/*++ /* NAME /* tls_dane 3 /* SUMMARY /* Support for RFC 6698, 7671, 7672 (DANE) certificate matching /* SYNOPSIS /* #include /* /* int tls_dane_avail() /* /* void tls_dane_flush() /* /* void tls_dane_verbose(on) /* int on; /* /* TLS_DANE *tls_dane_alloc() /* /* void tls_dane_free(dane) /* TLS_DANE *dane; /* /* void tls_dane_add_ee_digests(dane, mdalg, digest, delim) /* TLS_DANE *dane; /* const char *mdalg; /* const char *digest; /* const char *delim; /* /* int tls_dane_load_trustfile(dane, tafile) /* TLS_DANE *dane; /* const char *tafile; /* /* int tls_dane_match(TLSContext, usage, cert, depth) /* TLS_SESS_STATE *TLScontext; /* int usage; /* X509 *cert; /* int depth; /* /* void tls_dane_set_callback(ssl_ctx, TLScontext) /* SSL_CTX *ssl_ctx; /* TLS_SESS_STATE *TLScontext; /* /* TLS_DANE *tls_dane_resolve(port, proto, hostrr, forcetlsa) /* unsigned port; /* const char *proto; /* DNS_RR *hostrr; /* int forcetlsa; /* /* int tls_dane_unusable(dane) /* const TLS_DANE *dane; /* /* int tls_dane_notfound(dane) /* const TLS_DANE *dane; /* DESCRIPTION /* tls_dane_avail() returns true if the features required to support DANE /* are present in OpenSSL's libcrypto and in libresolv. Since OpenSSL's /* libcrypto is not initialized until we call tls_client_init(), calls /* to tls_dane_avail() must be deferred until this initialization is /* completed successufully. /* /* tls_dane_flush() flushes all entries from the cache, and deletes /* the cache. /* /* tls_dane_verbose() turns on verbose logging of TLSA record lookups. /* /* tls_dane_alloc() returns a pointer to a newly allocated TLS_DANE /* structure with null ta and ee digest sublists. /* /* tls_dane_free() frees the structure allocated by tls_dane_alloc(). /* /* tls_dane_add_ee_digests() splits "digest" using the characters in /* "delim" as delimiters and stores the results on the EE match list /* to match either a certificate or a public key. This is an incremental /* interface, that builds a TLS_DANE structure outside the cache by /* manually adding entries. /* /* tls_dane_load_trustfile() imports trust-anchor certificates and /* public keys from a file (rather than DNS TLSA records). /* /* tls_dane_match() matches the full and/or public key digest of /* "cert" against each candidate digest in TLScontext->dane. If usage /* is TLS_DANE_EE, the match is against end-entity digests, otherwise /* it is against trust-anchor digests. Returns true if a match is found, /* false otherwise. /* /* tls_dane_set_callback() wraps the SSL certificate verification logic /* in a function that modifies the input trust chain and trusted /* certificate store to map DANE TA validation onto the existing PKI /* verification model. When TLScontext is NULL the callback is /* cleared, otherwise it is set. This callback should only be set /* when out-of-band trust-anchors (via DNSSEC DANE TLSA records or /* per-destination local configuration) are provided. Such trust /* anchors always override the legacy public CA PKI. Otherwise, the /* callback MUST be cleared. /* /* tls_dane_resolve() maps a (port, protocol, hostrr) tuple to a /* corresponding TLS_DANE policy structure found in the DNS. The port /* argument is in network byte order. A null pointer is returned when /* the DNS query for the TLSA record tempfailed. In all other cases the /* return value is a pointer to the corresponding TLS_DANE structure. /* The caller must free the structure via tls_dane_free(). /* /* tls_dane_unusable() checks whether a cached TLS_DANE record is /* the result of a validated RRset, with no usable elements. In /* this case, TLS is mandatory, but certificate verification is /* not DANE-based. /* /* tls_dane_notfound() checks whether a cached TLS_DANE record is /* the result of a validated DNS lookup returning NODATA. In /* this case, TLS is not required by RFC, though users may elect /* a mandatory TLS fallback policy. /* /* Arguments: /* .IP dane /* Pointer to a TLS_DANE structure that lists the valid trust-anchor /* and end-entity full-certificate and/or public-key digests. /* .IP port /* The TCP port in network byte order. /* .IP proto /* Almost certainly "tcp". /* .IP hostrr /* DNS_RR pointer to TLSA base domain data. /* .IP forcetlsa /* When true, TLSA lookups are performed even when the qname and rname /* are insecure. This is only useful in the unlikely case that DLV is /* used to secure the TLSA RRset in an otherwise insecure zone. /* .IP TLScontext /* Client context with TA/EE matching data and related state. /* .IP usage /* Trust anchor (TLS_DANE_TA) or end-entity (TLS_DANE_EE) digests? /* .IP cert /* Certificate from peer trust chain (CA or leaf server). /* .IP depth /* The certificate depth for logging. /* .IP ssl_ctx /* The global SSL_CTX structure used to initialize child SSL /* conenctions. /* .IP mdalg /* Name of a message digest algorithm suitable for computing secure /* (1st pre-image resistant) message digests of certificates. For now, /* md5, sha1, or member of SHA-2 family if supported by OpenSSL. /* .IP digest /* The digest (or list of digests concatenated with characters from /* "delim") to be added to the TLS_DANE record. /* .IP delim /* The set of delimiter characters used above. /* LICENSE /* .ad /* .fi /* This software is free. You can do with it whatever you want. /* The original author kindly requests that you acknowledge /* the use of his software. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /* /* Wietse Venema /* Google, Inc. /* 111 8th Avenue /* New York, NY 10011, USA /* /* Viktor Dukhovni /*--*/ /* System library. */ #include #include #ifdef STRCASECMP_IN_STRINGS_H #include #endif #ifdef USE_TLS #include /* Utility library. */ #include #include #include #include #include /* event_time() */ #include #include #include #include #include #include #define STR(x) vstring_str(x) /* Global library */ #include /* DNS library. */ #include /* TLS library. */ #define TLS_INTERNAL #include /* Application-specific. */ #undef DANE_TLSA_SUPPORT #if defined(TLSEXT_MAXLEN_host_name) && RES_USE_DNSSEC && RES_USE_EDNS0 #define DANE_TLSA_SUPPORT static int dane_tlsa_support = 1; #else static int dane_tlsa_support = 0; #endif static const char *signalg; static ASN1_OBJECT *serverAuth; /* * https://www.iana.org/assignments/dane-parameters/dane-parameters.xhtml */ typedef struct { const char *mdalg; uint8_t dane_id; } iana_digest; static iana_digest iana_table[] = { {"", DNS_TLSA_MATCHING_TYPE_NO_HASH_USED}, {"sha256", DNS_TLSA_MATCHING_TYPE_SHA256}, {"sha512", DNS_TLSA_MATCHING_TYPE_SHA512}, {0, 0} }; typedef struct dane_digest { struct dane_digest *next; /* linkage */ const char *mdalg; /* OpenSSL name */ const EVP_MD *md; /* OpenSSL EVP handle */ int len; /* digest octet length */ int pref; /* tls_dane_digests index or -1 */ uint8_t dane_id; /* IANA id */ } dane_digest; #define MAXDIGESTS 256 /* RFC limit */ static dane_digest *digest_list; /* * This is not intended to be a long-term cache of pre-parsed TLSA data, * rather we primarily want to avoid fetching and parsing the TLSA records * for a single multi-homed MX host more than once per delivery. Therefore, * we keep the table reasonably small. */ #define CACHE_SIZE 20 static CTABLE *dane_cache; static int dane_initialized; static int dane_verbose; /* tls_dane_verbose - enable/disable verbose logging */ void tls_dane_verbose(int on) { dane_verbose = on; } /* add_digest - validate and append digest to digest list */ static dane_digest *add_digest(char *mdalg, int pref) { iana_digest *i; dane_digest *d; int dane_id = -1; const char *dane_mdalg = mdalg; char *value = split_at(mdalg, '='); const EVP_MD *md = 0; size_t mdlen = 0; if (value && *value) { unsigned long l; char *endcp; /* * XXX: safe_strtoul() does not flag empty or white-space only input. * Since we get idbuf by splitting white-space/comma delimited * tokens, this is not a problem here. Fixed as of 210131209. */ l = safe_strtoul(value, &endcp, 10); if ((l == 0 && (errno == EINVAL || endcp == value)) || l >= MAXDIGESTS || *endcp) { msg_warn("Invalid matching type number in %s: %s=%s", VAR_TLS_DANE_DIGESTS, mdalg, value); return (0); } dane_id = l; } /* * Check for known IANA conflicts */ for (i = iana_table; i->mdalg; ++i) { if (*mdalg && strcasecmp(i->mdalg, mdalg) == 0) { if (dane_id >= 0 && i->dane_id != dane_id) { msg_warn("Non-standard value in %s: %s%s%s", VAR_TLS_DANE_DIGESTS, mdalg, value ? "=" : "", value ? value : ""); return (0); } dane_id = i->dane_id; } else if (i->dane_id == dane_id) { if (*mdalg) { msg_warn("Non-standard algorithm in %s: %s%s%s", VAR_TLS_DANE_DIGESTS, mdalg, value ? "=" : "", value ? value : ""); return (0); } dane_mdalg = i->mdalg; } } /* * Check for unknown implicit digest or value */ if (dane_id < 0 || (dane_id > 0 && !*dane_mdalg)) { msg_warn("Unknown incompletely specified element in %s: %s%s%s", VAR_TLS_DANE_DIGESTS, mdalg, value ? "=" : "", value ? value : ""); return 0; } /* * Check for duplicate entries */ for (d = digest_list; d; d = d->next) { if (strcasecmp(d->mdalg, dane_mdalg) == 0 || d->dane_id == dane_id) { msg_warn("Duplicate element in %s: %s%s%s", VAR_TLS_DANE_DIGESTS, mdalg, value ? "=" : "", value ? value : ""); return (0); } } if (*dane_mdalg && ((md = tls_digest_byname(dane_mdalg, NULL)) == 0 || (mdlen = EVP_MD_size(md)) <= 0 || mdlen > EVP_MAX_MD_SIZE)) { msg_warn("Unimplemented digest algorithm in %s: %s%s%s", VAR_TLS_DANE_DIGESTS, mdalg, value ? "=" : "", value ? value : ""); return (0); } d = (dane_digest *) mymalloc(sizeof(*d)); d->next = digest_list; d->mdalg = mystrdup(dane_mdalg); d->md = md; d->len = mdlen; d->pref = pref; d->dane_id = dane_id; return (digest_list = d); } /* digest_byid - locate digest_table entry for given IANA id */ static dane_digest *digest_byid(uint8_t dane_id) { dane_digest *d; for (d = digest_list; d; d = d->next) if (d->dane_id == dane_id) return (d); return (0); } /* digest_pref_byid - digest preference by IANA id */ static int digest_pref_byid(uint8_t dane_id) { dane_digest *d = digest_byid(dane_id); return (d ? (d->pref) : (MAXDIGESTS + dane_id)); } /* dane_init - initialize DANE parameters */ static void dane_init(void) { int digest_pref = 0; char *cp; char *save; char *tok; static char fullmtype[] = "=0"; dane_digest *d; /* * Add the full matching type at highest preference and then the users * configured list. * * The most preferred digest will be used for hashing full values for * comparison. */ if (add_digest(fullmtype, 0)) { save = cp = mystrdup(var_tls_dane_digests); while ((tok = mystrtok(&cp, CHARS_COMMA_SP)) != 0) { if ((d = add_digest(tok, ++digest_pref)) == 0) { signalg = 0; break; } if (digest_pref == 1) { signalg = d->mdalg; } } myfree(save); } /* Don't report old news */ ERR_clear_error(); /* * DANE TLSA support requires working DANE digests. */ if ((serverAuth = OBJ_nid2obj(NID_server_auth)) == 0) { msg_warn("cannot designate intermediate TA certificates, " "no DANE support"); tls_print_errors(); dane_tlsa_support = 0; } else if (signalg == 0) { msg_warn("digest algorithm initializaton failed, no DANE support"); tls_print_errors(); dane_tlsa_support = 0; } dane_initialized = 1; } /* tls_dane_avail - check for availability of dane required digests */ int tls_dane_avail(void) { if (!dane_initialized) dane_init(); return (dane_tlsa_support); } /* tls_dane_flush - flush the cache */ void tls_dane_flush(void) { if (dane_cache) ctable_free(dane_cache); dane_cache = 0; } /* tls_dane_alloc - allocate a TLS_DANE structure */ TLS_DANE *tls_dane_alloc(void) { TLS_DANE *dane = (TLS_DANE *) mymalloc(sizeof(*dane)); dane->ta = 0; dane->ee = 0; dane->certs = 0; dane->pkeys = 0; dane->base_domain = 0; dane->flags = 0; dane->expires = 0; dane->refs = 1; return (dane); } static void ta_cert_insert(TLS_DANE *d, X509 *x) { TLS_CERTS *new = (TLS_CERTS *) mymalloc(sizeof(*new)); X509_up_ref(x); new->cert = x; new->next = d->certs; d->certs = new; } static void free_ta_certs(TLS_DANE *d) { TLS_CERTS *head; TLS_CERTS *next; for (head = d->certs; head; head = next) { next = head->next; X509_free(head->cert); myfree((void *) head); } } static void ta_pkey_insert(TLS_DANE *d, EVP_PKEY *k) { TLS_PKEYS *new = (TLS_PKEYS *) mymalloc(sizeof(*new)); EVP_PKEY_up_ref(k); new->pkey = k; new->next = d->pkeys; d->pkeys = new; } static void free_ta_pkeys(TLS_DANE *d) { TLS_PKEYS *head; TLS_PKEYS *next; for (head = d->pkeys; head; head = next) { next = head->next; EVP_PKEY_free(head->pkey); myfree((void *) head); } } static void tlsa_free(TLS_TLSA *tlsa) { myfree(tlsa->mdalg); if (tlsa->certs) argv_free(tlsa->certs); if (tlsa->pkeys) argv_free(tlsa->pkeys); myfree((void *) tlsa); } /* tls_dane_free - free a TLS_DANE structure */ void tls_dane_free(TLS_DANE *dane) { TLS_TLSA *tlsa; TLS_TLSA *next; if (--dane->refs > 0) return; /* De-allocate TA and EE lists */ for (tlsa = dane->ta; tlsa; tlsa = next) { next = tlsa->next; tlsa_free(tlsa); } for (tlsa = dane->ee; tlsa; tlsa = next) { next = tlsa->next; tlsa_free(tlsa); } /* De-allocate full trust-anchor certs and pkeys */ free_ta_certs(dane); free_ta_pkeys(dane); if (dane->base_domain) myfree(dane->base_domain); myfree((void *) dane); } /* dane_free - ctable style */ static void dane_free(void *dane, void *unused_context) { tls_dane_free((TLS_DANE *) dane); } /* dane_locate - list head address of TLSA sublist for given algorithm */ static TLS_TLSA **dane_locate(TLS_TLSA **tlsap, const char *mdalg) { TLS_TLSA *new; /* * Correct computation of the session cache serverid requires a TLSA * digest list that is sorted by algorithm name. Below we maintain the * sort order (by algorithm name canonicalized to lowercase). */ for (; *tlsap; tlsap = &(*tlsap)->next) { int cmp = strcasecmp(mdalg, (*tlsap)->mdalg); if (cmp == 0) return (tlsap); if (cmp < 0) break; } new = (TLS_TLSA *) mymalloc(sizeof(*new)); new->mdalg = lowercase(mystrdup(mdalg)); new->certs = 0; new->pkeys = 0; new->next = *tlsap; *tlsap = new; return (tlsap); } /* tls_dane_add_ee_digests - split and append digests */ void tls_dane_add_ee_digests(TLS_DANE *dane, const char *mdalg, const char *digest, const char *delim) { TLS_TLSA **tlsap = dane_locate(&dane->ee, mdalg); TLS_TLSA *tlsa = *tlsap; /* Delimited append, may append nothing */ if (tlsa->pkeys == 0) tlsa->pkeys = argv_split(digest, delim); else argv_split_append(tlsa->pkeys, digest, delim); /* Remove empty elements from the list */ if (tlsa->pkeys->argc == 0) { argv_free(tlsa->pkeys); tlsa->pkeys = 0; if (tlsa->certs == 0) { *tlsap = tlsa->next; tlsa_free(tlsa); } return; } /* * At the "fingerprint" security level certificate digests and public key * digests are interchangeable. Each leaf certificate is matched via * either the public key digest or full certificate digest. The DER * encoding of a certificate is not a valid public key, and conversely, * the DER encoding of a public key is not a valid certificate. An * attacker would need a 2nd-preimage that is feasible across types * (given cert digest == some pkey digest) and yet presumably difficult * within a type (e.g. given cert digest == some other cert digest). No * such attacks are known at this time, and it is expected that if any * are found they would work within as well as across the cert/pkey data * types. */ if (tlsa->certs == 0) tlsa->certs = argv_split(digest, delim); else argv_split_append(tlsa->certs, digest, delim); } /* dane_add - add a digest entry */ static void dane_add(TLS_DANE *dane, int certusage, int selector, const char *mdalg, char *digest) { TLS_TLSA **tlsap; TLS_TLSA *tlsa; ARGV **argvp; switch (certusage) { case DNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION: certusage = TLS_DANE_TA; break; case DNS_TLSA_USAGE_DOMAIN_ISSUED_CERTIFICATE: certusage = TLS_DANE_EE; /* Collapse 1/3 -> 3 */ break; default: msg_panic("Unsupported DANE certificate usage: %d", certusage); } switch (selector) { case DNS_TLSA_SELECTOR_FULL_CERTIFICATE: selector = TLS_DANE_CERT; break; case DNS_TLSA_SELECTOR_SUBJECTPUBLICKEYINFO: selector = TLS_DANE_PKEY; break; default: msg_panic("Unsupported DANE selector: %d", selector); } tlsap = (certusage == TLS_DANE_EE) ? &dane->ee : &dane->ta; tlsa = *(tlsap = dane_locate(tlsap, mdalg)); argvp = (selector == TLS_DANE_PKEY) ? &tlsa->pkeys : &tlsa->certs; if (*argvp == 0) *argvp = argv_alloc(1); argv_add(*argvp, digest, ARGV_END); } #define FILTER_CTX_AGILITY_OK (1<<0) #define FILTER_CTX_APPLY_AGILITY (1<<1) #define FILTER_CTX_PARSE_DATA (1<<2) #define FILTER_RR_DROP 0 #define FILTER_RR_KEEP 1 typedef struct filter_ctx { TLS_DANE *dane; /* Parsed result */ int count; /* Digest mtype count */ int target; /* Digest mtype target count */ int flags; /* Action/result bitmask */ } filter_ctx; typedef int (*tlsa_filter) (DNS_RR *, filter_ctx *); /* tlsa_apply - apply filter to each rr in turn */ static DNS_RR *tlsa_apply(DNS_RR *rr, tlsa_filter filter, filter_ctx *ctx) { DNS_RR *head = 0; /* First retained RR */ DNS_RR *tail = 0; /* Last retained RR */ DNS_RR *next; /* * XXX Code that modifies or destroys DNS_RR lists or entries belongs in * the DNS library, not here. */ for ( /* nop */ ; rr; rr = next) { next = rr->next; if (filter(rr, ctx) == FILTER_RR_KEEP) { tail = rr; if (!head) head = rr; } else { if (tail) tail->next = rr->next; rr->next = 0; dns_rr_free(rr); } } return (head); } /* usmdelta - packed usage/selector/mtype bits changing in next record */ static unsigned int usmdelta(uint8_t u, uint8_t s, uint8_t m, DNS_RR *next) { uint8_t *ip = (next && next->data_len >= 3) ? (uint8_t *) next->data : 0; uint8_t nu = ip ? *ip++ : ~u; uint8_t ns = ip ? *ip++ : ~s; uint8_t nm = ip ? *ip++ : ~m; return (((u ^ nu) << 16) | ((s ^ ns) << 8) | (m ^ nm)); } /* tlsa_rr_cmp - qsort TLSA rrs in case shuffled by name server */ static int tlsa_rr_cmp(DNS_RR *a, DNS_RR *b) { int cmp; /* * Sort in ascending order, by usage, selector, matching type preference * and payload. The usage, selector and matching type are the first * three unsigned octets of the RR data. */ if (a->data_len > 2 && b->data_len > 2) { uint8_t *ai = (uint8_t *) a->data; uint8_t *bi = (uint8_t *) b->data; #define signedcmp(x, y) (((int)(x)) - ((int)(y))) if ((cmp = signedcmp(ai[0], bi[0])) != 0 || (cmp = signedcmp(ai[1], bi[1])) != 0 || (cmp = digest_pref_byid(ai[2]) - digest_pref_byid(bi[2])) != 0) return (cmp); } if ((cmp = a->data_len - b->data_len) != 0) return (cmp); return (memcmp(a->data, b->data, a->data_len)); } /* parse_tlsa_rr - parse a validated TLSA RRset */ static int parse_tlsa_rr(DNS_RR *rr, filter_ctx *ctx) { uint8_t *ip; uint8_t usage; uint8_t selector; uint8_t mtype; ssize_t dlen; const unsigned char *data; const unsigned char *p; int iscname = strcasecmp(rr->rname, rr->qname); const char *q = (iscname) ? (rr)->qname : ""; const char *a = (iscname) ? " -> " : ""; const char *r = rr->rname; unsigned int change; if (rr->type != T_TLSA) msg_panic("unexpected non-TLSA RR type %u for %s%s%s", rr->type, q, a, r); /* Drop truncated records */ if ((dlen = rr->data_len - 3) < 0) { msg_warn("truncated length %u RR: %s%s%s IN TLSA ...", (unsigned) rr->data_len, q, a, r); ctx->flags &= ~FILTER_CTX_AGILITY_OK; return (FILTER_RR_DROP); } ip = (uint8_t *) rr->data; usage = *ip++; selector = *ip++; mtype = *ip++; change = usmdelta(usage, selector, mtype, rr->next); p = data = (const unsigned char *) ip; /* * Handle digest agility for non-zero matching types. */ if (mtype) { if (ctx->count && (ctx->flags & FILTER_CTX_APPLY_AGILITY)) { if (change & 0xffff00) /* New usage/selector, */ ctx->count = 0; /* disable drop */ return (FILTER_RR_DROP); } } /*- * Drop unsupported usages. * Note: NO SUPPORT for usages 0/1 which do not apply to SMTP. */ switch (usage) { case DNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION: case DNS_TLSA_USAGE_DOMAIN_ISSUED_CERTIFICATE: break; default: msg_warn("unsupported certificate usage %u in RR: " "%s%s%s IN TLSA %u ...", usage, q, a, r, usage); return (FILTER_RR_DROP); } /* * Drop unsupported selectors */ switch (selector) { case DNS_TLSA_SELECTOR_FULL_CERTIFICATE: case DNS_TLSA_SELECTOR_SUBJECTPUBLICKEYINFO: break; default: msg_warn("unsupported selector %u in RR: " "%s%s%s IN TLSA %u %u ...", selector, q, a, r, usage, selector); return (FILTER_RR_DROP); } if (mtype) { dane_digest *d = digest_byid(mtype); if (d == 0) { msg_warn("unsupported matching type %u in RR: " "%s%s%s IN TLSA %u %u %u ...", mtype, q, a, r, usage, selector, mtype); return (FILTER_RR_DROP); } if (dlen != d->len) { msg_warn("malformed %s digest, length %lu, in RR: " "%s%s%s IN TLSA %u %u %u ...", d->mdalg, (unsigned long) dlen, q, a, r, usage, selector, mtype); ctx->flags &= ~FILTER_CTX_AGILITY_OK; return (FILTER_RR_DROP); } /* New digest mtype next? Prepare to drop following RRs */ if (change && (change & 0xffff00) == 0 && (ctx->flags & FILTER_CTX_APPLY_AGILITY)) ++ctx->count; if (ctx->flags & FILTER_CTX_PARSE_DATA) { char *digest = tls_digest_encode(data, dlen); dane_add(ctx->dane, usage, selector, d->mdalg, digest); if (msg_verbose || dane_verbose) msg_info("using DANE RR: %s%s%s IN TLSA %u %u %u %s", q, a, r, usage, selector, mtype, digest); myfree(digest); } } else { X509 *x = 0; /* OpenSSL re-uses *x if x!=0 */ EVP_PKEY *k = 0; /* OpenSSL re-uses *k if k!=0 */ /* Validate the cert or public key via d2i_mumble() */ switch (selector) { case DNS_TLSA_SELECTOR_FULL_CERTIFICATE: if (!d2i_X509(&x, &p, dlen) || dlen != p - data) { msg_warn("malformed %s in RR: " "%s%s%s IN TLSA %u %u %u ...", "certificate", q, a, r, usage, selector, mtype); if (x) X509_free(x); return (FILTER_RR_DROP); } /* Also unusable if public key is malformed or unsupported */ k = X509_get_pubkey(x); EVP_PKEY_free(k); if (k == 0) { msg_warn("malformed %s in RR: %s%s%s IN TLSA %u %u %u ...", "or unsupported certificate public key", q, a, r, usage, selector, mtype); X509_free(x); return (FILTER_RR_DROP); } /* * When a full trust-anchor certificate is published via DNS, we * may need to use it to validate the server trust chain. Store * it away for later use. */ if (usage == DNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION && (ctx->flags & FILTER_CTX_PARSE_DATA)) ta_cert_insert(ctx->dane, x); X509_free(x); break; case DNS_TLSA_SELECTOR_SUBJECTPUBLICKEYINFO: if (!d2i_PUBKEY(&k, &p, dlen) || dlen != p - data) { msg_warn("malformed %s in RR: %s%s%s IN TLSA %u %u %u ...", "public key", q, a, r, usage, selector, mtype); if (k) EVP_PKEY_free(k); return (FILTER_RR_DROP); } /* * When a full trust-anchor public key is published via DNS, we * may need to use it to validate the server trust chain. Store * it away for later use. */ if (usage == DNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION && (ctx->flags & FILTER_CTX_PARSE_DATA)) ta_pkey_insert(ctx->dane, k); EVP_PKEY_free(k); break; } /* * The cert or key was valid, just digest the raw object, and encode * the digest value. */ if (ctx->flags & FILTER_CTX_PARSE_DATA) { char *digest = tls_data_fprint((char *) data, dlen, signalg); dane_add(ctx->dane, usage, selector, signalg, digest); if (msg_verbose || dane_verbose) msg_info("using DANE RR: %s%s%s IN TLSA %u %u %u <%s>; " "%s digest %s", q, a, r, usage, selector, mtype, (selector == DNS_TLSA_SELECTOR_FULL_CERTIFICATE) ? "certificate" : "public key", signalg, digest); myfree(digest); } } return (FILTER_RR_KEEP); } /* process_rrs - filter and parse the TLSA RRset */ static DNS_RR *process_rrs(TLS_DANE *dane, DNS_RR *rrset) { filter_ctx ctx; ctx.dane = dane; ctx.count = ctx.target = 0; ctx.flags = FILTER_CTX_APPLY_AGILITY | FILTER_CTX_PARSE_DATA; rrset = tlsa_apply(rrset, parse_tlsa_rr, &ctx); if (dane->ta == 0 && dane->ee == 0) dane->flags |= TLS_DANE_FLAG_EMPTY; return (rrset); } /* dane_lookup - TLSA record lookup, ctable style */ static void *dane_lookup(const char *tlsa_fqdn, void *unused_ctx) { static VSTRING *why = 0; int ret; DNS_RR *rrs = 0; TLS_DANE *dane; if (why == 0) why = vstring_alloc(10); dane = tls_dane_alloc(); ret = dns_lookup(tlsa_fqdn, T_TLSA, RES_USE_DNSSEC, &rrs, 0, why); switch (ret) { case DNS_OK: if (TLS_DANE_CACHE_TTL_MIN && rrs->ttl < TLS_DANE_CACHE_TTL_MIN) rrs->ttl = TLS_DANE_CACHE_TTL_MIN; if (TLS_DANE_CACHE_TTL_MAX && rrs->ttl > TLS_DANE_CACHE_TTL_MAX) rrs->ttl = TLS_DANE_CACHE_TTL_MAX; /* One more second to account for discrete time */ dane->expires = 1 + event_time() + rrs->ttl; if (rrs->dnssec_valid) { /* * Sort for deterministic digest in session cache lookup key. In * addition we must arrange for more preferred matching types * (full value or digest) to precede less preferred ones for the * same usage and selector. */ rrs = dns_rr_sort(rrs, tlsa_rr_cmp); rrs = process_rrs(dane, rrs); } else dane->flags |= TLS_DANE_FLAG_NORRS; if (rrs) dns_rr_free(rrs); break; case DNS_NOTFOUND: dane->flags |= TLS_DANE_FLAG_NORRS; dane->expires = 1 + event_time() + TLS_DANE_CACHE_TTL_MIN; break; default: msg_warn("DANE TLSA lookup problem: %s", STR(why)); dane->flags |= TLS_DANE_FLAG_ERROR; break; } return (void *) dane; } /* resolve_host - resolve TLSA RRs for hostname (rname or qname) */ static TLS_DANE *resolve_host(const char *host, const char *proto, unsigned port) { static VSTRING *query_domain; TLS_DANE *dane; if (query_domain == 0) query_domain = vstring_alloc(64); vstring_sprintf(query_domain, "_%u._%s.%s", ntohs(port), proto, host); dane = (TLS_DANE *) ctable_locate(dane_cache, STR(query_domain)); if (timecmp(event_time(), dane->expires) > 0) dane = (TLS_DANE *) ctable_refresh(dane_cache, STR(query_domain)); if (dane->base_domain == 0) dane->base_domain = mystrdup(host); /* Increment ref-count of cached entry */ ++dane->refs; return (dane); } /* qname_secure - Lookup qname DNSSEC status */ static int qname_secure(const char *qname) { static VSTRING *why; int ret = 0; DNS_RR *rrs; if (!why) why = vstring_alloc(10); /* * We assume that qname is already an fqdn, and does not need any * suffixes from RES_DEFNAME or RES_DNSRCH. This is typically the name * of an MX host, and must be a complete DNS name. DANE initialization * code in the SMTP client is responsible for checking that the default * resolver flags do not include RES_DEFNAME and RES_DNSRCH. */ ret = dns_lookup(qname, T_CNAME, RES_USE_DNSSEC, &rrs, 0, why); if (ret == DNS_OK) { ret = rrs->dnssec_valid; dns_rr_free(rrs); return (ret); } if (ret == DNS_NOTFOUND) vstring_sprintf(why, "no longer a CNAME"); msg_warn("DNSSEC status lookup error for %s: %s", qname, STR(why)); return (-1); } /* tls_dane_resolve - cached map: (name, proto, port) -> TLS_DANE */ TLS_DANE *tls_dane_resolve(unsigned port, const char *proto, DNS_RR *hostrr, int forcetlsa) { TLS_DANE *dane = 0; int iscname = strcasecmp(hostrr->rname, hostrr->qname); int isvalid = 1; if (!tls_dane_avail()) return (0); /* Error */ /* * By default suppress TLSA lookups for hosts in non-DNSSEC zones. If * the host zone is not DNSSEC validated, the TLSA qname sub-domain is * safely assumed to not be in a DNSSEC Look-aside Validation child zone. */ if (!forcetlsa && !hostrr->dnssec_valid) { isvalid = iscname ? qname_secure(hostrr->qname) : 0; if (isvalid < 0) return (0); /* Error */ } if (!isvalid) { dane = tls_dane_alloc(); dane->flags = TLS_DANE_FLAG_NORRS; } else { if (!dane_cache) dane_cache = ctable_create(CACHE_SIZE, dane_lookup, dane_free, 0); /* * Try the rname first if secure, if nothing there, try the qname if * different. Note, lookup errors are distinct from success with * nothing found. If the rname lookup fails we don't try the qname. */ if (hostrr->dnssec_valid) { dane = resolve_host(hostrr->rname, proto, port); if (tls_dane_notfound(dane) && iscname) { tls_dane_free(dane); dane = 0; } } if (!dane) dane = resolve_host(hostrr->qname, proto, port); if (dane->flags & TLS_DANE_FLAG_ERROR) { /* We don't return this object. */ tls_dane_free(dane); dane = 0; } } return (dane); } /* tls_dane_load_trustfile - load trust anchor certs or keys from file */ int tls_dane_load_trustfile(TLS_DANE *dane, const char *tafile) { BIO *bp; char *name = 0; char *header = 0; unsigned char *data = 0; long len; int tacount; char *errtype = 0; /* if error: cert or pkey? */ const char *mdalg; /* nop */ if (tafile == 0 || *tafile == 0) return (1); if (!dane_initialized) dane_init(); /* Per-destination TA support is available even when DANE is not */ mdalg = signalg ? signalg : "sha1"; /* * On each call, PEM_read() wraps a stdio file in a BIO_NOCLOSE bio, * calls PEM_read_bio() and then frees the bio. It is just as easy to * open a BIO as a stdio file, so we use BIOs and call PEM_read_bio() * directly. */ if ((bp = BIO_new_file(tafile, "r")) == NULL) { msg_warn("error opening trust anchor file: %s: %m", tafile); return (0); } /* Don't report old news */ ERR_clear_error(); for (tacount = 0; errtype == 0 && PEM_read_bio(bp, &name, &header, &data, &len); ++tacount) { const unsigned char *p = data; int usage = DNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION; int selector; char *digest; if (strcmp(name, PEM_STRING_X509) == 0 || strcmp(name, PEM_STRING_X509_OLD) == 0) { X509 *cert = d2i_X509(0, &p, len); if (cert && (p - data) == len) { selector = DNS_TLSA_SELECTOR_FULL_CERTIFICATE; digest = tls_data_fprint((char *) data, len, mdalg); dane_add(dane, usage, selector, mdalg, digest); myfree(digest); ta_cert_insert(dane, cert); } else errtype = "certificate"; if (cert) X509_free(cert); } else if (strcmp(name, PEM_STRING_PUBLIC) == 0) { EVP_PKEY *pkey = d2i_PUBKEY(0, &p, len); if (pkey && (p - data) == len) { selector = DNS_TLSA_SELECTOR_SUBJECTPUBLICKEYINFO; digest = tls_data_fprint((char *) data, len, mdalg); dane_add(dane, usage, selector, mdalg, digest); myfree(digest); ta_pkey_insert(dane, pkey); } else errtype = "public key"; if (pkey) EVP_PKEY_free(pkey); } /* * If any of these were null, PEM_read() would have failed. */ OPENSSL_free(name); OPENSSL_free(header); OPENSSL_free(data); } BIO_free(bp); if (errtype) { tls_print_errors(); msg_warn("error reading: %s: malformed trust-anchor %s", tafile, errtype); return (0); } if (ERR_GET_REASON(ERR_peek_last_error()) == PEM_R_NO_START_LINE) { /* Reached end of PEM file */ ERR_clear_error(); return (tacount > 0); } /* Some other PEM read error */ tls_print_errors(); return (0); } /* tls_dane_match - match cert against given list of TA or EE digests */ int tls_dane_match(TLS_SESS_STATE *TLScontext, int usage, X509 *cert, int depth) { const TLS_DANE *dane = TLScontext->dane; TLS_TLSA *tlsa = (usage == TLS_DANE_EE) ? dane->ee : dane->ta; const char *namaddr = TLScontext->namaddr; const char *ustr = (usage == TLS_DANE_EE) ? "end entity" : "trust anchor"; int matched; for (matched = 0; tlsa && !matched; tlsa = tlsa->next) { char **dgst; /* * Note, set_trust() needs to know whether the match was for a pkey * digest or a certificate digest. We return MATCHED_PKEY or * MATCHED_CERT accordingly. */ #define MATCHED_CERT 1 #define MATCHED_PKEY 2 if (tlsa->pkeys) { char *pkey_dgst = tls_pkey_fprint(cert, tlsa->mdalg); for (dgst = tlsa->pkeys->argv; !matched && *dgst; ++dgst) if (strcasecmp(pkey_dgst, *dgst) == 0) matched = MATCHED_PKEY; if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_CERTMATCH) && matched) msg_info("%s: depth=%d matched %s public-key %s digest=%s", namaddr, depth, ustr, tlsa->mdalg, pkey_dgst); myfree(pkey_dgst); } if (tlsa->certs != 0 && !matched) { char *cert_dgst = tls_cert_fprint(cert, tlsa->mdalg); for (dgst = tlsa->certs->argv; !matched && *dgst; ++dgst) if (strcasecmp(cert_dgst, *dgst) == 0) matched = MATCHED_CERT; if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_CERTMATCH) && matched) msg_info("%s: depth=%d matched %s certificate %s digest %s", namaddr, depth, ustr, tlsa->mdalg, cert_dgst); myfree(cert_dgst); } } return (matched); } /* add_ext - add simple extension (no config section references) */ static int add_ext(X509 *issuer, X509 *subject, int ext_nid, char *ext_val) { int ret = 0; X509V3_CTX v3ctx; X509_EXTENSION *ext; X509V3_set_ctx(&v3ctx, issuer, subject, 0, 0, 0); if ((ext = X509V3_EXT_conf_nid(0, &v3ctx, ext_nid, ext_val)) != 0) { ret = X509_add_ext(subject, ext, -1); X509_EXTENSION_free(ext); } return ret; } /* set_serial - set serial number to match akid or use subject's plus 1 */ static int set_serial(X509 *cert, AUTHORITY_KEYID *akid, X509 *subject) { int ret = 0; BIGNUM *bn; if (akid && akid->serial) return (X509_set_serialNumber(cert, akid->serial)); /* * Add one to subject's serial to avoid collisions between TA serial and * serial of signing root. */ if ((bn = ASN1_INTEGER_to_BN(X509_get_serialNumber(subject), 0)) != 0 && BN_add_word(bn, 1) && BN_to_ASN1_INTEGER(bn, X509_get_serialNumber(cert))) ret = 1; if (bn) BN_free(bn); return (ret); } /* add_akid - add authority key identifier */ static int add_akid(X509 *cert, AUTHORITY_KEYID *akid) { ASN1_OCTET_STRING *id; unsigned char c = 0; int nid = NID_authority_key_identifier; int ret = 0; /* * 0 will never be our subject keyid from a SHA-1 hash, but it could be * our subject keyid if forced from child's akid. If so, set our * authority keyid to 1. This way we are never self-signed, and thus * exempt from any potential (off by default for now in OpenSSL) * self-signature checks! */ id = ((akid && akid->keyid) ? akid->keyid : 0); if (id && ASN1_STRING_length(id) == 1 && *ASN1_STRING_get0_data(id) == c) c = 1; if ((akid = AUTHORITY_KEYID_new()) != 0 && (akid->keyid = ASN1_OCTET_STRING_new()) != 0 && ASN1_OCTET_STRING_set(akid->keyid, (void *) &c, 1) && X509_add1_ext_i2d(cert, nid, akid, 0, X509V3_ADD_DEFAULT) > 0) ret = 1; if (akid) AUTHORITY_KEYID_free(akid); return (ret); } /* add_skid - add subject key identifier to match child's akid */ static int add_skid(X509 *cert, AUTHORITY_KEYID *akid) { int nid = NID_subject_key_identifier; if (!akid || !akid->keyid) return (add_ext(0, cert, nid, "hash")); else return (X509_add1_ext_i2d(cert, nid, akid->keyid, 0, X509V3_ADD_DEFAULT) > 0); } /* akid_issuer_name - get akid issuer directory name */ static X509_NAME *akid_issuer_name(AUTHORITY_KEYID *akid) { if (akid && akid->issuer) { int i; general_name_stack_t *gens = akid->issuer; for (i = 0; i < sk_GENERAL_NAME_num(gens); ++i) { GENERAL_NAME *gn = sk_GENERAL_NAME_value(gens, i); if (gn->type == GEN_DIRNAME) return (gn->d.dirn); } } return (0); } /* set_issuer - set issuer DN to match akid if specified */ static int set_issuer_name(X509 *cert, AUTHORITY_KEYID *akid, X509_NAME *subj) { X509_NAME *name = akid_issuer_name(akid); /* * If subject's akid specifies an authority key identifier issuer name, * we must use that. */ if (name) return (X509_set_issuer_name(cert, name)); return (X509_set_issuer_name(cert, subj)); } /* grow_chain - add certificate to trusted or untrusted chain */ static void grow_chain(TLS_SESS_STATE *TLScontext, int trusted, X509 *cert) { x509_stack_t **xs = trusted ? &TLScontext->trusted : &TLScontext->untrusted; #define UNTRUSTED 0 #define TRUSTED 1 if (!*xs && (*xs = sk_X509_new_null()) == 0) msg_fatal("out of memory"); if (cert) { if (trusted && !X509_add1_trust_object(cert, serverAuth)) msg_fatal("out of memory"); X509_up_ref(cert); if (!sk_X509_push(*xs, cert)) msg_fatal("out of memory"); } } /* wrap_key - wrap TA "key" as issuer of "subject" */ static void wrap_key(TLS_SESS_STATE *TLScontext, int depth, EVP_PKEY *key, X509 *subject) { X509 *cert = 0; AUTHORITY_KEYID *akid; X509_NAME *name = X509_get_issuer_name(subject); /* * The subject name is never a NULL object unless we run out of memory. * It may be an empty sequence, but the containing object always exists * and its storage is owned by the certificate itself. */ if (name == 0 || (cert = X509_new()) == 0) msg_fatal("Out of memory"); /* * Record the depth of the intermediate wrapper certificate, logged in * the verify callback. */ if (TLScontext->tadepth < 0) { TLScontext->tadepth = depth + 1; if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_CERTMATCH)) msg_info("%s: depth=%d chain is trust-anchor signed", TLScontext->namaddr, depth); } akid = X509_get_ext_d2i(subject, NID_authority_key_identifier, 0, 0); ERR_clear_error(); /* CA cert valid for +/- 30 days. */ if (!X509_set_version(cert, 2) || !set_serial(cert, akid, subject) || !set_issuer_name(cert, akid, name) || !X509_gmtime_adj(X509_getm_notBefore(cert), -30 * 86400L) || !X509_gmtime_adj(X509_getm_notAfter(cert), 30 * 86400L) || !X509_set_subject_name(cert, name) || !X509_set_pubkey(cert, key) || !add_ext(0, cert, NID_basic_constraints, "CA:TRUE") || (key && !add_akid(cert, akid)) || !add_skid(cert, akid)) { tls_print_errors(); msg_fatal("error generating DANE wrapper certificate"); } if (akid) AUTHORITY_KEYID_free(akid); grow_chain(TLScontext, TRUSTED, cert); if (cert) X509_free(cert); } /* wrap_cert - wrap "tacert" as trust-anchor. */ static void wrap_cert(TLS_SESS_STATE *TLScontext, X509 *tacert, int depth) { if (TLScontext->tadepth < 0) TLScontext->tadepth = depth + 1; if (TLScontext->log_mask & (TLS_LOG_VERBOSE | TLS_LOG_CERTMATCH)) msg_info("%s: depth=%d trust-anchor certificate", TLScontext->namaddr, depth); grow_chain(TLScontext, TRUSTED, tacert); return; } /* ta_signed - is certificate signed by a TLSA cert or pkey */ static int ta_signed(TLS_SESS_STATE *TLScontext, X509 *cert, int depth) { const TLS_DANE *dane = TLScontext->dane; EVP_PKEY *pk; TLS_PKEYS *k; TLS_CERTS *x; int done = 0; /* * First check whether issued and signed by a TA cert, this is cheaper * than the bare-public key checks below, since we can determine whether * the candidate TA certificate issued the certificate to be checked * first (name comparisons), before we bother with signature checks * (public key operations). */ for (x = dane->certs; !done && x; x = x->next) { if (X509_check_issued(x->cert, cert) == X509_V_OK) { if ((pk = X509_get_pubkey(x->cert)) == 0) continue; /* Check signature, since some other TA may work if not this. */ if ((done = (X509_verify(cert, pk) > 0)) != 0) wrap_cert(TLScontext, x->cert, depth); EVP_PKEY_free(pk); } } /* * With bare TA public keys, we can't check whether the trust chain is * issued by the key, but we can determine whether it is signed by the * key, so we go with that. * * Ideally, the corresponding certificate was presented in the chain, and we * matched it by its public key digest one level up. This code is here * to handle adverse conditions imposed by sloppy administrators of * receiving systems with poorly constructed chains. * * We'd like to optimize out keys that should not match when the cert's * authority key id does not match the key id of this key computed via * the RFC keyid algorithm (SHA-1 digest of public key bit-string sans * ASN1 tag and length thus also excluding the unused bits field that is * logically part of the length). However, some CAs have a non-standard * authority keyid, so we lose. Too bad. * * This may push errors onto the stack when the certificate signature is not * of the right type or length, throw these away. */ for (k = dane->pkeys; !done && k; k = k->next) if ((done = (X509_verify(cert, k->pkey) > 0)) != 0) wrap_key(TLScontext, depth, k->pkey, cert); else ERR_clear_error(); return (done); } /* set_trust - configure for DANE validation */ static void set_trust(TLS_SESS_STATE *TLScontext, X509_STORE_CTX *ctx) { int n; int i; int match; int depth = 0; EVP_PKEY *takey; X509 *ca; X509 *cert = X509_STORE_CTX_get0_cert(ctx); x509_stack_t *in = X509_STORE_CTX_get0_untrusted(ctx); /* shallow copy */ if ((in = sk_X509_dup(in)) == 0) msg_fatal("out of memory"); /* * At each iteration we consume the issuer of the current cert. This * reduces the length of the "in" chain by one. If no issuer is found, * we are done. We also stop when a certificate matches a TA in the * peer's TLSA RRset. * * Caller ensures that the initial certificate is not self-signed. */ for (n = sk_X509_num(in); n > 0; --n, ++depth) { for (i = 0; i < n; ++i) if (X509_check_issued(sk_X509_value(in, i), cert) == X509_V_OK) break; /* * Final untrusted element with no issuer in the peer's chain, it may * however be signed by a pkey or cert obtained via a TLSA RR. */ if (i == n) break; /* Peer's chain contains an issuer ca. */ ca = sk_X509_delete(in, i); /* Is it a trust anchor? */ match = tls_dane_match(TLScontext, TLS_DANE_TA, ca, depth + 1); if (match) { switch (match) { case MATCHED_CERT: wrap_cert(TLScontext, ca, depth); break; case MATCHED_PKEY: if ((takey = X509_get_pubkey(ca)) == 0) msg_panic("trust-anchor certificate has null pkey"); wrap_key(TLScontext, depth, takey, cert); EVP_PKEY_free(takey); break; default: msg_panic("unexpected tls_dane_match result: %d", match); } cert = 0; break; } /* Add untrusted ca. */ grow_chain(TLScontext, UNTRUSTED, ca); /* Final untrusted self-signed element? */ if (X509_check_issued(ca, ca) == X509_V_OK) { cert = 0; break; } /* Restart with issuer as subject */ cert = ca; } /* * When the loop exits, if "cert" is set, it is not self-signed and has * no issuer in the chain, we check for a possible signature via a DNS * obtained TA cert or public key. Otherwise, we found no TAs and no * issuer, so set an empty list of TAs. */ if (!cert || !ta_signed(TLScontext, cert, depth)) { /* Create empty trust list if null, else NOP */ grow_chain(TLScontext, TRUSTED, 0); } /* shallow free */ if (in) sk_X509_free(in); } /* dane_cb - wrap chain verification for DANE */ static int dane_cb(X509_STORE_CTX *ctx, void *app_ctx) { const char *myname = "dane_cb"; TLS_SESS_STATE *TLScontext = (TLS_SESS_STATE *) app_ctx; X509 *cert = X509_STORE_CTX_get0_cert(ctx); /* * Degenerate case: depth 0 self-signed cert. * * XXX: Should we suppress name checks, ... when the leaf certificate is a * TA. After all they could sign any name they want. However, this * requires a bit of additional code. For now we allow depth 0 TAs, but * then the peer name has to match. */ if (X509_check_issued(cert, cert) == X509_V_OK) { /* * Empty untrusted chain, could be NULL, but then ABI check less * reliable, we may zero some other field, ... */ grow_chain(TLScontext, UNTRUSTED, 0); if (tls_dane_match(TLScontext, TLS_DANE_TA, cert, 0)) { TLScontext->tadepth = 0; grow_chain(TLScontext, TRUSTED, cert); } else grow_chain(TLScontext, TRUSTED, 0); } else { set_trust(TLScontext, ctx); } /* * Check that setting the untrusted chain updates the expected structure * member at the expected offset. */ X509_STORE_CTX_set0_trusted_stack(ctx, TLScontext->trusted); X509_STORE_CTX_set0_untrusted(ctx, TLScontext->untrusted); if (X509_STORE_CTX_get0_untrusted(ctx) != TLScontext->untrusted) msg_panic("%s: OpenSSL ABI change", myname); return X509_verify_cert(ctx); } /* tls_dane_set_callback - set or clear verification wrapper callback */ void tls_dane_set_callback(SSL_CTX *ctx, TLS_SESS_STATE *TLScontext) { if (TLS_DANE_HASTA(TLScontext->dane)) SSL_CTX_set_cert_verify_callback(ctx, dane_cb, (void *) TLScontext); else SSL_CTX_set_cert_verify_callback(ctx, 0, 0); } #ifdef TEST #include #include #include #include #include static int verify_chain(SSL *ssl, x509_stack_t *chain, TLS_SESS_STATE *tctx) { int ret; X509 *cert; X509_STORE_CTX *store_ctx; SSL_CTX *ssl_ctx = SSL_get_SSL_CTX(ssl); X509_STORE *store = SSL_CTX_get_cert_store(ssl_ctx); int store_ctx_idx = SSL_get_ex_data_X509_STORE_CTX_idx(); cert = sk_X509_value(chain, 0); if ((store_ctx = X509_STORE_CTX_new()) == NULL) { SSLerr(SSL_F_SSL_VERIFY_CERT_CHAIN, ERR_R_MALLOC_FAILURE); return 0; } if (!X509_STORE_CTX_init(store_ctx, store, cert, chain)) { X509_STORE_CTX_free(store_ctx); return 0; } X509_STORE_CTX_set_ex_data(store_ctx, store_ctx_idx, ssl); X509_STORE_CTX_set_default(store_ctx, "ssl_server"); X509_VERIFY_PARAM_set1(X509_STORE_CTX_get0_param(store_ctx), SSL_get0_param(ssl)); if (SSL_get_verify_callback(ssl)) X509_STORE_CTX_set_verify_cb(store_ctx, SSL_get_verify_callback(ssl)); ret = dane_cb(store_ctx, tctx); SSL_set_verify_result(ssl, X509_STORE_CTX_get_error(store_ctx)); X509_STORE_CTX_free(store_ctx); return (ret); } static void add_tlsa(TLS_DANE *dane, char *argv[]) { char *digest; X509 *cert = 0; BIO *bp; unsigned char *buf; unsigned char *buf2; int len; uint8_t u = atoi(argv[1]); uint8_t s = atoi(argv[2]); const char *mdname = argv[3]; EVP_PKEY *pkey; /* Unsupported usages are fatal */ switch (u) { case DNS_TLSA_USAGE_TRUST_ANCHOR_ASSERTION: case DNS_TLSA_USAGE_DOMAIN_ISSUED_CERTIFICATE: break; default: msg_fatal("unsupported certificate usage %u", u); } /* Unsupported selectors are fatal */ switch (s) { case DNS_TLSA_SELECTOR_FULL_CERTIFICATE: case DNS_TLSA_SELECTOR_SUBJECTPUBLICKEYINFO: break; default: msg_fatal("unsupported selector %u", s); } /* Unsupported digests are fatal */ if (*mdname && !tls_validate_digest(mdname)) msg_fatal("unsupported digest algorithm: %s", mdname); if ((bp = BIO_new_file(argv[4], "r")) == NULL) msg_fatal("error opening %s: %m", argv[4]); if (!PEM_read_bio_X509(bp, &cert, 0, 0)) { tls_print_errors(); msg_fatal("error loading certificate from %s: %m", argv[4]); } BIO_free(bp); /* * Extract ASN.1 DER form of certificate or public key. */ switch (s) { case DNS_TLSA_SELECTOR_FULL_CERTIFICATE: len = i2d_X509(cert, NULL); buf2 = buf = (unsigned char *) mymalloc(len); i2d_X509(cert, &buf2); if (!*mdname) ta_cert_insert(dane, cert); break; case DNS_TLSA_SELECTOR_SUBJECTPUBLICKEYINFO: pkey = X509_get_pubkey(cert); len = i2d_PUBKEY(pkey, NULL); buf2 = buf = (unsigned char *) mymalloc(len); i2d_PUBKEY(pkey, &buf2); if (!*mdname) ta_pkey_insert(dane, pkey); EVP_PKEY_free(pkey); break; } OPENSSL_assert(buf2 - buf == len); digest = tls_data_fprint((char *) buf, len, *mdname ? mdname : signalg); dane_add(dane, u, s, *mdname ? mdname : signalg, digest); myfree((void *) digest); myfree((void *) buf); } static x509_stack_t *load_chain(const char *chainfile) { BIO *bp; char *name = 0; char *header = 0; unsigned char *data = 0; long len; int count; char *errtype = 0; /* if error: cert or pkey? */ x509_stack_t *chain; typedef X509 *(*d2i_X509_t) (X509 **, const unsigned char **, long); if ((chain = sk_X509_new_null()) == 0) { perror("malloc"); exit(1); } /* * On each call, PEM_read() wraps a stdio file in a BIO_NOCLOSE bio, * calls PEM_read_bio() and then frees the bio. It is just as easy to * open a BIO as a stdio file, so we use BIOs and call PEM_read_bio() * directly. */ if ((bp = BIO_new_file(chainfile, "r")) == NULL) { fprintf(stderr, "error opening chainfile: %s: %m\n", chainfile); exit(1); } /* Don't report old news */ ERR_clear_error(); for (count = 0; errtype == 0 && PEM_read_bio(bp, &name, &header, &data, &len); ++count) { const unsigned char *p = data; if (strcmp(name, PEM_STRING_X509) == 0 || strcmp(name, PEM_STRING_X509_TRUSTED) == 0 || strcmp(name, PEM_STRING_X509_OLD) == 0) { d2i_X509_t d; X509 *cert; d = strcmp(name, PEM_STRING_X509_TRUSTED) ? d2i_X509_AUX : d2i_X509; if ((cert = d(0, &p, len)) == 0 || (p - data) != len) errtype = "certificate"; else if (sk_X509_push(chain, cert) == 0) { perror("malloc"); exit(1); } } else { fprintf(stderr, "unexpected chain file object: %s\n", name); exit(1); } /* * If any of these were null, PEM_read() would have failed. */ OPENSSL_free(name); OPENSSL_free(header); OPENSSL_free(data); } BIO_free(bp); if (errtype) { tls_print_errors(); fprintf(stderr, "error reading: %s: malformed %s", chainfile, errtype); exit(1); } if (ERR_GET_REASON(ERR_peek_last_error()) == PEM_R_NO_START_LINE) { /* Reached end of PEM file */ ERR_clear_error(); if (count > 0) return chain; fprintf(stderr, "no certificates found in: %s\n", chainfile); exit(1); } /* Some other PEM read error */ tls_print_errors(); fprintf(stderr, "error reading: %s\n", chainfile); exit(1); } static void usage(const char *progname) { fprintf(stderr, "Usage: %s certificate-usage selector matching-type" " certfile \\\n\t\tCAfile chainfile hostname [certname ...]\n", progname); fprintf(stderr, " where, certificate-usage = TLSA certificate usage,\n"); fprintf(stderr, "\t selector = TLSA selector,\n"); fprintf(stderr, "\t matching-type = empty string or OpenSSL digest algorithm name,\n"); fprintf(stderr, "\t PEM certfile provides certificate association data,\n"); fprintf(stderr, "\t PEM CAfile contains any usage 0/1 trusted roots,\n"); fprintf(stderr, "\t PEM chainfile = server chain file to verify\n"); fprintf(stderr, "\t hostname = destination hostname,\n"); fprintf(stderr, "\t each certname augments the hostname for name checks.\n"); exit(1); } /* match_servername - match servername against pattern */ static int match_servername(const char *certid, ARGV *margv) { const char *domain; const char *parent; int match_subdomain; int i; int idlen; int domlen; /* * XXX EAI support. */ /* * Match the certid against each pattern until we find a match. */ for (i = 0; i < margv->argc; ++i) { match_subdomain = 0; domain = margv->argv[i]; if (*domain == '.' && domain[1] != '\0') { ++domain; match_subdomain = 1; } /* * Sub-domain match: certid is any sub-domain of hostname. */ if (match_subdomain) { if ((idlen = strlen(certid)) > (domlen = strlen(domain)) + 1 && certid[idlen - domlen - 1] == '.' && !strcasecmp(certid + (idlen - domlen), domain)) return (1); else continue; } /* * Exact match and initial "*" match. The initial "*" in a certid * matches one (if var_tls_multi_label is false) or more hostname * components under the condition that the certid contains multiple * hostname components. */ if (!strcasecmp(certid, domain) || (certid[0] == '*' && certid[1] == '.' && certid[2] != 0 && (parent = strchr(domain, '.')) != 0 && (idlen = strlen(certid + 1)) <= (domlen = strlen(parent)) && strcasecmp(var_tls_multi_wildcard == 0 ? parent : parent + domlen - idlen, certid + 1) == 0)) return (1); } return (0); } static void check_name(TLS_SESS_STATE *tctx, X509 *cert, ARGV *margs) { char *cn; int matched = 0; general_name_stack_t *gens; if (SSL_get_verify_result(tctx->con) != X509_V_OK) return; tctx->peer_status |= TLS_CERT_FLAG_TRUSTED; gens = X509_get_ext_d2i(cert, NID_subject_alt_name, 0, 0); if (gens) { int has_dnsname = 0; int num_gens = sk_GENERAL_NAME_num(gens); int i; for (i = 0; !matched && i < num_gens; ++i) { const GENERAL_NAME *gn = sk_GENERAL_NAME_value(gens, i); const char *dnsname; if (gn->type != GEN_DNS) continue; has_dnsname = 1; tctx->peer_status |= TLS_CERT_FLAG_ALTNAME; dnsname = tls_dns_name(gn, tctx); if (dnsname && *dnsname && (matched = match_servername(dnsname, margs)) != 0) tctx->peer_status |= TLS_CERT_FLAG_MATCHED; } sk_GENERAL_NAME_pop_free(gens, GENERAL_NAME_free); if (has_dnsname) return; } cn = tls_peer_CN(cert, tctx); if (match_servername(cn, margs)) tctx->peer_status |= TLS_CERT_FLAG_MATCHED; myfree(cn); } static void check_print(TLS_SESS_STATE *tctx, X509 *cert) { if (TLS_DANE_HASEE(tctx->dane) && tls_dane_match(tctx, TLS_DANE_EE, cert, 0)) tctx->peer_status |= TLS_CERT_FLAG_TRUSTED | TLS_CERT_FLAG_MATCHED; } static void check_peer(TLS_SESS_STATE *tctx, X509 *cert, int argc, char **argv) { ARGV match; tctx->peer_status |= TLS_CERT_FLAG_PRESENT; check_print(tctx, cert); if (!TLS_CERT_IS_MATCHED(tctx)) { match.argc = argc; match.argv = argv; check_name(tctx, cert, &match); } } static SSL_CTX *ctx_init(const char *CAfile) { SSL_CTX *client_ctx; tls_param_init(); tls_check_version(); #if OPENSSL_VERSION_NUMBER < 0x10100000L SSL_load_error_strings(); SSL_library_init(); #endif if (!tls_validate_digest(LN_sha1)) msg_fatal("%s digest algorithm not available", LN_sha1); if (TLScontext_index < 0) if ((TLScontext_index = SSL_get_ex_new_index(0, 0, 0, 0, 0)) < 0) msg_fatal("Cannot allocate SSL application data index"); ERR_clear_error(); if ((client_ctx = SSL_CTX_new(TLS_client_method())) == 0) msg_fatal("cannot allocate client SSL_CTX"); SSL_CTX_set_verify_depth(client_ctx, 5); if (tls_set_ca_certificate_info(client_ctx, CAfile, "") < 0) { tls_print_errors(); msg_fatal("cannot load CAfile: %s", CAfile); } SSL_CTX_set_verify(client_ctx, SSL_VERIFY_NONE, tls_verify_certificate_callback); return (client_ctx); } int main(int argc, char *argv[]) { SSL_CTX *ssl_ctx; TLS_SESS_STATE *tctx; x509_stack_t *chain; var_procname = mystrdup(basename(argv[0])); set_mail_conf_str(VAR_PROCNAME, var_procname); msg_vstream_init(var_procname, VSTREAM_OUT); if (argc < 8) usage(argv[0]); ssl_ctx = ctx_init(argv[5]); if (!tls_dane_avail()) msg_fatal("DANE TLSA support not available"); tctx = tls_alloc_sess_context(TLS_LOG_NONE, argv[7]); tctx->namaddr = argv[7]; tctx->mdalg = LN_sha1; tctx->dane = tls_dane_alloc(); if ((tctx->con = SSL_new(ssl_ctx)) == 0 || !SSL_set_ex_data(tctx->con, TLScontext_index, tctx)) { tls_print_errors(); msg_fatal("Error allocating SSL connection"); } SSL_set_connect_state(tctx->con); add_tlsa((TLS_DANE *) tctx->dane, argv); tls_dane_set_callback(ssl_ctx, tctx); /* Verify saved server chain */ chain = load_chain(argv[6]); verify_chain(tctx->con, chain, tctx); check_peer(tctx, sk_X509_value(chain, 0), argc - 7, argv + 7); tls_print_errors(); msg_info("%s %s", TLS_CERT_IS_MATCHED(tctx) ? "Verified" : TLS_CERT_IS_TRUSTED(tctx) ? "Trusted" : "Untrusted", argv[7]); return (TLS_CERT_IS_MATCHED(tctx) ? 0 : 1); } #endif /* TEST */ #endif /* USE_TLS */