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ntp: add functions for adding extension fields

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This commit is contained in:
Miroslav Lichvar 2020-02-03 18:28:00 +01:00
parent 86d29221f3
commit 725beb360a
2 changed files with 92 additions and 1 deletions
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87
ntp_ext.c
View file

@ -21,7 +21,7 @@
=======================================================================
Functions for working with NTP extension fields
Functions for adding and parsing NTPv4 extension fields
*/
#include "config.h"
@ -37,6 +37,91 @@ struct ExtFieldHeader {
/* ================================================== */
static int
format_field(unsigned char *buffer, int buffer_length, int start,
int type, int body_length, int *length, void **body)
{
struct ExtFieldHeader *header;
if (buffer_length < 0 || start < 0 || buffer_length <= start ||
buffer_length - start < sizeof (*header) || start % 4 != 0)
return 0;
header = (struct ExtFieldHeader *)(buffer + start);
if (body_length < 0 || sizeof (*header) + body_length > 0xffff ||
start + sizeof (*header) + body_length > buffer_length || body_length % 4 != 0)
return 0;
header->type = htons(type);
header->length = htons(sizeof (*header) + body_length);
*length = sizeof (*header) + body_length;
*body = header + 1;
return 1;
}
/* ================================================== */
int
NEF_SetField(unsigned char *buffer, int buffer_length, int start,
int type, void *body, int body_length, int *length)
{
void *ef_body;
if (!format_field(buffer, buffer_length, start, type, body_length, length, &ef_body))
return 0;
memcpy(ef_body, body, body_length);
return 1;
}
/* ================================================== */
int
NEF_AddBlankField(NTP_Packet *packet, NTP_PacketInfo *info, int type, int body_length, void **body)
{
int ef_length, length = info->length;
if (length < NTP_HEADER_LENGTH || length >= sizeof (*packet) || length % 4 != 0)
return 0;
/* Only NTPv4 packets can have extension fields */
if (info->version != 4)
return 0;
if (!format_field((unsigned char *)packet, sizeof (*packet), length,
type, body_length, &ef_length, body))
return 0;
if (ef_length < NTP_MIN_EF_LENGTH)
return 0;
info->length += ef_length;
info->ext_fields++;
return 1;
}
/* ================================================== */
int
NEF_AddField(NTP_Packet *packet, NTP_PacketInfo *info,
int type, void *body, int body_length)
{
void *ef_body;
if (!NEF_AddBlankField(packet, info, type, body_length, &ef_body))
return 0;
memcpy(ef_body, body, body_length);
return 1;
}
/* ================================================== */
int
NEF_ParseSingleField(unsigned char *buffer, int buffer_length, int start,
int *length, int *type, void **body, int *body_length)

6
ntp_ext.h
View file

@ -29,6 +29,12 @@
#include "ntp.h"
extern int NEF_SetField(unsigned char *buffer, int buffer_length, int start,
int type, void *body, int body_length, int *length);
extern int NEF_AddBlankField(NTP_Packet *packet, NTP_PacketInfo *info, int type,
int body_length, void **body);
extern int NEF_AddField(NTP_Packet *packet, NTP_PacketInfo *info,
int type, void *body, int body_length);
extern int NEF_ParseSingleField(unsigned char *buffer, int buffer_length, int start,
int *length, int *type, void **body, int *body_length);
extern int NEF_ParseField(NTP_Packet *packet, int packet_length, int start,