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s4:librpc/rpc: define required schannel flags and enforce them

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BUG: https://bugzilla.samba.org/show_bug.cgi?id=15425

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
This commit is contained in:
Stefan Metzmacher 2024-10-02 16:38:53 +02:00 committed by Douglas Bagnall
parent 69b0cbd13d
commit 25294685b1
1 changed files with 56 additions and 5 deletions
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61
source4/librpc/rpc/dcerpc_schannel.c
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@ -42,6 +42,7 @@ struct schannel_key_state {
bool dcerpc_schannel_auto;
struct cli_credentials *credentials;
struct netlogon_creds_CredentialState *creds;
uint32_t required_negotiate_flags;
uint32_t local_negotiate_flags;
uint32_t remote_negotiate_flags;
struct netr_Credential credentials1;
@ -235,6 +236,29 @@ static void continue_srv_auth2(struct tevent_req *subreq)
return;
}
{
uint32_t rqf = s->required_negotiate_flags;
uint32_t rf = s->remote_negotiate_flags;
uint32_t lf = s->local_negotiate_flags;
if ((rf & NETLOGON_NEG_SUPPORTS_AES) &&
(lf & NETLOGON_NEG_SUPPORTS_AES))
{
rqf &= ~NETLOGON_NEG_ARCFOUR;
rqf &= ~NETLOGON_NEG_STRONG_KEYS;
}
if ((rqf & rf) != rqf) {
rqf = s->required_negotiate_flags;
DBG_ERR("The client capabilities don't match "
"the server capabilities: local[0x%08X] "
"required[0x%08X] remote[0x%08X]\n",
lf, rqf, rf);
composite_error(c, NT_STATUS_DOWNGRADE_DETECTED);
return;
}
}
/*
* Strong keys could be unsupported (NT4) or disabled. So retry with the
* flags returned by the server. - asn
@ -327,6 +351,8 @@ static struct composite_context *dcerpc_schannel_key_send(TALLOC_CTX *mem_ctx,
struct composite_context *epm_map_req;
enum netr_SchannelType schannel_type = cli_credentials_get_secure_channel_type(credentials);
struct cli_credentials *epm_creds = NULL;
bool reject_md5_servers = false;
bool require_strong_key = false;
/* composite context allocation and setup */
c = composite_create(mem_ctx, p->conn->event_ctx);
@ -340,19 +366,48 @@ static struct composite_context *dcerpc_schannel_key_send(TALLOC_CTX *mem_ctx,
s->pipe = p;
s->credentials = credentials;
s->local_negotiate_flags = NETLOGON_NEG_AUTH2_FLAGS;
s->required_negotiate_flags = NETLOGON_NEG_AUTHENTICATED_RPC;
/* allocate credentials */
if (s->pipe->conn->flags & DCERPC_SCHANNEL_128) {
s->local_negotiate_flags = NETLOGON_NEG_AUTH2_ADS_FLAGS;
require_strong_key = true;
}
if (s->pipe->conn->flags & DCERPC_SCHANNEL_AES) {
s->local_negotiate_flags = NETLOGON_NEG_AUTH2_ADS_FLAGS;
s->local_negotiate_flags |= NETLOGON_NEG_SUPPORTS_AES;
reject_md5_servers = true;
}
if (s->pipe->conn->flags & DCERPC_SCHANNEL_AUTO) {
s->local_negotiate_flags = NETLOGON_NEG_AUTH2_ADS_FLAGS;
s->local_negotiate_flags |= NETLOGON_NEG_SUPPORTS_AES;
s->dcerpc_schannel_auto = true;
reject_md5_servers = lpcfg_reject_md5_servers(lp_ctx);
require_strong_key = lpcfg_require_strong_key(lp_ctx);
}
if (lpcfg_weak_crypto(lp_ctx) == SAMBA_WEAK_CRYPTO_DISALLOWED) {
reject_md5_servers = true;
}
if (reject_md5_servers) {
require_strong_key = true;
}
if (require_strong_key) {
s->required_negotiate_flags |= NETLOGON_NEG_ARCFOUR;
s->required_negotiate_flags |= NETLOGON_NEG_STRONG_KEYS;
}
if (reject_md5_servers) {
s->required_negotiate_flags |= NETLOGON_NEG_PASSWORD_SET2;
s->required_negotiate_flags |= NETLOGON_NEG_SUPPORTS_AES;
}
s->local_negotiate_flags |= s->required_negotiate_flags;
if (s->required_negotiate_flags & NETLOGON_NEG_SUPPORTS_AES) {
s->required_negotiate_flags &= ~NETLOGON_NEG_ARCFOUR;
s->required_negotiate_flags &= ~NETLOGON_NEG_STRONG_KEYS;
}
/* type of authentication depends on schannel type */
@ -360,10 +415,6 @@ static struct composite_context *dcerpc_schannel_key_send(TALLOC_CTX *mem_ctx,
s->local_negotiate_flags |= NETLOGON_NEG_RODC_PASSTHROUGH;
}
if (lpcfg_weak_crypto(lp_ctx) == SAMBA_WEAK_CRYPTO_DISALLOWED) {
s->local_negotiate_flags &= ~NETLOGON_NEG_ARCFOUR;
}
epm_creds = cli_credentials_init_anon(s);
if (composite_nomem(epm_creds, c)) return c;