Fincer
/
openntpd-openssl
mirror of https://github.com/Fincer/openntpd-openssl
1
0
Fork 0
Code Issues 0 Releases 0 Wiki Activity
OpenNTPD daemon with OpenSSL implementation & flexible configurability
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
5 Commits
1 Branch
914 KiB
 
Tree: 8bcf88b367
Branches Tags
${ item.name }
Create branch ${ searchTerm }
from '8bcf88b367'
${ noResults }
openntpd-openssl/patches/3-patch_unhardcode-ports.patch

678 lines
20 KiB
Raw Blame History

From: Pekka Helenius <fincer89@hotmail.com>
Date: Sun, 02 Aug 2020 14:12:40 +0300
Subject: Unhardcode NTP server, client and constraint UDP & TCP port numbers
--- a/src/client.c 2020-08-02 02:03:13.840286484 +0300
+++ b/src/client.c 2020-08-02 02:04:23.993619892 +0300
@@ -76,13 +76,13 @@ client_addr_init(struct ntp_peer *p)
case AF_INET:
sa_in = (struct sockaddr_in *)&h->ss;
if (ntohs(sa_in->sin_port) == 0)
- sa_in->sin_port = htons(123);
+ sa_in->sin_port = htons(p->addr_head.port);
p->state = STATE_DNS_DONE;
break;
case AF_INET6:
sa_in6 = (struct sockaddr_in6 *)&h->ss;
if (ntohs(sa_in6->sin6_port) == 0)
- sa_in6->sin6_port = htons(123);
+ sa_in6->sin6_port = htons(p->addr_head.port);
p->state = STATE_DNS_DONE;
break;
default:
@@ -122,9 +122,10 @@ client_nextaddr(struct ntp_peer *p)
p->shift = 0;
p->trustlevel = TRUSTLEVEL_PATHETIC;
- if (p->addr == NULL)
+ if (p->addr == NULL) {
p->addr = p->addr_head.a;
- else if ((p->addr = p->addr->next) == NULL)
+ p->port = p->addr_head.port;
+ } else if ((p->addr = p->addr->next) == NULL)
return (1);
return (0);
--- a/src/ntp.c 2020-07-31 23:34:32.000000000 +0300
+++ b/src/ntp.c 2020-08-01 00:56:09.608057581 +0300
@@ -603,6 +603,8 @@ ntp_dispatch_imsg_dns(void)
peer->addr_head.name;
npeer->addr_head.pool =
peer->addr_head.pool;
+ npeer->addr_head.port =
+ peer->addr_head.port;
client_peer_init(npeer);
npeer->state = STATE_DNS_DONE;
peer_add(npeer);
@@ -611,6 +613,7 @@ ntp_dispatch_imsg_dns(void)
h->next = peer->addr;
peer->addr = h;
peer->addr_head.a = peer->addr;
+ peer->addr_head.port = peer->port;
peer->state = STATE_DNS_DONE;
}
}
--- a/src/config.c 2020-07-31 23:11:30.000000000 +0300
+++ b/src/config.c 2020-08-01 01:02:14.468057965 +0300
@@ -196,3 +196,10 @@ new_constraint(void)
return (p);
}
+int
+intdup(int in)
+{
+ int *out;
+ out = &in;
+ return *out;
+}
--- a/src/ntpd.h 2020-07-31 23:00:51.000000000 +0300
+++ b/src/ntpd.h 2020-08-01 01:27:06.418059534 +0300
@@ -95,7 +95,7 @@
#define CONSTRAINT_SCAN_INTERVAL (15*60)
#define CONSTRAINT_SCAN_TIMEOUT (10)
#define CONSTRAINT_MARGIN (2.0*60)
-#define CONSTRAINT_PORT "443" /* HTTPS port */
+
#define CONSTRAINT_MAXHEADERLENGTH 8192
#define CONSTRAINT_PASSFD (STDERR_FILENO + 1)
@@ -121,6 +121,7 @@ struct listen_addr {
struct sockaddr_storage sa;
int fd;
int rtable;
+ int port;
};
struct ntp_addr {
@@ -132,14 +133,17 @@ struct ntp_addr {
struct ntp_addr_wrap {
char *name;
char *path;
+ int port;
struct ntp_addr *a;
u_int8_t pool;
};
struct ntp_addr_msg {
struct ntp_addr a;
+ int port;
size_t namelen;
size_t pathlen;
+ size_t portlen;
};
struct ntp_status {
@@ -184,6 +188,7 @@ struct ntp_peer {
u_int8_t trusted;
int lasterror;
int senderrors;
+ int port;
};
struct ntp_sensor {
@@ -206,6 +211,7 @@ struct constraint {
TAILQ_ENTRY(constraint) entry;
struct ntp_addr_wrap addr_head;
struct ntp_addr *addr;
+ int port;
int senderrors;
enum client_state state;
u_int32_t id;
@@ -365,6 +371,7 @@ void host_dns_free(struct ntp_addr *)
struct ntp_peer *new_peer(void);
struct ntp_conf_sensor *new_sensor(char *);
struct constraint *new_constraint(void);
+int intdup(int);
/* ntp_msg.c */
int ntp_getmsg(struct sockaddr *, char *, ssize_t, struct ntp_msg *);
@@ -401,6 +408,7 @@ void priv_constraint_kill(u_int32_t);
int priv_constraint_dispatch(struct pollfd *);
void priv_constraint_check_child(pid_t, int);
char *get_string(u_int8_t *, size_t);
+int intlen(int);
/* util.c */
double gettime_corrected(void);
--- a/src/constraint.c 2020-08-02 01:56:09.060286035 +0300
+++ b/src/constraint.c 2020-08-02 01:56:47.110286075 +0300
@@ -66,11 +66,11 @@ void priv_constraint_readquery(struct c
uint8_t **);
struct httpsdate *
- httpsdate_init(const char *, const char *, const char *,
+ httpsdate_init(const char *, const int *, const char *,
const char *, const u_int8_t *, size_t);
void httpsdate_free(void *);
int httpsdate_request(struct httpsdate *, struct timeval *);
-void *httpsdate_query(const char *, const char *, const char *,
+void *httpsdate_query(const char *, const int *, const char *,
const char *, const u_int8_t *, size_t,
struct timeval *, struct timeval *);
@@ -125,13 +125,13 @@ constraint_addr_init(struct constraint *
case AF_INET:
sa_in = (struct sockaddr_in *)&h->ss;
if (ntohs(sa_in->sin_port) == 0)
- sa_in->sin_port = htons(443);
+ sa_in->sin_port = htons(cstr->addr_head.port);
cstr->state = STATE_DNS_DONE;
break;
case AF_INET6:
sa_in6 = (struct sockaddr_in6 *)&h->ss;
if (ntohs(sa_in6->sin6_port) == 0)
- sa_in6->sin6_port = htons(443);
+ sa_in6->sin6_port = htons(cstr->addr_head.port);
cstr->state = STATE_DNS_DONE;
break;
default:
@@ -206,6 +206,7 @@ constraint_query(struct constraint *cstr
memset(&am, 0, sizeof(am));
memcpy(&am.a, cstr->addr, sizeof(am.a));
+ memcpy(&am.port, &cstr->addr_head.port, sizeof(am.port));
iov[iov_cnt].iov_base = &am;
iov[iov_cnt++].iov_len = sizeof(am);
@@ -219,6 +220,11 @@ constraint_query(struct constraint *cstr
iov[iov_cnt].iov_base = cstr->addr_head.path;
iov[iov_cnt++].iov_len = am.pathlen;
}
+ if (cstr->addr_head.port) {
+ am.portlen = intlen(cstr->addr_head.port) + 1;
+ iov[iov_cnt].iov_base = &cstr->addr_head.port;
+ iov[iov_cnt++].iov_len = am.portlen;
+ }
imsg_composev(ibuf_main, IMSG_CONSTRAINT_QUERY,
cstr->id, 0, -1, iov, iov_cnt);
@@ -246,7 +252,7 @@ priv_constraint_msg(u_int32_t id, u_int8
return;
}
memcpy(&am, data, sizeof(am));
- if (len != (sizeof(am) + am.namelen + am.pathlen)) {
+ if (len != (sizeof(am) + am.namelen + am.pathlen + am.portlen)) {
log_warnx("constraint id %d: invalid query received", id);
return;
}
@@ -301,6 +307,7 @@ priv_constraint_readquery(struct constra
int n;
struct imsg imsg;
size_t mlen;
+ int port;
/* Read the message our parent left us. */
if (((n = imsg_read(&cstr->ibuf)) == -1 && errno != EAGAIN) || n == 0)
@@ -324,7 +331,7 @@ priv_constraint_readquery(struct constra
);
memcpy(am, imsg.data, sizeof(*am));
- if (mlen != (sizeof(*am) + am->namelen + am->pathlen))
+ if (mlen != (sizeof(*am) + am->namelen + am->pathlen + am->portlen))
fatalx("constraint: invalid message length received from parent process (%s)",
__func__
);
@@ -334,12 +341,15 @@ priv_constraint_readquery(struct constra
fatal("constraint: can't allocate memory (%s)", __func__);
memcpy(h, &am->a, sizeof(*h));
+ memcpy(&port, &am->port, sizeof(port));
h->next = NULL;
-
+
cstr->id = imsg.hdr.peerid;
cstr->addr = h;
cstr->addr_head.a = h;
-
+ cstr->port = port;
+ cstr->addr_head.port = port;
+
dptr = imsg.data;
memcpy(*data, dptr + sizeof(*am), mlen - sizeof(*am));
imsg_free(&imsg);
@@ -434,10 +444,14 @@ priv_constraint_child(const char *pw_dir
get_string(data, am.pathlen)) == NULL)
fatalx("constraint %s: invalid path", addr);
}
+ if (am.portlen) {
+ if (cstr.addr_head.port == 0)
+ fatalx("constraint %s: invalid port", addr);
+ }
/* Run! */
if ((ctx = httpsdate_query(addr,
- CONSTRAINT_PORT, cstr.addr_head.name, cstr.addr_head.path,
+ &cstr.addr_head.port, cstr.addr_head.name, cstr.addr_head.path,
conf->ca, conf->ca_len, &rectv, &xmttv)) == NULL) {
log_debug("constraint %s: failed to get proper time results", addr);
/* Abort with failure but without warning */
@@ -800,8 +814,14 @@ constraint_msg_dns(u_int32_t id, u_int8_
ncstr->addr_head.a = h;
ncstr->addr_head.name = strdup(cstr->addr_head.name);
ncstr->addr_head.path = strdup(cstr->addr_head.path);
+ ncstr->addr_head.port = intdup(cstr->addr_head.port);
+
+ // Unless we do this, we have value 0 in ncstr->port
+ ncstr->port = intdup(cstr->port);
+
if (ncstr->addr_head.name == NULL ||
- ncstr->addr_head.path == NULL)
+ ncstr->addr_head.path == NULL ||
+ ncstr->addr_head.port == 0 || ncstr->port == 0)
fatal("constraint id %d: DNS dispatching failed: invalid data", id);
ncstr->addr_head.pool = cstr->addr_head.pool;
ncstr->state = STATE_DNS_DONE;
@@ -811,6 +831,7 @@ constraint_msg_dns(u_int32_t id, u_int8_
h->next = ncstr->addr;
ncstr->addr = h;
ncstr->addr_head.a = h;
+ // TODO missing port?
}
} while (len);
@@ -912,10 +933,11 @@ constraint_check(double val)
}
struct httpsdate *
-httpsdate_init(const char *addr, const char *port, const char *hostname,
+httpsdate_init(const char *addr, const int *port, const char *hostname,
const char *path, const u_int8_t *ca, size_t ca_len)
{
struct httpsdate *httpsdate = NULL;
+ char port_s[sizeof(port)];
if ((httpsdate = calloc(1, sizeof(*httpsdate))) == NULL)
goto fail;
@@ -923,8 +945,10 @@ httpsdate_init(const char *addr, const c
if (hostname == NULL)
hostname = addr;
+ sprintf(port_s, "%d", *port);
+
if ((httpsdate->tls_addr = strdup(addr)) == NULL ||
- (httpsdate->tls_port = strdup(port)) == NULL ||
+ (httpsdate->tls_port = strdup(port_s)) == NULL ||
(httpsdate->tls_hostname = strdup(hostname)) == NULL ||
(httpsdate->tls_path = strdup(path)) == NULL)
goto fail;
@@ -1098,7 +1122,7 @@ httpsdate_request(struct httpsdate *http
}
void *
-httpsdate_query(const char *addr, const char *port, const char *hostname,
+httpsdate_query(const char *addr, const int *port, const char *hostname,
const char *path, const u_int8_t *ca, size_t ca_len,
struct timeval *rectv, struct timeval *xmttv)
{
@@ -1183,3 +1207,17 @@ get_string(u_int8_t *ptr, size_t len)
return strndup(ptr, i);
}
+
+int
+intlen(int val)
+{
+ int n = 1;
+ if (val < 0)
+ return 0;
+ while(val > 9) {
+ n++;
+ val /= 10;
+ }
+
+ return val;
+}
--- a/src/parse.y 2020-07-31 23:57:08.000000000 +0300
+++ b/src/parse.y 2020-08-01 01:51:28.041394057 +0300
@@ -60,6 +60,7 @@ int findeol(void);
struct sockaddr_in query_addr4;
struct sockaddr_in6 query_addr6;
int poolseqnum;
+struct servent *se;
struct opts {
int weight;
@@ -68,6 +69,7 @@ struct opts {
int rtable;
int trusted;
char *refstr;
+ int port;
} opts;
void opts_default(void);
@@ -86,18 +88,21 @@ typedef struct {
%token LISTEN ON CONSTRAINT CONSTRAINTS FROM QUERY TRUSTED
%token SERVER SERVERS SENSOR CORRECTION RTABLE REFID STRATUM WEIGHT
%token ERROR
+%token PORT
%token <v.string> STRING
%token <v.number> NUMBER
%type <v.addr> address url urllist
%type <v.opts> listen_opts listen_opts_l listen_opt
%type <v.opts> server_opts server_opts_l server_opt
%type <v.opts> sensor_opts sensor_opts_l sensor_opt
+%type <v.opts> constraint_opts constraint_opts_l constraint_opt
%type <v.opts> correction
%type <v.opts> rtable
%type <v.opts> refid
%type <v.opts> stratum
%type <v.opts> weight
%type <v.opts> trusted
+%type <v.opts> port
%%
grammar : /* empty */
@@ -125,6 +130,10 @@ main : LISTEN ON address listen_opts {
fatal("can't allocate memory for listening address");
la->fd = -1;
la->rtable = $4.rtable;
+
+ if ($4.port != 0)
+ la->port = $4.port;
+
memcpy(&la->sa, &h->ss,
sizeof(struct sockaddr_storage));
TAILQ_INSERT_TAIL(&conf->listen_addrs, la,
@@ -186,10 +195,22 @@ main : LISTEN ON address listen_opts {
p->trusted = $3.trusted;
conf->trusted_peers = conf->trusted_peers ||
$3.trusted;
+
+ if ($3.port == 0) {
+ if ((se = getservbyname("ntp", "udp")) == NULL) {
+ fatal("new server: can't find default system information for NTP protocol (getservbyname)");
+ } else {
+ $3.port = ntohs(se->s_port);
+ }
+ }
+ p->port = $3.port;
+ $2->port = p->port;
+
p->query_addr4 = query_addr4;
p->query_addr6 = query_addr6;
p->addr = h;
p->addr_head.a = h;
+ p->addr_head.port = intdup($2->port);
p->addr_head.pool = ++poolseqnum;
p->addr_head.name = strdup($2->name);
if (p->addr_head.name == NULL)
@@ -228,9 +249,21 @@ main : LISTEN ON address listen_opts {
p->trusted = $3.trusted;
conf->trusted_peers = conf->trusted_peers ||
$3.trusted;
+
+ if ($3.port == 0) {
+ if ((se = getservbyname("ntp", "udp")) == NULL) {
+ fatal("new server: can't find default system information for NTP protocol (getservbyname)");
+ } else {
+ $3.port = ntohs(se->s_port);
+ }
+ }
+ p->port = $3.port;
+ $2->port = p->port;
+
p->query_addr4 = query_addr4;
p->query_addr6 = query_addr6;
p->addr_head.a = p->addr;
+ p->addr_head.port = intdup($2->port);
p->addr_head.pool = 0;
p->addr_head.name = strdup($2->name);
if (p->addr_head.name == NULL)
@@ -241,7 +274,7 @@ main : LISTEN ON address listen_opts {
free($2->name);
free($2);
}
- | CONSTRAINTS FROM url {
+ | CONSTRAINTS FROM url constraint_opts {
struct constraint *p;
struct ntp_addr *h, *next;
@@ -266,6 +299,17 @@ main : LISTEN ON address listen_opts {
p = new_constraint();
p->addr = h;
p->addr_head.a = h;
+
+ if ($4.port == 0) {
+ if ((se = getservbyname("https", "tcp")) == NULL) {
+ fatal("new constraint: can't find default system information for HTTPS protocol (getservbyname)");
+ } else {
+ $4.port = ntohs(se->s_port);
+ }
+ }
+ p->port = $4.port;
+ p->addr_head.port = intdup($4.port);
+
p->addr_head.pool = ++poolseqnum;
p->addr_head.name = strdup($3->name);
p->addr_head.path = strdup($3->path);
@@ -281,7 +325,7 @@ main : LISTEN ON address listen_opts {
free($3->name);
free($3);
}
- | CONSTRAINT FROM urllist {
+ | CONSTRAINT FROM urllist constraint_opts {
struct constraint *p;
struct ntp_addr *h, *next;
@@ -304,6 +348,17 @@ main : LISTEN ON address listen_opts {
}
p->addr_head.a = p->addr;
+
+ if ($4.port == 0) {
+ if ((se = getservbyname("https", "tcp")) == NULL) {
+ fatal("new constraint: can't find default system information for HTTPS protocol (getservbyname)");
+ } else {
+ $4.port = ntohs(se->s_port);
+ }
+ }
+ p->port = $4.port;
+ p->addr_head.port = intdup($4.port);
+
p->addr_head.pool = 0;
p->addr_head.name = strdup($3->name);
p->addr_head.path = strdup($3->path);
@@ -410,6 +465,7 @@ listen_opts_l : listen_opts_l listen_opt
| listen_opt
;
listen_opt : rtable
+ | port
;
server_opts : { opts_default(); }
@@ -422,6 +478,18 @@ server_opts_l : server_opts_l server_opt
;
server_opt : weight
| trusted
+ | port
+ ;
+
+constraint_opts : { opts_default(); }
+ constraint_opts_l
+ { $$ = opts; }
+ | { opts_default(); $$ = opts; }
+ ;
+constraint_opts_l : constraint_opts_l constraint_opt
+ | constraint_opt
+ ;
+constraint_opt : port
;
sensor_opts : { opts_default(); }
@@ -478,6 +546,17 @@ weight : WEIGHT NUMBER {
}
opts.weight = $2;
}
+ ;
+
+port : PORT NUMBER {
+ if ($2 < 1 || $2 > 65535) {
+ yyerror("port must be between 1 and 65535");
+ YYERROR;
+ }
+ opts.port = $2;
+ }
+ ;
+
rtable : RTABLE NUMBER {
#ifdef RT_TABLEID_MAX
if ($2 < 0 || $2 > RT_TABLEID_MAX) {
@@ -502,6 +581,7 @@ opts_default(void)
memset(&opts, 0, sizeof opts);
opts.weight = 1;
opts.stratum = 1;
+ opts.port = 0;
}
struct keywords {
@@ -542,6 +622,7 @@ lookup(char *s)
{ "from", FROM},
{ "listen", LISTEN},
{ "on", ON},
+ { "port", PORT},
{ "query", QUERY},
{ "refid", REFID},
{ "rtable", RTABLE},
--- a/src/server.c 2020-08-01 00:04:05.000000000 +0300
+++ b/src/server.c 2020-08-01 01:14:42.328058753 +0300
@@ -107,14 +107,18 @@ setup_listeners(struct servent *se, stru
for (la = TAILQ_FIRST(&lconf->listen_addrs); la; ) {
switch (la->sa.ss_family) {
case AF_INET:
- if (((struct sockaddr_in *)&la->sa)->sin_port == 0)
- ((struct sockaddr_in *)&la->sa)->sin_port =
- se->s_port;
+ if ((la->port == 0) && \
+ (((struct sockaddr_in *)&la->sa)->sin_port == 0))
+ ((struct sockaddr_in *)&la->sa)->sin_port = se->s_port;
+ else
+ ((struct sockaddr_in *)&la->sa)->sin_port = ntohs(la->port);
break;
case AF_INET6:
- if (((struct sockaddr_in6 *)&la->sa)->sin6_port == 0)
- ((struct sockaddr_in6 *)&la->sa)->sin6_port =
- se->s_port;
+ if ((la->port == 0) && \
+ (((struct sockaddr_in6 *)&la->sa)->sin6_port == 0))
+ ((struct sockaddr_in6 *)&la->sa)->sin6_port = se->s_port;
+ else
+ ((struct sockaddr_in6 *)&la->sa)->sin6_port = ntohs(la->port);
break;
case AF_UNSPEC:
nla = TAILQ_NEXT(la, entry);
--- a/src/ntpd.conf.5 2020-07-31 23:00:51.000000000 +0300
+++ b/src/ntpd.conf.5 2020-08-01 01:22:25.424725907 +0300
@@ -14,7 +14,7 @@
.\" AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
.\" OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
-.Dd $Mdocdate: May 16 2020 $
+.Dd $Mdocdate: August 01 2020 $
.Dt NTPD.CONF 5
.Os
.Sh NAME
@@ -37,6 +37,7 @@ The basic configuration options are as f
.Bl -tag -width Ds
.It Xo Ic listen on Ar address
.Op Ic rtable Ar table-id
+.Op Ic port Ar port-number
.Xc
.Xr ntpd 8
has the ability to sync the local clock to remote NTP servers and, if
@@ -62,6 +63,12 @@ keyword will specify which routing table
By default
.Xr ntpd 8
will listen using the current routing table.
+The optional
+.Ic port
+keyword will specify which local UDP port the NTP server process should use for inbound connections.
+By default
+.Xr ntpd 8
+will listen to UDP port 123 for new client connections.
For example:
.Bd -literal -offset indent
listen on *
@@ -72,6 +79,7 @@ or
listen on 127.0.0.1
listen on ::1
listen on 127.0.0.1 rtable 4
+listen on 127.0.0.1 port 1230
.Ed
.It Ic query from Ar sourceaddr
Specify a local IP address the
@@ -165,6 +173,7 @@ than a server with a weight of 1.
.It Xo Ic server Ar address
.Op Ic trusted
.Op Ic weight Ar weight-value
+.Op Ic port Ar port-number
.Xc
Specify the IP address or the hostname of an NTP
server to synchronize to.
@@ -182,6 +191,7 @@ For example:
.Bd -literal -offset indent
server 10.0.0.2 weight 5
server ntp.example.org weight 1
+server ntp.foo.org port 123
.Ed
.Pp
To provide redundancy, it is good practice to configure multiple servers.
@@ -190,6 +200,7 @@ network latency.
.It Xo Ic servers Ar address
.Op Ic trusted
.Op Ic weight Ar weight-value
+.Op Ic port Ar port-number
.Xc
As with
.Cm server ,
@@ -204,6 +215,7 @@ For example:
.Bd -literal -offset indent
servers pool.ntp.org
servers pool.ntp.org weight 5
+servers pool.ntp.org weight 6 port 123
.Ed
.El
.Sh CONSTRAINTS
@@ -227,8 +239,13 @@ without libtls causes
to log a warning message on startup.
.Bl -tag -width Ds
.It Ic constraint from Ar url [ip...]
+.Op Ic port Ar port-number
Specify the URL, IP address or the hostname of an HTTPS server to
-provide a constraint.
+provide a constraint. The optional
+.Ic port
+number is an HTTPS server port to connect to. By default
+.Xr ntpd 8
+will connect to remote TCP port 443.
If the url is followed by one or more addresses the url and addresses will be
tried until a working one is found.
The url path and expected certificate name is always taken from the
@@ -242,8 +259,10 @@ will calculate a median constraint from
server ntp.example.org
constraint from www.example.com
constraint from "https://9.9.9.9" "2620:fe::9"
+constraint from www.google.com port 443
.Ed
.It Ic constraints from Ar url
+.Op Ic port Ar port-number
As with
.Ic constraint from ,
specify the URL, IP address or the hostname of an HTTPS server to
@@ -251,10 +270,16 @@ provide a constraint.
Should the hostname resolve to multiple IP addresses,
.Xr ntpd 8
will calculate a median constraint from all of them.
+The optional
+.Ic port
+number is an HTTPS server port to connect to. By default
+.Xr ntpd 8
+will connect to remote TCP port 443.
For example:
.Bd -literal -offset indent
servers pool.ntp.org
constraints from "https://www.google.com/"
+constraints from "https://duckduckgo.com/" port 443
.Ed
.El
.Sh FILES