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nts: improve NTS-NTP server/client code

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Add more comments, assertions, debug messages, and other minor
changes to make the code more robust.
This commit is contained in:
Miroslav Lichvar
2020-07-27 15:38:46 +02:00
parent def137bc80
commit d48f012809
3 changed files with 55 additions and 24 deletions
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26
nts_ntp_server.c
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@@ -112,15 +112,18 @@ NNS_CheckRequestAuth(NTP_Packet *packet, NTP_PacketInfo *info, uint32_t *kod)
for (parsed = NTP_HEADER_LENGTH; parsed < info->length; parsed += ef_length) {
if (!NEF_ParseField(packet, info->length, parsed,
&ef_length, &ef_type, &ef_body, &ef_body_length))
break;
/* This is not expected as the packet already passed NAU_ParsePacket() */
return 0;
switch (ef_type) {
case NTP_EF_NTS_UNIQUE_IDENTIFIER:
has_uniq_id = 1;
break;
case NTP_EF_NTS_COOKIE:
if (has_cookie || ef_body_length > sizeof (cookie.cookie))
if (has_cookie || ef_body_length > sizeof (cookie.cookie)) {
DEBUG_LOG("Unexpected cookie/length");
return 0;
}
cookie.length = ef_body_length;
memcpy(cookie.cookie, ef_body, ef_body_length);
has_cookie = 1;
@@ -199,13 +202,18 @@ NNS_CheckRequestAuth(NTP_Packet *packet, NTP_PacketInfo *info, uint32_t *kod)
return 0;
}
/* Prepare data for NNS_GenerateResponseAuth() to minimise the time spent
there (when the TX timestamp is already set) */
UTI_GetRandomBytes(server->nonce, sizeof (server->nonce));
server->num_cookies = MIN(NTS_MAX_COOKIES, requested_cookies);
for (i = 0; i < server->num_cookies; i++)
assert(sizeof (server->cookies) / sizeof (server->cookies[0]) == NTS_MAX_COOKIES);
for (i = 0; i < NTS_MAX_COOKIES && i < requested_cookies; i++)
if (!NKS_GenerateCookie(&context, &server->cookies[i]))
return 0;
server->num_cookies = i;
return 1;
}
@@ -224,14 +232,16 @@ NNS_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *req_info,
if (!server || req_info->mode != MODE_CLIENT || res_info->mode != MODE_SERVER)
return 0;
/* Make sure this is a response to the expected request */
/* Make sure this is a response to the request from the last call
of NNS_CheckRequestAuth() */
if (UTI_CompareNtp64(&server->req_tx, &request->transmit_ts) != 0)
assert(0);
for (parsed = NTP_HEADER_LENGTH; parsed < req_info->length; parsed += ef_length) {
if (!NEF_ParseField(request, req_info->length, parsed,
&ef_length, &ef_type, &ef_body, &ef_body_length))
break;
/* This is not expected as the packet already passed NAU_ParsePacket() */
return 0;
switch (ef_type) {
case NTP_EF_NTS_UNIQUE_IDENTIFIER:
@@ -249,7 +259,7 @@ NNS_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *req_info,
for (i = 0, plaintext_length = 0; i < server->num_cookies; i++) {
if (!NEF_SetField(plaintext, sizeof (plaintext), plaintext_length,
NTP_EF_NTS_COOKIE, &server->cookies[i].cookie,
NTP_EF_NTS_COOKIE, server->cookies[i].cookie,
server->cookies[i].length, &ef_length))
return 0;
@@ -259,6 +269,8 @@ NNS_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *req_info,
server->num_cookies = 0;
/* Generate an authenticator field which will make the length
of the response equal to the length of the request */
if (!NNA_GenerateAuthEF(response, res_info, server->siv,
server->nonce, sizeof (server->nonce),
plaintext, plaintext_length,