unbound/smallapp/unbound-anchor.c

/*
 * unbound-anchor.c - update the root anchor if necessary.
 *
 * Copyright (c) 2010, NLnet Labs. All rights reserved.
 *
 * This software is open source.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * Neither the name of the NLNET LABS nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * \file
 *
 * This file checks to see that the current 5011 keys work to prime the
 * current root anchor.  If not a certificate is used to update the anchor.
 *
 * This is a concept solution for distribution of the DNSSEC root
 * trust anchor.  It is a small tool, called "unbound-anchor", that
 * runs before the main validator starts.  I.e. in the init script:
 * unbound-anchor; unbound.  Thus it is meant to run at system boot time.
 *
 * Management-Abstract:
 *    * first run: fill root.key file with hardcoded DS record.
 *    * mostly: use RFC5011 tracking, quick . DNSKEY UDP query.
 *    * failover: use builtin certificate, do https and update.
 * Special considerations:
 *    * 30-days RFC5011 timer saves a lot of https traffic.
 *    * DNSKEY probe must be NOERROR, saves a lot of https traffic.
 *    * fail if clock before sign date of the root, if cert expired.
 *    * if the root goes back to unsigned, deals with it.
 *
 * It has hardcoded the root DS anchors and the ICANN CA root certificate.
 * It allows with options to override those.  It also takes root-hints (it
 * has to do a DNS resolve), and also has hardcoded defaults for those.
 *
 * Once it starts, just before the validator starts, it quickly checks if
 * the root anchor file needs to be updated.  First it tries to use
 * RFC5011-tracking of the root key.  If that fails (and for 30-days since
 * last successful probe), then it attempts to update using the
 * certificate.  So most of the time, the RFC5011 tracking will work fine,
 * and within a couple milliseconds, the main daemon can start.  It will
 * have only probed the . DNSKEY, not done expensive https transfers on the
 * root infrastructure.
 *
 * If there is no root key in the root.key file, it bootstraps the
 * RFC5011-tracking with its builtin DS anchors; if that fails it
 * bootstraps the RFC5011-tracking using the certificate.  (again to avoid
 * https, and it is also faster).
 * 
 * It uses the XML file by converting it to DS records and writing that to the
 * key file.  Unbound can detect that the 'special comments' are gone, and
 * the file contains a list of normal DNSKEY/DS records, and uses that to
 * bootstrap 5011 (the KSK is made VALID).
 *
 * The certificate update is done by fetching root-anchors.xml and
 * root-anchors.p7s via SSL.  The HTTPS certificate can be logged but is
 * not validated (https for channel security; the security comes from the
 * certificate).  The 'data.iana.org' domain name A and AAAA are resolved
 * without DNSSEC.  It tries a random IP until the transfer succeeds.  It
 * then checks the p7s signature.
 *
 * On any failure, it leaves the root key file untouched.  The main
 * validator has to cope with it, it cannot fix things (So a failure does
 * not go 'without DNSSEC', no downgrade).  If it used its builtin stuff or
 * did the https, it exits with an exit code, so that this can trigger the
 * init script to log the event and potentially alert the operator that can
 * do a manual check.
 *
 * The date is also checked.  Before 2010-07-15 is a failure (root not
 * signed yet; avoids attacks on system clock).  The
 * last-successful-RFC5011-probe (if available) has to be more than 30 days
 * in the past (otherwise, RFC5011 should have worked).  This keeps
 * unneccesary https traffic down.  If the main certificate is expired, it
 * fails.
 *
 * The dates on the keys in the xml are checked (uses the libexpat xml
 * parser), only the valid ones are used to re-enstate RFC5011 tracking.
 * If 0 keys are valid, the zone has gone to insecure (a special marker is
 * written in the keyfile that tells the main validator daemon the zone is
 * insecure).
 *
 * Only the root ICANN CA is shipped, not the intermediate ones.  The
 * intermediate CAs are included in the p7s file that was downloaded.  (the
 * root cert is valid to 2028 and the intermediate to 2014, today).
 *
 * Obviously, the tool also has options so the operator can provide a new
 * keyfile, a new certificate and new URLs, and fresh root hints.  By
 * default it logs nothing on failure and success; it 'just works'.
 *
 */

#include "config.h"
#include "libunbound/unbound.h"
#include <ldns/rr.h>
#include <expat.h>
#ifndef HAVE_EXPAT_H
#error "need libexpat to parse root-anchors.xml file."
#endif
#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif
#ifdef HAVE_OPENSSL_SSL_H
#include <openssl/ssl.h>
#endif
#ifdef HAVE_OPENSSL_ERR_H
#include <openssl/err.h>
#endif
#ifdef HAVE_OPENSSL_RAND_H
#include <openssl/rand.h>
#endif
#include <openssl/x509.h>
#include <openssl/pem.h>

/** name of server in URL to fetch HTTPS from */
#define URLNAME "data.iana.org"
/** path on HTTPS server to xml file */
#define XMLNAME "/root-anchors/root-anchors.xml"
/** path on HTTPS server to p7s file */
#define P7SNAME "/root-anchors/root-anchors.p7s"
/** port number for https access */
#define HTTPS_PORT 443

/** verbosity for this application */
static int verb = 0;

/** list of IP addresses */
struct ip_list {
	/** next in list */
	struct ip_list* next;
	/** length of addr */
	socklen_t len;
	/** address ready to connect to */
	struct sockaddr_storage addr;
	/** has the address been used */
	int used;
};

/** Give unbound-anchor usage, and exit (1). */
static void
usage()
{
	printf("Usage:	unbound-anchor [opts]\n");
	printf("	Setup or update root anchor. "
		"Most options have defaults.\n");
	printf("	Run this program before you start the validator.\n");
	printf("\n");
	printf("	The anchor and cert have default builtin content\n");
	printf("	if the file does not exist or is empty.\n");
	printf("\n");
	printf("-a file		root key file, default %s\n", ROOT_ANCHOR_FILE);
	printf("		The key is input and output for this tool.\n");
	printf("-c file		cert file, default %s\n", ROOT_CERT_FILE);
	printf("-l		list builtin key and cert on stdout\n");
	printf("-u name		server in https url, default %s\n", URLNAME);
	printf("-x path		pathname to xml, default %s\n", XMLNAME);
	printf("-s path		pathname to p7s, default %s\n", P7SNAME);
	printf("-4		work using IPv4 only\n");
	printf("-6		work using IPv6 only\n");
	printf("-f resolv.conf	use given resolv.conf to resolve -u name\n");
	printf("-r root.hints	use given root.hints to resolve -u name\n"
		"		builtin root hints are used by default\n");
	printf("-v		more verbose\n");
	printf("-C conf		debug, read config\n");
	printf("-P port		use port for https connect, default 443\n");
	printf("-F 		debug, force update with cert\n");
	printf("-h		show this usage help\n");
	printf("Version %s\n", PACKAGE_VERSION);
	printf("BSD licensed, see LICENSE in source package for details.\n");
	printf("Report bugs to %s\n", PACKAGE_BUGREPORT);
	exit(1);
}

/** return the built in root update certificate */
static const char*
get_builtin_cert(void)
{
	return
/* The ICANN CA fetched at 24 Sep 2010.  Valid to 2028 */
"-----BEGIN CERTIFICATE-----\n"
"MIIDdzCCAl+gAwIBAgIBATANBgkqhkiG9w0BAQsFADBdMQ4wDAYDVQQKEwVJQ0FO\n"
"TjEmMCQGA1UECxMdSUNBTk4gQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkxFjAUBgNV\n"
"BAMTDUlDQU5OIFJvb3QgQ0ExCzAJBgNVBAYTAlVTMB4XDTA5MTIyMzA0MTkxMloX\n"
"DTI5MTIxODA0MTkxMlowXTEOMAwGA1UEChMFSUNBTk4xJjAkBgNVBAsTHUlDQU5O\n"
"IENlcnRpZmljYXRpb24gQXV0aG9yaXR5MRYwFAYDVQQDEw1JQ0FOTiBSb290IENB\n"
"MQswCQYDVQQGEwJVUzCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAKDb\n"
"cLhPNNqc1NB+u+oVvOnJESofYS9qub0/PXagmgr37pNublVThIzyLPGCJ8gPms9S\n"
"G1TaKNIsMI7d+5IgMy3WyPEOECGIcfqEIktdR1YWfJufXcMReZwU4v/AdKzdOdfg\n"
"ONiwc6r70duEr1IiqPbVm5T05l1e6D+HkAvHGnf1LtOPGs4CHQdpIUcy2kauAEy2\n"
"paKcOcHASvbTHK7TbbvHGPB+7faAztABLoneErruEcumetcNfPMIjXKdv1V1E3C7\n"
"MSJKy+jAqqQJqjZoQGB0necZgUMiUv7JK1IPQRM2CXJllcyJrm9WFxY0c1KjBO29\n"
"iIKK69fcglKcBuFShUECAwEAAaNCMEAwDwYDVR0TAQH/BAUwAwEB/zAOBgNVHQ8B\n"
"Af8EBAMCAf4wHQYDVR0OBBYEFLpS6UmDJIZSL8eZzfyNa2kITcBQMA0GCSqGSIb3\n"
"DQEBCwUAA4IBAQAP8emCogqHny2UYFqywEuhLys7R9UKmYY4suzGO4nkbgfPFMfH\n"
"6M+Zj6owwxlwueZt1j/IaCayoKU3QsrYYoDRolpILh+FPwx7wseUEV8ZKpWsoDoD\n"
"2JFbLg2cfB8u/OlE4RYmcxxFSmXBg0yQ8/IoQt/bxOcEEhhiQ168H2yE5rxJMt9h\n"
"15nu5JBSewrCkYqYYmaxyOC3WrVGfHZxVI7MpIFcGdvSb2a1uyuua8l0BKgk3ujF\n"
"0/wsHNeP22qNyVO+XVBzrM8fk8BSUFuiT/6tZTYXRtEt5aKQZgXbKU5dUF3jT9qg\n"
"j/Br5BZw3X/zd325TvnswzMC1+ljLzHnQGGk\n"
"-----END CERTIFICATE-----\n"
		;
}

/** return the built in root DS trust anchor */
static const char*
get_builtin_ds(void)
{
	return
". IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5\n";
		;
}

/** print hex data */
static void
print_data(char* msg, char* data, int len)
{
	int i;
	printf("%s: ", msg);
	for(i=0; i<len; i++) {
		printf(" %2.2x", (unsigned char)data[i]);
	}
	printf("\n");
}

/** print ub context creation error and exit */
static void
ub_ctx_error_exit(struct ub_ctx* ctx, const char* str, const char* str2)
{
	ub_ctx_delete(ctx);
	if(str && str2 && verb) printf("%s: %s\n", str, str2);
	if(verb) printf("error: could not create unbound resolver context\n");
	exit(0);
}

/**
 * Create a new unbound context with the commandline settings applied
 */
static struct ub_ctx* 
create_unbound_context(char* res_conf, char* root_hints, char* debugconf,
        int ip4only, int ip6only)
{
	int r;
	struct ub_ctx* ctx = ub_ctx_create();
	if(!ctx) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	/* do not waste time and network traffic to fetch extra nameservers */
	r = ub_ctx_set_option(ctx, "target-fetch-policy:", "0 0 0 0 0");
	if(r && verb) printf("ctx targetfetchpolicy: %s\n", ub_strerror(r));
	/* read config file first, so its settings can be overridden */
	if(debugconf) {
		r = ub_ctx_config(ctx, debugconf);
		if(r) ub_ctx_error_exit(ctx, debugconf, ub_strerror(r));
	}
	if(res_conf) {
		r = ub_ctx_resolvconf(ctx, res_conf);
		if(r) ub_ctx_error_exit(ctx, res_conf, ub_strerror(r));
	}
	if(root_hints) {
		r = ub_ctx_set_option(ctx, "root-hints:", root_hints);
		if(r) ub_ctx_error_exit(ctx, root_hints, ub_strerror(r));
	}
	if(ip4only) {
		r = ub_ctx_set_option(ctx, "do-ip6:", "no");
		if(r) ub_ctx_error_exit(ctx, "ip4only", ub_strerror(r));
	}
	if(ip6only) {
		r = ub_ctx_set_option(ctx, "do-ip4:", "no");
		if(r) ub_ctx_error_exit(ctx, "ip6only", ub_strerror(r));
	}
	return ctx;
}

/** printout certificate in detail */
static void
verb_cert(char* msg, X509* x)
{
	if(verb == 0 || verb == 1) return;
	if(verb == 2) {
		if(msg) printf("%s\n", msg);
		X509_print_ex_fp(stdout, x, 0, (unsigned long)-1
			^(X509_FLAG_NO_SUBJECT
			|X509_FLAG_NO_ISSUER|X509_FLAG_NO_VALIDITY));
		return;
	}
	if(msg) printf("%s\n", msg);
	X509_print_fp(stdout, x);
}

/** printout certificates in detail */
static void
verb_certs(char* msg, STACK_OF(X509)* sk)
{
	int i, num = sk_X509_num(sk);
	if(verb == 0 || verb == 1) return;
	for(i=0; i<num; i++) {
		printf("%s (%d/%d)\n", msg, i, num);
		verb_cert(NULL, sk_X509_value(sk, i));
	}
}

/** read certificates from a PEM bio */
static STACK_OF(X509)*
read_cert_bio(BIO* bio)
{
	STACK_OF(X509) *sk = sk_X509_new_null();
	if(!sk) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	while(!BIO_eof(bio)) {
		X509* x = PEM_read_bio_X509(bio, NULL, 0, NULL);
		if(x == NULL) {
			if(verb) {
				printf("failed to read X509\n");
			 	ERR_print_errors_fp(stdout);
			}
			continue;
		}
		if(!sk_X509_push(sk, x)) {
			if(verb) printf("out of memory\n");
			exit(0);
		}
	}
	return sk;
}

/* read the certificate file */
static STACK_OF(X509)*
read_cert_file(char* file)
{
	STACK_OF(X509)* sk;
	FILE* in;
	int content = 0;
	char buf[128];
	if(file == NULL || strcmp(file, "") == 0) {
		return NULL;
	}
	sk = sk_X509_new_null();
	if(!sk) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	in = fopen(file, "r");
	if(!in) {
		if(verb) printf("%s: %s\n", file, strerror(errno));
#ifndef S_SPLINT_S
		sk_X509_pop_free(sk, X509_free);
#endif
		return NULL;
	}
	while(!feof(in)) {
		X509* x = PEM_read_X509(in, NULL, 0, NULL);
		if(x == NULL) {
			if(verb) {
				printf("failed to read X509 file\n");
			 	ERR_print_errors_fp(stdout);
			}
			continue;
		}
		if(!sk_X509_push(sk, x)) {
			if(verb) printf("out of memory\n");
			fclose(in);
			exit(0);
		}
		/* read away newline after --END CERT-- */
		(void)fgets(buf, (int)sizeof(buf), in);
		content = 1;
	}
	fclose(in);
	if(!content) {
		if(verb) printf("%s is empty\n", file);
#ifndef S_SPLINT_S
		sk_X509_pop_free(sk, X509_free);
#endif
		return NULL;
	}
	return sk;
}

/** read certificates from the builtin certificate */
static STACK_OF(X509)*
read_builtin_cert(void)
{
	const char* builtin_cert = get_builtin_cert();
	STACK_OF(X509)* sk;
	BIO *bio = BIO_new_mem_buf((void*)builtin_cert,
		(int)strlen(builtin_cert));
	if(!bio) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	sk = read_cert_bio(bio);
	if(!sk) {
		if(verb) printf("internal error, out of memory\n");
		exit(0);
	}
	BIO_free(bio);
	return sk;
}

/** read update cert file or use builtin */
static STACK_OF(X509)*
read_cert_or_builtin(char* file)
{
	STACK_OF(X509) *sk = read_cert_file(file);
	if(!sk) {
		if(verb) printf("using builtin certificate\n");
		sk = read_builtin_cert();
	}
	if(verb) printf("have %d trusted certificates\n", sk_X509_num(sk));
	verb_certs("trusted certificates", sk);
	return sk;
}

static void
do_list_builtin(void)
{
	const char* builtin_cert = get_builtin_cert();
	const char* builtin_ds = get_builtin_ds();
	printf("%s\n", builtin_ds);
	printf("%s\n", builtin_cert);
	exit(0);
}

/** printout IP address with message */
static void
verb_addr(char* msg, struct ip_list* ip)
{
	if(verb) {
		char out[100];
		void* a = &((struct sockaddr_in*)&ip->addr)->sin_addr;
		if(ip->len != (socklen_t)sizeof(struct sockaddr_in))
			a = &((struct sockaddr_in6*)&ip->addr)->sin6_addr;

		if(inet_ntop((int)((struct sockaddr_in*)&ip->addr)->sin_family,
			a, out, (socklen_t)sizeof(out))==0)
			printf("%s (inet_ntop error)\n", msg);
		else printf("%s %s\n", msg, out);
	}
}

/** free ip_list */
static void
ip_list_free(struct ip_list* p)
{
	struct ip_list* np;
	while(p) {
		np = p->next;
		free(p);
		p = np;
	}
}

/** create ip_list entry for a RR record */
static struct ip_list*
RR_to_ip(int tp, char* data, int len, int port)
{
	struct ip_list* ip = (struct ip_list*)calloc(1, sizeof(*ip));
	uint16_t p = (uint16_t)port;
	if(tp == LDNS_RR_TYPE_A) {
		struct sockaddr_in* sa = (struct sockaddr_in*)&ip->addr;
		ip->len = (socklen_t)sizeof(*sa);
		sa->sin_family = AF_INET;
		sa->sin_port = (in_port_t)htons(p);
		if(len != (int)sizeof(sa->sin_addr)) {
			if(verb) printf("skipped badly formatted A\n");
			free(ip);
			return NULL;
		}
		memmove(&sa->sin_addr, data, sizeof(sa->sin_addr));

	} else if(tp == LDNS_RR_TYPE_AAAA) {
		struct sockaddr_in6* sa = (struct sockaddr_in6*)&ip->addr;
		ip->len = (socklen_t)sizeof(*sa);
		sa->sin6_family = AF_INET6;
		sa->sin6_port = (in_port_t)htons(p);
		if(len != (int)sizeof(sa->sin6_addr)) {
			if(verb) printf("skipped badly formatted AAAA\n");
			free(ip);
			return NULL;
		}
		memmove(&sa->sin6_addr, data, sizeof(sa->sin6_addr));
	} else {
		if(verb) printf("internal error: bad type in RRtoip\n");
		free(ip);
		return NULL;
	}
	verb_addr("resolved server address", ip);
	return ip;
}

/** Resolve name, type, class and add addresses to iplist */
static void
resolve_host_ip(struct ub_ctx* ctx, char* host, int port, int tp, int cl,
	struct ip_list** head)
{
	struct ub_result* res = NULL;
	int r;
	int i;

	r = ub_resolve(ctx, host, tp, cl, &res);
	if(r) {
		if(verb) printf("error: resolve %s %s: %s\n", host,
			(tp==LDNS_RR_TYPE_A)?"A":"AAAA", ub_strerror(r));
		return;
	}
	if(!res) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	for(i = 0; res->data[i]; i++) {
		struct ip_list* ip = RR_to_ip(tp, res->data[i], res->len[i],
			port);
		if(!ip) continue;
		ip->next = *head;
		*head = ip;
	}
	ub_resolve_free(res);
}

/** parse a text IP address into a sockaddr */
static struct ip_list*
parse_ip_addr(char* str, int port)
{
	socklen_t len = 0;
	struct sockaddr_storage* addr = NULL;
	struct sockaddr_in6 a6;
	struct sockaddr_in a;
	struct ip_list* ip;
	uint16_t p = (uint16_t)port;
	memset(&a6, 0, sizeof(a6));
	memset(&a, 0, sizeof(a));

	if(inet_pton(AF_INET6, str, &a6.sin6_addr) > 0) {
		/* it is an IPv6 */
		a6.sin6_family = AF_INET6;
		a6.sin6_port = (in_port_t)htons(p);
		addr = (struct sockaddr_storage*)&a6;
		len = (socklen_t)sizeof(struct sockaddr_in6);
	}
	if(inet_pton(AF_INET, str, &a.sin_addr) > 0) {
		/* it is an IPv4 */
		a.sin_family = AF_INET;
		a.sin_port = (in_port_t)htons(p);
		addr = (struct sockaddr_storage*)&a;
		len = (socklen_t)sizeof(struct sockaddr_in);
	}
	if(!len) return NULL;
	ip = (struct ip_list*)calloc(1, sizeof(*ip));
	if(!ip) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	ip->len = len;
	memmove(&ip->addr, addr, len);
	if(verb) printf("server address is %s\n", str);
	return ip;
}

/**
 * Resolve a domain name (even though the resolver is down and there is
 * no trust anchor).  Without DNSSEC validation.
 * @param host: the name to resolve.
 * 	If this name is an IP4 or IP6 address this address is returned.
 * @param port: the port number used for the returned IP structs.
 * @param res_conf: resolv.conf (if any).
 * @param root_hints: root hints (if any).
 * @param debugconf: unbound.conf for debugging options.
 * @param ip4only: use only ip4 for resolve and only lookup A
 * @param ip6only: use only ip6 for resolve and only lookup AAAA
 * 	default is to lookup A and AAAA using ip4 and ip6.
 * @return list of IP addresses.
 */
static struct ip_list*
resolve_name(char* host, int port, char* res_conf, char* root_hints,
	char* debugconf, int ip4only, int ip6only)
{
	struct ub_ctx* ctx;
	struct ip_list* list = NULL;
	/* first see if name is an IP address itself */
	if( (list=parse_ip_addr(host, port)) ) {
		return list;
	}
	
	/* create resolver context */
	ctx = create_unbound_context(res_conf, root_hints, debugconf,
        	ip4only, ip6only);

	/* try resolution of A */
	if(!ip6only) {
		resolve_host_ip(ctx, host, port, LDNS_RR_TYPE_A,
			LDNS_RR_CLASS_IN, &list);
	}

	/* try resolution of AAAA */
	if(!ip4only) {
		resolve_host_ip(ctx, host, port, LDNS_RR_TYPE_AAAA,
			LDNS_RR_CLASS_IN, &list);
	}

	ub_ctx_delete(ctx);
	if(!list) {
		if(verb) printf("%s has no IP addresses I can use\n", host);
		exit(0);
	}
	return list;
}

/** clear used flags */
static void
wipe_ip_usage(struct ip_list* p)
{
	while(p) {
		p->used = 0;
		p = p->next;
	}
}

/** cound unused IPs */
static int
count_unused(struct ip_list* p)
{
	int num = 0;
	while(p) {
		if(!p->used) num++;
		p = p->next;
	}
	return num;
}

/** pick random unused element from IP list */
static struct ip_list*
pick_random_ip(struct ip_list* list)
{
	struct ip_list* p = list;
	int num = count_unused(list);
	int sel;
	if(num == 0) return NULL;
	/* not perfect, but random enough */
	sel = (int)ldns_get_random() % num;
	while(sel > 0 && p) {
		if(!p->used) sel--;
		p = p->next;
	}
	while(p && p->used)
		p = p->next;
	if(!p) return NULL; /* robustness */
	return p;
}

/** close the fd */
static void
fd_close(int fd)
{
#ifndef USE_WINSOCK
	close(fd);
#else
	closesocket(fd);
#endif
}

/** connect to IP address */
static int
connect_to_ip(struct ip_list* ip)
{
	int fd;
	verb_addr("connect to", ip);
	fd = socket(ip->len==(socklen_t)sizeof(struct sockaddr_in)?
		AF_INET:AF_INET6, SOCK_STREAM, 0);
	if(fd == -1) {
		if(verb) printf("socket: %s\n", strerror(errno));
		return -1;
	}
	if(connect(fd, (struct sockaddr*)&ip->addr, ip->len) < 0) {
		if(verb) printf("connect: %s\n", strerror(errno));
		fd_close(fd);
		return -1;
	}
	return fd;
}

/** create SSL context */
static SSL_CTX*
setup_sslctx(void)
{
	SSL_CTX* sslctx = SSL_CTX_new(SSLv23_client_method());
	if(!sslctx) {
		if(verb) printf("SSL_CTX_new error\n");
		return NULL;
	}
	return sslctx;
}

/** initiate TLS on a connection */
static SSL*
TLS_initiate(SSL_CTX* sslctx, int fd)
{
	X509* x;
	int r;
	SSL* ssl = SSL_new(sslctx);
	if(!ssl) {
		if(verb) printf("SSL_new error\n");
		return NULL;
	}
	SSL_set_connect_state(ssl);
	(void)SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
	if(!SSL_set_fd(ssl, fd)) {
		if(verb) printf("SSL_set_fd error\n");
		SSL_free(ssl);
		return NULL;
	}
	while(1) {
		ERR_clear_error();
		if( (r=SSL_do_handshake(ssl)) == 1)
			break;
		r = SSL_get_error(ssl, r);
		if(r != SSL_ERROR_WANT_READ && r != SSL_ERROR_WANT_WRITE) {
			if(verb) printf("SSL handshake failed\n");
			SSL_free(ssl);
			return NULL;
		}
		/* wants to be called again */
	}
	x = SSL_get_peer_certificate(ssl);
	if(!x) {
		if(verb) printf("Server presented no peer certificate\n");
		SSL_free(ssl);
		return NULL;
	}
	verb_cert("server SSL certificate", x);
	X509_free(x);
	return ssl;
}

/** perform neat TLS shutdown */
static void
TLS_shutdown(int fd, SSL* ssl, SSL_CTX* sslctx)
{
	/* shutdown the SSL connection nicely */
	if(SSL_shutdown(ssl) == 0) {
		SSL_shutdown(ssl);
	}
	SSL_free(ssl);
	SSL_CTX_free(sslctx);
	fd_close(fd);
}

/** write a line over SSL */
static int
write_ssl_line(SSL* ssl, char* str, char* sec)
{
	char buf[1024];
	size_t l;
	if(sec) {
		snprintf(buf, sizeof(buf), str, sec);
	} else {
		snprintf(buf, sizeof(buf), "%s", str);
	}
	l = strlen(buf);
	if(l+2 >= sizeof(buf)) {
		if(verb) printf("line too long\n");
		return 0;
	}
	if(verb >= 2) printf("SSL_write: %s\n", buf);
	buf[l] = '\r';
	buf[l+1] = '\n';
	buf[l+2] = 0;
	/* add \r\n */
	if(SSL_write(ssl, buf, (int)strlen(buf)) <= 0) {
		if(verb) printf("could not SSL_write %s", str);
		return 0;
	}
	return 1;
}

/** process header line, check rcode and keeping track of size */
static int
process_one_header(char* buf, size_t* clen, int* chunked)
{
	if(verb>=2) printf("header: '%s'\n", buf);
	if(strncasecmp(buf, "HTTP/1.1 ", 9) == 0) {
		/* check returncode */
		if(buf[9] != '2') {
			if(verb) printf("bad status %s\n", buf+9);
			return 0;
		}
	} else if(strncasecmp(buf, "Content-Length: ", 16) == 0) {
		if(!*chunked)
			*clen = (size_t)atoi(buf+16);
	} else if(strncasecmp(buf, "Transfer-Encoding: chunked", 19+7) == 0) {
		*clen = 0;
		*chunked = 1;
	}
	return 1;
}

/** 
 * Read one line from SSL
 * zero terminates.
 * skips "\r\n" (but not copied to buf).
 * @param ssl: the SSL connection to read from (blocking).
 * @param buf: buffer to return line in.
 * @param len: size of the buffer.
 * @return 0 on error, 1 on success.
 */
static int
read_ssl_line(SSL* ssl, char* buf, size_t len)
{
	size_t n = 0;
	int r;
	int endnl = 0;
	while(1) {
		if(n >= len) {
			if(verb) printf("line too long\n");
			return 0;
		}
		if((r = SSL_read(ssl, buf+n, 1)) <= 0) {
			if(SSL_get_error(ssl, r) == SSL_ERROR_ZERO_RETURN) {
				/* EOF */
				break;
			}
			if(verb) printf("could not SSL_read\n");
			return 0;
		}
		if(endnl && buf[n] == '\n') {
			break;
		} else if(endnl) {
			/* bad data */
			if(verb) printf("error: stray linefeeds\n");
			return 0;
		} else if(buf[n] == '\r') {
			/* skip \r, and also \n on the wire */
			endnl = 1;
			continue;
		} else if(buf[n] == '\n') {
			/* skip the \n, we are done */
			break;
		} else n++;
	}
	buf[n] = 0;
	return 1;
}

/** read http headers and process them */
static size_t
read_http_headers(SSL* ssl, size_t* clen)
{
	char buf[1024];
	int chunked = 0;
	*clen = 0;
	while(read_ssl_line(ssl, buf, sizeof(buf))) {
		if(buf[0] == 0)
			return 1;
		if(!process_one_header(buf, clen, &chunked))
			return 0;
	}
	return 0;
}

/** read a data chunk */
static char*
read_data_chunk(SSL* ssl, size_t len)
{
	size_t got = 0;
	int r;
	char* data = malloc(len+1);
	if(!data) {
		if(verb) printf("out of memory\n");
		return NULL;
	}
	while(got < len) {
		if((r = SSL_read(ssl, data+got, (int)(len-got))) <= 0) {
			if(SSL_get_error(ssl, r) == SSL_ERROR_ZERO_RETURN) {
				/* EOF */
				if(verb) printf("could not SSL_read: unexpected EOF\n");
				free(data);
				return NULL;
			}
			if(verb) printf("could not SSL_read\n");
			free(data);
			return NULL;
		}
		if(verb >= 2) printf("at %d/%d\n", (int)got, (int)len);
		got += r;
	}
	if(verb>=2) printf("read %d data\n", (int)len);
	data[len] = 0;
	return data;
}

/** parse chunk header */
static int
parse_chunk_header(char* buf, size_t* result)
{
	char* e = NULL;
	size_t v = (size_t)strtol(buf, &e, 16);
	if(e == buf)
		return 0;
	*result = v;
	return 1;
}

/** read chunked data from connection */
static BIO*
do_chunked_read(SSL* ssl)
{
	char buf[1024];
	size_t len;
	char* body;
	BIO* mem = BIO_new(BIO_s_mem());
	if(!mem) {
		if(verb) printf("out of memory\n");
		return NULL;
	}
	while(read_ssl_line(ssl, buf, sizeof(buf))) {
		/* read the chunked start line */
		if(verb>=2) printf("chunk header: %s\n", buf);
		if(!parse_chunk_header(buf, &len)) {
			BIO_free(mem);
			return NULL;
		}
		if(verb>=2) printf("chunk len: %d\n", (int)len);
		if(len == 0) {
			char z = 0;
			/* skip end-of-chunk-trailer lines,
			 * until the empty line after that */
			do {
				if(!read_ssl_line(ssl, buf, sizeof(buf))) {
					BIO_free(mem);
					return NULL;
				}
			} while (strlen(buf) > 0);
			/* end of chunks, zero terminate it */
			if(BIO_write(mem, &z, 1) <= 0) {
				if(verb) printf("out of memory\n");
				BIO_free(mem);
				return NULL;
			}
			return mem;
		}
		/* read the chunked body */
		body = read_data_chunk(ssl, len);
		if(!body) {
			BIO_free(mem);
			return NULL;
		}
		if(BIO_write(mem, body, (int)len) <= 0) {
			if(verb) printf("out of memory\n");
			free(body);
			BIO_free(mem);
			return NULL;
		}
		free(body);
		/* skip empty line after data chunk */
		if(!read_ssl_line(ssl, buf, sizeof(buf))) {
			BIO_free(mem);
			return NULL;
		}
	}
	BIO_free(mem);
	return NULL;
}

/** start HTTP1.1 transaction on SSL */
static int
write_http_get(SSL* ssl, char* pathname, char* urlname)
{
	if(write_ssl_line(ssl, "GET %s HTTP/1.1", pathname) &&
	   write_ssl_line(ssl, "Host: %s", urlname) &&
	   write_ssl_line(ssl, "User-Agent: unbound-anchor/%s",
	   	PACKAGE_VERSION) &&
	   /* We do not really do multiple queries per connection,
	    * but this header setting is also not needed.
	    * write_ssl_line(ssl, "Connection: close", NULL) &&*/
	   write_ssl_line(ssl, "", NULL)) {
		return 1;
	}
	return 0;
}

/** read HTTP result from SSL */
static BIO*
read_http_result(SSL* ssl)
{
	size_t len = 0;
	char* data;
	BIO* m;
	if(!read_http_headers(ssl, &len)) {
		return NULL;
	}
	if(len == 0) {
		/* do the chunked version */
		BIO* tmp = do_chunked_read(ssl);
		char* d = NULL;
		size_t l;
		l = (size_t)BIO_get_mem_data(tmp, &d);
		if(verb>=2) printf("chunked data is %d\n", (int)l);
		if(l == 0 || d == NULL) {
			if(verb) printf("out of memory\n");
			return NULL;
		}
		/* the result is zero terminated for robustness, but we 
		 * do not include that in the BIO len (for binary data) */
		len = l-1;
		data = (char*)malloc(l);
		if(data == NULL) {
			if(verb) printf("out of memory\n");
			return NULL;
		}
		memcpy(data, d, l);
		BIO_free(tmp);
	} else {
		data = read_data_chunk(ssl, len);
	}
	if(verb >= 4) print_data("read data", data, (int)len);
	m = BIO_new_mem_buf(data, (int)len);
	if(!m) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	return m;
}

/** https to an IP addr, return BIO with pathname or NULL */
static BIO*
https_to_ip(struct ip_list* ip, char* pathname, char* urlname)
{
	int fd;
	SSL* ssl;
	BIO* bio;
	SSL_CTX* sslctx = setup_sslctx();
	if(!sslctx) {
		return NULL;
	}
	fd = connect_to_ip(ip);
	if(fd == -1) {
		SSL_CTX_free(sslctx);
		return NULL;
	}
	ssl = TLS_initiate(sslctx, fd);
	if(!ssl) {
		SSL_CTX_free(sslctx);
		fd_close(fd);
		return NULL;
	}
	if(!write_http_get(ssl, pathname, urlname)) {
		if(verb) printf("could not write to server\n");
		SSL_free(ssl);
		SSL_CTX_free(sslctx);
		fd_close(fd);
		return NULL;
	}
	bio = read_http_result(ssl);
	TLS_shutdown(fd, ssl, sslctx);
	return bio;
}

/**
 * Do a HTTPS, HTTP1.1 over TLS, to fetch a file
 * @param ip_list: list of IP addresses to use to fetch from.
 * @param pathname: pathname of file on server to GET.
 * @param urlname: name to pass as the virtual host for this request.
 * @return a memory BIO with the file in it.
 */
static BIO*
https(struct ip_list* ip_list, char* pathname, char* urlname)
{
	struct ip_list* ip;
	BIO* bio = NULL;
	/* try random address first, and work through the list */
	wipe_ip_usage(ip_list);
	while( (ip = pick_random_ip(ip_list)) ) {
		ip->used = 1;
		bio = https_to_ip(ip, pathname, urlname);
		if(bio) break;
	}
	if(!bio) {
		if(verb) printf("could not fetch %s\n", pathname);
		exit(0);
	} else {
		if(verb) printf("fetched %s (%d bytes)\n",
			pathname, (int)BIO_ctrl_pending(bio));
	}
	return bio;
}

/** free up a downloaded file BIO */
static void
free_file_bio(BIO* bio)
{
	char* pp = NULL;
	BIO_reset(bio);
	(void)BIO_get_mem_data(bio, &pp);
	free(pp);
	BIO_free(bio);
}

/** XML parse private data during the parse */
struct xml_data {
	/** the parser, reference */
	XML_Parser parser;
	/** the current tag; malloced; or NULL outside of tags */
	char* tag;
	/** current date to use during the parse */
	time_t date;
	/** number of keys usefully read in */
	int num_keys;
	/** the compiled anchors as DS records */
	BIO* ds;

	/** do we want to use this anchor? */
	int use_key;
	/** the current anchor: Zone */
	BIO* czone;
	/** the current anchor: KeyTag */
	BIO* ctag;
	/** the current anchor: Algorithm */
	BIO* calgo;
	/** the current anchor: DigestType */
	BIO* cdigtype;
	/** the current anchor: Digest*/
	BIO* cdigest;
};

/** The BIO for the tag */
static BIO*
xml_selectbio(struct xml_data* data, const char* tag)
{
	BIO* b = NULL;
	if(strcasecmp(tag, "KeyTag") == 0)
		b = data->ctag;
	else if(strcasecmp(tag, "Algorithm") == 0)
		b = data->calgo;
	else if(strcasecmp(tag, "DigestType") == 0)
		b = data->cdigtype;
	else if(strcasecmp(tag, "Digest") == 0)
		b = data->cdigest;
	return b;
}

/**
 * XML handle character data, the data inside an element.
 * @param userData: xml_data structure
 * @param s: the character data.  May not all be in one callback.
 * 	NOT zero terminated.
 * @param len: length of this part of the data.
 */
void
xml_charhandle(void *userData, const XML_Char *s, int len)
{
	struct xml_data* data = (struct xml_data*)userData;
	BIO* b = NULL;
	/* skip characters outside of elements */
	if(!data->tag)
		return;
	if(verb>=4) {
		int i;
		printf("%s%s charhandle: '",
			data->use_key?"use ":"",
			data->tag?data->tag:"none");
		for(i=0; i<len; i++)
			printf("%c", s[i]);
		printf("'\n");
	}
	if(strcasecmp(data->tag, "Zone") == 0) {
		if(BIO_write(data->czone, s, len) <= 0) {
			if(verb) printf("out of memory in BIO_write\n");
			exit(0);
		}
		return;
	}
	/* only store if key is used */
	if(!data->use_key)
		return;
	b = xml_selectbio(data, data->tag);
	if(b) {
		if(BIO_write(b, s, len) <= 0) {
			if(verb) printf("out of memory in BIO_write\n");
			exit(0);
		}
	}
}

/**
 * XML fetch value of particular attribute(by name) or NULL if not present.
 * @param atts: attribute array (from xml_startelem).
 * @param name: name of attribute to look for.
 * @return the value or NULL. (ptr into atts).
 */
static const XML_Char*
find_att(const XML_Char **atts, XML_Char* name)
{
	int i;
	for(i=0; atts[i]; i+=2) {
		if(strcasecmp(atts[i], name) == 0)
			return atts[i+1];
	}
	return NULL;
}

/**
 * XML convert DateTime element to time_t.
 * [-]CCYY-MM-DDThh:mm:ss[Z|(+|-)hh:mm]
 * (with optional .ssssss fractional seconds)
 * @param str: the string
 * @return a time_t representation or 0 on failure.
 */
static time_t
xml_convertdate(const char* str)
{
	time_t t = 0;
	struct tm tm;
	const char* s;
	/* for this application, ignore minus in front;
	 * only positive dates are expected */
	s = str;
	if(s[0] == '-') s++;
	memset(&tm, 0, sizeof(tm));
	/* parse initial content of the string (lots of whitespace allowed) */
	s = strptime(s, "%t%Y%t-%t%m%t-%t%d%tT%t%H%t:%t%M%t:%t%S%t", &tm);
	if(!s) {
		if(verb) printf("xml_convertdate parse failure %s\n", str);
		return 0;
	}
	/* parse remainder of date string */
	if(*s == '.') {
		/* optional '.' and fractional seconds */
		int frac = 0, n = 0;
		if(sscanf(s+1, "%d%n", &frac, &n) < 1) {
			if(verb) printf("xml_convertdate f failure %s\n", str);
			return 0;
		}
		/* fraction is not used, time_t has second accuracy */
		s++;
		s+=n;
	}
	if(*s == 'Z' || *s == 'z') {
		/* nothing to do for this */
		s++;
	} else if(*s == '+' || *s == '-') {
		/* optional timezone spec: Z or +hh:mm or -hh:mm */
		int hr = 0, mn = 0, n = 0;
		if(sscanf(s+1, "%d:%d%n", &hr, &mn, &n) < 2) {
			if(verb) printf("xml_convertdate tz failure %s\n", str);
			return 0;
		}
		if(*s == '+') {
			tm.tm_hour += hr;
			tm.tm_min += mn;
		} else {
			tm.tm_hour -= hr;
			tm.tm_min -= mn;
		}
		s++;
		s += n;
	}
	if(*s != 0) {
		/* not ended properly */
		/* but ignore, (lenient) */
	}

	t = mktime(&tm);
	if(t == (time_t)-1) {
		if(verb) printf("xml_convertdate mktime failure\n");
		return 0;
	}
	return t;
}

/**
 * XML handle the KeyDigest start tag, check validity periods.
 */
static void
handle_keydigest(struct xml_data* data, const XML_Char **atts)
{
	data->use_key = 0;
	if(find_att(atts, "validFrom")) {
		time_t from = xml_convertdate(find_att(atts, "validFrom"));
		if(from == 0) {
			if(verb) printf("error: xml cannot be parsed\n");
			exit(0);
		}
		if(data->date < from)
			return;
	}
	if(find_att(atts, "validUntil")) {
		time_t until = xml_convertdate(find_att(atts, "validUntil"));
		if(until == 0) {
			if(verb) printf("error: xml cannot be parsed\n");
			exit(0);
		}
		if(data->date > until)
			return;
	}
	/* yes we want to use this key */
	data->use_key = 1;
	BIO_reset(data->ctag);
	BIO_reset(data->calgo);
	BIO_reset(data->cdigtype);
	BIO_reset(data->cdigest);
}

/** See if XML element equals the zone name */
static int
xml_is_zone_name(BIO* zone, char* name)
{
	char buf[1024];
	char* z = NULL;
	long zlen;
	BIO_seek(zone, 0);
	zlen = BIO_get_mem_data(zone, &z);
	if(!zlen || !z) return 0;
	if(zlen >= (long)sizeof(buf)) return 0;
	memmove(buf, z, (size_t)zlen);
	buf[zlen] = 0;
	return (strncasecmp(buf, name, strlen(name)) == 0);
}

/** 
 * XML start of element. This callback is called whenever an XML tag starts.
 * XML_Char is UTF8.
 * @param userData: the xml_data structure.
 * @param name: the tag that starts.
 * @param atts: array of strings, pairs of attr = value, ends with NULL.
 * 	i.e. att[0]="att[1]" att[2]="att[3]" att[4]isNull
 */
static void
xml_startelem(void *userData, const XML_Char *name, const XML_Char **atts)
{
	struct xml_data* data = (struct xml_data*)userData;
	BIO* b;
	if(verb>=4) printf("xml tag start '%s'\n", name);
	free(data->tag);
	data->tag = strdup(name);
	if(!data->tag) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	if(verb>=4) {
		int i;
		for(i=0; atts[i]; i+=2) {
			printf("  %s='%s'\n", atts[i], atts[i+1]);
		}
	}
	/* handle attributes to particular types */
	if(strcasecmp(name, "KeyDigest") == 0) {
		handle_keydigest(data, atts);
		return;
	} else if(strcasecmp(name, "Zone") == 0) {
		BIO_reset(data->czone);
		return;
	}

	/* write whitespace separators to outputBIO here */
	if(!data->use_key)
		return;
	b = xml_selectbio(data, data->tag);
	if(b) {
		/* empty it */
		BIO_reset(b);
	}
}

/** Append str to bio */
static void
xml_append_str(BIO* b, const char* s)
{
	if(BIO_write(b, s, (int)strlen(s)) <= 0) {
		if(verb) printf("out of memory in BIO_write\n");
		exit(0);
	}
}

/** Append bio to bio */
static void
xml_append_bio(BIO* b, BIO* a)
{
	char* z = NULL;
	long i, len;
	BIO_seek(a, 0);
	len = BIO_get_mem_data(a, &z);
	if(!len || !z) {
		if(verb) printf("out of memory in BIO_write\n");
		exit(0);
	}
	/* remove newlines in the data here */
	for(i=0; i<len; i++) {
		if(z[i] == '\r' || z[i] == '\n')
			z[i] = ' ';
	}
	/* write to BIO */
	if(BIO_write(b, z, len) <= 0) {
		if(verb) printf("out of memory in BIO_write\n");
		exit(0);
	}
}

/** write the parsed xml-DS to the DS list */
static void
xml_append_ds(struct xml_data* data)
{
	/* write DS to accumulated DS */
	xml_append_str(data->ds, ". IN DS ");
	xml_append_bio(data->ds, data->ctag);
	xml_append_str(data->ds, " ");
	xml_append_bio(data->ds, data->calgo);
	xml_append_str(data->ds, " ");
	xml_append_bio(data->ds, data->cdigtype);
	xml_append_str(data->ds, " ");
	xml_append_bio(data->ds, data->cdigest);
	xml_append_str(data->ds, "\n");
	data->num_keys++;
}

/**
 * XML end of element. This callback is called whenever an XML tag ends.
 * XML_Char is UTF8.
 * @param userData: the xml_data structure
 * @param name: the tag that ends.
 */
static void
xml_endelem(void *userData, const XML_Char *name)
{
	struct xml_data* data = (struct xml_data*)userData;
	if(verb>=4) printf("xml tag end   '%s'\n", name);
	free(data->tag);
	data->tag = NULL;
	if(strcasecmp(name, "KeyDigest") == 0) {
		if(data->use_key)
			xml_append_ds(data);
		data->use_key = 0;
	} else if(strcasecmp(name, "Zone") == 0) {
		if(!xml_is_zone_name(data->czone, ".")) {
			if(verb) printf("xml not for the right zone\n");
			exit(0);
		}
	}
}

/**
 * XML parser setup of the callbacks for the tags
 */
static void
xml_parse_setup(XML_Parser parser, struct xml_data* data, time_t now)
{
	char buf[1024];
	memset(data, 0, sizeof(*data));
	XML_SetUserData(parser, data);
	data->parser = parser;
	data->date = now;
	data->ds = BIO_new(BIO_s_mem());
	data->ctag = BIO_new(BIO_s_mem());
	data->czone = BIO_new(BIO_s_mem());
	data->calgo = BIO_new(BIO_s_mem());
	data->cdigtype = BIO_new(BIO_s_mem());
	data->cdigest = BIO_new(BIO_s_mem());
	if(!data->ds || !data->ctag || !data->calgo || !data->czone ||
		!data->cdigtype || !data->cdigest) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	snprintf(buf, sizeof(buf), "; created by unbound-anchor on %s",
		ctime(&now));
	if(BIO_write(data->ds, buf, (int)strlen(buf)) <= 0) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	XML_SetElementHandler(parser, xml_startelem, xml_endelem);
	XML_SetCharacterDataHandler(parser, xml_charhandle);
}

/**
 * Perform XML parsing of the root-anchors file
 * Its format description can be read here
 * https://data.iana.org/root-anchors/draft-icann-dnssec-trust-anchor.txt
 * It uses libexpat.
 * @param xml: BIO with xml data.
 * @param now: the current time for checking DS validity periods.
 * @return memoryBIO with the DS data in zone format.
 * 	or NULL if the zone is insecure.
 * 	(It exit()s on error)
 */
static BIO*
xml_parse(BIO* xml, time_t now)
{
	char* pp;
	int len;
	XML_Parser parser;
	struct xml_data data;

	parser = XML_ParserCreate(NULL);
	if(!parser) {
		if(verb) printf("could not XML_ParserCreate\n");
		exit(0);
	}

	/* setup callbacks */
	xml_parse_setup(parser, &data, now);

	/* parse it */
	BIO_reset(xml);
	len = (int)BIO_get_mem_data(xml, &pp);
	if(!len || !pp) {
		if(verb) printf("out of memory\n");
		exit(0);
	}
	if(!XML_Parse(parser, pp, len, 1 /*isfinal*/ )) {
		const char *e = XML_ErrorString(XML_GetErrorCode(parser));
		if(verb) printf("XML_Parse failure %s\n",
			e?e:"");
		exit(0);
	}

	/* parsed */
	if(verb) printf("XML was parsed successfully, %d keys\n",
			data.num_keys);
	free(data.tag);
	XML_ParserFree(parser);

	if(verb >= 4) {
		char* pp = NULL;
		int len;
		BIO_seek(data.ds, 0);
		len = BIO_get_mem_data(data.ds, &pp);
		printf("got DS bio %d: '", len);
		(void)fwrite(pp, (size_t)len, 1, stdout);
		printf("'\n");
	}
	BIO_free(data.czone);
	BIO_free(data.ctag);
	BIO_free(data.calgo);
	BIO_free(data.cdigtype);
	BIO_free(data.cdigest);

	if(data.num_keys == 0) {
		/* the root zone seems to have gone insecure */
		BIO_free(data.ds);
		return NULL;
	} else {
		return data.ds;
	}
}

/** verify a PKCS7 signature, false on failure */
static int
verify_p7sig(BIO* data, BIO* p7s, STACK_OF(X509)* trust)
{
	X509_VERIFY_PARAM* param = X509_VERIFY_PARAM_new();
	PKCS7* p7;
	X509_STORE *store = X509_STORE_new();
	int secure = 0;
	int i;

	BIO_reset(p7s);
	BIO_reset(data);

	if(!param || !store) {
		if(verb) printf("out of memory\n");
		X509_VERIFY_PARAM_free(param);
		X509_STORE_free(store);
		return 0;
	}

	/* convert p7s to p7 (the signature) */
	p7 = d2i_PKCS7_bio(p7s, NULL);
	if(!p7) {
		if(verb) printf("could not parse p7s signature file\n");
		X509_VERIFY_PARAM_free(param);
		X509_STORE_free(store);
		return 0;
	}
	if(verb >= 2) printf("parsed the PKCS7 signature\n");

	/* convert trust to trusted certificate store */
	/* do the selfcheck on the root certificate; it checks that the
	 * input is valid */
#ifdef X509_V_FLAG_CHECK_SS_SIGNATURE
	X509_VERIFY_PARAM_set_flags(param, X509_V_FLAG_CHECK_SS_SIGNATURE);
#endif
	X509_STORE_set1_param(store, param);
	for(i=0; i<sk_X509_num(trust); i++) {
		if(!X509_STORE_add_cert(store, sk_X509_value(trust, i))) {
			if(verb) printf("failed X509_STORE_add_cert\n");
			X509_STORE_free(store);
			PKCS7_free(p7);
			return 0;
		}
	}
	if(verb >= 2) printf("setup the X509_STORE\n");

	if(PKCS7_verify(p7, NULL, store, data, NULL, 0) == 1) {
		secure = 1;
		if(verb) printf("the PKCS7 signature verified\n");
	} else {
		if(verb) {
			ERR_print_errors_fp(stdout);
		}
	}

	X509_STORE_free(store);
	PKCS7_free(p7);
	return secure;
}

/** write unsigned root anchor file, a 5011 revoked tp */
static void
write_unsigned_root(char* root_anchor_file)
{
	FILE* out;
	time_t now = time(NULL);
	out = fopen(root_anchor_file, "w");
	if(!out) {
		if(verb) printf("%s: %s\n", root_anchor_file, strerror(errno));
		return;
	}
	if(fprintf(out, "; autotrust trust anchor file\n"
		";;REVOKED\n"
		";;id: . 1\n"
		"; This file was written by unbound-anchor on %s"
		"; It indicates that the root does not use DNSSEC\n"
		"; to restart DNSSEC overwrite this file with a\n"
		"; valid trustanchor or (empty-it and run unbound-anchor)\n"
		, ctime(&now)) < 0) {
		if(verb) printf("failed to write 'unsigned' to %s\n",
			root_anchor_file);
		if(verb && errno != 0) printf("%s\n", strerror(errno));
	}
	fclose(out);
}

/** write root anchor file */
static void
write_root_anchor(char* root_anchor_file, BIO* ds)
{
	char* pp = NULL;
	int len;
	FILE* out;
	BIO_seek(ds, 0);
	len = BIO_get_mem_data(ds, &pp);
	if(!len || !pp) {
		if(verb) printf("out of memory\n");
		return;
	}
	out = fopen(root_anchor_file, "w");
	if(!out) {
		if(verb) printf("%s: %s\n", root_anchor_file, strerror(errno));
		return;
	}
	if(fwrite(pp, (size_t)len, 1, out) != 1) {
		if(verb) printf("failed to write all data to %s\n",
			root_anchor_file);
		if(verb && errno != 0) printf("%s\n", strerror(errno));
	}
	fclose(out);
}

/** Perform the verification and update of the trustanchor file */
static void
verify_and_update_anchor(char* root_anchor_file, BIO* xml, BIO* p7s,
	STACK_OF(X509)* cert)
{
	BIO* ds;

	/* verify xml file */
	if(!verify_p7sig(xml, p7s, cert)) {
		printf("the PKCS7 signature failed\n");
		exit(0);
	}

	/* parse the xml file into DS records */
	ds = xml_parse(xml, time(NULL));
	if(!ds) {
		/* the root zone is unsigned now */
		write_unsigned_root(root_anchor_file);
	} else {
		/* reinstate 5011 tracking */
		write_root_anchor(root_anchor_file, ds);
	}
	BIO_free(ds);
}

/** perform actual certupdate work */
static int
do_certupdate(char* root_anchor_file, char* root_cert_file,
	char* urlname, char* xmlname, char* p7sname,
	char* res_conf, char* root_hints, char* debugconf,
	int ip4only, int ip6only, int port, struct ub_result* dnskey)
{
	STACK_OF(X509)* cert;
	BIO *xml, *p7s;
	struct ip_list* ip_list = NULL;

	/* read pem file or provide builtin */
	cert = read_cert_or_builtin(root_cert_file);

	/* lookup A, AAAA for the urlname (or parse urlname if IP address) */
	ip_list = resolve_name(urlname, port, res_conf, root_hints, debugconf,
		ip4only, ip6only);

	/* fetch the necessary files over HTTPS */
	xml = https(ip_list, xmlname, urlname);
	p7s = https(ip_list, p7sname, urlname);

	/* verify and update the root anchor */
	verify_and_update_anchor(root_anchor_file, xml, p7s, cert);
	if(verb) printf("success: the anchor has been updated "
			"using the cert\n");

	free_file_bio(xml);
	free_file_bio(p7s);
#ifndef S_SPLINT_S
	sk_X509_pop_free(cert, X509_free);
#endif
	ub_resolve_free(dnskey);
	ip_list_free(ip_list);
	return 1;
}

/**
 * Try to read the root RFC5011 autotrust anchor file,
 * @param file: filename.
 * @return:
 * 	0 if does not exist or empty
 * 	1 if trust-point-revoked-5011
 * 	2 if it is OK.
 */
static int
try_read_anchor(char* file)
{
	int empty = 1;
	char line[10240];
	char* p;
	FILE* in = fopen(file, "r");
	if(!in) {
		/* only if the file does not exist, can we fix it */
		if(errno != ENOENT) {
			if(verb) printf("%s: %s\n", file, strerror(errno));
			if(verb) printf("error: cannot access the file\n");
			exit(0);
		}
		if(verb) printf("%s does not exist\n", file);
		return 0;
	}
	while(fgets(line, (int)sizeof(line), in)) {
		line[sizeof(line)-1] = 0;
		if(strncmp(line, ";;REVOKED", 9) == 0) {
			fclose(in);
			if(verb) printf("%s : the trust point is revoked\n"
				"and the zone is considered unsigned.\n"
				"if you wish to re-enable, delete the file\n",
				file);
			return 1;
		}
		p=line;
		while(*p == ' ' || *p == '\t')
			p++;
		if(p[0]==0 || p[0]=='\n' || p[0]==';') continue;
		/* this line is a line of content */
		empty = 0;
	}
	fclose(in);
	if(empty) {
		if(verb) printf("%s is empty\n", file);
		return 0;
	}
	if(verb) printf("%s has content\n", file);
	return 2;
}

/** Write the builtin root anchor to a file */
static void
write_builtin_anchor(char* file)
{
	const char* builtin_root_anchor = get_builtin_ds();
	FILE* out = fopen(file, "w");
	if(!out) {
		if(verb) printf("%s: %s\n", file, strerror(errno));
		if(verb) printf("  could not write builtin anchor\n");
		return;
	}
	if(!fwrite(builtin_root_anchor, strlen(builtin_root_anchor), 1, out)) {
		if(verb) printf("%s: %s\n", file, strerror(errno));
		if(verb) printf("  could not complete write builtin anchor\n");
	}
	fclose(out);
}

/** 
 * Check the root anchor file.
 * If does not exist, provide builtin and write file.
 * If empty, provide builtin and write file.
 * If trust-point-revoked-5011 file: make the program exit.
 * @param root_anchor_file: filename of the root anchor.
 * @param used_builtin: set to 1 if the builtin is written.
 * @return 0 if trustpoint is insecure, 1 on success.  Exit on failure.
 */
static int
provide_builtin(char* root_anchor_file, int* used_builtin)
{
	/* try to read it */
	switch(try_read_anchor(root_anchor_file))
	{
		case 0: /* no exist or empty */
			write_builtin_anchor(root_anchor_file);
			*used_builtin = 1;
			break;
		case 1: /* revoked tp */
			return 0;	
		case 2: /* it is fine */
		default:
			break;
	}
	return 1;
}

/**
 * add an autotrust anchor for the root to the context
 */
static void
add_5011_probe_root(struct ub_ctx* ctx, char* root_anchor_file)
{
	int r;
	r = ub_ctx_set_option(ctx, "auto-trust-anchor-file:", root_anchor_file);
	if(r) {
		if(verb) printf("add 5011 probe to ctx: %s\n", ub_strerror(r));
		ub_ctx_delete(ctx);
		exit(0);
	}
}

/**
 * Prime the root key and return the result.  Exit on error.
 * @param ctx: the unbound context to perform the priming with.
 * @return: the result of the prime, on error it exit()s.
 */
static struct ub_result*
prime_root_key(struct ub_ctx* ctx)
{
	struct ub_result* res = NULL;
	int r;
	r = ub_resolve(ctx, ".", LDNS_RR_TYPE_DNSKEY, LDNS_RR_CLASS_IN, &res);
	if(r) {
		if(verb) printf("resolve DNSKEY: %s\n", ub_strerror(r));
		ub_ctx_delete(ctx);
		exit(0);
	}
	if(!res) {
		if(verb) printf("out of memory\n");
		ub_ctx_delete(ctx);
		exit(0);
	}
	return res;
}

/** read last successful probe time from autotrust file (if possible) */
static int32_t
read_last_success_time(char* file)
{
	FILE* in = fopen(file, "r");
	char line[1024];
	if(!in) {
		if(verb) printf("%s: %s\n", file, strerror(errno));
		return 0;
	}
	while(fgets(line, (int)sizeof(line), in)) {
		if(strncmp(line, ";;last_success: ", 16) == 0) {
			char* e;
			time_t x = (unsigned int)strtol(line+16, &e, 10);
			fclose(in);
			if(line+16 == e) {
				if(verb) printf("failed to parse "
					"last_success probe time\n");
				return 0;
			}
			if(verb) printf("last successful probe: %s", ctime(&x));
			return (int32_t)x;
		}
	}
	fclose(in);
	if(verb) printf("no last_success probe time in anchor file\n");
	return 0;
}

/**
 * Read autotrust 5011 probe file and see if the date
 * compared to the current date allows a certupdate.
 * If the last successful probe was recent then 5011 cannot be behind,
 * and the failure cannot be solved with a certupdate.
 * The debugconf is to validation-override the date for testing.
 * @param root_anchor_file: filename of root key
 * @return true if certupdate is ok.
 */
static int
probe_date_allows_certupdate(char* root_anchor_file)
{
	int32_t last_success = read_last_success_time(root_anchor_file);
	int32_t now = (int32_t)time(NULL);
	int32_t leeway = 30 * 24 * 3600; /* 30 days leeway */
	/* if the date is before 2010-07-15:00.00.00 then the root has not
	 * been signed yet, and thus we refuse to take action. */
	if(time(NULL) < xml_convertdate("2010-07-15T00:00:00")) {
		if(verb) printf("the date is before the root was first signed,"
			" please correct the clock\n");
		return 0;
	}
	if(last_success == 0)
		return 1; /* no probe time */
	if(now - last_success < 0) {
		if(verb) printf("the last successful probe is in the future,"
			" clock was modified\n");
		return 0;
	}
	if(now - last_success >= leeway) {
		if(verb) printf("the last successful probe was more than 30 "
			"days ago\n");
		return 1;
	}
	if(verb) printf("the last successful probe is recent\n");
	return 0;
}

/** perform the unbound-anchor work */
static int
do_root_update_work(char* root_anchor_file, char* root_cert_file,
	char* urlname, char* xmlname, char* p7sname,
	char* res_conf, char* root_hints, char* debugconf,
	int ip4only, int ip6only, int force, int port)
{
	struct ub_ctx* ctx;
	struct ub_result* dnskey;
	int used_builtin = 0;

	/* see if builtin rootanchor needs to be provided, or if
	 * rootanchor is 'revoked-trust-point' */
	if(!provide_builtin(root_anchor_file, &used_builtin))
		return 0;

	/* make unbound context with 5011-probe for root anchor,
	 * and probe . DNSKEY */
	ctx = create_unbound_context(res_conf, root_hints, debugconf,
		ip4only, ip6only);
	add_5011_probe_root(ctx, root_anchor_file);
	dnskey = prime_root_key(ctx);
	ub_ctx_delete(ctx);
	
	/* if secure: exit */
	if(dnskey->secure && !force) {
		if(verb) printf("success: the anchor is ok\n");
		ub_resolve_free(dnskey);
		return used_builtin;
	}
	if(force && verb) printf("debug cert update forced\n");

	/* if not (and NOERROR): check date and do certupdate */
	if((dnskey->rcode == 0 &&
		probe_date_allows_certupdate(root_anchor_file)) || force) {
		if(do_certupdate(root_anchor_file, root_cert_file, urlname,
			xmlname, p7sname, res_conf, root_hints, debugconf,
			ip4only, ip6only, port, dnskey))
			return 1;
		return used_builtin;
	}
	if(verb) printf("fail: the anchor is NOT ok and could not be fixed\n");
	ub_resolve_free(dnskey);
	return used_builtin;
}

/** getopt global, in case header files fail to declare it. */
extern int optind;
/** getopt global, in case header files fail to declare it. */
extern char* optarg;

/** Main routine for unbound-anchor */
int main(int argc, char* argv[])
{
	int c;
	char* root_anchor_file = ROOT_ANCHOR_FILE;
	char* root_cert_file = ROOT_CERT_FILE;
	char* urlname = URLNAME;
	char* xmlname = XMLNAME;
	char* p7sname = P7SNAME;
	char* res_conf = NULL;
	char* root_hints = NULL;
	char* debugconf = NULL;
	int dolist=0, ip4only=0, ip6only=0, force=0, port = HTTPS_PORT;
	/* parse the options */
	while( (c=getopt(argc, argv, "46C:FP:a:c:f:hlr:s:u:vx:")) != -1) {
		switch(c) {
		case 'l':
			dolist = 1;
			break;
		case '4':
			ip4only = 1;
			break;
		case '6':
			ip6only = 1;
			break;
		case 'a':
			root_anchor_file = optarg;
			break;
		case 'c':
			root_cert_file = optarg;
			break;
		case 'u':
			urlname = optarg;
			break;
		case 'x':
			xmlname = optarg;
			break;
		case 's':
			p7sname = optarg;
			break;
		case 'f':
			res_conf = optarg;
			break;
		case 'r':
			root_hints = optarg;
			break;
		case 'C':
			debugconf = optarg;
			break;
		case 'F':
			force = 1;
			break;
		case 'P':
			port = atoi(optarg);
			break;
		case 'v':
			verb++;
			break;
		case '?':
		case 'h':
		default:
			usage();
		}
	}
	argc -= optind;
	argv += optind;
	if(argc != 0)
		usage();

	ERR_load_crypto_strings();
	ERR_load_SSL_strings();
	OpenSSL_add_all_algorithms();
	(void)SSL_library_init();

	if(dolist) do_list_builtin();

	return do_root_update_work(root_anchor_file, root_cert_file, urlname,
		xmlname, p7sname, res_conf, root_hints, debugconf, ip4only,
		ip6only, force, port);
}