Adding upstream version 4.94.2.upstream/4.94.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1719 insertions, 0 deletions

diff --git a/src/dane-openssl.c b/src/dane-openssl.c
new file mode 100644
index 0000000..6ed3529
--- /dev/null
+++ b/src/dane-openssl.c
@@ -0,0 +1,1719 @@
+/*
+ *  Author: Viktor Dukhovni
+ *  License: THIS CODE IS IN THE PUBLIC DOMAIN.
+ *
+ * Copyright (c) The Exim Maintainers 2014 - 2019
+ */
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <openssl/opensslv.h>
+#include <openssl/err.h>
+#include <openssl/crypto.h>
+#include <openssl/safestack.h>
+#include <openssl/objects.h>
+#include <openssl/x509.h>
+#include <openssl/x509v3.h>
+#include <openssl/evp.h>
+#include <openssl/bn.h>
+
+#if OPENSSL_VERSION_NUMBER < 0x1000000fL
+# error "OpenSSL 1.0.0 or higher required"
+#endif
+
+#if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
+# define X509_up_ref(x) CRYPTO_add(&((x)->references), 1, CRYPTO_LOCK_X509)
+#endif
+
+/* LibreSSL 2.9.0 and later - 2.9.0 has removed a number of macros ... */
+#ifdef LIBRESSL_VERSION_NUMBER
+# if LIBRESSL_VERSION_NUMBER >= 0x2090000fL
+#  define EXIM_HAVE_ASN1_MACROS
+# endif
+#endif
+/* OpenSSL */
+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
+# define EXIM_HAVE_ASN1_MACROS
+# define EXIM_OPAQUE_X509
+/* Older OpenSSL and all LibreSSL */
+#else
+# define X509_STORE_CTX_get_verify(ctx)		(ctx)->verify
+# define X509_STORE_CTX_get_verify_cb(ctx)	(ctx)->verify_cb
+# define X509_STORE_CTX_get0_cert(ctx)		(ctx)->cert
+# define X509_STORE_CTX_get0_chain(ctx)		(ctx)->chain
+# define X509_STORE_CTX_get0_untrusted(ctx)	(ctx)->untrusted
+
+# define X509_STORE_CTX_set_verify(ctx, verify_chain)	(ctx)->verify = (verify_chain)
+# define X509_STORE_CTX_set0_verified_chain(ctx, sk)	(ctx)->chain = (sk)
+# define X509_STORE_CTX_set_error_depth(ctx, val)	(ctx)->error_depth = (val)
+# define X509_STORE_CTX_set_current_cert(ctx, cert)	(ctx)->current_cert = (cert)
+
+# define ASN1_STRING_get0_data	ASN1_STRING_data
+# define X509_getm_notBefore	X509_get_notBefore
+# define X509_getm_notAfter	X509_get_notAfter
+
+# define CRYPTO_ONCE_STATIC_INIT 0
+# define CRYPTO_THREAD_run_once	 run_once
+typedef int CRYPTO_ONCE;
+#endif
+
+
+#include "danessl.h"
+
+#define DANESSL_F_ADD_SKID		100
+#define DANESSL_F_ADD_TLSA		101
+#define DANESSL_F_CHECK_END_ENTITY	102
+#define DANESSL_F_CTX_INIT		103
+#define DANESSL_F_GROW_CHAIN		104
+#define DANESSL_F_INIT			105
+#define DANESSL_F_LIBRARY_INIT		106
+#define DANESSL_F_LIST_ALLOC		107
+#define DANESSL_F_MATCH			108
+#define DANESSL_F_PUSH_EXT		109
+#define DANESSL_F_SET_TRUST_ANCHOR	110
+#define DANESSL_F_VERIFY_CERT		111
+#define DANESSL_F_WRAP_CERT		112
+#define DANESSL_F_DANESSL_VERIFY_CHAIN	113
+
+#define DANESSL_R_BAD_CERT		100
+#define DANESSL_R_BAD_CERT_PKEY		101
+#define DANESSL_R_BAD_DATA_LENGTH	102
+#define DANESSL_R_BAD_DIGEST		103
+#define DANESSL_R_BAD_NULL_DATA		104
+#define DANESSL_R_BAD_PKEY		105
+#define DANESSL_R_BAD_SELECTOR		106
+#define DANESSL_R_BAD_USAGE		107
+#define DANESSL_R_INIT			108
+#define DANESSL_R_LIBRARY_INIT		109
+#define DANESSL_R_NOSIGN_KEY		110
+#define DANESSL_R_SCTX_INIT		111
+#define DANESSL_R_SUPPORT		112
+
+#ifndef OPENSSL_NO_ERR
+#define	DANESSL_F_PLACEHOLDER		0		/* FIRST! Value TBD */
+static ERR_STRING_DATA dane_str_functs[] = {
+    /*	error				string */
+    {DANESSL_F_PLACEHOLDER,		"DANE library"},	/* FIRST!!! */
+    {DANESSL_F_ADD_SKID,		"add_skid"},
+    {DANESSL_F_ADD_TLSA,		"DANESSL_add_tlsa"},
+    {DANESSL_F_CHECK_END_ENTITY,	"check_end_entity"},
+    {DANESSL_F_CTX_INIT,		"DANESSL_CTX_init"},
+    {DANESSL_F_GROW_CHAIN,		"grow_chain"},
+    {DANESSL_F_INIT,			"DANESSL_init"},
+    {DANESSL_F_LIBRARY_INIT,		"DANESSL_library_init"},
+    {DANESSL_F_LIST_ALLOC,		"list_alloc"},
+    {DANESSL_F_MATCH,			"match"},
+    {DANESSL_F_PUSH_EXT,		"push_ext"},
+    {DANESSL_F_SET_TRUST_ANCHOR,	"set_trust_anchor"},
+    {DANESSL_F_VERIFY_CERT,		"verify_cert"},
+    {DANESSL_F_WRAP_CERT,		"wrap_cert"},
+    {0,					NULL}
+};
+static ERR_STRING_DATA dane_str_reasons[] = {
+    /*	error				string */
+    {DANESSL_R_BAD_CERT,	"Bad TLSA record certificate"},
+    {DANESSL_R_BAD_CERT_PKEY,	"Bad TLSA record certificate public key"},
+    {DANESSL_R_BAD_DATA_LENGTH,	"Bad TLSA record digest length"},
+    {DANESSL_R_BAD_DIGEST,	"Bad TLSA record digest"},
+    {DANESSL_R_BAD_NULL_DATA,	"Bad TLSA record null data"},
+    {DANESSL_R_BAD_PKEY,	"Bad TLSA record public key"},
+    {DANESSL_R_BAD_SELECTOR,	"Bad TLSA record selector"},
+    {DANESSL_R_BAD_USAGE,	"Bad TLSA record usage"},
+    {DANESSL_R_INIT,		"DANESSL_init() required"},
+    {DANESSL_R_LIBRARY_INIT,	"DANESSL_library_init() required"},
+    {DANESSL_R_NOSIGN_KEY,	"Certificate usage 2 requires EC support"},
+    {DANESSL_R_SCTX_INIT,	"DANESSL_CTX_init() required"},
+    {DANESSL_R_SUPPORT,		"DANE library features not supported"},
+    {0,				NULL}
+};
+#endif
+
+#define DANEerr(f, r) ERR_PUT_error(err_lib_dane, (f), (r), __FUNCTION__, __LINE__)
+
+static int err_lib_dane = -1;
+static int dane_idx = -1;
+
+#ifdef X509_V_FLAG_PARTIAL_CHAIN       /* OpenSSL >= 1.0.2 */
+static int wrap_to_root = 0;
+#else
+static int wrap_to_root = 1;
+#endif
+
+static void (*cert_free)(void *) = (void (*)(void *)) X509_free;
+static void (*pkey_free)(void *) = (void (*)(void *)) EVP_PKEY_free;
+
+typedef struct dane_list
+{
+    struct dane_list *next;
+    void *value;
+} *dane_list;
+
+#define LINSERT(h, e) do { (e)->next = (h); (h) = (e); } while (0)
+
+typedef struct dane_host_list
+{
+    struct dane_host_list *next;
+    char *value;
+} *dane_host_list;
+
+typedef struct dane_data
+{
+    size_t datalen;
+    unsigned char data[0];
+} *dane_data;
+
+typedef struct dane_data_list
+{
+    struct dane_data_list *next;
+    dane_data value;
+} *dane_data_list;
+
+typedef struct dane_mtype
+{
+    int mdlen;
+    const EVP_MD *md;
+    dane_data_list data;
+} *dane_mtype;
+
+typedef struct dane_mtype_list
+{
+    struct dane_mtype_list *next;
+    dane_mtype value;
+} *dane_mtype_list;
+
+typedef struct dane_selector
+{
+    uint8_t selector;
+    dane_mtype_list mtype;
+} *dane_selector;
+
+typedef struct dane_selector_list
+{
+    struct dane_selector_list *next;
+    dane_selector value;
+} *dane_selector_list;
+
+typedef struct dane_pkey_list
+{
+    struct dane_pkey_list *next;
+    EVP_PKEY *value;
+} *dane_pkey_list;
+
+typedef struct dane_cert_list
+{
+    struct dane_cert_list *next;
+    X509 *value;
+} *dane_cert_list;
+
+typedef struct ssl_dane
+{
+    int            (*verify)(X509_STORE_CTX *);
+    STACK_OF(X509) *roots;
+    STACK_OF(X509) *chain;
+    X509           *match;		/* Matched cert */
+    const char     *thost;		/* TLSA base domain */
+    char	   *mhost;		/* Matched peer name */
+    dane_pkey_list pkeys;
+    dane_cert_list certs;
+    dane_host_list hosts;
+    dane_selector_list selectors[DANESSL_USAGE_LAST + 1];
+    int            depth;
+    int		   mdpth;		/* Depth of matched cert */
+    int		   multi;		/* Multi-label wildcards? */
+    int		   count;		/* Number of TLSA records */
+} ssl_dane;
+
+#ifndef X509_V_ERR_HOSTNAME_MISMATCH
+# define X509_V_ERR_HOSTNAME_MISMATCH X509_V_ERR_APPLICATION_VERIFICATION
+#endif
+
+
+
+static int
+match(dane_selector_list slist, X509 *cert, int depth)
+{
+int matched;
+
+/*
+ * Note, set_trust_anchor() 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 (DANESSL_SELECTOR_CERT + 1)
+#define MATCHED_PKEY (DANESSL_SELECTOR_SPKI + 1)
+
+/*
+ * Loop over each selector, mtype, and associated data element looking
+ * for a match.
+ */
+for (matched = 0; !matched && slist; slist = slist->next)
+  {
+  unsigned char mdbuf[EVP_MAX_MD_SIZE];
+  unsigned char *buf = NULL;
+  unsigned char *buf2;
+  unsigned int len = 0;
+
+  /*
+   * Extract ASN.1 DER form of certificate or public key.
+   */
+  switch(slist->value->selector)
+    {
+    case DANESSL_SELECTOR_CERT:
+      len = i2d_X509(cert, NULL);
+      buf2 = buf = US  OPENSSL_malloc(len);
+      if(buf) i2d_X509(cert, &buf2);
+      break;
+    case DANESSL_SELECTOR_SPKI:
+      len = i2d_X509_PUBKEY(X509_get_X509_PUBKEY(cert), NULL);
+      buf2 = buf = US  OPENSSL_malloc(len);
+      if(buf) i2d_X509_PUBKEY(X509_get_X509_PUBKEY(cert), &buf2);
+      break;
+    }
+
+  if (!buf)
+    {
+    DANEerr(DANESSL_F_MATCH, ERR_R_MALLOC_FAILURE);
+    return 0;
+    }
+  OPENSSL_assert(buf2 - buf == len);
+
+  /*
+   * Loop over each mtype and data element
+   */
+  for (dane_mtype_list m = slist->value->mtype; !matched && m; m = m->next)
+    {
+    unsigned char *cmpbuf = buf;
+    unsigned int cmplen = len;
+
+    /*
+     * If it is a digest, compute the corresponding digest of the
+     * DER data for comparison, otherwise, use the full object.
+     */
+    if (m->value->md)
+      {
+      cmpbuf = mdbuf;
+      if (!EVP_Digest(buf, len, cmpbuf, &cmplen, m->value->md, 0))
+	  matched = -1;
+      }
+    for (dane_data_list d = m->value->data; !matched && d; d = d->next)
+	if (  cmplen == d->value->datalen
+	   && memcmp(cmpbuf, d->value->data, cmplen) == 0)
+	    matched = slist->value->selector + 1;
+    }
+
+  OPENSSL_free(buf);
+  }
+
+return matched;
+}
+
+static int
+push_ext(X509 *cert, X509_EXTENSION *ext)
+{
+if (ext)
+  {
+  if (X509_add_ext(cert, ext, -1))
+      return 1;
+  X509_EXTENSION_free(ext);
+  }
+DANEerr(DANESSL_F_PUSH_EXT, ERR_R_MALLOC_FAILURE);
+return 0;
+}
+
+static int
+add_ext(X509 *issuer, X509 *subject, int ext_nid, char *ext_val)
+{
+X509V3_CTX v3ctx;
+
+X509V3_set_ctx(&v3ctx, issuer, subject, 0, 0, 0);
+return push_ext(subject, X509V3_EXT_conf_nid(0, &v3ctx, ext_nid, ext_val));
+}
+
+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;
+}
+
+static int
+add_akid(X509 *cert, AUTHORITY_KEYID *akid)
+{
+int nid = NID_authority_key_identifier;
+ASN1_OCTET_STRING *id;
+unsigned char c = 0;
+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
+#ifdef EXIM_HAVE_ASN1_MACROS
+   && ASN1_OCTET_STRING_set(akid->keyid, (void *) &c, 1)
+#else
+   && M_ASN1_OCTET_STRING_set(akid->keyid, (void *) &c, 1)
+#endif
+   && X509_add1_ext_i2d(cert, nid, akid, 0, X509V3_ADD_APPEND))
+  ret = 1;
+if (akid)
+  AUTHORITY_KEYID_free(akid);
+return ret;
+}
+
+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");
+return X509_add1_ext_i2d(cert, nid, akid->keyid, 0, X509V3_ADD_APPEND) > 0;
+}
+
+static X509_NAME *
+akid_issuer_name(AUTHORITY_KEYID *akid)
+{
+if (akid && akid->issuer)
+  {
+  GENERAL_NAMES *gens = akid->issuer;
+
+  for (int 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;
+}
+
+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.
+ */
+return X509_set_issuer_name(cert,
+			    name ? name : subj);
+}
+
+static int
+grow_chain(ssl_dane *dane, int trusted, X509 *cert)
+{
+STACK_OF(X509) **xs = trusted ? &dane->roots : &dane->chain;
+static ASN1_OBJECT *serverAuth = 0;
+
+#define UNTRUSTED 0
+#define TRUSTED 1
+
+if (  trusted && !serverAuth
+   && !(serverAuth = OBJ_nid2obj(NID_server_auth)))
+  {
+  DANEerr(DANESSL_F_GROW_CHAIN, ERR_R_MALLOC_FAILURE);
+  return 0;
+  }
+if (!*xs && !(*xs = sk_X509_new_null()))
+  {
+  DANEerr(DANESSL_F_GROW_CHAIN, ERR_R_MALLOC_FAILURE);
+  return 0;
+  }
+
+if (cert)
+  {
+  if (trusted && !X509_add1_trust_object(cert, serverAuth))
+    return 0;
+#ifdef EXIM_OPAQUE_X509
+  X509_up_ref(cert);
+#else
+  CRYPTO_add(&cert->references, 1, CRYPTO_LOCK_X509);
+#endif
+  if (!sk_X509_push(*xs, cert))
+    {
+    X509_free(cert);
+    DANEerr(DANESSL_F_GROW_CHAIN, ERR_R_MALLOC_FAILURE);
+    return 0;
+    }
+  }
+return 1;
+}
+
+static int
+wrap_issuer(ssl_dane *dane, EVP_PKEY *key, X509 *subject, int depth, int top)
+{
+int ret = 1;
+X509 *cert = 0;
+AUTHORITY_KEYID *akid;
+X509_NAME *name = X509_get_issuer_name(subject);
+EVP_PKEY *newkey = key ? key : X509_get_pubkey(subject);
+
+#define WRAP_MID 0              /* Ensure intermediate. */
+#define WRAP_TOP 1              /* Ensure self-signed. */
+
+if (!name || !newkey || !(cert = X509_new()))
+  return 0;
+
+/*
+ * Record the depth of the trust-anchor certificate.
+ */
+if (dane->depth < 0)
+  dane->depth = depth + 1;
+
+/*
+ * XXX: Uncaught error condition:
+ *
+ * The return value is NULL both when the extension is missing, and when
+ * OpenSSL rans out of memory while parsing the extension.
+ */
+ERR_clear_error();
+akid = X509_get_ext_d2i(subject, NID_authority_key_identifier, 0, 0);
+/* XXX: Should we peek at the error stack here??? */
+
+/*
+ * If top is true generate a self-issued root CA, otherwise an
+ * intermediate CA and possibly its self-signed issuer.
+ *
+ * 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, newkey)
+   || !add_ext(0, cert, NID_basic_constraints, "CA:TRUE")
+   || (!top && !add_akid(cert, akid))
+   || !add_skid(cert, akid)
+   || (  !top && wrap_to_root
+      && !wrap_issuer(dane, newkey, cert, depth, WRAP_TOP)))
+  ret = 0;
+
+if (akid)
+  AUTHORITY_KEYID_free(akid);
+if (!key)
+  EVP_PKEY_free(newkey);
+if (ret)
+  ret = grow_chain(dane, !top && wrap_to_root ? UNTRUSTED : TRUSTED, cert);
+if (cert)
+  X509_free(cert);
+return ret;
+}
+
+static int
+wrap_cert(ssl_dane *dane, X509 *tacert, int depth)
+{
+if (dane->depth < 0)
+  dane->depth = depth + 1;
+
+/*
+ * If the TA certificate is self-issued, or need not be, use it directly.
+ * Otherwise, synthesize requisite ancestors.
+ */
+if (  !wrap_to_root
+   || X509_check_issued(tacert, tacert) == X509_V_OK)
+  return grow_chain(dane, TRUSTED, tacert);
+
+if (wrap_issuer(dane, 0, tacert, depth, WRAP_MID))
+  return grow_chain(dane, UNTRUSTED, tacert);
+return 0;
+}
+
+static int
+ta_signed(ssl_dane *dane, X509 *cert, int depth)
+{
+EVP_PKEY *pk;
+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 (dane_cert_list x = dane->certs; !done && x; x = x->next)
+  {
+  if (X509_check_issued(x->value, cert) == X509_V_OK)
+    {
+    if (!(pk = X509_get_pubkey(x->value)))
+      {
+      /*
+       * The cert originally contained a valid pkey, which does
+       * not just vanish, so this is most likely a memory error.
+       */
+      done = -1;
+      break;
+      }
+    /* Check signature, since some other TA may work if not this. */
+    if (X509_verify(cert, pk) > 0)
+      done = wrap_cert(dane, x->value, depth) ? 1 : -1;
+    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 (dane_pkey_list k = dane->pkeys; !done && k; k = k->next)
+  if (X509_verify(cert, k->value) > 0)
+    done = wrap_issuer(dane, k->value, cert, depth, WRAP_MID) ? 1 : -1;
+  else
+    ERR_clear_error();
+
+return done;
+}
+
+static int
+set_trust_anchor(X509_STORE_CTX *ctx, ssl_dane *dane, X509 *cert)
+{
+int matched = 0;
+int depth = 0;
+EVP_PKEY *takey;
+X509 *ca;
+STACK_OF(X509) *in = X509_STORE_CTX_get0_untrusted(ctx);
+
+if (!grow_chain(dane, UNTRUSTED, 0))
+  return -1;
+
+/*
+ * Accept a degenerate case: depth 0 self-signed trust-anchor.
+ */
+if (X509_check_issued(cert, cert) == X509_V_OK)
+  {
+  dane->depth = 0;
+  matched = match(dane->selectors[DANESSL_USAGE_DANE_TA], cert, 0);
+  if (matched > 0 && !grow_chain(dane, TRUSTED, cert))
+    matched = -1;
+  return matched;
+  }
+
+/* Make a shallow copy of the input untrusted chain. */
+if (!(in = sk_X509_dup(in)))
+  {
+  DANEerr(DANESSL_F_SET_TRUST_ANCHOR, ERR_R_MALLOC_FAILURE);
+  return -1;
+  }
+
+/*
+ * 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 (int n = sk_X509_num(in); n > 0; --n, ++depth)
+  {
+  int i;
+  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);
+
+  /* If not a trust anchor, record untrusted ca and continue. */
+  if ((matched = match(dane->selectors[DANESSL_USAGE_DANE_TA], ca,
+		     depth + 1)) == 0)
+    {
+    if (grow_chain(dane, UNTRUSTED, ca))
+      {
+      if (X509_check_issued(ca, ca) != X509_V_OK)
+	{
+	/* Restart with issuer as subject */
+	cert = ca;
+	continue;
+	}
+      /* Final self-signed element, skip ta_signed() check. */
+      cert = 0;
+      }
+    else
+      matched = -1;
+    }
+  else if(matched == MATCHED_CERT)
+    {
+    if(!wrap_cert(dane, ca, depth))
+      matched = -1;
+    }
+  else if(matched == MATCHED_PKEY)
+    {
+    if (  !(takey = X509_get_pubkey(ca))
+       || !wrap_issuer(dane, takey, cert, depth, WRAP_MID))
+      {
+      if (takey)
+	EVP_PKEY_free(takey);
+      else
+	DANEerr(DANESSL_F_SET_TRUST_ANCHOR, ERR_R_MALLOC_FAILURE);
+      matched = -1;
+      }
+    }
+  break;
+  }
+
+/* Shallow free the duplicated input untrusted chain. */
+sk_X509_free(in);
+
+/*
+ * 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.
+ */
+if (matched == 0 && cert)
+  matched = ta_signed(dane, cert, depth);
+
+return matched;
+}
+
+static int
+check_end_entity(X509_STORE_CTX *ctx, ssl_dane *dane, X509 *cert)
+{
+int matched;
+
+matched = match(dane->selectors[DANESSL_USAGE_DANE_EE], cert, 0);
+if (matched > 0)
+  {
+  dane->mdpth = 0;
+  dane->match = cert;
+  X509_up_ref(cert);
+  if(!X509_STORE_CTX_get0_chain(ctx))
+    {
+    STACK_OF(X509) * sk = sk_X509_new_null();
+    if (sk && sk_X509_push(sk, cert))
+      {
+      X509_up_ref(cert);
+      X509_STORE_CTX_set0_verified_chain(ctx, sk);
+      }
+    else
+      {
+      if (sk) sk_X509_free(sk);
+      DANEerr(DANESSL_F_CHECK_END_ENTITY, ERR_R_MALLOC_FAILURE);
+      return -1;
+      }
+    }
+  }
+return matched;
+}
+
+static int
+match_name(const char *certid, ssl_dane *dane)
+{
+int multi = dane->multi;
+
+for (dane_host_list hosts = dane->hosts; hosts; hosts = hosts->next)
+  {
+  int match_subdomain = 0;
+  const char *domain = hosts->value;
+  const char *parent;
+  int idlen;
+  int domlen;
+
+  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 multi 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(multi ? parent + domlen - idlen : parent, certid+1) == 0))
+    return 1;
+  }
+return 0;
+}
+
+static const char *
+check_name(const char *name, int len)
+{
+const char *cp = name + len;
+
+while (len > 0 && !*--cp)
+  --len;                          /* Ignore trailing NULs */
+if (len <= 0)
+  return 0;
+for (cp = name; *cp; cp++)
+  {
+  char c = *cp;
+  if (!((c >= 'a' && c <= 'z') ||
+	(c >= '0' && c <= '9') ||
+	(c >= 'A' && c <= 'Z') ||
+	(c == '.' || c == '-') ||
+	(c == '*')))
+    return 0;                   /* Only LDH, '.' and '*' */
+  }
+if (cp - name != len)               /* Guard against internal NULs */
+  return 0;
+return name;
+}
+
+static const char *
+parse_dns_name(const GENERAL_NAME *gn)
+{
+if (gn->type != GEN_DNS)
+  return 0;
+if (ASN1_STRING_type(gn->d.ia5) != V_ASN1_IA5STRING)
+  return 0;
+return check_name(CCS  ASN1_STRING_get0_data(gn->d.ia5),
+		  ASN1_STRING_length(gn->d.ia5));
+}
+
+static char *
+parse_subject_name(X509 *cert)
+{
+X509_NAME *name = X509_get_subject_name(cert);
+X509_NAME_ENTRY *entry;
+ASN1_STRING *entry_str;
+unsigned char *namebuf;
+int nid = NID_commonName;
+int len;
+int i;
+
+if (!name || (i = X509_NAME_get_index_by_NID(name, nid, -1)) < 0)
+  return 0;
+if (!(entry = X509_NAME_get_entry(name, i)))
+  return 0;
+if (!(entry_str = X509_NAME_ENTRY_get_data(entry)))
+  return 0;
+
+if ((len = ASN1_STRING_to_UTF8(&namebuf, entry_str)) < 0)
+  return 0;
+if (len <= 0 || check_name(CS  namebuf, len) == 0)
+  {
+  OPENSSL_free(namebuf);
+  return 0;
+  }
+return CS  namebuf;
+}
+
+static int
+name_check(ssl_dane *dane, X509 *cert)
+{
+int matched = 0;
+BOOL got_altname = FALSE;
+GENERAL_NAMES *gens;
+
+gens = X509_get_ext_d2i(cert, NID_subject_alt_name, 0, 0);
+if (gens)
+  {
+  int n = sk_GENERAL_NAME_num(gens);
+
+  for (int i = 0; i < n; ++i)
+    {
+    const GENERAL_NAME *gn = sk_GENERAL_NAME_value(gens, i);
+    const char *certid;
+
+    if (gn->type != GEN_DNS)
+	continue;
+    got_altname = TRUE;
+    certid = parse_dns_name(gn);
+    if (certid && *certid)
+      {
+      if ((matched = match_name(certid, dane)) == 0)
+	continue;
+      if (!(dane->mhost = OPENSSL_strdup(certid)))
+	matched = -1;
+      DEBUG(D_tls) debug_printf("Dane name_check: matched SAN %s\n", certid);
+      break;
+      }
+    }
+  GENERAL_NAMES_free(gens);
+  }
+
+/*
+ * XXX: Should the subjectName be skipped when *any* altnames are present,
+ * or only when DNS altnames are present?
+ */
+if (!got_altname)
+  {
+  char *certid = parse_subject_name(cert);
+  if (certid != 0 && *certid && (matched = match_name(certid, dane)) != 0)
+    {
+    DEBUG(D_tls) debug_printf("Dane name_check: matched SN %s\n", certid);
+    dane->mhost = OPENSSL_strdup(certid);
+    }
+  if (certid)
+    OPENSSL_free(certid);
+  }
+return matched;
+}
+
+static int
+verify_chain(X509_STORE_CTX *ctx)
+{
+int (*cb)(int, X509_STORE_CTX *) = X509_STORE_CTX_get_verify_cb(ctx);
+X509 *cert = X509_STORE_CTX_get0_cert(ctx);
+STACK_OF(X509) * chain = X509_STORE_CTX_get0_chain(ctx);
+int chain_length = sk_X509_num(chain);
+int ssl_idx = SSL_get_ex_data_X509_STORE_CTX_idx();
+SSL *ssl = X509_STORE_CTX_get_ex_data(ctx, ssl_idx);
+ssl_dane *dane = SSL_get_ex_data(ssl, dane_idx);
+dane_selector_list issuer_rrs = dane->selectors[DANESSL_USAGE_PKIX_TA];
+dane_selector_list leaf_rrs = dane->selectors[DANESSL_USAGE_PKIX_EE];
+int matched = 0;
+
+DEBUG(D_tls) debug_printf("Dane verify_chain\n");
+
+/* Restore OpenSSL's internal_verify() as the signature check function */
+X509_STORE_CTX_set_verify(ctx, dane->verify);
+
+if ((matched = name_check(dane, cert)) < 0)
+  {
+  X509_STORE_CTX_set_error(ctx, X509_V_ERR_OUT_OF_MEM);
+  return 0;
+  }
+
+if (!matched)
+  {
+  X509_STORE_CTX_set_error_depth(ctx, 0);
+  X509_STORE_CTX_set_current_cert(ctx, cert);
+  X509_STORE_CTX_set_error(ctx, X509_V_ERR_HOSTNAME_MISMATCH);
+  if (!cb(0, ctx))
+    return 0;
+  }
+matched = 0;
+
+/*
+ * Satisfy at least one usage 0 or 1 constraint, unless we've already
+ * matched a usage 2 trust anchor.
+ *
+ * XXX: internal_verify() doesn't callback with top certs that are not
+ * self-issued.  This is fixed in OpenSSL 1.1.0.
+ */
+if (dane->roots && sk_X509_num(dane->roots))
+  {
+  X509 *top = sk_X509_value(chain, dane->depth);
+
+  dane->mdpth = dane->depth;
+  dane->match = top;
+  X509_up_ref(top);
+
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+  if (X509_check_issued(top, top) != X509_V_OK)
+    {
+    X509_STORE_CTX_set_error_depth(ctx, dane->depth);
+    X509_STORE_CTX_set_current_cert(ctx, top);
+    if (!cb(1, ctx))
+      return 0;
+    }
+#endif
+  /* Pop synthetic trust-anchor ancestors off the chain! */
+  while (--chain_length > dane->depth)
+      X509_free(sk_X509_pop(chain));
+  }
+else
+  {
+  int n = 0;
+  X509 *xn = cert;
+
+  /*
+   * Check for an EE match, then a CA match at depths > 0, and
+   * finally, if the EE cert is self-issued, for a depth 0 CA match.
+   */
+  if (leaf_rrs)
+    matched = match(leaf_rrs, xn, 0);
+  if (matched) DEBUG(D_tls) debug_printf("Dane verify_chain: matched EE\n");
+
+  if (!matched && issuer_rrs)
+    for (n = chain_length-1; !matched && n >= 0; --n)
+      {
+      xn = sk_X509_value(chain, n);
+      if (n > 0 || X509_check_issued(xn, xn) == X509_V_OK)
+	matched = match(issuer_rrs, xn, n);
+      }
+  if (matched) DEBUG(D_tls) debug_printf("Dane verify_chain: matched %s\n",
+    n>0 ? "CA" : "selfisssued EE");
+
+  if (!matched)
+    {
+    X509_STORE_CTX_set_error_depth(ctx, 0);
+    X509_STORE_CTX_set_current_cert(ctx, cert);
+    X509_STORE_CTX_set_error(ctx, X509_V_ERR_CERT_UNTRUSTED);
+    if (!cb(0, ctx))
+      return 0;
+    }
+  else
+    {
+    dane->mdpth = n;
+    dane->match = xn;
+    X509_up_ref(xn);
+    }
+  }
+
+/* Tail recurse into OpenSSL's internal_verify */
+return dane->verify(ctx);
+}
+
+static void
+dane_reset(ssl_dane *dane)
+{
+dane->depth = -1;
+if (dane->mhost)
+  {
+  OPENSSL_free(dane->mhost);
+  dane->mhost = 0;
+  }
+if (dane->roots)
+  {
+  sk_X509_pop_free(dane->roots, X509_free);
+  dane->roots = 0;
+  }
+if (dane->chain)
+  {
+  sk_X509_pop_free(dane->chain, X509_free);
+  dane->chain = 0;
+  }
+if (dane->match)
+  {
+  X509_free(dane->match);
+  dane->match = 0;
+  }
+dane->mdpth = -1;
+}
+
+static int
+verify_cert(X509_STORE_CTX *ctx, void *unused_ctx)
+{
+static int ssl_idx = -1;
+SSL *ssl;
+ssl_dane *dane;
+int (*cb)(int, X509_STORE_CTX *) = X509_STORE_CTX_get_verify_cb(ctx);
+X509 *cert = X509_STORE_CTX_get0_cert(ctx);
+int matched;
+
+DEBUG(D_tls) debug_printf("Dane verify_cert\n");
+
+if (ssl_idx < 0)
+  ssl_idx = SSL_get_ex_data_X509_STORE_CTX_idx();
+if (dane_idx < 0)
+  {
+  DANEerr(DANESSL_F_VERIFY_CERT, ERR_R_MALLOC_FAILURE);
+  return -1;
+  }
+
+ssl = X509_STORE_CTX_get_ex_data(ctx, ssl_idx);
+if (!(dane = SSL_get_ex_data(ssl, dane_idx)) || !cert)
+  return X509_verify_cert(ctx);
+
+/* Reset for verification of a new chain, perhaps a renegotiation. */
+dane_reset(dane);
+
+if (dane->selectors[DANESSL_USAGE_DANE_EE])
+  {
+  if ((matched = check_end_entity(ctx, dane, cert)) > 0)
+    {
+    X509_STORE_CTX_set_error_depth(ctx, 0);
+    X509_STORE_CTX_set_current_cert(ctx, cert);
+    return cb(1, ctx);
+    }
+  if (matched < 0)
+    {
+    X509_STORE_CTX_set_error(ctx, X509_V_ERR_OUT_OF_MEM);
+    return -1;
+    }
+  }
+
+if (dane->selectors[DANESSL_USAGE_DANE_TA])
+  {
+  if ((matched = set_trust_anchor(ctx, dane, cert)) < 0)
+    {
+    X509_STORE_CTX_set_error(ctx, X509_V_ERR_OUT_OF_MEM);
+    return -1;
+    }
+  if (matched)
+    {
+    /*
+     * Check that setting the untrusted chain updates the expected
+     * structure member at the expected offset.
+     */
+    X509_STORE_CTX_trusted_stack(ctx, dane->roots);
+    X509_STORE_CTX_set_chain(ctx, dane->chain);
+    OPENSSL_assert(dane->chain == X509_STORE_CTX_get0_untrusted(ctx));
+    }
+  }
+
+/*
+ * Name checks and usage 0/1 constraint enforcement are delayed until
+ * X509_verify_cert() builds the full chain and calls our verify_chain()
+ * wrapper.
+ */
+dane->verify = X509_STORE_CTX_get_verify(ctx);
+X509_STORE_CTX_set_verify(ctx, verify_chain);
+
+if (X509_verify_cert(ctx))
+  return 1;
+
+/*
+ * If the chain is invalid, clear any matching cert or hostname, to
+ * protect callers that might erroneously rely on these alone without
+ * checking the validation status.
+ */
+if (dane->match)
+  {
+  X509_free(dane->match);
+  dane->match = 0;
+  }
+if (dane->mhost)
+  {
+  OPENSSL_free(dane->mhost);
+  dane->mhost = 0;
+  }
+ return 0;
+}
+
+static dane_list
+list_alloc(size_t vsize)
+{
+void *value = (void *) OPENSSL_malloc(vsize);
+dane_list l;
+
+if (!value)
+  {
+  DANEerr(DANESSL_F_LIST_ALLOC, ERR_R_MALLOC_FAILURE);
+  return 0;
+  }
+if (!(l = (dane_list) OPENSSL_malloc(sizeof(*l))))
+  {
+  OPENSSL_free(value);
+  DANEerr(DANESSL_F_LIST_ALLOC, ERR_R_MALLOC_FAILURE);
+  return 0;
+  }
+l->next = 0;
+l->value = value;
+return l;
+}
+
+static void
+list_free(void *list, void (*f)(void *))
+{
+dane_list next;
+
+for (dane_list head = (dane_list) list; head; head = next)
+  {
+  next = head->next;
+  if (f && head->value)
+      f(head->value);
+  OPENSSL_free(head);
+  }
+}
+
+static void
+ossl_free(void * p)
+{
+OPENSSL_free(p);
+}
+
+static void
+dane_mtype_free(void *p)
+{
+list_free(((dane_mtype) p)->data, ossl_free);
+OPENSSL_free(p);
+}
+
+static void
+dane_selector_free(void *p)
+{
+list_free(((dane_selector) p)->mtype, dane_mtype_free);
+OPENSSL_free(p);
+}
+
+
+
+/*
+
+Tidy up once the connection is finished with.
+
+Arguments
+  ssl		The ssl connection handle
+
+=> Before calling SSL_free()
+tls_close() and tls_getc() [the error path] are the obvious places.
+Could we do it earlier - right after verification?  In tls_client_start()
+right after SSL_connect() returns, in that case.
+
+*/
+
+void
+DANESSL_cleanup(SSL *ssl)
+{
+ssl_dane *dane;
+
+DEBUG(D_tls) debug_printf("Dane lib-cleanup\n");
+
+if (dane_idx < 0 || !(dane = SSL_get_ex_data(ssl, dane_idx)))
+  return;
+(void) SSL_set_ex_data(ssl, dane_idx, 0);
+
+dane_reset(dane);
+if (dane->hosts)
+  list_free(dane->hosts, ossl_free);
+for (int u = 0; u <= DANESSL_USAGE_LAST; ++u)
+  if (dane->selectors[u])
+    list_free(dane->selectors[u], dane_selector_free);
+if (dane->pkeys)
+  list_free(dane->pkeys, pkey_free);
+if (dane->certs)
+  list_free(dane->certs, cert_free);
+OPENSSL_free(dane);
+}
+
+static dane_host_list
+host_list_init(const char **src)
+{
+dane_host_list head = NULL;
+
+while (*src)
+  {
+  dane_host_list elem = (dane_host_list) OPENSSL_malloc(sizeof(*elem));
+  if (elem == 0)
+    {
+    list_free(head, ossl_free);
+    return 0;
+    }
+  elem->value = OPENSSL_strdup(*src++);
+  LINSERT(head, elem);
+  }
+return head;
+}
+
+
+int
+DANESSL_get_match_cert(SSL *ssl, X509 **match, const char **mhost, int *depth)
+{
+ssl_dane *dane;
+
+if (dane_idx < 0 || (dane = SSL_get_ex_data(ssl, dane_idx)) == 0)
+  {
+  DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_INIT);
+  return -1;
+  }
+
+if (dane->match)
+  {
+  if (match)
+    *match = dane->match;
+  if (mhost)
+    *mhost = dane->mhost;
+  if (depth)
+    *depth = dane->mdpth;
+  }
+
+  return (dane->match != 0);
+}
+
+
+#ifdef never_called
+int
+DANESSL_verify_chain(SSL *ssl, STACK_OF(X509) *chain)
+{
+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()))
+  {
+  DANEerr(DANESSL_F_DANESSL_VERIFY_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_is_server(ssl) ? "ssl_client" : "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 = verify_cert(store_ctx, NULL);
+
+SSL_set_verify_result(ssl, X509_STORE_CTX_get_error(store_ctx));
+X509_STORE_CTX_cleanup(store_ctx);
+
+return (ret);
+}
+#endif
+
+
+
+
+/*
+
+Call this for each TLSA record found for the target, after the
+DANE setup has been done on the ssl connection handle.
+
+Arguments:
+  ssl		Connection handle
+  usage		TLSA record field
+  selector	TLSA record field
+  mdname	??? message digest name?
+  data		??? TLSA record megalump?
+  dlen		length of data
+
+Return
+  -1 on error
+  0  action not taken
+  1  record accepted
+*/
+
+int
+DANESSL_add_tlsa(SSL *ssl, uint8_t usage, uint8_t selector, const char *mdname,
+        unsigned const char *data, size_t dlen)
+{
+ssl_dane *dane;
+dane_selector_list s = 0;
+dane_mtype_list m = 0;
+dane_data_list d = 0;
+dane_cert_list xlist = 0;
+dane_pkey_list klist = 0;
+const EVP_MD *md = 0;
+
+DEBUG(D_tls) debug_printf("Dane add-tlsa: usage %u sel %u mdname \"%s\"\n",
+			  usage, selector, mdname);
+
+if(dane_idx < 0 || !(dane = SSL_get_ex_data(ssl, dane_idx)))
+  {
+  DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_INIT);
+  return -1;
+  }
+
+if (usage > DANESSL_USAGE_LAST)
+  {
+  DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_USAGE);
+  return 0;
+  }
+if (selector > DANESSL_SELECTOR_LAST)
+  {
+  DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_SELECTOR);
+  return 0;
+  }
+
+/* Support built-in standard one-digit mtypes */
+if (mdname && *mdname && mdname[1] == '\0')
+  switch (*mdname - '0')
+  {
+  case DANESSL_MATCHING_FULL: mdname = 0;	   break;
+  case DANESSL_MATCHING_2256: mdname = "sha256"; break;
+  case DANESSL_MATCHING_2512: mdname = "sha512"; break;
+  }
+if (mdname && *mdname && !(md = EVP_get_digestbyname(mdname)))
+  {
+  DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_DIGEST);
+  return 0;
+  }
+if (mdname && *mdname && dlen != EVP_MD_size(md))
+  {
+  DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_DATA_LENGTH);
+  return 0;
+  }
+if (!data)
+  {
+  DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_NULL_DATA);
+  return 0;
+  }
+
+/*
+ * Full Certificate or Public Key when NULL or empty digest name
+ */
+if (!mdname || !*mdname)
+  {
+  X509 *x = 0;
+  EVP_PKEY *k = 0;
+  const unsigned char *p = data;
+
+#define xklistinit(lvar, ltype, var, freeFunc) do { \
+	  (lvar) = (ltype) OPENSSL_malloc(sizeof(*(lvar))); \
+	  if ((lvar) == 0) { \
+	      DANEerr(DANESSL_F_ADD_TLSA, ERR_R_MALLOC_FAILURE); \
+	      freeFunc((var)); \
+	      return 0; \
+	  } \
+	  (lvar)->next = 0; \
+	  lvar->value = var; \
+      } while (0)
+#define xkfreeret(ret) do { \
+	  if (xlist) list_free(xlist, cert_free); \
+	  if (klist) list_free(klist, pkey_free); \
+	  return (ret); \
+      } while (0)
+
+  switch (selector)
+    {
+    case DANESSL_SELECTOR_CERT:
+      if (!d2i_X509(&x, &p, dlen) || dlen != p - data)
+	{
+	if (x)
+	  X509_free(x);
+	DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_CERT);
+	return 0;
+	}
+      k = X509_get_pubkey(x);
+      EVP_PKEY_free(k);
+      if (k == 0)
+	{
+	X509_free(x);
+	DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_CERT_PKEY);
+	return 0;
+	}
+      if (usage == DANESSL_USAGE_DANE_TA)
+	xklistinit(xlist, dane_cert_list, x, X509_free);
+      break;
+
+    case DANESSL_SELECTOR_SPKI:
+      if (!d2i_PUBKEY(&k, &p, dlen) || dlen != p - data)
+	{
+	if (k)
+	  EVP_PKEY_free(k);
+      DANEerr(DANESSL_F_ADD_TLSA, DANESSL_R_BAD_PKEY);
+      return 0;
+	}
+      if (usage == DANESSL_USAGE_DANE_TA)
+	xklistinit(klist, dane_pkey_list, k, EVP_PKEY_free);
+      break;
+    }
+  }
+
+/* Find insertion point and don't add duplicate elements. */
+for (s = dane->selectors[usage]; s; s = s->next)
+  if (s->value->selector == selector)
+    {
+    for (m = s->value->mtype; m; m = m->next)
+      if (m->value->md == md)
+	{
+	for (d = m->value->data; d; d = d->next)
+	  if (  d->value->datalen == dlen
+	     && memcmp(d->value->data, data, dlen) == 0)
+	    xkfreeret(1);
+	break;
+	}
+    break;
+    }
+
+if ((d = (dane_data_list) list_alloc(sizeof(*d->value) + dlen)) == 0)
+  xkfreeret(0);
+d->value->datalen = dlen;
+memcpy(d->value->data, data, dlen);
+if (!m)
+  {
+  if ((m = (dane_mtype_list) list_alloc(sizeof(*m->value))) == 0)
+    {
+    list_free(d, ossl_free);
+    xkfreeret(0);
+    }
+  m->value->data = 0;
+  if ((m->value->md = md) != 0)
+    m->value->mdlen = dlen;
+  if (!s)
+    {
+    if ((s = (dane_selector_list) list_alloc(sizeof(*s->value))) == 0)
+      {
+      list_free(m, dane_mtype_free);
+      xkfreeret(0);
+      }
+    s->value->mtype = 0;
+    s->value->selector = selector;
+    LINSERT(dane->selectors[usage], s);
+    }
+  LINSERT(s->value->mtype, m);
+  }
+LINSERT(m->value->data, d);
+
+if (xlist)
+  LINSERT(dane->certs, xlist);
+else if (klist)
+  LINSERT(dane->pkeys, klist);
+++dane->count;
+return 1;
+}
+
+
+
+
+/*
+Call this once we have an ssl connection handle but before
+making the TLS connection.
+
+=> In tls_client_start() after the call to SSL_new()
+and before the call to SSL_connect().  Exactly where
+probably does not matter.
+We probably want to keep our existing SNI handling;
+call this with NULL.
+
+Arguments:
+  ssl		Connection handle
+  sni_domain	Optional peer server name
+  hostnames	list of names to chack against peer cert
+
+Return
+  -1 on fatal error
+  0  nonfatal error
+  1  success
+*/
+
+int
+DANESSL_init(SSL *ssl, const char *sni_domain, const char **hostnames)
+{
+ssl_dane *dane;
+
+DEBUG(D_tls) debug_printf("Dane ssl_init\n");
+if (dane_idx < 0)
+  {
+  DANEerr(DANESSL_F_INIT, DANESSL_R_LIBRARY_INIT);
+  return -1;
+  }
+
+if (sni_domain && !SSL_set_tlsext_host_name(ssl, sni_domain))
+  return 0;
+
+if ((dane = (ssl_dane *) OPENSSL_malloc(sizeof(ssl_dane))) == 0)
+  {
+  DANEerr(DANESSL_F_INIT, ERR_R_MALLOC_FAILURE);
+  return 0;
+  }
+if (!SSL_set_ex_data(ssl, dane_idx, dane))
+  {
+  DANEerr(DANESSL_F_INIT, ERR_R_MALLOC_FAILURE);
+  OPENSSL_free(dane);
+  return 0;
+  }
+
+dane->verify = 0;
+dane->hosts = 0;
+dane->thost = 0;
+dane->pkeys = 0;
+dane->certs = 0;
+dane->chain = 0;
+dane->match = 0;
+dane->roots = 0;
+dane->depth = -1;
+dane->mhost = 0;			/* Future SSL control interface */
+dane->mdpth = 0;			/* Future SSL control interface */
+dane->multi = 0;			/* Future SSL control interface */
+dane->count = 0;
+dane->hosts = 0;
+
+for (int i = 0; i <= DANESSL_USAGE_LAST; ++i)
+  dane->selectors[i] = 0;
+
+if (hostnames && (dane->hosts = host_list_init(hostnames)) == 0)
+  {
+  DANEerr(DANESSL_F_INIT, ERR_R_MALLOC_FAILURE);
+  DANESSL_cleanup(ssl);
+  return 0;
+  }
+
+return 1;
+}
+
+
+/*
+
+Call this once we have a context to work with, but
+before DANESSL_init()
+
+=> in tls_client_start(), after tls_init() call gives us the ctx,
+if we decide we want to (policy) and can (TLSA records available)
+replacing (? what about fallback) everything from testing tls_verify_hosts
+down to just before calling SSL_new() for the conn handle.
+
+Arguments
+  ctx		SSL context
+
+Return
+  -1	Error
+  1	Success
+*/
+
+int
+DANESSL_CTX_init(SSL_CTX *ctx)
+{
+DEBUG(D_tls) debug_printf("Dane ctx-init\n");
+if (dane_idx >= 0)
+  {
+  SSL_CTX_set_cert_verify_callback(ctx, verify_cert, 0);
+  return 1;
+  }
+DANEerr(DANESSL_F_CTX_INIT, DANESSL_R_LIBRARY_INIT);
+return -1;
+}
+
+static void
+dane_init(void)
+{
+/*
+ * Store library id in zeroth function slot, used to locate the library
+ * name.  This must be done before we load the error strings.
+ */
+err_lib_dane = ERR_get_next_error_library();
+
+#ifndef OPENSSL_NO_ERR
+if (err_lib_dane > 0)
+  {
+  dane_str_functs[0].error |= ERR_PACK(err_lib_dane, 0, 0);
+  ERR_load_strings(err_lib_dane, dane_str_functs);
+  ERR_load_strings(err_lib_dane, dane_str_reasons);
+  }
+#endif
+
+/*
+ * Register SHA-2 digests, if implemented and not already registered.
+ */
+#if defined(LN_sha256) && defined(NID_sha256) && !defined(OPENSSL_NO_SHA256)
+if (!EVP_get_digestbyname(LN_sha224)) EVP_add_digest(EVP_sha224());
+if (!EVP_get_digestbyname(LN_sha256)) EVP_add_digest(EVP_sha256());
+#endif
+#if defined(LN_sha512) && defined(NID_sha512) && !defined(OPENSSL_NO_SHA512)
+if (!EVP_get_digestbyname(LN_sha384)) EVP_add_digest(EVP_sha384());
+if (!EVP_get_digestbyname(LN_sha512)) EVP_add_digest(EVP_sha512());
+#endif
+
+/*
+ * Register an SSL index for the connection-specific ssl_dane structure.
+ * Using a separate index makes it possible to add DANE support to
+ * existing OpenSSL releases that don't have a suitable pointer in the
+ * SSL structure.
+ */
+dane_idx = SSL_get_ex_new_index(0, 0, 0, 0, 0);
+}
+
+
+#if OPENSSL_VERSION_NUMBER < 0x10100000L || defined(LIBRESSL_VERSION_NUMBER)
+static void
+run_once(volatile int * once, void (*init)(void))
+{
+int wlock = 0;
+
+CRYPTO_r_lock(CRYPTO_LOCK_SSL_CTX);
+if (!*once)
+  {
+  CRYPTO_r_unlock(CRYPTO_LOCK_SSL_CTX);
+  CRYPTO_w_lock(CRYPTO_LOCK_SSL_CTX);
+  wlock = 1;
+  if (!*once)
+    {
+    *once = 1;
+    init();
+    }
+  }
+if (wlock)
+  CRYPTO_w_unlock(CRYPTO_LOCK_SSL_CTX);
+else
+  CRYPTO_r_unlock(CRYPTO_LOCK_SSL_CTX);
+}
+#endif
+
+
+
+/*
+
+Call this once.  Probably early in startup will do; may need
+to be after SSL library init.
+
+=> put after call to tls_init() for now
+
+Return
+  1	Success
+  0	Fail
+*/
+
+int
+DANESSL_library_init(void)
+{
+static CRYPTO_ONCE once = CRYPTO_ONCE_STATIC_INIT;
+
+DEBUG(D_tls) debug_printf("Dane lib-init\n");
+(void) CRYPTO_THREAD_run_once(&once, dane_init);
+
+#if defined(LN_sha256)
+/* No DANE without SHA256 support */
+if (dane_idx >= 0 && EVP_get_digestbyname(LN_sha256) != 0)
+  return 1;
+#endif
+DANEerr(DANESSL_F_LIBRARY_INIT, DANESSL_R_SUPPORT);
+return 0;
+}
+
+
+/* vi: aw ai sw=2
+*/