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tcpdump/print-ntp.c
Francois-Xavier Le Bail 1729c1d31f NTP: Use GET_U_1() to replace a direct dereference
2024-09-30 20:23:34 +02:00

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/*
* Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* By Jeffrey Mogul/DECWRL
* loosely based on print-bootp.c
*/
/* \summary: Network Time Protocol (NTP) printer */
/*
* specification:
*
* RFC 1119 - NTPv2
* RFC 1305 - NTPv3
* RFC 5905 - NTPv4
*/
#include <config.h>
#include "netdissect-stdinc.h"
#include "netdissect-ctype.h"
#define ND_LONGJMP_FROM_TCHECK
#include "netdissect.h"
#include "addrtoname.h"
#include "extract.h"
#include "ntp.h"
/*
* Based on ntp.h from the U of MD implementation
* This file is based on Version 2 of the NTP spec (RFC1119).
*/
/* RFC 5905 updated by RFC 7822
* 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |LI | VN |Mode | Stratum | Poll | Precision |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Root Delay |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Root Dispersion |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Reference Identifier |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* | Reference Timestamp (64) |
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* | Originate Timestamp (64) |
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* | Receive Timestamp (64) |
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* | Transmit Timestamp (64) |
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* . .
* . Optional Extensions (variable) .
* . .
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
/* Length of the NTP data message with the mandatory fields ("the header")
* and without any optional fields (extension, Key Identifier,
* Message Digest).
*/
#define NTP_TIMEMSG_MINLEN 48U
struct ntp_time_data {
nd_uint8_t status; /* status of local clock and leap info */
nd_uint8_t stratum; /* Stratum level */
nd_int8_t ppoll; /* poll value */
nd_int8_t precision;
struct s_fixedpt root_delay;
struct s_fixedpt root_dispersion;
nd_uint32_t refid;
struct l_fixedpt ref_timestamp;
struct l_fixedpt org_timestamp;
struct l_fixedpt rec_timestamp;
struct l_fixedpt xmt_timestamp;
/* extension fields and/or MAC follow */
};
struct ntp_extension_field {
nd_uint16_t type;
nd_uint16_t length;
/* body follows */
};
/*
* Leap Second Codes (high order two bits)
*/
#define NO_WARNING 0x00 /* no warning */
#define PLUS_SEC 0x40 /* add a second (61 seconds) */
#define MINUS_SEC 0x80 /* minus a second (59 seconds) */
#define ALARM 0xc0 /* alarm condition (clock unsynchronized) */
/*
* Clock Status Bits that Encode Version
*/
#define NTPVERSION_1 0x08
#define VERSIONMASK 0x38
#define VERSIONSHIFT 3
#define LEAPMASK 0xc0
#define LEAPSHIFT 6
#ifdef MODEMASK
#undef MODEMASK /* Solaris sucks */
#endif
#define MODEMASK 0x07
#define MODESHIFT 0
/*
* Code values
*/
#define MODE_UNSPEC 0 /* unspecified */
#define MODE_SYM_ACT 1 /* symmetric active */
#define MODE_SYM_PAS 2 /* symmetric passive */
#define MODE_CLIENT 3 /* client */
#define MODE_SERVER 4 /* server */
#define MODE_BROADCAST 5 /* broadcast */
#define MODE_CONTROL 6 /* control message */
#define MODE_RES2 7 /* reserved */
/*
* Stratum Definitions
*/
#define UNSPECIFIED 0
#define PRIM_REF 1 /* radio clock */
#define INFO_QUERY 62 /* **** THIS implementation dependent **** */
#define INFO_REPLY 63 /* **** THIS implementation dependent **** */
static void p_sfix(netdissect_options *ndo, const struct s_fixedpt *);
static void p_ntp_delta(netdissect_options *, const struct l_fixedpt *, const struct l_fixedpt *);
static void p_poll(netdissect_options *, const int);
static u_int p_ext_fields(netdissect_options *, const u_char *, u_int length);
static const struct tok ntp_mode_values[] = {
{ MODE_UNSPEC, "unspecified" },
{ MODE_SYM_ACT, "symmetric active" },
{ MODE_SYM_PAS, "symmetric passive" },
{ MODE_CLIENT, "Client" },
{ MODE_SERVER, "Server" },
{ MODE_BROADCAST, "Broadcast" },
{ MODE_CONTROL, "Control Message" },
{ MODE_RES2, "Reserved" },
{ 0, NULL }
};
static const struct tok ntp_leapind_values[] = {
{ NO_WARNING, "" },
{ PLUS_SEC, "+1s" },
{ MINUS_SEC, "-1s" },
{ ALARM, "clock unsynchronized" },
{ 0, NULL }
};
static const struct tok ntp_stratum_values[] = {
{ UNSPECIFIED, "unspecified" },
{ PRIM_REF, "primary reference" },
{ 0, NULL }
};
static const struct tok ntp_ef_types[] = {
{ 0x0104, "Unique Identifier" },
{ 0x0204, "NTS Cookie" },
{ 0x0304, "NTS Cookie Placeholder" },
{ 0x0404, "NTS Authenticator and Encrypted Extension Fields" },
{ 0x2005, "Checksum Complement" },
{ 0, NULL }
};
/* draft-ietf-ntp-mode-6-cmds-02
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |LI | VN |Mode |R|E|M| OpCode | Sequence Number |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Status | Association ID |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Offset | Count |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* / Data (up to 468 bytes) /
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Padding (optional) |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | |
* / Authenticator (optional, 96 bytes) /
* | |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*
* Figure 1: NTP Control Message Header
*/
/* Length of the NTP control message with the mandatory fields ("the header")
* and without any optional fields (Data, Padding, Authenticator).
*/
#define NTP_CTRLMSG_MINLEN 12U
struct ntp_control_data {
nd_uint8_t magic; /* LI, VN, Mode */
nd_uint8_t control; /* R, E, M, OpCode */
nd_uint16_t sequence; /* Sequence Number */
nd_uint16_t status; /* Status */
nd_uint16_t assoc; /* Association ID */
nd_uint16_t offset; /* Offset */
nd_uint16_t count; /* Count */
nd_uint8_t data[564]; /* Data, [Padding, [Authenticator]] */
};
/*
* Print NTP time requests and responses
*/
static void
ntp_time_print(netdissect_options *ndo,
const struct ntp_time_data *bp, u_int length, u_int version)
{
const u_char *mac;
uint8_t stratum;
u_int efs_len;
if (length < NTP_TIMEMSG_MINLEN)
goto invalid;
stratum = GET_U_1(bp->stratum);
ND_PRINT(", Stratum %u (%s)",
stratum,
tok2str(ntp_stratum_values, (stratum >=2 && stratum<=15) ? "secondary reference" : "reserved", stratum));
ND_PRINT(", poll %d", GET_S_1(bp->ppoll));
p_poll(ndo, GET_S_1(bp->ppoll));
ND_PRINT(", precision %d", GET_S_1(bp->precision));
ND_PRINT("\n\tRoot Delay: ");
p_sfix(ndo, &bp->root_delay);
ND_PRINT(", Root dispersion: ");
p_sfix(ndo, &bp->root_dispersion);
ND_PRINT(", Reference-ID: ");
/* Interpretation depends on stratum */
switch (stratum) {
case UNSPECIFIED:
/* NTPv4 (RFC 5905, section 7.4) formalizes that refid _may_
* contain a printable, four-character, left justified, zero
* filled ASCII string ("kiss code") for status reporting
* and debugging. Some kiss codes are defined in the RFC as
* initial set for a new IANA registry, but the list may be
* modified or extended in the future, and unregistered kiss
* codes are possible (and are being seen in the field).
*/
if (!ND_ASCII_ISPRINT(GET_U_1(bp->refid))) {
ND_PRINT("(unspec)");
ND_TCHECK_4(bp->refid);
} else {
nd_printjn(ndo, (const u_char *)&(bp->refid), 4);
}
break;
case PRIM_REF:
nd_printjn(ndo, (const u_char *)&(bp->refid), 4);
break;
case INFO_QUERY:
ND_PRINT("%s INFO_QUERY", GET_IPADDR_STRING(bp->refid));
/* this doesn't have more content */
return;
case INFO_REPLY:
ND_PRINT("%s INFO_REPLY", GET_IPADDR_STRING(bp->refid));
/* this is too complex to be worth printing */
return;
default:
/* In NTPv4 (RFC 5905) refid is an IPv4 address or first 32 bits of
MD5 sum of IPv6 address */
ND_PRINT("0x%08x", GET_BE_U_4(bp->refid));
break;
}
ND_PRINT("\n\t Reference Timestamp: ");
p_ntp_time(ndo, &(bp->ref_timestamp));
ND_PRINT("\n\t Originator Timestamp: ");
p_ntp_time(ndo, &(bp->org_timestamp));
ND_PRINT("\n\t Receive Timestamp: ");
p_ntp_time(ndo, &(bp->rec_timestamp));
ND_PRINT("\n\t Transmit Timestamp: ");
p_ntp_time(ndo, &(bp->xmt_timestamp));
ND_PRINT("\n\t Originator - Receive Timestamp: ");
p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->rec_timestamp));
ND_PRINT("\n\t Originator - Transmit Timestamp: ");
p_ntp_delta(ndo, &(bp->org_timestamp), &(bp->xmt_timestamp));
if (version == 4)
efs_len = p_ext_fields(ndo, (const u_char *)bp + NTP_TIMEMSG_MINLEN, length - NTP_TIMEMSG_MINLEN);
else
efs_len = 0;
mac = (const u_char *)bp + NTP_TIMEMSG_MINLEN + efs_len;
if (length == NTP_TIMEMSG_MINLEN + efs_len + 4) { /* Optional: key-id (crypto-NAK) */
ND_PRINT("\n\tKey id: %u", GET_BE_U_4(mac));
} else if (length == NTP_TIMEMSG_MINLEN + efs_len + 4 + 16) { /* Optional: key-id + 128-bit digest */
ND_PRINT("\n\tKey id: %u", GET_BE_U_4(mac));
ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x",
GET_BE_U_4(mac + 4),
GET_BE_U_4(mac + 8),
GET_BE_U_4(mac + 12),
GET_BE_U_4(mac + 16));
} else if (length == NTP_TIMEMSG_MINLEN + efs_len + 4 + 20) { /* Optional: key-id + 160-bit digest */
ND_PRINT("\n\tKey id: %u", GET_BE_U_4(mac));
ND_PRINT("\n\tAuthentication: %08x%08x%08x%08x%08x",
GET_BE_U_4(mac + 4),
GET_BE_U_4(mac + 8),
GET_BE_U_4(mac + 12),
GET_BE_U_4(mac + 16),
GET_BE_U_4(mac + 20));
} else if (length > NTP_TIMEMSG_MINLEN + efs_len) {
ND_PRINT("\n\t(%u more bytes after the header and extension fields)",
length - NTP_TIMEMSG_MINLEN - efs_len);
}
return;
invalid:
nd_print_invalid(ndo);
ND_TCHECK_LEN(bp, length);
}
/*
* Print NTP control message requests and responses
*/
static void
ntp_control_print(netdissect_options *ndo,
const struct ntp_control_data *cd, u_int length)
{
uint8_t control, R, E, M, opcode;
uint16_t sequence, status, assoc, offset, count;
if (length < NTP_CTRLMSG_MINLEN)
goto invalid;
control = GET_U_1(cd->control);
R = (control & 0x80) != 0;
E = (control & 0x40) != 0;
M = (control & 0x20) != 0;
opcode = control & 0x1f;
ND_PRINT(", %s, %s, %s, OpCode=%u\n",
R ? "Response" : "Request", E ? "Error" : "OK",
M ? "More" : "Last", opcode);
sequence = GET_BE_U_2(cd->sequence);
ND_PRINT("\tSequence=%hu", sequence);
status = GET_BE_U_2(cd->status);
ND_PRINT(", Status=%#hx", status);
assoc = GET_BE_U_2(cd->assoc);
ND_PRINT(", Assoc.=%hu", assoc);
offset = GET_BE_U_2(cd->offset);
ND_PRINT(", Offset=%hu", offset);
count = GET_BE_U_2(cd->count);
ND_PRINT(", Count=%hu", count);
if (NTP_CTRLMSG_MINLEN + count > length)
goto invalid;
if (count != 0) {
ND_TCHECK_LEN(cd->data, count);
ND_PRINT("\n\tTO-BE-DONE: data not interpreted");
}
return;
invalid:
nd_print_invalid(ndo);
ND_TCHECK_LEN(cd, length);
}
union ntpdata {
struct ntp_time_data td;
struct ntp_control_data cd;
};
/*
* Print NTP requests, handling the common VN, LI, and Mode
*/
void
ntp_print(netdissect_options *ndo,
const u_char *cp, u_int length)
{
const union ntpdata *bp = (const union ntpdata *)cp;
u_int mode, version, leapind;
uint8_t status;
ndo->ndo_protocol = "ntp";
status = GET_U_1(bp->td.status);
version = (status & VERSIONMASK) >> VERSIONSHIFT;
ND_PRINT("NTPv%u", version);
mode = (status & MODEMASK) >> MODESHIFT;
if (!ndo->ndo_vflag) {
ND_PRINT(", %s, length %u",
tok2str(ntp_mode_values, "Unknown mode", mode),
length);
return;
}
ND_PRINT(", %s, length %u\n",
tok2str(ntp_mode_values, "Unknown mode", mode), length);
/* leapind = (status & LEAPMASK) >> LEAPSHIFT; */
leapind = (status & LEAPMASK);
ND_PRINT("\tLeap indicator: %s (%u)",
tok2str(ntp_leapind_values, "Unknown", leapind),
leapind);
switch (mode) {
case MODE_UNSPEC:
case MODE_SYM_ACT:
case MODE_SYM_PAS:
case MODE_CLIENT:
case MODE_SERVER:
case MODE_BROADCAST:
ntp_time_print(ndo, &bp->td, length, version);
break;
case MODE_CONTROL:
ntp_control_print(ndo, &bp->cd, length);
break;
default:
break; /* XXX: not implemented! */
}
}
static void
p_sfix(netdissect_options *ndo,
const struct s_fixedpt *sfp)
{
int i;
int f;
double ff;
i = GET_BE_U_2(sfp->int_part);
f = GET_BE_U_2(sfp->fraction);
ff = f / 65536.0; /* shift radix point by 16 bits */
f = (int)(ff * 1000000.0); /* Treat fraction as parts per million */
ND_PRINT("%d.%06d", i, f);
}
/* Prints time difference between *lfp and *olfp */
static void
p_ntp_delta(netdissect_options *ndo,
const struct l_fixedpt *olfp,
const struct l_fixedpt *lfp)
{
uint32_t u, uf;
uint32_t ou, ouf;
uint32_t i;
uint32_t f;
double ff;
int signbit;
u = GET_BE_U_4(lfp->int_part);
ou = GET_BE_U_4(olfp->int_part);
uf = GET_BE_U_4(lfp->fraction);
ouf = GET_BE_U_4(olfp->fraction);
if (ou == 0 && ouf == 0) {
p_ntp_time(ndo, lfp);
return;
}
if (u > ou) { /* new is definitely greater than old */
signbit = 0;
i = u - ou;
f = uf - ouf;
if (ouf > uf) /* must borrow from high-order bits */
i -= 1;
} else if (u < ou) { /* new is definitely less than old */
signbit = 1;
i = ou - u;
f = ouf - uf;
if (uf > ouf) /* must borrow from the high-order bits */
i -= 1;
} else { /* int_part is zero */
i = 0;
if (uf > ouf) {
signbit = 0;
f = uf - ouf;
} else {
signbit = 1;
f = ouf - uf;
}
}
ff = f;
if (ff < 0.0) /* some compilers are buggy */
ff += FMAXINT;
ff = ff / FMAXINT; /* shift radix point by 32 bits */
f = (uint32_t)(ff * 1000000000.0); /* treat fraction as parts per billion */
ND_PRINT("%s%u.%09u", signbit ? "-" : "+", i, f);
}
/* Prints polling interval in log2 as seconds or fraction of second */
static void
p_poll(netdissect_options *ndo,
const int poll_interval)
{
if (poll_interval <= -32 || poll_interval >= 32)
return;
if (poll_interval >= 0)
ND_PRINT(" (%us)", 1U << poll_interval);
else
ND_PRINT(" (1/%us)", 1U << -poll_interval);
}
/* Prints an NTPv4 extension field */
static void
p_ntp_ef(netdissect_options *ndo, u_int type, u_int length, const u_char *ef_body)
{
ND_PRINT("\n\t %s", tok2str(ntp_ef_types, "Unknown type", type));
ND_PRINT(" (0x%04x), length %u", type, length);
if (ndo->ndo_vflag > 2)
hex_print(ndo, "\n\t ", ef_body, length - 4);
else {
/*
* If we're not going to print it, at least make sure
* it's present in the packet, so if ef_len is too long,
* we stop.
*/
ND_TCHECK_LEN(ef_body, length - 4);
}
}
/* Prints list of extension fields per RFC 7822 */
static u_int
p_ext_fields(netdissect_options *ndo, const u_char *cp, u_int length)
{
const struct ntp_extension_field *ef;
u_int ef_type, ef_len, efs_len;
int first_ef;
first_ef = 1;
efs_len = 0;
/* RFC 7822 requires the last EF in the packet to have at least
28 octets to avoid ambiguity with MACs */
while (length - efs_len >= 28) {
ef = (const struct ntp_extension_field *)(cp + efs_len);
ef_type = GET_BE_U_2(ef->type);
ef_len = GET_BE_U_2(ef->length);
if (efs_len + ef_len > length || ef_len < 4 || ef_len % 4 != 0) {
nd_print_invalid(ndo);
break;
}
if (first_ef) {
ND_PRINT("\n\tExtension fields:");
first_ef = 0;
}
p_ntp_ef(ndo, ef_type, ef_len, (const u_char *)(ef + 1));
/*
* The entire extension field is guaranteed to be in the
* captured data, as p_ntp_ef() will longjmp out if it
* isn't.
*
* As the total length of the captured data fits in a
* u_int, this means that the total length of all the
* extension fields will fit in a u_int, so this will
* never overflow.
*/
efs_len += ef_len;
}
return efs_len;
}
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