diff options
Diffstat (limited to 'src/tls-gnu.c')
| -rw-r--r-- | src/tls-gnu.c | 2998 |
1 files changed, 2998 insertions, 0 deletions
diff --git a/src/tls-gnu.c b/src/tls-gnu.c new file mode 100644 index 0000000..c404dc2 --- /dev/null +++ b/src/tls-gnu.c @@ -0,0 +1,2998 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ + +/* Copyright (c) University of Cambridge 1995 - 2018 */ +/* See the file NOTICE for conditions of use and distribution. */ + +/* Copyright (c) Phil Pennock 2012 */ + +/* This file provides TLS/SSL support for Exim using the GnuTLS library, +one of the available supported implementations. This file is #included into +tls.c when USE_GNUTLS has been set. + +The code herein is a revamp of GnuTLS integration using the current APIs; the +original tls-gnu.c was based on a patch which was contributed by Nikos +Mavrogiannopoulos. The revamp is partially a rewrite, partially cut&paste as +appropriate. + +APIs current as of GnuTLS 2.12.18; note that the GnuTLS manual is for GnuTLS 3, +which is not widely deployed by OS vendors. Will note issues below, which may +assist in updating the code in the future. Another sources of hints is +mod_gnutls for Apache (SNI callback registration and handling). + +Keeping client and server variables more split than before and is currently +the norm, in anticipation of TLS in ACL callouts. + +I wanted to switch to gnutls_certificate_set_verify_function() so that +certificate rejection could happen during handshake where it belongs, rather +than being dropped afterwards, but that was introduced in 2.10.0 and Debian +(6.0.5) is still on 2.8.6. So for now we have to stick with sub-par behaviour. + +(I wasn't looking for libraries quite that old, when updating to get rid of +compiler warnings of deprecated APIs. If it turns out that a lot of the rest +require current GnuTLS, then we'll drop support for the ancient libraries). +*/ + +#include <gnutls/gnutls.h> +/* needed for cert checks in verification and DN extraction: */ +#include <gnutls/x509.h> +/* man-page is incorrect, gnutls_rnd() is not in gnutls.h: */ +#include <gnutls/crypto.h> + +/* needed to disable PKCS11 autoload unless requested */ +#if GNUTLS_VERSION_NUMBER >= 0x020c00 +# include <gnutls/pkcs11.h> +# define SUPPORT_PARAM_TO_PK_BITS +#endif +#if GNUTLS_VERSION_NUMBER < 0x030103 && !defined(DISABLE_OCSP) +# warning "GnuTLS library version too old; define DISABLE_OCSP in Makefile" +# define DISABLE_OCSP +#endif +#if GNUTLS_VERSION_NUMBER < 0x020a00 && !defined(DISABLE_EVENT) +# warning "GnuTLS library version too old; tls:cert event unsupported" +# define DISABLE_EVENT +#endif +#if GNUTLS_VERSION_NUMBER >= 0x030306 +# define SUPPORT_CA_DIR +#else +# undef SUPPORT_CA_DIR +#endif +#if GNUTLS_VERSION_NUMBER >= 0x030014 +# define SUPPORT_SYSDEFAULT_CABUNDLE +#endif +#if GNUTLS_VERSION_NUMBER >= 0x030104 +# define GNUTLS_CERT_VFY_STATUS_PRINT +#endif +#if GNUTLS_VERSION_NUMBER >= 0x030109 +# define SUPPORT_CORK +#endif +#if GNUTLS_VERSION_NUMBER >= 0x030506 && !defined(DISABLE_OCSP) +# define SUPPORT_SRV_OCSP_STACK +#endif + +#ifdef SUPPORT_DANE +# if GNUTLS_VERSION_NUMBER >= 0x030000 +# define DANESSL_USAGE_DANE_TA 2 +# define DANESSL_USAGE_DANE_EE 3 +# else +# error GnuTLS version too early for DANE +# endif +# if GNUTLS_VERSION_NUMBER < 0x999999 +# define GNUTLS_BROKEN_DANE_VALIDATION +# endif +#endif + +#ifndef DISABLE_OCSP +# include <gnutls/ocsp.h> +#endif +#ifdef SUPPORT_DANE +# include <gnutls/dane.h> +#endif + +/* GnuTLS 2 vs 3 + +GnuTLS 3 only: + gnutls_global_set_audit_log_function() + +Changes: + gnutls_certificate_verify_peers2(): is new, drop the 2 for old version +*/ + +/* Local static variables for GnuTLS */ + +/* Values for verify_requirement */ + +enum peer_verify_requirement + { VERIFY_NONE, VERIFY_OPTIONAL, VERIFY_REQUIRED, VERIFY_DANE }; + +/* This holds most state for server or client; with this, we can set up an +outbound TLS-enabled connection in an ACL callout, while not stomping all +over the TLS variables available for expansion. + +Some of these correspond to variables in globals.c; those variables will +be set to point to content in one of these instances, as appropriate for +the stage of the process lifetime. + +Not handled here: global tls_channelbinding_b64. +*/ + +typedef struct exim_gnutls_state { + gnutls_session_t session; + gnutls_certificate_credentials_t x509_cred; + gnutls_priority_t priority_cache; + enum peer_verify_requirement verify_requirement; + int fd_in; + int fd_out; + BOOL peer_cert_verified; + BOOL peer_dane_verified; + BOOL trigger_sni_changes; + BOOL have_set_peerdn; + const struct host_item *host; /* NULL if server */ + gnutls_x509_crt_t peercert; + uschar *peerdn; + uschar *ciphersuite; + uschar *received_sni; + + const uschar *tls_certificate; + const uschar *tls_privatekey; + const uschar *tls_sni; /* client send only, not received */ + const uschar *tls_verify_certificates; + const uschar *tls_crl; + const uschar *tls_require_ciphers; + + uschar *exp_tls_certificate; + uschar *exp_tls_privatekey; + uschar *exp_tls_verify_certificates; + uschar *exp_tls_crl; + uschar *exp_tls_require_ciphers; + const uschar *exp_tls_verify_cert_hostnames; +#ifndef DISABLE_EVENT + uschar *event_action; +#endif +#ifdef SUPPORT_DANE + char * const * dane_data; + const int * dane_data_len; +#endif + + tls_support *tlsp; /* set in tls_init() */ + + uschar *xfer_buffer; + int xfer_buffer_lwm; + int xfer_buffer_hwm; + BOOL xfer_eof; /*XXX never gets set! */ + BOOL xfer_error; +} exim_gnutls_state_st; + +static const exim_gnutls_state_st exim_gnutls_state_init = { + .session = NULL, + .x509_cred = NULL, + .priority_cache = NULL, + .verify_requirement = VERIFY_NONE, + .fd_in = -1, + .fd_out = -1, + .peer_cert_verified = FALSE, + .peer_dane_verified = FALSE, + .trigger_sni_changes =FALSE, + .have_set_peerdn = FALSE, + .host = NULL, + .peercert = NULL, + .peerdn = NULL, + .ciphersuite = NULL, + .received_sni = NULL, + + .tls_certificate = NULL, + .tls_privatekey = NULL, + .tls_sni = NULL, + .tls_verify_certificates = NULL, + .tls_crl = NULL, + .tls_require_ciphers =NULL, + + .exp_tls_certificate = NULL, + .exp_tls_privatekey = NULL, + .exp_tls_verify_certificates = NULL, + .exp_tls_crl = NULL, + .exp_tls_require_ciphers = NULL, + .exp_tls_verify_cert_hostnames = NULL, +#ifndef DISABLE_EVENT + .event_action = NULL, +#endif + .tlsp = NULL, + + .xfer_buffer = NULL, + .xfer_buffer_lwm = 0, + .xfer_buffer_hwm = 0, + .xfer_eof = FALSE, + .xfer_error = FALSE, +}; + +/* Not only do we have our own APIs which don't pass around state, assuming +it's held in globals, GnuTLS doesn't appear to let us register callback data +for callbacks, or as part of the session, so we have to keep a "this is the +context we're currently dealing with" pointer and rely upon being +single-threaded to keep from processing data on an inbound TLS connection while +talking to another TLS connection for an outbound check. This does mean that +there's no way for heart-beats to be responded to, for the duration of the +second connection. +XXX But see gnutls_session_get_ptr() +*/ + +static exim_gnutls_state_st state_server; + +/* dh_params are initialised once within the lifetime of a process using TLS; +if we used TLS in a long-lived daemon, we'd have to reconsider this. But we +don't want to repeat this. */ + +static gnutls_dh_params_t dh_server_params = NULL; + +/* No idea how this value was chosen; preserving it. Default is 3600. */ + +static const int ssl_session_timeout = 200; + +static const char * const exim_default_gnutls_priority = "NORMAL"; + +/* Guard library core initialisation */ + +static BOOL exim_gnutls_base_init_done = FALSE; + +#ifndef DISABLE_OCSP +static BOOL gnutls_buggy_ocsp = FALSE; +#endif + + +/* ------------------------------------------------------------------------ */ +/* macros */ + +#define MAX_HOST_LEN 255 + +/* Set this to control gnutls_global_set_log_level(); values 0 to 9 will setup +the library logging; a value less than 0 disables the calls to set up logging +callbacks. Possibly GNuTLS also looks for an environment variable +"GNUTLS_DEBUG_LEVEL". */ +#ifndef EXIM_GNUTLS_LIBRARY_LOG_LEVEL +# define EXIM_GNUTLS_LIBRARY_LOG_LEVEL -1 +#endif + +#ifndef EXIM_CLIENT_DH_MIN_BITS +# define EXIM_CLIENT_DH_MIN_BITS 1024 +#endif + +/* With GnuTLS 2.12.x+ we have gnutls_sec_param_to_pk_bits() with which we +can ask for a bit-strength. Without that, we stick to the constant we had +before, for now. */ +#ifndef EXIM_SERVER_DH_BITS_PRE2_12 +# define EXIM_SERVER_DH_BITS_PRE2_12 1024 +#endif + +#define exim_gnutls_err_check(rc, Label) do { \ + if ((rc) != GNUTLS_E_SUCCESS) \ + return tls_error((Label), US gnutls_strerror(rc), host, errstr); \ + } while (0) + +#define expand_check_tlsvar(Varname, errstr) \ + expand_check(state->Varname, US #Varname, &state->exp_##Varname, errstr) + +#if GNUTLS_VERSION_NUMBER >= 0x020c00 +# define HAVE_GNUTLS_SESSION_CHANNEL_BINDING +# define HAVE_GNUTLS_SEC_PARAM_CONSTANTS +# define HAVE_GNUTLS_RND +/* The security fix we provide with the gnutls_allow_auto_pkcs11 option + * (4.82 PP/09) introduces a compatibility regression. The symbol simply + * isn't available sometimes, so this needs to become a conditional + * compilation; the sanest way to deal with this being a problem on + * older OSes is to block it in the Local/Makefile with this compiler + * definition */ +# ifndef AVOID_GNUTLS_PKCS11 +# define HAVE_GNUTLS_PKCS11 +# endif /* AVOID_GNUTLS_PKCS11 */ +#endif + + + + +/* ------------------------------------------------------------------------ */ +/* Callback declarations */ + +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +static void exim_gnutls_logger_cb(int level, const char *message); +#endif + +static int exim_sni_handling_cb(gnutls_session_t session); + +#ifndef DISABLE_OCSP +static int server_ocsp_stapling_cb(gnutls_session_t session, void * ptr, + gnutls_datum_t * ocsp_response); +#endif + + + +/* ------------------------------------------------------------------------ */ +/* Static functions */ + +/************************************************* +* 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 + msg additional error string (may be NULL) + usually obtained from gnutls_strerror() + host NULL if setting up a server; + the connected host if setting up a client + errstr pointer to returned error string + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_error(const uschar *prefix, const uschar *msg, const host_item *host, + uschar ** errstr) +{ +if (errstr) + *errstr = string_sprintf("(%s)%s%s", prefix, msg ? ": " : "", msg ? msg : US""); +return host ? FAIL : DEFER; +} + + + + +/************************************************* +* Deal with logging errors during I/O * +*************************************************/ + +/* We have to get the identity of the peer from saved data. + +Argument: + state the current GnuTLS exim state container + rc the GnuTLS error code, or 0 if it's a local error + when text identifying read or write + text local error text when ec is 0 + +Returns: nothing +*/ + +static void +record_io_error(exim_gnutls_state_st *state, int rc, uschar *when, uschar *text) +{ +const uschar * msg; +uschar * errstr; + +if (rc == GNUTLS_E_FATAL_ALERT_RECEIVED) + msg = string_sprintf("%s: %s", US gnutls_strerror(rc), + US gnutls_alert_get_name(gnutls_alert_get(state->session))); +else + msg = US gnutls_strerror(rc); + +(void) tls_error(when, msg, state->host, &errstr); + +if (state->host) + log_write(0, LOG_MAIN, "H=%s [%s] TLS error on connection %s", + state->host->name, state->host->address, errstr); +else + { + uschar * conn_info = smtp_get_connection_info(); + if (Ustrncmp(conn_info, US"SMTP ", 5) == 0) conn_info += 5; + /* I'd like to get separated H= here, but too hard for now */ + log_write(0, LOG_MAIN, "TLS error on %s %s", conn_info, errstr); + } +} + + + + +/************************************************* +* Set various Exim expansion vars * +*************************************************/ + +#define exim_gnutls_cert_err(Label) \ + do \ + { \ + if (rc != GNUTLS_E_SUCCESS) \ + { \ + DEBUG(D_tls) debug_printf("TLS: cert problem: %s: %s\n", \ + (Label), gnutls_strerror(rc)); \ + return rc; \ + } \ + } while (0) + +static int +import_cert(const gnutls_datum_t * cert, gnutls_x509_crt_t * crtp) +{ +int rc; + +rc = gnutls_x509_crt_init(crtp); +exim_gnutls_cert_err(US"gnutls_x509_crt_init (crt)"); + +rc = gnutls_x509_crt_import(*crtp, cert, GNUTLS_X509_FMT_DER); +exim_gnutls_cert_err(US"failed to import certificate [gnutls_x509_crt_import(cert)]"); + +return rc; +} + +#undef exim_gnutls_cert_err + + +/* We set various Exim global variables from the state, once a session has +been established. With TLS callouts, may need to change this to stack +variables, or just re-call it with the server state after client callout +has finished. + +Make sure anything set here is unset in tls_getc(). + +Sets: + tls_active fd + tls_bits strength indicator + tls_certificate_verified bool indicator + tls_channelbinding_b64 for some SASL mechanisms + tls_cipher a string + tls_peercert pointer to library internal + tls_peerdn a string + tls_sni a (UTF-8) string + tls_ourcert pointer to library internal + +Argument: + state the relevant exim_gnutls_state_st * +*/ + +static void +extract_exim_vars_from_tls_state(exim_gnutls_state_st * state) +{ +gnutls_cipher_algorithm_t cipher; +#ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING +int old_pool; +int rc; +gnutls_datum_t channel; +#endif +tls_support * tlsp = state->tlsp; + +tlsp->active.sock = state->fd_out; +tlsp->active.tls_ctx = state; + +cipher = gnutls_cipher_get(state->session); +/* returns size in "bytes" */ +tlsp->bits = gnutls_cipher_get_key_size(cipher) * 8; + +tlsp->cipher = state->ciphersuite; + +DEBUG(D_tls) debug_printf("cipher: %s\n", state->ciphersuite); + +tlsp->certificate_verified = state->peer_cert_verified; +#ifdef SUPPORT_DANE +tlsp->dane_verified = state->peer_dane_verified; +#endif + +/* note that tls_channelbinding_b64 is not saved to the spool file, since it's +only available for use for authenticators while this TLS session is running. */ + +tls_channelbinding_b64 = NULL; +#ifdef HAVE_GNUTLS_SESSION_CHANNEL_BINDING +channel.data = NULL; +channel.size = 0; +rc = gnutls_session_channel_binding(state->session, GNUTLS_CB_TLS_UNIQUE, &channel); +if (rc) { + DEBUG(D_tls) debug_printf("Channel binding error: %s\n", gnutls_strerror(rc)); +} else { + old_pool = store_pool; + store_pool = POOL_PERM; + tls_channelbinding_b64 = b64encode(channel.data, (int)channel.size); + store_pool = old_pool; + DEBUG(D_tls) debug_printf("Have channel bindings cached for possible auth usage.\n"); +} +#endif + +/* peercert is set in peer_status() */ +tlsp->peerdn = state->peerdn; +tlsp->sni = state->received_sni; + +/* record our certificate */ + { + const gnutls_datum_t * cert = gnutls_certificate_get_ours(state->session); + gnutls_x509_crt_t crt; + + tlsp->ourcert = cert && import_cert(cert, &crt)==0 ? crt : NULL; + } +} + + + + +/************************************************* +* Setup up DH parameters * +*************************************************/ + +/* Generating the D-H parameters may take a long time. They only need to +be re-generated every so often, depending on security policy. What we do is to +keep these parameters in a file in the spool directory. If the file does not +exist, we generate them. This means that it is easy to cause a regeneration. + +The new file is written as a temporary file and renamed, so that an incomplete +file is never present. If two processes both compute some new parameters, you +waste a bit of effort, but it doesn't seem worth messing around with locking to +prevent this. + +Returns: OK/DEFER/FAIL +*/ + +static int +init_server_dh(uschar ** errstr) +{ +int fd, rc; +unsigned int dh_bits; +gnutls_datum_t m; +uschar filename_buf[PATH_MAX]; +uschar *filename = NULL; +size_t sz; +uschar *exp_tls_dhparam; +BOOL use_file_in_spool = FALSE; +BOOL use_fixed_file = FALSE; +host_item *host = NULL; /* dummy for macros */ + +DEBUG(D_tls) debug_printf("Initialising GnuTLS server params.\n"); + +rc = gnutls_dh_params_init(&dh_server_params); +exim_gnutls_err_check(rc, US"gnutls_dh_params_init"); + +m.data = NULL; +m.size = 0; + +if (!expand_check(tls_dhparam, US"tls_dhparam", &exp_tls_dhparam, errstr)) + return DEFER; + +if (!exp_tls_dhparam) + { + DEBUG(D_tls) debug_printf("Loading default hard-coded DH params\n"); + m.data = US std_dh_prime_default(); + m.size = Ustrlen(m.data); + } +else if (Ustrcmp(exp_tls_dhparam, "historic") == 0) + use_file_in_spool = TRUE; +else if (Ustrcmp(exp_tls_dhparam, "none") == 0) + { + DEBUG(D_tls) debug_printf("Requested no DH parameters.\n"); + return OK; + } +else if (exp_tls_dhparam[0] != '/') + { + if (!(m.data = US std_dh_prime_named(exp_tls_dhparam))) + return tls_error(US"No standard prime named", exp_tls_dhparam, NULL, errstr); + m.size = Ustrlen(m.data); + } +else + { + use_fixed_file = TRUE; + filename = exp_tls_dhparam; + } + +if (m.data) + { + rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); + exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3"); + DEBUG(D_tls) debug_printf("Loaded fixed standard D-H parameters\n"); + return OK; + } + +#ifdef HAVE_GNUTLS_SEC_PARAM_CONSTANTS +/* If you change this constant, also change dh_param_fn_ext so that we can use a +different filename and ensure we have sufficient bits. */ +dh_bits = gnutls_sec_param_to_pk_bits(GNUTLS_PK_DH, GNUTLS_SEC_PARAM_NORMAL); +if (!dh_bits) + return tls_error(US"gnutls_sec_param_to_pk_bits() failed", NULL, NULL, errstr); +DEBUG(D_tls) + debug_printf("GnuTLS tells us that for D-H PK, NORMAL is %d bits.\n", + dh_bits); +#else +dh_bits = EXIM_SERVER_DH_BITS_PRE2_12; +DEBUG(D_tls) + debug_printf("GnuTLS lacks gnutls_sec_param_to_pk_bits(), using %d bits.\n", + dh_bits); +#endif + +/* Some clients have hard-coded limits. */ +if (dh_bits > tls_dh_max_bits) + { + DEBUG(D_tls) + debug_printf("tls_dh_max_bits clamping override, using %d bits instead.\n", + tls_dh_max_bits); + dh_bits = tls_dh_max_bits; + } + +if (use_file_in_spool) + { + if (!string_format(filename_buf, sizeof(filename_buf), + "%s/gnutls-params-%d", spool_directory, dh_bits)) + return tls_error(US"overlong filename", NULL, NULL, errstr); + filename = filename_buf; + } + +/* Open the cache file for reading and if successful, read it and set up the +parameters. */ + +if ((fd = Uopen(filename, O_RDONLY, 0)) >= 0) + { + struct stat statbuf; + FILE *fp; + int saved_errno; + + if (fstat(fd, &statbuf) < 0) /* EIO */ + { + saved_errno = errno; + (void)close(fd); + return tls_error(US"TLS cache stat failed", US strerror(saved_errno), NULL, errstr); + } + if (!S_ISREG(statbuf.st_mode)) + { + (void)close(fd); + return tls_error(US"TLS cache not a file", NULL, NULL, errstr); + } + if (!(fp = fdopen(fd, "rb"))) + { + saved_errno = errno; + (void)close(fd); + return tls_error(US"fdopen(TLS cache stat fd) failed", + US strerror(saved_errno), NULL, errstr); + } + + m.size = statbuf.st_size; + if (!(m.data = malloc(m.size))) + { + fclose(fp); + return tls_error(US"malloc failed", US strerror(errno), NULL, errstr); + } + if (!(sz = fread(m.data, m.size, 1, fp))) + { + saved_errno = errno; + fclose(fp); + free(m.data); + return tls_error(US"fread failed", US strerror(saved_errno), NULL, errstr); + } + fclose(fp); + + rc = gnutls_dh_params_import_pkcs3(dh_server_params, &m, GNUTLS_X509_FMT_PEM); + free(m.data); + exim_gnutls_err_check(rc, US"gnutls_dh_params_import_pkcs3"); + DEBUG(D_tls) debug_printf("read D-H parameters from file \"%s\"\n", filename); + } + +/* If the file does not exist, fall through to compute new data and cache it. +If there was any other opening error, it is serious. */ + +else if (errno == ENOENT) + { + rc = -1; + DEBUG(D_tls) + debug_printf("D-H parameter cache file \"%s\" does not exist\n", filename); + } +else + return tls_error(string_open_failed(errno, "\"%s\" for reading", filename), + NULL, NULL, errstr); + +/* If ret < 0, either the cache file does not exist, or the data it contains +is not useful. One particular case of this is when upgrading from an older +release of Exim in which the data was stored in a different format. We don't +try to be clever and support both formats; we just regenerate new data in this +case. */ + +if (rc < 0) + { + uschar *temp_fn; + unsigned int dh_bits_gen = dh_bits; + + if ((PATH_MAX - Ustrlen(filename)) < 10) + return tls_error(US"Filename too long to generate replacement", + filename, NULL, errstr); + + temp_fn = string_copy(US"%s.XXXXXXX"); + if ((fd = mkstemp(CS temp_fn)) < 0) /* modifies temp_fn */ + return tls_error(US"Unable to open temp file", US strerror(errno), NULL, errstr); + (void)fchown(fd, exim_uid, exim_gid); /* Probably not necessary */ + + /* GnuTLS overshoots! + * If we ask for 2236, we might get 2237 or more. + * But there's no way to ask GnuTLS how many bits there really are. + * We can ask how many bits were used in a TLS session, but that's it! + * The prime itself is hidden behind too much abstraction. + * So we ask for less, and proceed on a wing and a prayer. + * First attempt, subtracted 3 for 2233 and got 2240. + */ + if (dh_bits >= EXIM_CLIENT_DH_MIN_BITS + 10) + { + dh_bits_gen = dh_bits - 10; + DEBUG(D_tls) + debug_printf("being paranoid about DH generation, make it '%d' bits'\n", + dh_bits_gen); + } + + DEBUG(D_tls) + debug_printf("requesting generation of %d bit Diffie-Hellman prime ...\n", + dh_bits_gen); + rc = gnutls_dh_params_generate2(dh_server_params, dh_bits_gen); + exim_gnutls_err_check(rc, US"gnutls_dh_params_generate2"); + + /* gnutls_dh_params_export_pkcs3() will tell us the exact size, every time, + and I confirmed that a NULL call to get the size first is how the GnuTLS + sample apps handle this. */ + + sz = 0; + m.data = NULL; + rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, + m.data, &sz); + if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) + exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3(NULL) sizing"); + m.size = sz; + if (!(m.data = malloc(m.size))) + return tls_error(US"memory allocation failed", US strerror(errno), NULL, errstr); + + /* this will return a size 1 less than the allocation size above */ + rc = gnutls_dh_params_export_pkcs3(dh_server_params, GNUTLS_X509_FMT_PEM, + m.data, &sz); + if (rc != GNUTLS_E_SUCCESS) + { + free(m.data); + exim_gnutls_err_check(rc, US"gnutls_dh_params_export_pkcs3() real"); + } + m.size = sz; /* shrink by 1, probably */ + + if ((sz = write_to_fd_buf(fd, m.data, (size_t) m.size)) != m.size) + { + free(m.data); + return tls_error(US"TLS cache write D-H params failed", + US strerror(errno), NULL, errstr); + } + free(m.data); + if ((sz = write_to_fd_buf(fd, US"\n", 1)) != 1) + return tls_error(US"TLS cache write D-H params final newline failed", + US strerror(errno), NULL, errstr); + + if ((rc = close(fd))) + return tls_error(US"TLS cache write close() failed", US strerror(errno), NULL, errstr); + + if (Urename(temp_fn, filename) < 0) + return tls_error(string_sprintf("failed to rename \"%s\" as \"%s\"", + temp_fn, filename), US strerror(errno), NULL, errstr); + + DEBUG(D_tls) debug_printf("wrote D-H parameters to file \"%s\"\n", filename); + } + +DEBUG(D_tls) debug_printf("initialized server D-H parameters\n"); +return OK; +} + + + + +/* Create and install a selfsigned certificate, for use in server mode */ + +static int +tls_install_selfsign(exim_gnutls_state_st * state, uschar ** errstr) +{ +gnutls_x509_crt_t cert = NULL; +time_t now; +gnutls_x509_privkey_t pkey = NULL; +const uschar * where; +int rc; + +where = US"initialising pkey"; +if ((rc = gnutls_x509_privkey_init(&pkey))) goto err; + +where = US"initialising cert"; +if ((rc = gnutls_x509_crt_init(&cert))) goto err; + +where = US"generating pkey"; +if ((rc = gnutls_x509_privkey_generate(pkey, GNUTLS_PK_RSA, +#ifdef SUPPORT_PARAM_TO_PK_BITS +# ifndef GNUTLS_SEC_PARAM_MEDIUM +# define GNUTLS_SEC_PARAM_MEDIUM GNUTLS_SEC_PARAM_HIGH +# endif + gnutls_sec_param_to_pk_bits(GNUTLS_PK_RSA, GNUTLS_SEC_PARAM_MEDIUM), +#else + 2048, +#endif + 0))) + goto err; + +where = US"configuring cert"; +now = 1; +if ( (rc = gnutls_x509_crt_set_version(cert, 3)) + || (rc = gnutls_x509_crt_set_serial(cert, &now, sizeof(now))) + || (rc = gnutls_x509_crt_set_activation_time(cert, now = time(NULL))) + || (rc = gnutls_x509_crt_set_expiration_time(cert, now + 60 * 60)) /* 1 hr */ + || (rc = gnutls_x509_crt_set_key(cert, pkey)) + + || (rc = gnutls_x509_crt_set_dn_by_oid(cert, + GNUTLS_OID_X520_COUNTRY_NAME, 0, "UK", 2)) + || (rc = gnutls_x509_crt_set_dn_by_oid(cert, + GNUTLS_OID_X520_ORGANIZATION_NAME, 0, "Exim Developers", 15)) + || (rc = gnutls_x509_crt_set_dn_by_oid(cert, + GNUTLS_OID_X520_COMMON_NAME, 0, + smtp_active_hostname, Ustrlen(smtp_active_hostname))) + ) + goto err; + +where = US"signing cert"; +if ((rc = gnutls_x509_crt_sign(cert, cert, pkey))) goto err; + +where = US"installing selfsign cert"; + /* Since: 2.4.0 */ +if ((rc = gnutls_certificate_set_x509_key(state->x509_cred, &cert, 1, pkey))) + goto err; + +rc = OK; + +out: + if (cert) gnutls_x509_crt_deinit(cert); + if (pkey) gnutls_x509_privkey_deinit(pkey); + return rc; + +err: + rc = tls_error(where, US gnutls_strerror(rc), NULL, errstr); + goto out; +} + + + + +/* Add certificate and key, from files. + +Return: + Zero or negative: good. Negate value for certificate index if < 0. + Greater than zero: FAIL or DEFER code. +*/ + +static int +tls_add_certfile(exim_gnutls_state_st * state, const host_item * host, + uschar * certfile, uschar * keyfile, uschar ** errstr) +{ +int rc = gnutls_certificate_set_x509_key_file(state->x509_cred, + CS certfile, CS keyfile, GNUTLS_X509_FMT_PEM); +if (rc < 0) + return tls_error( + string_sprintf("cert/key setup: cert=%s key=%s", certfile, keyfile), + US gnutls_strerror(rc), host, errstr); +return -rc; +} + + +/************************************************* +* Variables re-expanded post-SNI * +*************************************************/ + +/* Called from both server and client code, via tls_init(), and also from +the SNI callback after receiving an SNI, if tls_certificate includes "tls_sni". + +We can tell the two apart by state->received_sni being non-NULL in callback. + +The callback should not call us unless state->trigger_sni_changes is true, +which we are responsible for setting on the first pass through. + +Arguments: + state exim_gnutls_state_st * + errstr error string pointer + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_expand_session_files(exim_gnutls_state_st * state, uschar ** errstr) +{ +struct stat statbuf; +int rc; +const host_item *host = state->host; /* macro should be reconsidered? */ +uschar *saved_tls_certificate = NULL; +uschar *saved_tls_privatekey = NULL; +uschar *saved_tls_verify_certificates = NULL; +uschar *saved_tls_crl = NULL; +int cert_count; + +/* We check for tls_sni *before* expansion. */ +if (!host) /* server */ + if (!state->received_sni) + { + if ( state->tls_certificate + && ( Ustrstr(state->tls_certificate, US"tls_sni") + || Ustrstr(state->tls_certificate, US"tls_in_sni") + || Ustrstr(state->tls_certificate, US"tls_out_sni") + ) ) + { + DEBUG(D_tls) debug_printf("We will re-expand TLS session files if we receive SNI.\n"); + state->trigger_sni_changes = TRUE; + } + } + else + { + /* useful for debugging */ + saved_tls_certificate = state->exp_tls_certificate; + saved_tls_privatekey = state->exp_tls_privatekey; + saved_tls_verify_certificates = state->exp_tls_verify_certificates; + saved_tls_crl = state->exp_tls_crl; + } + +rc = gnutls_certificate_allocate_credentials(&state->x509_cred); +exim_gnutls_err_check(rc, US"gnutls_certificate_allocate_credentials"); + +#ifdef SUPPORT_SRV_OCSP_STACK +gnutls_certificate_set_flags(state->x509_cred, GNUTLS_CERTIFICATE_API_V2); +#endif + +/* remember: expand_check_tlsvar() is expand_check() but fiddling with +state members, assuming consistent naming; and expand_check() returns +false if expansion failed, unless expansion was forced to fail. */ + +/* check if we at least have a certificate, before doing expensive +D-H generation. */ + +if (!expand_check_tlsvar(tls_certificate, errstr)) + return DEFER; + +/* certificate is mandatory in server, optional in client */ + +if ( !state->exp_tls_certificate + || !*state->exp_tls_certificate + ) + if (!host) + return tls_install_selfsign(state, errstr); + else + DEBUG(D_tls) debug_printf("TLS: no client certificate specified; okay\n"); + +if (state->tls_privatekey && !expand_check_tlsvar(tls_privatekey, errstr)) + return DEFER; + +/* tls_privatekey is optional, defaulting to same file as certificate */ + +if (state->tls_privatekey == NULL || *state->tls_privatekey == '\0') + { + state->tls_privatekey = state->tls_certificate; + state->exp_tls_privatekey = state->exp_tls_certificate; + } + + +if (state->exp_tls_certificate && *state->exp_tls_certificate) + { + DEBUG(D_tls) debug_printf("certificate file = %s\nkey file = %s\n", + state->exp_tls_certificate, state->exp_tls_privatekey); + + if (state->received_sni) + if ( Ustrcmp(state->exp_tls_certificate, saved_tls_certificate) == 0 + && Ustrcmp(state->exp_tls_privatekey, saved_tls_privatekey) == 0 + ) + { + DEBUG(D_tls) debug_printf("TLS SNI: cert and key unchanged\n"); + } + else + { + DEBUG(D_tls) debug_printf("TLS SNI: have a changed cert/key pair.\n"); + } + + if (!host) /* server */ + { + const uschar * clist = state->exp_tls_certificate; + const uschar * klist = state->exp_tls_privatekey; + const uschar * olist; + int csep = 0, ksep = 0, osep = 0, cnt = 0; + uschar * cfile, * kfile, * ofile; + +#ifndef DISABLE_OCSP + if (!expand_check(tls_ocsp_file, US"tls_ocsp_file", &ofile, errstr)) + return DEFER; + olist = ofile; +#endif + + while (cfile = string_nextinlist(&clist, &csep, NULL, 0)) + + if (!(kfile = string_nextinlist(&klist, &ksep, NULL, 0))) + return tls_error(US"cert/key setup: out of keys", NULL, host, errstr); + else if (0 < (rc = tls_add_certfile(state, host, cfile, kfile, errstr))) + return rc; + else + { + int gnutls_cert_index = -rc; + DEBUG(D_tls) debug_printf("TLS: cert/key %s registered\n", cfile); + + /* Set the OCSP stapling server info */ + +#ifndef DISABLE_OCSP + if (tls_ocsp_file) + if (gnutls_buggy_ocsp) + { + DEBUG(D_tls) + debug_printf("GnuTLS library is buggy for OCSP; avoiding\n"); + } + else if ((ofile = string_nextinlist(&olist, &osep, NULL, 0))) + { + /* Use the full callback method for stapling just to get + observability. More efficient would be to read the file once only, + if it never changed (due to SNI). Would need restart on file update, + or watch datestamp. */ + +# ifdef SUPPORT_SRV_OCSP_STACK + rc = gnutls_certificate_set_ocsp_status_request_function2( + state->x509_cred, gnutls_cert_index, + server_ocsp_stapling_cb, ofile); + + exim_gnutls_err_check(rc, + US"gnutls_certificate_set_ocsp_status_request_function2"); +# else + if (cnt++ > 0) + { + DEBUG(D_tls) + debug_printf("oops; multiple OCSP files not supported\n"); + break; + } + gnutls_certificate_set_ocsp_status_request_function( + state->x509_cred, server_ocsp_stapling_cb, ofile); +# endif + + DEBUG(D_tls) debug_printf("OCSP response file = %s\n", ofile); + } + else + DEBUG(D_tls) debug_printf("ran out of OCSP response files in list\n"); +#endif + } + } + else + { + if (0 < (rc = tls_add_certfile(state, host, + state->exp_tls_certificate, state->exp_tls_privatekey, errstr))) + return rc; + DEBUG(D_tls) debug_printf("TLS: cert/key registered\n"); + } + + } /* tls_certificate */ + + +/* Set the trusted CAs file if one is provided, and then add the CRL if one is +provided. Experiment shows that, if the certificate file is empty, an unhelpful +error message is provided. However, if we just refrain from setting anything up +in that case, certificate verification fails, which seems to be the correct +behaviour. */ + +if (state->tls_verify_certificates && *state->tls_verify_certificates) + { + if (!expand_check_tlsvar(tls_verify_certificates, errstr)) + return DEFER; +#ifndef SUPPORT_SYSDEFAULT_CABUNDLE + if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0) + state->exp_tls_verify_certificates = NULL; +#endif + if (state->tls_crl && *state->tls_crl) + if (!expand_check_tlsvar(tls_crl, errstr)) + return DEFER; + + if (!(state->exp_tls_verify_certificates && + *state->exp_tls_verify_certificates)) + { + DEBUG(D_tls) + debug_printf("TLS: tls_verify_certificates expanded empty, ignoring\n"); + /* With no tls_verify_certificates, we ignore tls_crl too */ + return OK; + } + } +else + { + DEBUG(D_tls) + debug_printf("TLS: tls_verify_certificates not set or empty, ignoring\n"); + return OK; + } + +#ifdef SUPPORT_SYSDEFAULT_CABUNDLE +if (Ustrcmp(state->exp_tls_verify_certificates, "system") == 0) + cert_count = gnutls_certificate_set_x509_system_trust(state->x509_cred); +else +#endif + { + if (Ustat(state->exp_tls_verify_certificates, &statbuf) < 0) + { + log_write(0, LOG_MAIN|LOG_PANIC, "could not stat %s " + "(tls_verify_certificates): %s", state->exp_tls_verify_certificates, + strerror(errno)); + return DEFER; + } + +#ifndef SUPPORT_CA_DIR + /* The test suite passes in /dev/null; we could check for that path explicitly, + but who knows if someone has some weird FIFO which always dumps some certs, or + other weirdness. The thing we really want to check is that it's not a + directory, since while OpenSSL supports that, GnuTLS does not. + So s/!S_ISREG/S_ISDIR/ and change some messaging ... */ + if (S_ISDIR(statbuf.st_mode)) + { + DEBUG(D_tls) + debug_printf("verify certificates path is a dir: \"%s\"\n", + state->exp_tls_verify_certificates); + log_write(0, LOG_MAIN|LOG_PANIC, + "tls_verify_certificates \"%s\" is a directory", + state->exp_tls_verify_certificates); + return DEFER; + } +#endif + + DEBUG(D_tls) debug_printf("verify certificates = %s size=" OFF_T_FMT "\n", + state->exp_tls_verify_certificates, statbuf.st_size); + + if (statbuf.st_size == 0) + { + DEBUG(D_tls) + debug_printf("cert file empty, no certs, no verification, ignoring any CRL\n"); + return OK; + } + + cert_count = + +#ifdef SUPPORT_CA_DIR + (statbuf.st_mode & S_IFMT) == S_IFDIR + ? + gnutls_certificate_set_x509_trust_dir(state->x509_cred, + CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM) + : +#endif + gnutls_certificate_set_x509_trust_file(state->x509_cred, + CS state->exp_tls_verify_certificates, GNUTLS_X509_FMT_PEM); + } + +if (cert_count < 0) + { + rc = cert_count; + exim_gnutls_err_check(rc, US"setting certificate trust"); + } +DEBUG(D_tls) debug_printf("Added %d certificate authorities.\n", cert_count); + +if (state->tls_crl && *state->tls_crl && + state->exp_tls_crl && *state->exp_tls_crl) + { + DEBUG(D_tls) debug_printf("loading CRL file = %s\n", state->exp_tls_crl); + cert_count = gnutls_certificate_set_x509_crl_file(state->x509_cred, + CS state->exp_tls_crl, GNUTLS_X509_FMT_PEM); + if (cert_count < 0) + { + rc = cert_count; + exim_gnutls_err_check(rc, US"gnutls_certificate_set_x509_crl_file"); + } + DEBUG(D_tls) debug_printf("Processed %d CRLs.\n", cert_count); + } + +return OK; +} + + + + +/************************************************* +* Set X.509 state variables * +*************************************************/ + +/* In GnuTLS, the registered cert/key are not replaced by a later +set of a cert/key, so for SNI support we need a whole new x509_cred +structure. Which means various other non-re-expanded pieces of state +need to be re-set in the new struct, so the setting logic is pulled +out to this. + +Arguments: + state exim_gnutls_state_st * + errstr error string pointer + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_set_remaining_x509(exim_gnutls_state_st *state, uschar ** errstr) +{ +int rc; +const host_item *host = state->host; /* macro should be reconsidered? */ + +/* Create D-H parameters, or read them from the cache file. This function does +its own SMTP error messaging. This only happens for the server, TLS D-H ignores +client-side params. */ + +if (!state->host) + { + if (!dh_server_params) + { + rc = init_server_dh(errstr); + if (rc != OK) return rc; + } + gnutls_certificate_set_dh_params(state->x509_cred, dh_server_params); + } + +/* Link the credentials to the session. */ + +rc = gnutls_credentials_set(state->session, GNUTLS_CRD_CERTIFICATE, state->x509_cred); +exim_gnutls_err_check(rc, US"gnutls_credentials_set"); + +return OK; +} + +/************************************************* +* Initialize for GnuTLS * +*************************************************/ + + +#ifndef DISABLE_OCSP + +static BOOL +tls_is_buggy_ocsp(void) +{ +const uschar * s; +uschar maj, mid, mic; + +s = CUS gnutls_check_version(NULL); +maj = atoi(CCS s); +if (maj == 3) + { + while (*s && *s != '.') s++; + mid = atoi(CCS ++s); + if (mid <= 2) + return TRUE; + else if (mid >= 5) + return FALSE; + else + { + while (*s && *s != '.') s++; + mic = atoi(CCS ++s); + return mic <= (mid == 3 ? 16 : 3); + } + } +return FALSE; +} + +#endif + + +/* Called from both server and client code. In the case of a server, errors +before actual TLS negotiation return DEFER. + +Arguments: + host connected host, if client; NULL if server + certificate certificate file + privatekey private key file + sni TLS SNI to send, sometimes when client; else NULL + cas CA certs file + crl CRL file + require_ciphers tls_require_ciphers setting + caller_state returned state-info structure + errstr error string pointer + +Returns: OK/DEFER/FAIL +*/ + +static int +tls_init( + const host_item *host, + const uschar *certificate, + const uschar *privatekey, + const uschar *sni, + const uschar *cas, + const uschar *crl, + const uschar *require_ciphers, + exim_gnutls_state_st **caller_state, + tls_support * tlsp, + uschar ** errstr) +{ +exim_gnutls_state_st *state; +int rc; +size_t sz; +const char *errpos; +uschar *p; +BOOL want_default_priorities; + +if (!exim_gnutls_base_init_done) + { + DEBUG(D_tls) debug_printf("GnuTLS global init required.\n"); + +#ifdef HAVE_GNUTLS_PKCS11 + /* By default, gnutls_global_init will init PKCS11 support in auto mode, + which loads modules from a config file, which sounds good and may be wanted + by some sysadmin, but also means in common configurations that GNOME keyring + environment variables are used and so breaks for users calling mailq. + To prevent this, we init PKCS11 first, which is the documented approach. */ + if (!gnutls_allow_auto_pkcs11) + { + rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); + exim_gnutls_err_check(rc, US"gnutls_pkcs11_init"); + } +#endif + + rc = gnutls_global_init(); + exim_gnutls_err_check(rc, US"gnutls_global_init"); + +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 + DEBUG(D_tls) + { + gnutls_global_set_log_function(exim_gnutls_logger_cb); + /* arbitrarily chosen level; bump up to 9 for more */ + gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); + } +#endif + +#ifndef DISABLE_OCSP + if (tls_ocsp_file && (gnutls_buggy_ocsp = tls_is_buggy_ocsp())) + log_write(0, LOG_MAIN, "OCSP unusable with this GnuTLS library version"); +#endif + + exim_gnutls_base_init_done = TRUE; + } + +if (host) + { + /* For client-side sessions we allocate a context. This lets us run + several in parallel. */ + int old_pool = store_pool; + store_pool = POOL_PERM; + state = store_get(sizeof(exim_gnutls_state_st)); + store_pool = old_pool; + + memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); + state->tlsp = tlsp; + DEBUG(D_tls) debug_printf("initialising GnuTLS client session\n"); + rc = gnutls_init(&state->session, GNUTLS_CLIENT); + } +else + { + state = &state_server; + memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); + state->tlsp = tlsp; + DEBUG(D_tls) debug_printf("initialising GnuTLS server session\n"); + rc = gnutls_init(&state->session, GNUTLS_SERVER); + } +exim_gnutls_err_check(rc, US"gnutls_init"); + +state->host = host; + +state->tls_certificate = certificate; +state->tls_privatekey = privatekey; +state->tls_require_ciphers = require_ciphers; +state->tls_sni = sni; +state->tls_verify_certificates = cas; +state->tls_crl = crl; + +/* This handles the variables that might get re-expanded after TLS SNI; +that's tls_certificate, tls_privatekey, tls_verify_certificates, tls_crl */ + +DEBUG(D_tls) + debug_printf("Expanding various TLS configuration options for session credentials.\n"); +if ((rc = tls_expand_session_files(state, errstr)) != OK) return rc; + +/* These are all other parts of the x509_cred handling, since SNI in GnuTLS +requires a new structure afterwards. */ + +if ((rc = tls_set_remaining_x509(state, errstr)) != OK) return rc; + +/* set SNI in client, only */ +if (host) + { + if (!expand_check(sni, US"tls_out_sni", &state->tlsp->sni, errstr)) + return DEFER; + if (state->tlsp->sni && *state->tlsp->sni) + { + DEBUG(D_tls) + debug_printf("Setting TLS client SNI to \"%s\"\n", state->tlsp->sni); + sz = Ustrlen(state->tlsp->sni); + rc = gnutls_server_name_set(state->session, + GNUTLS_NAME_DNS, state->tlsp->sni, sz); + exim_gnutls_err_check(rc, US"gnutls_server_name_set"); + } + } +else if (state->tls_sni) + DEBUG(D_tls) debug_printf("*** PROBABLY A BUG *** " \ + "have an SNI set for a server [%s]\n", state->tls_sni); + +/* This is the priority string support, +http://www.gnutls.org/manual/html_node/Priority-Strings.html +and replaces gnutls_require_kx, gnutls_require_mac & gnutls_require_protocols. +This was backwards incompatible, but means Exim no longer needs to track +all algorithms and provide string forms for them. */ + +want_default_priorities = TRUE; + +if (state->tls_require_ciphers && *state->tls_require_ciphers) + { + if (!expand_check_tlsvar(tls_require_ciphers, errstr)) + return DEFER; + if (state->exp_tls_require_ciphers && *state->exp_tls_require_ciphers) + { + DEBUG(D_tls) debug_printf("GnuTLS session cipher/priority \"%s\"\n", + state->exp_tls_require_ciphers); + + rc = gnutls_priority_init(&state->priority_cache, + CS state->exp_tls_require_ciphers, &errpos); + want_default_priorities = FALSE; + p = state->exp_tls_require_ciphers; + } + } +if (want_default_priorities) + { + DEBUG(D_tls) + debug_printf("GnuTLS using default session cipher/priority \"%s\"\n", + exim_default_gnutls_priority); + rc = gnutls_priority_init(&state->priority_cache, + exim_default_gnutls_priority, &errpos); + p = US exim_default_gnutls_priority; + } + +exim_gnutls_err_check(rc, string_sprintf( + "gnutls_priority_init(%s) failed at offset %ld, \"%.6s..\"", + p, errpos - CS p, errpos)); + +rc = gnutls_priority_set(state->session, state->priority_cache); +exim_gnutls_err_check(rc, US"gnutls_priority_set"); + +gnutls_db_set_cache_expiration(state->session, ssl_session_timeout); + +/* Reduce security in favour of increased compatibility, if the admin +decides to make that trade-off. */ +if (gnutls_compat_mode) + { +#if LIBGNUTLS_VERSION_NUMBER >= 0x020104 + DEBUG(D_tls) debug_printf("lowering GnuTLS security, compatibility mode\n"); + gnutls_session_enable_compatibility_mode(state->session); +#else + DEBUG(D_tls) debug_printf("Unable to set gnutls_compat_mode - GnuTLS version too old\n"); +#endif + } + +*caller_state = state; +return OK; +} + + + +/************************************************* +* Extract peer information * +*************************************************/ + +/* Called from both server and client code. +Only this is allowed to set state->peerdn and state->have_set_peerdn +and we use that to detect double-calls. + +NOTE: the state blocks last while the TLS connection is up, which is fine +for logging in the server side, but for the client side, we log after teardown +in src/deliver.c. While the session is up, we can twist about states and +repoint tls_* globals, but those variables used for logging or other variable +expansion that happens _after_ delivery need to have a longer life-time. + +So for those, we get the data from POOL_PERM; the re-invoke guard keeps us from +doing this more than once per generation of a state context. We set them in +the state context, and repoint tls_* to them. After the state goes away, the +tls_* copies of the pointers remain valid and client delivery logging is happy. + +tls_certificate_verified is a BOOL, so the tls_peerdn and tls_cipher issues +don't apply. + +Arguments: + state exim_gnutls_state_st * + errstr pointer to error string + +Returns: OK/DEFER/FAIL +*/ + +static int +peer_status(exim_gnutls_state_st *state, uschar ** errstr) +{ +uschar cipherbuf[256]; +const gnutls_datum_t *cert_list; +int old_pool, rc; +unsigned int cert_list_size = 0; +gnutls_protocol_t protocol; +gnutls_cipher_algorithm_t cipher; +gnutls_kx_algorithm_t kx; +gnutls_mac_algorithm_t mac; +gnutls_certificate_type_t ct; +gnutls_x509_crt_t crt; +uschar *p, *dn_buf; +size_t sz; + +if (state->have_set_peerdn) + return OK; +state->have_set_peerdn = TRUE; + +state->peerdn = NULL; + +/* tls_cipher */ +cipher = gnutls_cipher_get(state->session); +protocol = gnutls_protocol_get_version(state->session); +mac = gnutls_mac_get(state->session); +kx = gnutls_kx_get(state->session); + +string_format(cipherbuf, sizeof(cipherbuf), + "%s:%s:%d", + gnutls_protocol_get_name(protocol), + gnutls_cipher_suite_get_name(kx, cipher, mac), + (int) gnutls_cipher_get_key_size(cipher) * 8); + +/* I don't see a way that spaces could occur, in the current GnuTLS +code base, but it was a concern in the old code and perhaps older GnuTLS +releases did return "TLS 1.0"; play it safe, just in case. */ +for (p = cipherbuf; *p != '\0'; ++p) + if (isspace(*p)) + *p = '-'; +old_pool = store_pool; +store_pool = POOL_PERM; +state->ciphersuite = string_copy(cipherbuf); +store_pool = old_pool; +state->tlsp->cipher = state->ciphersuite; + +/* tls_peerdn */ +cert_list = gnutls_certificate_get_peers(state->session, &cert_list_size); + +if (cert_list == NULL || cert_list_size == 0) + { + DEBUG(D_tls) debug_printf("TLS: no certificate from peer (%p & %d)\n", + cert_list, cert_list_size); + if (state->verify_requirement >= VERIFY_REQUIRED) + return tls_error(US"certificate verification failed", + US"no certificate received from peer", state->host, errstr); + return OK; + } + +ct = gnutls_certificate_type_get(state->session); +if (ct != GNUTLS_CRT_X509) + { + const uschar *ctn = US gnutls_certificate_type_get_name(ct); + DEBUG(D_tls) + debug_printf("TLS: peer cert not X.509 but instead \"%s\"\n", ctn); + if (state->verify_requirement >= VERIFY_REQUIRED) + return tls_error(US"certificate verification not possible, unhandled type", + ctn, state->host, errstr); + return OK; + } + +#define exim_gnutls_peer_err(Label) \ + do { \ + if (rc != GNUTLS_E_SUCCESS) \ + { \ + DEBUG(D_tls) debug_printf("TLS: peer cert problem: %s: %s\n", \ + (Label), gnutls_strerror(rc)); \ + if (state->verify_requirement >= VERIFY_REQUIRED) \ + return tls_error((Label), US gnutls_strerror(rc), state->host, errstr); \ + return OK; \ + } \ + } while (0) + +rc = import_cert(&cert_list[0], &crt); +exim_gnutls_peer_err(US"cert 0"); + +state->tlsp->peercert = state->peercert = crt; + +sz = 0; +rc = gnutls_x509_crt_get_dn(crt, NULL, &sz); +if (rc != GNUTLS_E_SHORT_MEMORY_BUFFER) + { + exim_gnutls_peer_err(US"getting size for cert DN failed"); + return FAIL; /* should not happen */ + } +dn_buf = store_get_perm(sz); +rc = gnutls_x509_crt_get_dn(crt, CS dn_buf, &sz); +exim_gnutls_peer_err(US"failed to extract certificate DN [gnutls_x509_crt_get_dn(cert 0)]"); + +state->peerdn = dn_buf; + +return OK; +#undef exim_gnutls_peer_err +} + + + + +/************************************************* +* Verify peer certificate * +*************************************************/ + +/* Called from both server and client code. +*Should* be using a callback registered with +gnutls_certificate_set_verify_function() to fail the handshake if we dislike +the peer information, but that's too new for some OSes. + +Arguments: + state exim_gnutls_state_st * + errstr where to put an error message + +Returns: + FALSE if the session should be rejected + TRUE if the cert is okay or we just don't care +*/ + +static BOOL +verify_certificate(exim_gnutls_state_st * state, uschar ** errstr) +{ +int rc; +uint verify; + +if (state->verify_requirement == VERIFY_NONE) + return TRUE; + +DEBUG(D_tls) debug_printf("TLS: checking peer certificate\n"); +*errstr = NULL; + +if ((rc = peer_status(state, errstr)) != OK) + { + verify = GNUTLS_CERT_INVALID; + *errstr = US"certificate not supplied"; + } +else + + { +#ifdef SUPPORT_DANE + if (state->verify_requirement == VERIFY_DANE && state->host) + { + /* Using dane_verify_session_crt() would be easy, as it does it all for us + including talking to a DNS resolver. But we want to do that bit ourselves + as the testsuite intercepts and fakes its own DNS environment. */ + + dane_state_t s; + dane_query_t r; + uint lsize; + const gnutls_datum_t * certlist = + gnutls_certificate_get_peers(state->session, &lsize); + int usage = tls_out.tlsa_usage; + +# ifdef GNUTLS_BROKEN_DANE_VALIDATION + /* Split the TLSA records into two sets, TA and EE selectors. Run the + dane-verification separately so that we know which selector verified; + then we know whether to do name-verification (needed for TA but not EE). */ + + if (usage == ((1<<DANESSL_USAGE_DANE_TA) | (1<<DANESSL_USAGE_DANE_EE))) + { /* a mixed-usage bundle */ + int i, j, nrec; + const char ** dd; + int * ddl; + + for(nrec = 0; state->dane_data_len[nrec]; ) nrec++; + nrec++; + + dd = store_get(nrec * sizeof(uschar *)); + ddl = store_get(nrec * sizeof(int)); + nrec--; + + if ((rc = dane_state_init(&s, 0))) + goto tlsa_prob; + + for (usage = DANESSL_USAGE_DANE_EE; + usage >= DANESSL_USAGE_DANE_TA; usage--) + { /* take records with this usage */ + for (j = i = 0; i < nrec; i++) + if (state->dane_data[i][0] == usage) + { + dd[j] = state->dane_data[i]; + ddl[j++] = state->dane_data_len[i]; + } + if (j) + { + dd[j] = NULL; + ddl[j] = 0; + + if ((rc = dane_raw_tlsa(s, &r, (char * const *)dd, ddl, 1, 0))) + goto tlsa_prob; + + if ((rc = dane_verify_crt_raw(s, certlist, lsize, + gnutls_certificate_type_get(state->session), + r, 0, + usage == DANESSL_USAGE_DANE_EE + ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0, + &verify))) + { + DEBUG(D_tls) + debug_printf("TLSA record problem: %s\n", dane_strerror(rc)); + } + else if (verify == 0) /* verification passed */ + { + usage = 1 << usage; + break; + } + } + } + + if (rc) goto tlsa_prob; + } + else +# endif + { + if ( (rc = dane_state_init(&s, 0)) + || (rc = dane_raw_tlsa(s, &r, state->dane_data, state->dane_data_len, + 1, 0)) + || (rc = dane_verify_crt_raw(s, certlist, lsize, + gnutls_certificate_type_get(state->session), + r, 0, +# ifdef GNUTLS_BROKEN_DANE_VALIDATION + usage == (1 << DANESSL_USAGE_DANE_EE) + ? DANE_VFLAG_ONLY_CHECK_EE_USAGE : 0, +# else + 0, +# endif + &verify)) + ) + goto tlsa_prob; + } + + if (verify != 0) /* verification failed */ + { + gnutls_datum_t str; + (void) dane_verification_status_print(verify, &str, 0); + *errstr = US str.data; /* don't bother to free */ + goto badcert; + } + +# ifdef GNUTLS_BROKEN_DANE_VALIDATION + /* If a TA-mode TLSA record was used for verification we must additionally + verify the cert name (but not the CA chain). For EE-mode, skip it. */ + + if (usage & (1 << DANESSL_USAGE_DANE_EE)) +# endif + { + state->peer_dane_verified = state->peer_cert_verified = TRUE; + goto goodcert; + } +# ifdef GNUTLS_BROKEN_DANE_VALIDATION + /* Assume that the name on the A-record is the one that should be matching + the cert. An alternate view is that the domain part of the email address + is also permissible. */ + + if (gnutls_x509_crt_check_hostname(state->tlsp->peercert, + CS state->host->name)) + { + state->peer_dane_verified = state->peer_cert_verified = TRUE; + goto goodcert; + } +# endif + } +#endif /*SUPPORT_DANE*/ + + rc = gnutls_certificate_verify_peers2(state->session, &verify); + } + +/* Handle the result of verification. INVALID is set if any others are. */ + +if (rc < 0 || verify & (GNUTLS_CERT_INVALID|GNUTLS_CERT_REVOKED)) + { + state->peer_cert_verified = FALSE; + if (!*errstr) + { +#ifdef GNUTLS_CERT_VFY_STATUS_PRINT + DEBUG(D_tls) + { + gnutls_datum_t txt; + + if (gnutls_certificate_verification_status_print(verify, + gnutls_certificate_type_get(state->session), &txt, 0) + == GNUTLS_E_SUCCESS) + { + debug_printf("%s\n", txt.data); + gnutls_free(txt.data); + } + } +#endif + *errstr = verify & GNUTLS_CERT_REVOKED + ? US"certificate revoked" : US"certificate invalid"; + } + + DEBUG(D_tls) + debug_printf("TLS certificate verification failed (%s): peerdn=\"%s\"\n", + *errstr, state->peerdn ? state->peerdn : US"<unset>"); + + if (state->verify_requirement >= VERIFY_REQUIRED) + goto badcert; + DEBUG(D_tls) + debug_printf("TLS verify failure overridden (host in tls_try_verify_hosts)\n"); + } + +else + { + /* Client side, check the server's certificate name versus the name on the + A-record for the connection we made. What to do for server side - what name + to use for client? We document that there is no such checking for server + side. */ + + if ( state->exp_tls_verify_cert_hostnames + && !gnutls_x509_crt_check_hostname(state->tlsp->peercert, + CS state->exp_tls_verify_cert_hostnames) + ) + { + DEBUG(D_tls) + debug_printf("TLS certificate verification failed: cert name mismatch\n"); + if (state->verify_requirement >= VERIFY_REQUIRED) + goto badcert; + return TRUE; + } + + state->peer_cert_verified = TRUE; + DEBUG(D_tls) debug_printf("TLS certificate verified: peerdn=\"%s\"\n", + state->peerdn ? state->peerdn : US"<unset>"); + } + +goodcert: + state->tlsp->peerdn = state->peerdn; + return TRUE; + +#ifdef SUPPORT_DANE +tlsa_prob: + *errstr = string_sprintf("TLSA record problem: %s", + rc == DANE_E_REQUESTED_DATA_NOT_AVAILABLE ? "none usable" : dane_strerror(rc)); +#endif + +badcert: + gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_BAD_CERTIFICATE); + return FALSE; +} + + + + +/* ------------------------------------------------------------------------ */ +/* Callbacks */ + +/* Logging function which can be registered with + * gnutls_global_set_log_function() + * gnutls_global_set_log_level() 0..9 + */ +#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 +static void +exim_gnutls_logger_cb(int level, const char *message) +{ + size_t len = strlen(message); + if (len < 1) + { + DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); + return; + } + DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, + message[len-1] == '\n' ? "" : "\n"); +} +#endif + + +/* Called after client hello, should handle SNI work. +This will always set tls_sni (state->received_sni) if available, +and may trigger presenting different certificates, +if state->trigger_sni_changes is TRUE. + +Should be registered with + gnutls_handshake_set_post_client_hello_function() + +"This callback must return 0 on success or a gnutls error code to terminate the +handshake.". + +For inability to get SNI information, we return 0. +We only return non-zero if re-setup failed. +Only used for server-side TLS. +*/ + +static int +exim_sni_handling_cb(gnutls_session_t session) +{ +char sni_name[MAX_HOST_LEN]; +size_t data_len = MAX_HOST_LEN; +exim_gnutls_state_st *state = &state_server; +unsigned int sni_type; +int rc, old_pool; +uschar * dummy_errstr; + +rc = gnutls_server_name_get(session, sni_name, &data_len, &sni_type, 0); +if (rc != GNUTLS_E_SUCCESS) + { + DEBUG(D_tls) { + if (rc == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) + debug_printf("TLS: no SNI presented in handshake.\n"); + else + debug_printf("TLS failure: gnutls_server_name_get(): %s [%d]\n", + gnutls_strerror(rc), rc); + } + return 0; + } + +if (sni_type != GNUTLS_NAME_DNS) + { + DEBUG(D_tls) debug_printf("TLS: ignoring SNI of unhandled type %u\n", sni_type); + return 0; + } + +/* We now have a UTF-8 string in sni_name */ +old_pool = store_pool; +store_pool = POOL_PERM; +state->received_sni = string_copyn(US sni_name, data_len); +store_pool = old_pool; + +/* We set this one now so that variable expansions below will work */ +state->tlsp->sni = state->received_sni; + +DEBUG(D_tls) debug_printf("Received TLS SNI \"%s\"%s\n", sni_name, + state->trigger_sni_changes ? "" : " (unused for certificate selection)"); + +if (!state->trigger_sni_changes) + return 0; + +if ((rc = tls_expand_session_files(state, &dummy_errstr)) != OK) + { + /* If the setup of certs/etc failed before handshake, TLS would not have + been offered. The best we can do now is abort. */ + return GNUTLS_E_APPLICATION_ERROR_MIN; + } + +rc = tls_set_remaining_x509(state, &dummy_errstr); +if (rc != OK) return GNUTLS_E_APPLICATION_ERROR_MIN; + +return 0; +} + + + +#ifndef DISABLE_OCSP + +static int +server_ocsp_stapling_cb(gnutls_session_t session, void * ptr, + gnutls_datum_t * ocsp_response) +{ +int ret; +DEBUG(D_tls) debug_printf("OCSP stapling callback: %s\n", US ptr); + +if ((ret = gnutls_load_file(ptr, ocsp_response)) < 0) + { + DEBUG(D_tls) debug_printf("Failed to load ocsp stapling file %s\n", + CS ptr); + tls_in.ocsp = OCSP_NOT_RESP; + return GNUTLS_E_NO_CERTIFICATE_STATUS; + } + +tls_in.ocsp = OCSP_VFY_NOT_TRIED; +return 0; +} + +#endif + + +#ifndef DISABLE_EVENT +/* +We use this callback to get observability and detail-level control +for an exim TLS connection (either direction), raising a tls:cert event +for each cert in the chain presented by the peer. Any event +can deny verification. + +Return 0 for the handshake to continue or non-zero to terminate. +*/ + +static int +verify_cb(gnutls_session_t session) +{ +const gnutls_datum_t * cert_list; +unsigned int cert_list_size = 0; +gnutls_x509_crt_t crt; +int rc; +uschar * yield; +exim_gnutls_state_st * state = gnutls_session_get_ptr(session); + +if ((cert_list = gnutls_certificate_get_peers(session, &cert_list_size))) + while (cert_list_size--) + { + if ((rc = import_cert(&cert_list[cert_list_size], &crt)) != GNUTLS_E_SUCCESS) + { + DEBUG(D_tls) debug_printf("TLS: peer cert problem: depth %d: %s\n", + cert_list_size, gnutls_strerror(rc)); + break; + } + + state->tlsp->peercert = crt; + if ((yield = event_raise(state->event_action, + US"tls:cert", string_sprintf("%d", cert_list_size)))) + { + log_write(0, LOG_MAIN, + "SSL verify denied by event-action: depth=%d: %s", + cert_list_size, yield); + return 1; /* reject */ + } + state->tlsp->peercert = NULL; + } + +return 0; +} + +#endif + + + +/* ------------------------------------------------------------------------ */ +/* Exported functions */ + + + + +/************************************************* +* 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 list of allowed ciphers or NULL + errstr pointer to error string + +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; +exim_gnutls_state_st * state = NULL; + +/* Check for previous activation */ +if (tls_in.active.sock >= 0) + { + tls_error(US"STARTTLS received after TLS started", US "", NULL, errstr); + smtp_printf("554 Already in TLS\r\n", FALSE); + return FAIL; + } + +/* Initialize the library. If it fails, it will already have logged the error +and sent an SMTP response. */ + +DEBUG(D_tls) debug_printf("initialising GnuTLS as a server\n"); + +if ((rc = tls_init(NULL, tls_certificate, tls_privatekey, + NULL, tls_verify_certificates, tls_crl, + require_ciphers, &state, &tls_in, errstr)) != OK) return rc; + +/* If this is a host for which certificate verification is mandatory or +optional, set up appropriately. */ + +if (verify_check_host(&tls_verify_hosts) == OK) + { + DEBUG(D_tls) + debug_printf("TLS: a client certificate will be required.\n"); + state->verify_requirement = VERIFY_REQUIRED; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); + } +else if (verify_check_host(&tls_try_verify_hosts) == OK) + { + DEBUG(D_tls) + debug_printf("TLS: a client certificate will be requested but not required.\n"); + state->verify_requirement = VERIFY_OPTIONAL; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); + } +else + { + DEBUG(D_tls) + debug_printf("TLS: a client certificate will not be requested.\n"); + state->verify_requirement = VERIFY_NONE; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); + } + +#ifndef DISABLE_EVENT +if (event_action) + { + state->event_action = event_action; + gnutls_session_set_ptr(state->session, state); + gnutls_certificate_set_verify_function(state->x509_cred, verify_cb); + } +#endif + +/* Register SNI handling; always, even if not in tls_certificate, so that the +expansion variable $tls_sni is always available. */ + +gnutls_handshake_set_post_client_hello_function(state->session, + exim_sni_handling_cb); + +/* 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. */ + +if (!state->tlsp->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 GnuTLS library doesn't. +From 3.1.0 there is gnutls_handshake_set_timeout() - but it requires you +to set (and clear down afterwards) up a pull-timeout callback function that does +a select, so we're no better off unless avoiding signals becomes an issue. */ + +gnutls_transport_set_ptr2(state->session, + (gnutls_transport_ptr_t)(long) fileno(smtp_in), + (gnutls_transport_ptr_t)(long) fileno(smtp_out)); +state->fd_in = fileno(smtp_in); +state->fd_out = fileno(smtp_out); + +sigalrm_seen = FALSE; +if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout); +do + rc = gnutls_handshake(state->session); +while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen); +ALARM_CLR(0); + +if (rc != GNUTLS_E_SUCCESS) + { + /* It seems that, except in the case of a timeout, we have to close the + connection right here; otherwise if the other end is running OpenSSL it hangs + until the server times out. */ + + if (sigalrm_seen) + { + tls_error(US"gnutls_handshake", US"timed out", NULL, errstr); + gnutls_db_remove_session(state->session); + } + else + { + tls_error(US"gnutls_handshake", US gnutls_strerror(rc), NULL, errstr); + (void) gnutls_alert_send_appropriate(state->session, rc); + gnutls_deinit(state->session); + gnutls_certificate_free_credentials(state->x509_cred); + millisleep(500); + shutdown(state->fd_out, SHUT_WR); + for (rc = 1024; fgetc(smtp_in) != EOF && rc > 0; ) rc--; /* drain skt */ + (void)fclose(smtp_out); + (void)fclose(smtp_in); + smtp_out = smtp_in = NULL; + } + + return FAIL; + } + +DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); + +/* Verify after the fact */ + +if (!verify_certificate(state, errstr)) + { + if (state->verify_requirement != VERIFY_OPTIONAL) + { + (void) tls_error(US"certificate verification failed", *errstr, NULL, errstr); + return FAIL; + } + DEBUG(D_tls) + debug_printf("TLS: continuing on only because verification was optional, after: %s\n", + *errstr); + } + +/* Figure out peer DN, and if authenticated, etc. */ + +if ((rc = peer_status(state, NULL)) != OK) return rc; + +/* Sets various Exim expansion variables; always safe within server */ + +extract_exim_vars_from_tls_state(state); + +/* TLS has been set up. Adjust the input functions to read via TLS, +and initialize appropriately. */ + +state->xfer_buffer = store_malloc(ssl_xfer_buffer_size); + +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; + +return OK; +} + + + + +static void +tls_client_setup_hostname_checks(host_item * host, exim_gnutls_state_st * state, + smtp_transport_options_block * ob) +{ +if (verify_check_given_host(CUSS &ob->tls_verify_cert_hostnames, host) == OK) + { + state->exp_tls_verify_cert_hostnames = +#ifdef SUPPORT_I18N + string_domain_utf8_to_alabel(host->name, NULL); +#else + host->name; +#endif + DEBUG(D_tls) + debug_printf("TLS: server cert verification includes hostname: \"%s\".\n", + state->exp_tls_verify_cert_hostnames); + } +} + + + + +#ifdef SUPPORT_DANE +/* Given our list of RRs from the TLSA lookup, build a lookup block in +GnuTLS-DANE's preferred format. Hang it on the state str for later +use in DANE verification. + +We point at the dnsa data not copy it, so it must remain valid until +after verification is done.*/ + +static BOOL +dane_tlsa_load(exim_gnutls_state_st * state, dns_answer * dnsa) +{ +dns_record * rr; +dns_scan dnss; +int i; +const char ** dane_data; +int * dane_data_len; + +for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS), i = 1; + rr; + rr = dns_next_rr(dnsa, &dnss, RESET_NEXT) + ) if (rr->type == T_TLSA) i++; + +dane_data = store_get(i * sizeof(uschar *)); +dane_data_len = store_get(i * sizeof(int)); + +for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS), i = 0; + 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 = p[0], sel = p[1], type = p[2]; + + DEBUG(D_tls) + debug_printf("TLSA: %d %d %d size %d\n", usage, sel, type, rr->size); + + if ( (usage != DANESSL_USAGE_DANE_TA && usage != DANESSL_USAGE_DANE_EE) + || (sel != 0 && sel != 1) + ) + continue; + switch(type) + { + case 0: /* Full: cannot check at present */ + break; + case 1: if (rr->size != 3 + 256/8) continue; /* sha2-256 */ + break; + case 2: if (rr->size != 3 + 512/8) continue; /* sha2-512 */ + break; + default: continue; + } + + tls_out.tlsa_usage |= 1<<usage; + dane_data[i] = CS p; + dane_data_len[i++] = rr->size; + } + +if (!i) return FALSE; + +dane_data[i] = NULL; +dane_data_len[i] = 0; + +state->dane_data = (char * const *)dane_data; +state->dane_data_len = dane_data_len; +return TRUE; +} +#endif + + + +/************************************************* +* Start a TLS session in a client * +*************************************************/ + +/* Called from the smtp transport after STARTTLS has been accepted. + +Arguments: + fd the fd of the connection + host connected host (for messages and option-tests) + addr the first address (not used) + tb transport (always smtp) + tlsa_dnsa non-NULL, either request or require dane for this host, and + a TLSA record found. Therefore, dane verify required. + Which implies cert must be requested and supplied, dane + verify must pass, and cert verify irrelevant (incl. + hostnames), and (caller handled) require_tls + tlsp record details of channel configuration + 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 ARG_UNUSED, + 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; +int rc; +exim_gnutls_state_st * state = NULL; +uschar *cipher_list = NULL; + +#ifndef DISABLE_OCSP +BOOL require_ocsp = + verify_check_given_host(CUSS &ob->hosts_require_ocsp, host) == OK; +BOOL request_ocsp = require_ocsp ? TRUE + : verify_check_given_host(CUSS &ob->hosts_request_ocsp, host) == OK; +#endif + +DEBUG(D_tls) debug_printf("initialising GnuTLS as a client on fd %d\n", fd); + +#ifdef SUPPORT_DANE +if (tlsa_dnsa && ob->dane_require_tls_ciphers) + { + /* not using expand_check_tlsvar because not yet in state */ + if (!expand_check(ob->dane_require_tls_ciphers, US"dane_require_tls_ciphers", + &cipher_list, errstr)) + return NULL; + cipher_list = cipher_list && *cipher_list + ? ob->dane_require_tls_ciphers : ob->tls_require_ciphers; + } +#endif + +if (!cipher_list) + cipher_list = ob->tls_require_ciphers; + +if (tls_init(host, ob->tls_certificate, ob->tls_privatekey, + ob->tls_sni, ob->tls_verify_certificates, ob->tls_crl, + cipher_list, &state, tlsp, errstr) != OK) + return NULL; + + { + int dh_min_bits = ob->tls_dh_min_bits; + if (dh_min_bits < EXIM_CLIENT_DH_MIN_MIN_BITS) + { + DEBUG(D_tls) + debug_printf("WARNING: tls_dh_min_bits far too low," + " clamping %d up to %d\n", + dh_min_bits, EXIM_CLIENT_DH_MIN_MIN_BITS); + dh_min_bits = EXIM_CLIENT_DH_MIN_MIN_BITS; + } + + DEBUG(D_tls) debug_printf("Setting D-H prime minimum" + " acceptable bits to %d\n", + dh_min_bits); + gnutls_dh_set_prime_bits(state->session, dh_min_bits); + } + +/* Stick to the old behaviour for compatibility if tls_verify_certificates is +set but both tls_verify_hosts and tls_try_verify_hosts are unset. Check only +the specified host patterns if one of them is defined */ + +#ifdef SUPPORT_DANE +if (tlsa_dnsa && dane_tlsa_load(state, tlsa_dnsa)) + { + DEBUG(D_tls) + debug_printf("TLS: server certificate DANE required.\n"); + state->verify_requirement = VERIFY_DANE; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); + } +else +#endif + if ( ( state->exp_tls_verify_certificates + && !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 + ) + { + tls_client_setup_hostname_checks(host, state, ob); + DEBUG(D_tls) + debug_printf("TLS: server certificate verification required.\n"); + state->verify_requirement = VERIFY_REQUIRED; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUIRE); + } +else if (verify_check_given_host(CUSS &ob->tls_try_verify_hosts, host) == OK) + { + tls_client_setup_hostname_checks(host, state, ob); + DEBUG(D_tls) + debug_printf("TLS: server certificate verification optional.\n"); + state->verify_requirement = VERIFY_OPTIONAL; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_REQUEST); + } +else + { + DEBUG(D_tls) + debug_printf("TLS: server certificate verification not required.\n"); + state->verify_requirement = VERIFY_NONE; + gnutls_certificate_server_set_request(state->session, GNUTLS_CERT_IGNORE); + } + +#ifndef DISABLE_OCSP + /* supported since GnuTLS 3.1.3 */ +if (request_ocsp) + { + DEBUG(D_tls) debug_printf("TLS: will request OCSP stapling\n"); + if ((rc = gnutls_ocsp_status_request_enable_client(state->session, + NULL, 0, NULL)) != OK) + { + tls_error(US"cert-status-req", US gnutls_strerror(rc), state->host, errstr); + return NULL; + } + tlsp->ocsp = OCSP_NOT_RESP; + } +#endif + +#ifndef DISABLE_EVENT +if (tb && tb->event_action) + { + state->event_action = tb->event_action; + gnutls_session_set_ptr(state->session, state); + gnutls_certificate_set_verify_function(state->x509_cred, verify_cb); + } +#endif + +gnutls_transport_set_ptr(state->session, (gnutls_transport_ptr_t)(long) fd); +state->fd_in = fd; +state->fd_out = fd; + +DEBUG(D_tls) debug_printf("about to gnutls_handshake\n"); +/* There doesn't seem to be a built-in timeout on connection. */ + +sigalrm_seen = FALSE; +ALARM(ob->command_timeout); +do + rc = gnutls_handshake(state->session); +while (rc == GNUTLS_E_AGAIN || rc == GNUTLS_E_INTERRUPTED && !sigalrm_seen); +ALARM_CLR(0); + +if (rc != GNUTLS_E_SUCCESS) + { + if (sigalrm_seen) + { + gnutls_alert_send(state->session, GNUTLS_AL_FATAL, GNUTLS_A_USER_CANCELED); + tls_error(US"gnutls_handshake", US"timed out", state->host, errstr); + } + else + tls_error(US"gnutls_handshake", US gnutls_strerror(rc), state->host, errstr); + return NULL; + } + +DEBUG(D_tls) debug_printf("gnutls_handshake was successful\n"); + +/* Verify late */ + +if (!verify_certificate(state, errstr)) + { + tls_error(US"certificate verification failed", *errstr, state->host, errstr); + return NULL; + } + +#ifndef DISABLE_OCSP +if (require_ocsp) + { + DEBUG(D_tls) + { + gnutls_datum_t stapling; + gnutls_ocsp_resp_t resp; + gnutls_datum_t printed; + if ( (rc= gnutls_ocsp_status_request_get(state->session, &stapling)) == 0 + && (rc= gnutls_ocsp_resp_init(&resp)) == 0 + && (rc= gnutls_ocsp_resp_import(resp, &stapling)) == 0 + && (rc= gnutls_ocsp_resp_print(resp, GNUTLS_OCSP_PRINT_FULL, &printed)) == 0 + ) + { + debug_printf("%.4096s", printed.data); + gnutls_free(printed.data); + } + else + (void) tls_error(US"ocsp decode", US gnutls_strerror(rc), state->host, errstr); + } + + if (gnutls_ocsp_status_request_is_checked(state->session, 0) == 0) + { + tlsp->ocsp = OCSP_FAILED; + tls_error(US"certificate status check failed", NULL, state->host, errstr); + return NULL; + } + DEBUG(D_tls) debug_printf("Passed OCSP checking\n"); + tlsp->ocsp = OCSP_VFIED; + } +#endif + +/* Figure out peer DN, and if authenticated, etc. */ + +if (peer_status(state, errstr) != OK) + return NULL; + +/* Sets various Exim expansion variables; may need to adjust for ACL callouts */ + +extract_exim_vars_from_tls_state(state); + +return state; +} + + + + +/************************************************* +* 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 TLS session in the parent process). + +Arguments: + ct_ctx client 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 +*/ + +void +tls_close(void * ct_ctx, int shutdown) +{ +exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server; + +if (!state->tlsp || state->tlsp->active.sock < 0) return; /* TLS was not active */ + +if (shutdown) + { + DEBUG(D_tls) debug_printf("tls_close(): shutting down TLS%s\n", + shutdown > 1 ? " (with response-wait)" : ""); + + ALARM(2); + gnutls_bye(state->session, shutdown > 1 ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR); + ALARM_CLR(0); + } + +gnutls_deinit(state->session); +gnutls_certificate_free_credentials(state->x509_cred); + + +state->tlsp->active.sock = -1; +state->tlsp->active.tls_ctx = NULL; +if (state->xfer_buffer) store_free(state->xfer_buffer); +memcpy(state, &exim_gnutls_state_init, sizeof(exim_gnutls_state_init)); +} + + + + +static BOOL +tls_refill(unsigned lim) +{ +exim_gnutls_state_st * state = &state_server; +ssize_t inbytes; + +DEBUG(D_tls) debug_printf("Calling gnutls_record_recv(%p, %p, %u)\n", + state->session, state->xfer_buffer, ssl_xfer_buffer_size); + +sigalrm_seen = FALSE; +if (smtp_receive_timeout > 0) ALARM(smtp_receive_timeout); + +do + inbytes = gnutls_record_recv(state->session, state->xfer_buffer, + MIN(ssl_xfer_buffer_size, lim)); +while (inbytes == GNUTLS_E_AGAIN); + +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(); + +/* Timeouts do not get this far. A zero-byte return appears to mean that the +TLS session has been closed down, not that the socket itself has been closed +down. Revert to non-TLS handling. */ + +if (sigalrm_seen) + { + DEBUG(D_tls) debug_printf("Got tls read timeout\n"); + state->xfer_error = TRUE; + return FALSE; + } + +else if (inbytes == 0) + { + DEBUG(D_tls) debug_printf("Got TLS_EOF\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; + + gnutls_deinit(state->session); + gnutls_certificate_free_credentials(state->x509_cred); + + state->session = NULL; + state->tlsp->active.sock = -1; + state->tlsp->active.tls_ctx = NULL; + state->tlsp->bits = 0; + state->tlsp->certificate_verified = FALSE; + tls_channelbinding_b64 = NULL; + state->tlsp->cipher = NULL; + state->tlsp->peercert = NULL; + state->tlsp->peerdn = NULL; + + return FALSE; + } + +/* Handle genuine errors */ + +else if (inbytes < 0) + { + DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__); + record_io_error(state, (int) inbytes, US"recv", NULL); + state->xfer_error = TRUE; + return FALSE; + } +#ifndef DISABLE_DKIM +dkim_exim_verify_feed(state->xfer_buffer, inbytes); +#endif +state->xfer_buffer_hwm = (int) inbytes; +state->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 GnuTLS reading function. +Only used by the server-side TLS. + +This feeds DKIM and should be used for all message-body reads. + +Arguments: lim Maximum amount to read/buffer +Returns: the next character or EOF +*/ + +int +tls_getc(unsigned lim) +{ +exim_gnutls_state_st * state = &state_server; + +if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm) + if (!tls_refill(lim)) + return state->xfer_error ? EOF : smtp_getc(lim); + +/* Something in the buffer; return next uschar */ + +return state->xfer_buffer[state->xfer_buffer_lwm++]; +} + +uschar * +tls_getbuf(unsigned * len) +{ +exim_gnutls_state_st * state = &state_server; +unsigned size; +uschar * buf; + +if (state->xfer_buffer_lwm >= state->xfer_buffer_hwm) + if (!tls_refill(*len)) + { + if (!state->xfer_error) return smtp_getbuf(len); + *len = 0; + return NULL; + } + +if ((size = state->xfer_buffer_hwm - state->xfer_buffer_lwm) > *len) + size = *len; +buf = &state->xfer_buffer[state->xfer_buffer_lwm]; +state->xfer_buffer_lwm += size; +*len = size; +return buf; +} + + +void +tls_get_cache() +{ +#ifndef DISABLE_DKIM +exim_gnutls_state_st * state = &state_server; +int n = state->xfer_buffer_hwm - state->xfer_buffer_lwm; +if (n > 0) + dkim_exim_verify_feed(state->xfer_buffer+state->xfer_buffer_lwm, n); +#endif +} + + +BOOL +tls_could_read(void) +{ +return state_server.xfer_buffer_lwm < state_server.xfer_buffer_hwm + || gnutls_record_check_pending(state_server.session) > 0; +} + + + + +/************************************************* +* Read bytes from TLS channel * +*************************************************/ + +/* This does not feed DKIM, so if the caller uses this for reading message body, +then the caller must feed DKIM. + +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 +*/ + +int +tls_read(void * ct_ctx, uschar *buff, size_t len) +{ +exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server; +ssize_t inbytes; + +if (len > INT_MAX) + len = INT_MAX; + +if (state->xfer_buffer_lwm < state->xfer_buffer_hwm) + DEBUG(D_tls) + debug_printf("*** PROBABLY A BUG *** " \ + "tls_read() called with data in the tls_getc() buffer, %d ignored\n", + state->xfer_buffer_hwm - state->xfer_buffer_lwm); + +DEBUG(D_tls) + debug_printf("Calling gnutls_record_recv(%p, %p, " SIZE_T_FMT ")\n", + state->session, buff, len); + +do + inbytes = gnutls_record_recv(state->session, buff, len); +while (inbytes == GNUTLS_E_AGAIN); + +if (inbytes > 0) return inbytes; +if (inbytes == 0) + { + DEBUG(D_tls) debug_printf("Got TLS_EOF\n"); + } +else + { + DEBUG(D_tls) debug_printf("%s: err from gnutls_record_recv(\n", __FUNCTION__); + record_io_error(state, (int)inbytes, US"recv", NULL); + } + +return -1; +} + + + + +/************************************************* +* 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 more data expected soon + +Returns: the number of bytes after a successful write, + -1 after a failed write +*/ + +int +tls_write(void * ct_ctx, const uschar * buff, size_t len, BOOL more) +{ +ssize_t outbytes; +size_t left = len; +exim_gnutls_state_st * state = ct_ctx ? ct_ctx : &state_server; +#ifdef SUPPORT_CORK +static BOOL corked = FALSE; + +if (more && !corked) gnutls_record_cork(state->session); +#endif + +DEBUG(D_tls) debug_printf("%s(%p, " SIZE_T_FMT "%s)\n", __FUNCTION__, + buff, left, more ? ", more" : ""); + +while (left > 0) + { + DEBUG(D_tls) debug_printf("gnutls_record_send(SSL, %p, " SIZE_T_FMT ")\n", + buff, left); + + do + outbytes = gnutls_record_send(state->session, buff, left); + while (outbytes == GNUTLS_E_AGAIN); + + DEBUG(D_tls) debug_printf("outbytes=" SSIZE_T_FMT "\n", outbytes); + if (outbytes < 0) + { + DEBUG(D_tls) debug_printf("%s: gnutls_record_send err\n", __FUNCTION__); + record_io_error(state, outbytes, US"send", NULL); + return -1; + } + if (outbytes == 0) + { + record_io_error(state, 0, US"send", US"TLS channel closed on write"); + return -1; + } + + left -= outbytes; + buff += outbytes; + } + +if (len > INT_MAX) + { + DEBUG(D_tls) + debug_printf("Whoops! Wrote more bytes (" SIZE_T_FMT ") than INT_MAX\n", + len); + len = INT_MAX; + } + +#ifdef SUPPORT_CORK +if (more != corked) + { + if (!more) (void) gnutls_record_uncork(state->session, 0); + corked = more; + } +#endif + +return (int) len; +} + + + + +/************************************************* +* 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] +*/ + +#ifdef HAVE_GNUTLS_RND +int +vaguely_random_number(int max) +{ +unsigned int r; +int i, needed_len; +uschar *p; +uschar smallbuf[sizeof(r)]; + +if (max <= 1) + return 0; + +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; + +i = gnutls_rnd(GNUTLS_RND_NONCE, smallbuf, needed_len); +if (i < 0) + { + DEBUG(D_all) debug_printf("gnutls_rnd() failed, 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; +} +#else /* HAVE_GNUTLS_RND */ +int +vaguely_random_number(int max) +{ + return vaguely_random_number_fallback(max); +} +#endif /* HAVE_GNUTLS_RND */ + + + + +/************************************************* +* 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) +{ +int rc; +uschar *expciphers = NULL; +gnutls_priority_t priority_cache; +const char *errpos; +uschar * dummy_errstr; + +#define validate_check_rc(Label) do { \ + if (rc != GNUTLS_E_SUCCESS) { if (exim_gnutls_base_init_done) gnutls_global_deinit(); \ + return string_sprintf("%s failed: %s", (Label), gnutls_strerror(rc)); } } while (0) +#define return_deinit(Label) do { gnutls_global_deinit(); return (Label); } while (0) + +if (exim_gnutls_base_init_done) + log_write(0, LOG_MAIN|LOG_PANIC, + "already initialised GnuTLS, Exim developer bug"); + +#ifdef HAVE_GNUTLS_PKCS11 +if (!gnutls_allow_auto_pkcs11) + { + rc = gnutls_pkcs11_init(GNUTLS_PKCS11_FLAG_MANUAL, NULL); + validate_check_rc(US"gnutls_pkcs11_init"); + } +#endif +rc = gnutls_global_init(); +validate_check_rc(US"gnutls_global_init()"); +exim_gnutls_base_init_done = TRUE; + +if (!(tls_require_ciphers && *tls_require_ciphers)) + return_deinit(NULL); + +if (!expand_check(tls_require_ciphers, US"tls_require_ciphers", &expciphers, + &dummy_errstr)) + return_deinit(US"failed to expand tls_require_ciphers"); + +if (!(expciphers && *expciphers)) + return_deinit(NULL); + +DEBUG(D_tls) + debug_printf("tls_require_ciphers expands to \"%s\"\n", expciphers); + +rc = gnutls_priority_init(&priority_cache, CS expciphers, &errpos); +validate_check_rc(string_sprintf( + "gnutls_priority_init(%s) failed at offset %ld, \"%.8s..\"", + expciphers, errpos - CS expciphers, errpos)); + +#undef return_deinit +#undef validate_check_rc +gnutls_global_deinit(); + +return NULL; +} + + + + +/************************************************* +* Report the library versions. * +*************************************************/ + +/* See a description in tls-openssl.c for an explanation of why this exists. + +Arguments: a FILE* to print the results to +Returns: nothing +*/ + +void +tls_version_report(FILE *f) +{ +fprintf(f, "Library version: GnuTLS: Compile: %s\n" + " Runtime: %s\n", + LIBGNUTLS_VERSION, + gnutls_check_version(NULL)); +} + +/* vi: aw ai sw=2 +*/ +/* End of tls-gnu.c */ |