DWS/chrony
1
0
Fork 0
mirror of https://gitlab.com/chrony/chrony.git synced 2025-12-03 18:05:06 -05:00
Code Issues Packages Projects Releases Wiki Activity

nts: switch client to compliant key exporter on NTS NAK

Browse Source 
Implement a fallback for the NTS-NTP client to switch to the compliant
AES-128-GCM-SIV exporter context when the server is using the compliant
context, but does not support the new NTS-KE record negotiating its use,
assuming it can respond with an NTS NAK to the request authenticated
with the incorrect key.

Export both sets of keys when processing the NTS-KE response. If an NTS
NAK is the only valid response from the server after the last NTS-KE
session, switch to the keys exported with the compliant context for the
following requests instead of dropping all cookies and restarting
NTS-KE. Don't switch back to the original keys if an NTS NAK is received
again.
This commit is contained in:
Miroslav Lichvar
2024-09-19 14:19:12 +02:00
parent 0707865413
commit 689605b6a2
5 changed files with 48 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
nts_ke_client.c
View File

@@ -52,6 +52,7 @@ struct NKC_Instance_Record {
int compliant_128gcm;
NKE_Context context;
NKE_Context alt_context;
NKE_Cookie cookies[NKE_MAX_COOKIES];
int num_cookies;
char server_name[NKE_MAX_RECORD_BODY_LENGTH + 2];
@@ -149,6 +150,7 @@ process_response(NKC_Instance inst)
assert(sizeof (uint16_t) == 2);
inst->compliant_128gcm = 0;
inst->alt_context.algorithm = AEAD_SIV_INVALID;
inst->num_cookies = 0;
inst->ntp_address.ip_addr.family = IPADDR_UNSPEC;
inst->ntp_address.port = 0;
@@ -286,9 +288,18 @@ handle_message(void *arg)
/* With AES-128-GCM-SIV, set the algorithm ID in the RFC5705 key exporter
context incorrectly for compatibility with older chrony servers unless
the server confirmed support for the compliant context */
if (exporter_algorithm == AEAD_AES_128_GCM_SIV && !inst->compliant_128gcm)
the server confirmed support for the compliant context. Generate both
sets of keys in case the server uses the compliant context, but does not
support the negotiation record, assuming it will respond with an NTS NAK
to a request authenticated with the noncompliant key. */
if (exporter_algorithm == AEAD_AES_128_GCM_SIV && !inst->compliant_128gcm) {
inst->alt_context.algorithm = inst->context.algorithm;
if (!NKSN_GetKeys(inst->session, inst->alt_context.algorithm, exporter_algorithm,
NKE_NEXT_PROTOCOL_NTPV4, &inst->alt_context.c2s, &inst->alt_context.s2c))
return 0;
exporter_algorithm = AEAD_AES_SIV_CMAC_256;
}
if (!NKSN_GetKeys(inst->session, inst->context.algorithm, exporter_algorithm,
NKE_NEXT_PROTOCOL_NTPV4, &inst->context.c2s, &inst->context.s2c))
@@ -456,7 +467,7 @@ NKC_IsActive(NKC_Instance inst)
/* ================================================== */
int
NKC_GetNtsData(NKC_Instance inst, NKE_Context *context,
NKC_GetNtsData(NKC_Instance inst, NKE_Context *context, NKE_Context *alt_context,
NKE_Cookie *cookies, int *num_cookies, int max_cookies,
IPSockAddr *ntp_address)
{
@@ -466,6 +477,7 @@ NKC_GetNtsData(NKC_Instance inst, NKE_Context *context,
return 0;
*context = inst->context;
*alt_context = inst->alt_context;
for (i = 0; i < inst->num_cookies && i < max_cookies; i++)
cookies[i] = inst->cookies[i];