA bundle. Then add the ones specified in the config, if any. */ + + if (!SSL_CTX_set_default_verify_paths(sctx)) + return tls_error(US"SSL_CTX_set_default_verify_paths", host, NULL, errstr); + + if (Ustrcmp(expcerts, "system") != 0) + { + struct stat statbuf; + + if (Ustat(expcerts, &statbuf) < 0) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "failed to stat %s for certificates", expcerts); + return DEFER; + } + else + { + uschar *file, *dir; + if ((statbuf.st_mode & S_IFMT) == S_IFDIR) + { file = NULL; dir = expcerts; } + else + { + file = expcerts; dir = NULL; +#ifndef DISABLE_OCSP + /* In the server if we will be offering an OCSP proof, load chain from + file for verifying the OCSP proof at load time. */ + + if ( !host + && statbuf.st_size > 0 + && server_static_cbinfo->u_ocsp.server.file + && !chain_from_pem_file(file, server_static_cbinfo->verify_stack) + ) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "failed to load cert chain from %s", file); + return DEFER; + } +#endif + } + + /* If a certificate file is empty, the next function fails with an + unhelpful error message. If we skip it, we get the correct behaviour (no + certificates are recognized, but the error message is still misleading (it + says no certificate was supplied). But this is better. */ + + if ( (!file || statbuf.st_size > 0) + && !SSL_CTX_load_verify_locations(sctx, CS file, CS dir)) + return tls_error(US"SSL_CTX_load_verify_locations", host, NULL, errstr); + + /* Load the list of CAs for which we will accept certs, for sending + to the client. This is only for the one-file tls_verify_certificates + variant. + If a list isn't loaded into the server, but + some verify locations are set, the server end appears to make + a wildcard request for client certs. + Meanwhile, the client library as default behaviour *ignores* the list + we send over the wire - see man SSL_CTX_set_client_cert_cb. + Because of this, and that the dir variant is likely only used for + the public-CA bundle (not for a private CA), not worth fixing. + */ + if (file) + { + STACK_OF(X509_NAME) * names = SSL_load_client_CA_file(CS file); + + SSL_CTX_set_client_CA_list(sctx, names); + DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", + sk_X509_NAME_num(names)); + } + } + } + + /* Handle a certificate revocation list. */ + +#if OPENSSL_VERSION_NUMBER > 0x00907000L + + /* This bit of code is now the version supplied by Lars Mainka. (I have + merely reformatted it into the Exim code style.) + + "From here I changed the code to add support for multiple crl's + in pem format in one file or to support hashed directory entries in + pem format instead of a file. This method now uses the library function + X509_STORE_load_locations to add the CRL location to the SSL context. + OpenSSL will then handle the verify against CA certs and CRLs by + itself in the verify callback." */ + + if (!expand_check(crl, US"tls_crl", &expcrl, errstr)) return DEFER; + if (expcrl && *expcrl) + { + struct stat statbufcrl; + if (Ustat(expcrl, &statbufcrl) < 0) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "failed to stat %s for certificates revocation lists", expcrl); + return DEFER; + } + else + { + /* is it a file or directory? */ + uschar *file, *dir; + X509_STORE *cvstore = SSL_CTX_get_cert_store(sctx); + if ((statbufcrl.st_mode & S_IFMT) == S_IFDIR) + { + file = NULL; + dir = expcrl; + DEBUG(D_tls) debug_printf("SSL CRL value is a directory %s\n", dir); + } + else + { + file = expcrl; + dir = NULL; + DEBUG(D_tls) debug_printf("SSL CRL value is a file %s\n", file); + } + if (X509_STORE_load_locations(cvstore, CS file, CS dir) == 0) + return tls_error(US"X509_STORE_load_locations", host, NULL, errstr); + + /* setting the flags to check against the complete crl chain */ + + X509_STORE_set_flags(cvstore, + X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL); + } + } + +#endif /* OPENSSL_VERSION_NUMBER > 0x00907000L */ + + /* If verification is optional, don't fail if no certificate */ + + SSL_CTX_set_verify(sctx, + SSL_VERIFY_PEER | (optional ? 0 : SSL_VERIFY_FAIL_IF_NO_PEER_CERT), + cert_vfy_cb); + } + +return OK; +} + + + +/************************************************* +* Start a TLS session in a server * +*************************************************/ + +/* This is called when Exim is running as a server, after having received +the STARTTLS command. It must respond to that command, and then negotiate +a TLS session. + +Arguments: + require_ciphers allowed ciphers + errstr pointer to error message + +Returns: OK on success + DEFER for errors before the start of the negotiation + FAIL for errors during the negotiation; the server can't + continue running. +*/ + +int +tls_server_start(const uschar * require_ciphers, uschar ** errstr) +{ +int rc; +uschar * expciphers; +tls_ext_ctx_cb * cbinfo; +static uschar peerdn[256]; +static uschar cipherbuf[256]; + +/* Check for previous activation */ + +if (tls_in.active.sock >= 0) + { + tls_error(US"STARTTLS received after TLS started", NULL, US"", errstr); + smtp_printf("554 Already in TLS\r\n", FALSE); + return FAIL; + } + +/* Initialize the SSL library. If it fails, it will already have logged +the error. */ + +rc = tls_init(&server_ctx, NULL, tls_dhparam, tls_certificate, tls_privatekey, +#ifndef DISABLE_OCSP + tls_ocsp_file, /*XXX stack*/ +#endif + NULL, &server_static_cbinfo, errstr); +if (rc != OK) return rc; +cbinfo = server_static_cbinfo; + +if (!expand_check(require_ciphers, US"tls_require_ciphers", &expciphers, errstr)) + return FAIL; + +/* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they +were historically separated by underscores. So that I can use either form in my +tests, and also for general convenience, we turn underscores into hyphens here. + +XXX SSL_CTX_set_cipher_list() is replaced by SSL_CTX_set_ciphersuites() +for TLS 1.3 . Since we do not call it at present we get the default list: +TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256 +*/ + +if (expciphers) + { + uschar * s = expciphers; + while (*s != 0) { if (*s == '_') *s = '-'; s++; } + DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); + if (!SSL_CTX_set_cipher_list(server_ctx, CS expciphers)) + return tls_error(US"SSL_CTX_set_cipher_list", NULL, NULL, errstr); + cbinfo->server_cipher_list = expciphers; + } + +/* If this is a host for which certificate verification is mandatory or +optional, set up appropriately. */ + +tls_in.certificate_verified = FALSE; +#ifdef SUPPORT_DANE +tls_in.dane_verified = FALSE; +#endif +server_verify_callback_called = FALSE; + +if (verify_check_host(&tls_verify_hosts) == OK) + { + rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, + FALSE, verify_callback_server, errstr); + if (rc != OK) return rc; + server_verify_optional = FALSE; + } +else if (verify_check_host(&tls_try_verify_hosts) == OK) + { + rc = setup_certs(server_ctx, tls_verify_certificates, tls_crl, NULL, + TRUE, verify_callback_server, errstr); + if (rc != OK) return rc; + server_verify_optional = TRUE; + } + +/* Prepare for new connection */ + +if (!(server_ssl = SSL_new(server_ctx))) + return tls_error(US"SSL_new", NULL, NULL, errstr); + +/* Warning: we used to SSL_clear(ssl) here, it was removed. + * + * With the SSL_clear(), we get strange interoperability bugs with + * OpenSSL 1.0.1b and TLS1.1/1.2. It looks as though this may be a bug in + * OpenSSL itself, as a clear should not lead to inability to follow protocols. + * + * The SSL_clear() call is to let an existing SSL* be reused, typically after + * session shutdown. In this case, we have a brand new object and there's no + * obvious reason to immediately clear it. I'm guessing that this was + * originally added because of incomplete initialisation which the clear fixed, + * in some historic release. + */ + +/* Set context and tell client to go ahead, except in the case of TLS startup +on connection, where outputting anything now upsets the clients and tends to +make them disconnect. We need to have an explicit fflush() here, to force out +the response. Other smtp_printf() calls do not need it, because in non-TLS +mode, the fflush() happens when smtp_getc() is called. */ + +SSL_set_session_id_context(server_ssl, sid_ctx, Ustrlen(sid_ctx)); +if (!tls_in.on_connect) + { + smtp_printf("220 TLS go ahead\r\n", FALSE); + fflush(smtp_out); + } + +/* Now negotiate the TLS session. We put our own timer on it, since it seems +that the OpenSSL library doesn't. */ + +SSL_set_wfd(server_ssl, fileno(smtp_out)); +SSL_set_rfd(server_ssl, fileno(smtp_in)); +SSL_set_accept_state(server_ssl); + +DEBUG(D_tls) debug_printf("Calling SSL_accept\n"); + +sigalrm_seen = FALSE; +if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout); +rc = SSL_accept(server_ssl); +ALARM_CLR(0); + +if (rc <= 0) + { + (void) tls_error(US"SSL_accept", NULL, sigalrm_seen ? US"timed out" : NULL, errstr); + return FAIL; + } + +DEBUG(D_tls) debug_printf("SSL_accept was successful\n"); +ERR_clear_error(); /* Even success can leave errors in the stack. Seen with + anon-authentication ciphersuite negociated. */ + +/* TLS has been set up. Adjust the input functions to read via TLS, +and initialize things. */ + +peer_cert(server_ssl, &tls_in, peerdn, sizeof(peerdn)); + +construct_cipher_name(server_ssl, cipherbuf, sizeof(cipherbuf), &tls_in.bits); +tls_in.cipher = cipherbuf; + +DEBUG(D_tls) + { + uschar buf[2048]; + if (SSL_get_shared_ciphers(server_ssl, CS buf, sizeof(buf)) != NULL) + debug_printf("Shared ciphers: %s\n", buf); + } + +/* Record the certificate we presented */ + { + X509 * crt = SSL_get_certificate(server_ssl); + tls_in.ourcert = crt ? X509_dup(crt) : NULL; + } + +/* Only used by the server-side tls (tls_in), including tls_getc. + Client-side (tls_out) reads (seem to?) go via + smtp_read_response()/ip_recv(). + Hence no need to duplicate for _in and _out. + */ +if (!ssl_xfer_buffer) ssl_xfer_buffer = store_malloc(ssl_xfer_buffer_size); +ssl_xfer_buffer_lwm = ssl_xfer_buffer_hwm = 0; +ssl_xfer_eof = ssl_xfer_error = FALSE; + +receive_getc = tls_getc; +receive_getbuf = tls_getbuf; +receive_get_cache = tls_get_cache; +receive_ungetc = tls_ungetc; +receive_feof = tls_feof; +receive_ferror = tls_ferror; +receive_smtp_buffered = tls_smtp_buffered; + +tls_in.active.sock = fileno(smtp_out); +tls_in.active.tls_ctx = NULL; /* not using explicit ctx for server-side */ +return OK; +} + + + + +static int +tls_client_basic_ctx_init(SSL_CTX * ctx, + host_item * host, smtp_transport_options_block * ob, tls_ext_ctx_cb * cbinfo, + uschar ** errstr) +{ +int rc; +/* stick to the old behaviour for compatibility if tls_verify_certificates is + set but both tls_verify_hosts and tls_try_verify_hosts is not set. Check only + the specified host patterns if one of them is defined */ + +if ( ( !ob->tls_verify_hosts + && (!ob->tls_try_verify_hosts || !*ob->tls_try_verify_hosts) + ) + || verify_check_given_host(CUSS &ob->tls_verify_hosts, host) == OK + ) + client_verify_optional = FALSE; +else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK) + client_verify_optional = TRUE; +else + return OK; + +if ((rc = setup_certs(ctx, ob->tls_verify_certificates, + ob->tls_crl, host, client_verify_optional, verify_callback_client, + errstr)) != OK) + return rc; + +if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK) + { + cbinfo->verify_cert_hostnames = +#ifdef SUPPORT_I18N + string_domain_utf8_to_alabel(host->name, NULL); +#else + host->name; +#endif + DEBUG(D_tls) debug_printf("Cert hostname to check: \"%s\"\n", + cbinfo->verify_cert_hostnames); + } +return OK; +} + + +#ifdef SUPPORT_DANE +static int +dane_tlsa_load(SSL * ssl, host_item * host, dns_answer * dnsa, uschar ** errstr) +{ +dns_record * rr; +dns_scan dnss; +const char * hostnames[2] = { CS host->name, NULL }; +int found = 0; + +if (DANESSL_init(ssl, NULL, hostnames) != 1) + return tls_error(US"hostnames load", host, NULL, errstr); + +for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); + rr; + rr = dns_next_rr(dnsa, &dnss, RESET_NEXT) + ) if (rr->type == T_TLSA && rr->size > 3) + { + const uschar * p = rr->data; + uint8_t usage, selector, mtype; + const char * mdname; + + usage = *p++; + + /* Only DANE-TA(2) and DANE-EE(3) are supported */ + if (usage != 2 && usage != 3) continue; + + selector = *p++; + mtype = *p++; + + switch (mtype) + { + default: continue; /* Only match-types 0, 1, 2 are supported */ + case 0: mdname = NULL; break; + case 1: mdname = "sha256"; break; + case 2: mdname = "sha512"; break; + } + + found++; + switch (DANESSL_add_tlsa(ssl, usage, selector, mdname, p, rr->size - 3)) + { + default: + return tls_error(US"tlsa load", host, NULL, errstr); + case 0: /* action not taken */ + case 1: break; + } + + tls_out.tlsa_usage |= 1<<usage; + } + +if (found) + return OK; + +log_write(0, LOG_MAIN, "DANE error: No usable TLSA records"); +return DEFER; +} +#endif /*SUPPORT_DANE*/ + + + +/************************************************* +* Start a TLS session in a client * +*************************************************/ + +/* Called from the smtp transport after STARTTLS has been accepted. + +Argument: + fd the fd of the connection + host connected host (for messages and option-tests) + addr the first address (for some randomness; can be NULL) + tb transport (always smtp) + tlsa_dnsa tlsa lookup, if DANE, else null + tlsp record details of channel configuration here; must be non-NULL + errstr error string pointer + +Returns: Pointer to TLS session context, or NULL on error +*/ + +void * +tls_client_start(int fd, host_item *host, address_item *addr, + transport_instance * tb, +#ifdef SUPPORT_DANE + dns_answer * tlsa_dnsa, +#endif + tls_support * tlsp, uschar ** errstr) +{ +smtp_transport_options_block * ob = tb + ? (smtp_transport_options_block *)tb->options_block + : &smtp_transport_option_defaults; +exim_openssl_client_tls_ctx * exim_client_ctx; +static uschar peerdn[256]; +uschar * expciphers; +int rc; +static uschar cipherbuf[256]; + +#ifndef DISABLE_OCSP +BOOL request_ocsp = FALSE; +BOOL require_ocsp = FALSE; +#endif + +rc = store_pool; +store_pool = POOL_PERM; +exim_client_ctx = store_get(sizeof(exim_openssl_client_tls_ctx)); +store_pool = rc; + +#ifdef SUPPORT_DANE +tlsp->tlsa_usage = 0; +#endif + +#ifndef DISABLE_OCSP + { +# ifdef SUPPORT_DANE + if ( tlsa_dnsa + && ob->hosts_request_ocsp[0] == '*' + && ob->hosts_request_ocsp[1] == '\0' + ) + { + /* Unchanged from default. Use a safer one under DANE */ + request_ocsp = TRUE; + ob->hosts_request_ocsp = US"${if or { {= {0}{$tls_out_tlsa_usage}} " + " {= {4}{$tls_out_tlsa_usage}} } " + " {*}{}}"; + } +# endif + + if ((require_ocsp = + verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK)) + request_ocsp = TRUE; + else +# ifdef SUPPORT_DANE + if (!request_ocsp) +# endif + request_ocsp = + verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK; + } +#endif + +rc = tls_init(&exim_client_ctx->ctx, host, NULL, + ob->tls_certificate, ob->tls_privatekey, +#ifndef DISABLE_OCSP + (void *)(long)request_ocsp, +#endif + addr, &client_static_cbinfo, errstr); +if (rc != OK) return NULL; + +tlsp->certificate_verified = FALSE; +client_verify_callback_called = FALSE; + +expciphers = NULL; +#ifdef SUPPORT_DANE +if (tlsa_dnsa) + { + /* We fall back to tls_require_ciphers if unset, empty or forced failure, but + other failures should be treated as problems. */ + if (ob->dane_require_tls_ciphers && + !expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers", + &expciphers, errstr)) + return NULL; + if (expciphers && *expciphers == '\0') + expciphers = NULL; + } +#endif +if (!expciphers && + !expand_check(ob->tls_require_ciphers, US"tls_require_ciphers", + &expciphers, errstr)) + return NULL; + +/* In OpenSSL, cipher components are separated by hyphens. In GnuTLS, they +are separated by underscores. So that I can use either form in my tests, and +also for general convenience, we turn underscores into hyphens here. */ + +if (expciphers) + { + uschar *s = expciphers; + while (*s) { if (*s == '_') *s = '-'; s++; } + DEBUG(D_tls) debug_printf("required ciphers: %s\n", expciphers); + if (!SSL_CTX_set_cipher_list(exim_client_ctx->ctx, CS expciphers)) + { + tls_error(US"SSL_CTX_set_cipher_list", host, NULL, errstr); + return NULL; + } + } + +#ifdef SUPPORT_DANE +if (tlsa_dnsa) + { + SSL_CTX_set_verify(exim_client_ctx->ctx, + SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT, + verify_callback_client_dane); + + if (!DANESSL_library_init()) + { + tls_error(US"library init", host, NULL, errstr); + return NULL; + } + if (DANESSL_CTX_init(exim_client_ctx->ctx) <= 0) + { + tls_error(US"context init", host, NULL, errstr); + return NULL; + } + } +else + +#endif + + if (tls_client_basic_ctx_init(exim_client_ctx->ctx, host, ob, + client_static_cbinfo, errstr) != OK) + return NULL; + +if (!(exim_client_ctx->ssl = SSL_new(exim_client_ctx->ctx))) + { + tls_error(US"SSL_new", host, NULL, errstr); + return NULL; + } +SSL_set_session_id_context(exim_client_ctx->ssl, sid_ctx, Ustrlen(sid_ctx)); +SSL_set_fd(exim_client_ctx->ssl, fd); +SSL_set_connect_state(exim_client_ctx->ssl); + +if (ob->tls_sni) + { + if (!expand_check(ob->tls_sni, US"tls_sni", &tlsp->sni, errstr)) + return NULL; + if (!tlsp->sni) + { + DEBUG(D_tls) debug_printf("Setting TLS SNI forced to fail, not sending\n"); + } + else if (!Ustrlen(tlsp->sni)) + tlsp->sni = NULL; + else + { +#ifdef EXIM_HAVE_OPENSSL_TLSEXT + DEBUG(D_tls) debug_printf("Setting TLS SNI \"%s\"\n", tlsp->sni); + SSL_set_tlsext_host_name(exim_client_ctx->ssl, tlsp->sni); +#else + log_write(0, LOG_MAIN, "SNI unusable with this OpenSSL library version; ignoring \"%s\"\n", + tlsp->sni); +#endif + } + } + +#ifdef SUPPORT_DANE +if (tlsa_dnsa) + if (dane_tlsa_load(exim_client_ctx->ssl, host, tlsa_dnsa, errstr) != OK) + return NULL; +#endif + +#ifndef DISABLE_OCSP +/* Request certificate status at connection-time. If the server +does OCSP stapling we will get the callback (set in tls_init()) */ +# ifdef SUPPORT_DANE +if (request_ocsp) + { + const uschar * s; + if ( ((s = ob->hosts_require_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage")) + || ((s = ob->hosts_request_ocsp) && Ustrstr(s, US"tls_out_tlsa_usage")) + ) + { /* Re-eval now $tls_out_tlsa_usage is populated. If + this means we avoid the OCSP request, we wasted the setup + cost in tls_init(). */ + require_ocsp = verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK; + request_ocsp = require_ocsp + || verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK; + } + } +# endif + +if (request_ocsp) + { + SSL_set_tlsext_status_type(exim_client_ctx->ssl, TLSEXT_STATUSTYPE_ocsp); + client_static_cbinfo->u_ocsp.client.verify_required = require_ocsp; + tlsp->ocsp = OCSP_NOT_RESP; + } +#endif + +#ifndef DISABLE_EVENT +client_static_cbinfo->event_action = tb ? tb->event_action : NULL; +#endif + +/* There doesn't seem to be a built-in timeout on connection. */ + +DEBUG(D_tls) debug_printf("Calling SSL_connect\n"); +sigalrm_seen = FALSE; +ALARM(ob->command_timeout); +rc = SSL_connect(exim_client_ctx->ssl); +ALARM_CLR(0); + +#ifdef SUPPORT_DANE +if (tlsa_dnsa) + DANESSL_cleanup(exim_client_ctx->ssl); +#endif + +if (rc <= 0) + { + tls_error(US"SSL_connect", host, sigalrm_seen ? US"timed out" : NULL, errstr); + return NULL; + } + +DEBUG(D_tls) debug_printf("SSL_connect succeeded\n"); + +peer_cert(exim_client_ctx->ssl, tlsp, peerdn, sizeof(peerdn)); + +construct_cipher_name(exim_client_ctx->ssl, cipherbuf, sizeof(cipherbuf), &tlsp->bits); +tlsp->cipher = cipherbuf; + +/* Record the certificate we presented */ + { + X509 * crt = SSL_get_certificate(exim_client_ctx->ssl); + tlsp->ourcert = crt ? X509_dup(crt) : NULL; + } + +tlsp->active.sock = fd; +tlsp->active.tls_ctx = exim_client_ctx; +return exim_client_ctx; +} + + + + + +static BOOL +tls_refill(unsigned lim) +{ +int error; +int inbytes; + +DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", server_ssl, + ssl_xfer_buffer, ssl_xfer_buffer_size); + +if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout); +inbytes = SSL_read(server_ssl, CS ssl_xfer_buffer, + MIN(ssl_xfer_buffer_size, lim)); +error = SSL_get_error(server_ssl, inbytes); +if (smtp_receive_timeout > 0) ALARM_CLR(0); + +if (had_command_timeout) /* set by signal handler */ + smtp_command_timeout_exit(); /* does not return */ +if (had_command_sigterm) + smtp_command_sigterm_exit(); +if (had_data_timeout) + smtp_data_timeout_exit(); +if (had_data_sigint) + smtp_data_sigint_exit(); + +/* SSL_ERROR_ZERO_RETURN appears to mean that the SSL session has been +closed down, not that the socket itself has been closed down. Revert to +non-SSL handling. */ + +switch(error) + { + case SSL_ERROR_NONE: + break; + + case SSL_ERROR_ZERO_RETURN: + DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); + + receive_getc = smtp_getc; + receive_getbuf = smtp_getbuf; + receive_get_cache = smtp_get_cache; + receive_ungetc = smtp_ungetc; + receive_feof = smtp_feof; + receive_ferror = smtp_ferror; + receive_smtp_buffered = smtp_buffered; + + if (SSL_get_shutdown(server_ssl) == SSL_RECEIVED_SHUTDOWN) + SSL_shutdown(server_ssl); + +#ifndef DISABLE_OCSP + sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free); + server_static_cbinfo->verify_stack = NULL; +#endif + SSL_free(server_ssl); + SSL_CTX_free(server_ctx); + server_ctx = NULL; + server_ssl = NULL; + tls_in.active.sock = -1; + tls_in.active.tls_ctx = NULL; + tls_in.bits = 0; + tls_in.cipher = NULL; + tls_in.peerdn = NULL; + tls_in.sni = NULL; + + return FALSE; + + /* Handle genuine errors */ + case SSL_ERROR_SSL: + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + log_write(0, LOG_MAIN, "TLS error (SSL_read): %s", ssl_errstring); + ssl_xfer_error = TRUE; + return FALSE; + + default: + DEBUG(D_tls) debug_printf("Got SSL error %d\n", error); + DEBUG(D_tls) if (error == SSL_ERROR_SYSCALL) + debug_printf(" - syscall %s\n", strerror(errno)); + ssl_xfer_error = TRUE; + return FALSE; + } + +#ifndef DISABLE_DKIM +dkim_exim_verify_feed(ssl_xfer_buffer, inbytes); +#endif +ssl_xfer_buffer_hwm = inbytes; +ssl_xfer_buffer_lwm = 0; +return TRUE; +} + + +/************************************************* +* TLS version of getc * +*************************************************/ + +/* This gets the next byte from the TLS input buffer. If the buffer is empty, +it refills the buffer via the SSL reading function. + +Arguments: lim Maximum amount to read/buffer +Returns: the next character or EOF + +Only used by the server-side TLS. +*/ + +int +tls_getc(unsigned lim) +{ +if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) + if (!tls_refill(lim)) + return ssl_xfer_error ? EOF : smtp_getc(lim); + +/* Something in the buffer; return next uschar */ + +return ssl_xfer_buffer[ssl_xfer_buffer_lwm++]; +} + +uschar * +tls_getbuf(unsigned * len) +{ +unsigned size; +uschar * buf; + +if (ssl_xfer_buffer_lwm >= ssl_xfer_buffer_hwm) + if (!tls_refill(*len)) + { + if (!ssl_xfer_error) return smtp_getbuf(len); + *len = 0; + return NULL; + } + +if ((size = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm) > *len) + size = *len; +buf = &ssl_xfer_buffer[ssl_xfer_buffer_lwm]; +ssl_xfer_buffer_lwm += size; +*len = size; +return buf; +} + + +void +tls_get_cache() +{ +#ifndef DISABLE_DKIM +int n = ssl_xfer_buffer_hwm - ssl_xfer_buffer_lwm; +if (n > 0) + dkim_exim_verify_feed(ssl_xfer_buffer+ssl_xfer_buffer_lwm, n); +#endif +} + + +BOOL +tls_could_read(void) +{ +return ssl_xfer_buffer_lwm < ssl_xfer_buffer_hwm || SSL_pending(server_ssl) > 0; +} + + +/************************************************* +* Read bytes from TLS channel * +*************************************************/ + +/* +Arguments: + ct_ctx client context pointer, or NULL for the one global server context + buff buffer of data + len size of buffer + +Returns: the number of bytes read + -1 after a failed read, including EOF + +Only used by the client-side TLS. +*/ + +int +tls_read(void * ct_ctx, uschar *buff, size_t len) +{ +SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl; +int inbytes; +int error; + +DEBUG(D_tls) debug_printf("Calling SSL_read(%p, %p, %u)\n", ssl, + buff, (unsigned int)len); + +inbytes = SSL_read(ssl, CS buff, len); +error = SSL_get_error(ssl, inbytes); + +if (error == SSL_ERROR_ZERO_RETURN) + { + DEBUG(D_tls) debug_printf("Got SSL_ERROR_ZERO_RETURN\n"); + return -1; + } +else if (error != SSL_ERROR_NONE) + return -1; + +return inbytes; +} + + + + + +/************************************************* +* Write bytes down TLS channel * +*************************************************/ + +/* +Arguments: + ct_ctx client context pointer, or NULL for the one global server context + buff buffer of data + len number of bytes + more further data expected soon + +Returns: the number of bytes after a successful write, + -1 after a failed write + +Used by both server-side and client-side TLS. +*/ + +int +tls_write(void * ct_ctx, const uschar *buff, size_t len, BOOL more) +{ +int outbytes, error, left; +SSL * ssl = ct_ctx ? ((exim_openssl_client_tls_ctx *)ct_ctx)->ssl : server_ssl; +static gstring * corked = NULL; + +DEBUG(D_tls) debug_printf("%s(%p, %lu%s)\n", __FUNCTION__, + buff, (unsigned long)len, more ? ", more" : ""); + +/* Lacking a CORK or MSG_MORE facility (such as GnuTLS has) we copy data when +"more" is notified. This hack is only ok if small amounts are involved AND only +one stream does it, in one context (i.e. no store reset). Currently it is used +for the responses to the received SMTP MAIL , RCPT, DATA sequence, only. */ +/*XXX + if PIPE_COMMAND, banner & ehlo-resp for smmtp-on-connect. Suspect there's +a store reset there. */ + +if (!ct_ctx && (more || corked)) + { +#ifdef EXPERIMENTAL_PIPE_CONNECT + int save_pool = store_pool; + store_pool = POOL_PERM; +#endif + + corked = string_catn(corked, buff, len); + +#ifdef EXPERIMENTAL_PIPE_CONNECT + store_pool = save_pool; +#endif + + if (more) + return len; + buff = CUS corked->s; + len = corked->ptr; + corked = NULL; + } + +for (left = len; left > 0;) + { + DEBUG(D_tls) debug_printf("SSL_write(%p, %p, %d)\n", ssl, buff, left); + outbytes = SSL_write(ssl, CS buff, left); + error = SSL_get_error(ssl, outbytes); + DEBUG(D_tls) debug_printf("outbytes=%d error=%d\n", outbytes, error); + switch (error) + { + case SSL_ERROR_SSL: + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + log_write(0, LOG_MAIN, "TLS error (SSL_write): %s", ssl_errstring); + return -1; + + case SSL_ERROR_NONE: + left -= outbytes; + buff += outbytes; + break; + + case SSL_ERROR_ZERO_RETURN: + log_write(0, LOG_MAIN, "SSL channel closed on write"); + return -1; + + case SSL_ERROR_SYSCALL: + log_write(0, LOG_MAIN, "SSL_write: (from %s) syscall: %s", + sender_fullhost ? sender_fullhost : US"<unknown>", + strerror(errno)); + return -1; + + default: + log_write(0, LOG_MAIN, "SSL_write error %d", error); + return -1; + } + } +return len; +} + + + +/************************************************* +* Close down a TLS session * +*************************************************/ + +/* This is also called from within a delivery subprocess forked from the +daemon, to shut down the TLS library, without actually doing a shutdown (which +would tamper with the SSL session in the parent process). + +Arguments: + ct_ctx client TLS context pointer, or NULL for the one global server context + shutdown 1 if TLS close-alert is to be sent, + 2 if also response to be waited for + +Returns: nothing + +Used by both server-side and client-side TLS. +*/ + +void +tls_close(void * ct_ctx, int shutdown) +{ +exim_openssl_client_tls_ctx * o_ctx = ct_ctx; +SSL_CTX **ctxp = o_ctx ? &o_ctx->ctx : &server_ctx; +SSL **sslp = o_ctx ? &o_ctx->ssl : &server_ssl; +int *fdp = o_ctx ? &tls_out.active.sock : &tls_in.active.sock; + +if (*fdp < 0) return; /* TLS was not active */ + +if (shutdown) + { + int rc; + DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n", + shutdown > 1 ? " (with response-wait)" : ""); + + if ( (rc = SSL_shutdown(*sslp)) == 0 /* send "close notify" alert */ + && shutdown > 1) + { + ALARM(2); + rc = SSL_shutdown(*sslp); /* wait for response */ + ALARM_CLR(0); + } + + if (rc < 0) DEBUG(D_tls) + { + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + debug_printf("SSL_shutdown: %s\n", ssl_errstring); + } + } + +#ifndef DISABLE_OCSP +if (!o_ctx) /* server side */ + { + sk_X509_pop_free(server_static_cbinfo->verify_stack, X509_free); + server_static_cbinfo->verify_stack = NULL; + } +#endif + +SSL_CTX_free(*ctxp); +SSL_free(*sslp); +*ctxp = NULL; +*sslp = NULL; +*fdp = -1; +} + + + + +/************************************************* +* 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 */ + +#ifdef EXIM_NEED_OPENSSL_INIT +SSL_load_error_strings(); +OpenSSL_add_ssl_algorithms(); +#endif +#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, + &err)) + 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; + +#ifdef EXIM_HAVE_OPENSSL_TLS_METHOD +if (!(ctx = SSL_CTX_new(TLS_server_method()))) +#else +if (!(ctx = SSL_CTX_new(SSLv23_server_method()))) +#endif + { + ERR_error_string_n(ERR_get_error(), ssl_errstring, sizeof(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_n(ERR_get_error(), ssl_errstring, sizeof(ssl_errstring)); + err = string_sprintf("SSL_CTX_set_cipher_list(%s) failed: %s", + expciphers, ssl_errstring); + } + +SSL_CTX_free(ctx); + +return err; +} + + + + +/************************************************* +* Report the library versions. * +*************************************************/ + +/* There have historically been some issues with binary compatibility in +OpenSSL libraries; if Exim (like many other applications) is built against +one version of OpenSSL but the run-time linker picks up another version, +it can result in serious failures, including crashing with a SIGSEGV. So +report the version found by the compiler and the run-time version. + +Note: some OS vendors backport security fixes without changing the version +number/string, and the version date remains unchanged. The _build_ date +will change, so we can more usefully assist with version diagnosis by also +reporting the build date. + +Arguments: a FILE* to print the results to +Returns: nothing +*/ + +void +tls_version_report(FILE *f) +{ +fprintf(f, "Library version: OpenSSL: Compile: %s\n" + " Runtime: %s\n" + " : %s\n", + OPENSSL_VERSION_TEXT, + SSLeay_version(SSLEAY_VERSION), + SSLeay_version(SSLEAY_BUILT_ON)); +/* third line is 38 characters for the %s and the line is 73 chars long; +the OpenSSL output includes a "built on: " prefix already. */ +} + + + + +/************************************************* +* Random number generation * +*************************************************/ + +/* Pseudo-random number generation. The result is not expected to be +cryptographically strong but not so weak that someone will shoot themselves +in the foot using it as a nonce in input in some email header scheme or +whatever weirdness they'll twist this into. The result should handle fork() +and avoid repeating sequences. OpenSSL handles that for us. + +Arguments: + max range maximum +Returns a random number in range [0, max-1] +*/ + +int +vaguely_random_number(int max) +{ +unsigned int r; +int i, needed_len; +static pid_t pidlast = 0; +pid_t pidnow; +uschar *p; +uschar smallbuf[sizeof(r)]; + +if (max <= 1) + return 0; + +pidnow = getpid(); +if (pidnow != pidlast) + { + /* Although OpenSSL documents that "OpenSSL makes sure that the PRNG state + is unique for each thread", this doesn't apparently apply across processes, + so our own warning from vaguely_random_number_fallback() applies here too. + Fix per PostgreSQL. */ + if (pidlast != 0) + RAND_cleanup(); + pidlast = pidnow; + } + +/* OpenSSL auto-seeds from /dev/random, etc, but this a double-check. */ +if (!RAND_status()) + { + randstuff r; + gettimeofday(&r.tv, NULL); + r.p = getpid(); + + RAND_seed(US (&r), sizeof(r)); + } +/* We're after pseudo-random, not random; if we still don't have enough data +in the internal PRNG then our options are limited. We could sleep and hope +for entropy to come along (prayer technique) but if the system is so depleted +in the first place then something is likely to just keep taking it. Instead, +we'll just take whatever little bit of pseudo-random we can still manage to +get. */ + +needed_len = sizeof(r); +/* Don't take 8 times more entropy than needed if int is 8 octets and we were +asked for a number less than 10. */ +for (r = max, i = 0; r; ++i) + r >>= 1; +i = (i + 7) / 8; +if (i < needed_len) + needed_len = i; + +#ifdef EXIM_HAVE_RAND_PSEUDO +/* We do not care if crypto-strong */ +i = RAND_pseudo_bytes(smallbuf, needed_len); +#else +i = RAND_bytes(smallbuf, needed_len); +#endif + +if (i < 0) + { + DEBUG(D_all) + debug_printf("OpenSSL RAND_pseudo_bytes() not supported by RAND method, using fallback.\n"); + return vaguely_random_number_fallback(max); + } + +r = 0; +for (p = smallbuf; needed_len; --needed_len, ++p) + { + r *= 256; + r += *p; + } + +/* We don't particularly care about weighted results; if someone wants +smooth distribution and cares enough then they should submit a patch then. */ +return r % max; +} + + + + +/************************************************* +* OpenSSL option parse * +*************************************************/ + +/* Parse one option for tls_openssl_options_parse below + +Arguments: + name one option name + value place to store a value for it +Returns success or failure in parsing +*/ + + + +static BOOL +tls_openssl_one_option_parse(uschar *name, long *value) +{ +int first = 0; +int last = exim_openssl_options_size; +while (last > first) + { + int middle = (first + last)/2; + int c = Ustrcmp(name, exim_openssl_options[middle].name); + if (c == 0) + { + *value = exim_openssl_options[middle].value; + return TRUE; + } + else if (c > 0) + first = middle + 1; + else + last = middle; + } +return FALSE; +} + + + + +/************************************************* +* OpenSSL option parsing logic * +*************************************************/ + +/* OpenSSL has a number of compatibility options which an administrator might +reasonably wish to set. Interpret a list similarly to decode_bits(), so that +we look like log_selector. + +Arguments: + option_spec the administrator-supplied string of options + results ptr to long storage for the options bitmap +Returns success or failure +*/ + +BOOL +tls_openssl_options_parse(uschar *option_spec, long *results) +{ +long result, item; +uschar *s, *end; +uschar keep_c; +BOOL adding, item_parsed; + +result = SSL_OP_NO_TICKET; +/* Prior to 4.80 we or'd in SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS; removed + * from default because it increases BEAST susceptibility. */ +#ifdef SSL_OP_NO_SSLv2 +result |= SSL_OP_NO_SSLv2; +#endif +#ifdef SSL_OP_SINGLE_DH_USE +result |= SSL_OP_SINGLE_DH_USE; +#endif + +if (!option_spec) + { + *results = result; + return TRUE; + } + +for (s=option_spec; *s != '\0'; /**/) + { + while (isspace(*s)) ++s; + if (*s == '\0') + break; + if (*s != '+' && *s != '-') + { + DEBUG(D_tls) debug_printf("malformed openssl option setting: " + "+ or - expected but found \"%s\"\n", s); + return FALSE; + } + adding = *s++ == '+'; + for (end = s; (*end != '\0') && !isspace(*end); ++end) /**/ ; + keep_c = *end; + *end = '\0'; + item_parsed = tls_openssl_one_option_parse(s, &item); + *end = keep_c; + if (!item_parsed) + { + DEBUG(D_tls) debug_printf("openssl option setting unrecognised: \"%s\"\n", s); + return FALSE; + } + DEBUG(D_tls) debug_printf("openssl option, %s from %lx: %lx (%s)\n", + adding ? "adding" : "removing", result, item, s); + if (adding) + result |= item; + else + result &= ~item; + s = end; + } + +*results = result; +return TRUE; +} + +#endif /*!MACRO_PREDEF*/ +/* vi: aw ai sw=2 +*/ +/* End of tls-openssl.c */ |