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samba/samba-s4u.patch
Andreas Schneider a37ea2e618 Fix CVE-2022-32742 
resolves: rhbz#2108332
2022-07-27 18:10:10 +02:00

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From 5d7ec9a00b6f4c6768c606d37d235415f2006445 Mon Sep 17 00:00:00 2001
From: Isaac Boukris <iboukris@gmail.com>
Date: Fri, 27 Sep 2019 18:25:03 +0300
Subject: [PATCH 1/3] mit-kdc: add basic loacl realm S4U support
Signed-off-by: Isaac Boukris <iboukris@gmail.com>
Pair-Programmed-With: Andreas Schneider <asn@samba.org>
---
source4/kdc/mit-kdb/kdb_samba_policies.c | 124 +++++++++++------------
source4/kdc/mit_samba.c | 47 ++-------
source4/kdc/mit_samba.h | 6 +-
3 files changed, 71 insertions(+), 106 deletions(-)
diff --git a/source4/kdc/mit-kdb/kdb_samba_policies.c b/source4/kdc/mit-kdb/kdb_samba_policies.c
index 793fe366c35..22534c09974 100644
--- a/source4/kdc/mit-kdb/kdb_samba_policies.c
+++ b/source4/kdc/mit-kdb/kdb_samba_policies.c
@@ -200,13 +200,17 @@ static krb5_error_code ks_verify_pac(krb5_context context,
krb5_keyblock *krbtgt_key,
krb5_timestamp authtime,
krb5_authdata **tgt_auth_data,
- krb5_pac *pac)
+ krb5_pac *out_pac)
{
struct mit_samba_context *mit_ctx;
krb5_authdata **authdata = NULL;
- krb5_pac ipac = NULL;
- DATA_BLOB logon_data = { NULL, 0 };
+ krb5_keyblock *header_server_key = NULL;
+ krb5_key_data *impersonator_kd = NULL;
+ krb5_keyblock impersonator_key = {0};
krb5_error_code code;
+ krb5_pac pac;
+
+ *out_pac = NULL;
mit_ctx = ks_get_context(context);
if (mit_ctx == NULL) {
@@ -238,41 +242,43 @@ static krb5_error_code ks_verify_pac(krb5_context context,
code = krb5_pac_parse(context,
authdata[0]->contents,
authdata[0]->length,
- &ipac);
+ &pac);
if (code != 0) {
goto done;
}
- /* TODO: verify this is correct
- *
- * In the constrained delegation case, the PAC is from a service
- * ticket rather than a TGT; we must verify the server and KDC
- * signatures to assert that the server did not forge the PAC.
+ /*
+ * For constrained delegation in MIT version < 1.18 we aren't provided
+ * with the 2nd ticket server key to verify the PAC.
+ * We can workaround that by fetching the key from the client db entry,
+ * which is the impersonator account in that version.
+ * TODO: use the provided entry in the new 1.18 version.
*/
if (flags & KRB5_KDB_FLAG_CONSTRAINED_DELEGATION) {
- code = krb5_pac_verify(context,
- ipac,
- authtime,
- client_princ,
- server_key,
- krbtgt_key);
+ /* The impersonator must be local. */
+ if (client == NULL) {
+ code = KRB5KDC_ERR_BADOPTION;
+ goto done;
+ }
+ /* Fetch and decrypt 2nd ticket server's current key. */
+ code = krb5_dbe_find_enctype(context, client, -1, -1, 0,
+ &impersonator_kd);
+ if (code != 0) {
+ goto done;
+ }
+ code = krb5_dbe_decrypt_key_data(context, NULL,
+ impersonator_kd,
+ &impersonator_key, NULL);
+ if (code != 0) {
+ goto done;
+ }
+ header_server_key = &impersonator_key;
} else {
- code = krb5_pac_verify(context,
- ipac,
- authtime,
- client_princ,
- krbtgt_key,
- NULL);
- }
- if (code != 0) {
- goto done;
+ header_server_key = krbtgt_key;
}
- /* check and update PAC */
- code = krb5_pac_parse(context,
- authdata[0]->contents,
- authdata[0]->length,
- pac);
+ code = krb5_pac_verify(context, pac, authtime, client_princ,
+ header_server_key, NULL);
if (code != 0) {
goto done;
}
@@ -280,17 +286,22 @@ static krb5_error_code ks_verify_pac(krb5_context context,
code = mit_samba_reget_pac(mit_ctx,
context,
flags,
- client_princ,
client,
server,
krbtgt,
krbtgt_key,
- pac);
+ &pac);
+ if (code != 0) {
+ goto done;
+ }
+
+ *out_pac = pac;
+ pac = NULL;
done:
+ krb5_free_keyblock_contents(context, &impersonator_key);
krb5_free_authdata(context, authdata);
- krb5_pac_free(context, ipac);
- free(logon_data.data);
+ krb5_pac_free(context, pac);
return code;
}
@@ -319,6 +330,7 @@ krb5_error_code kdb_samba_db_sign_auth_data(krb5_context context,
krb5_authdata **pac_auth_data = NULL;
krb5_authdata **authdata = NULL;
krb5_boolean is_as_req;
+ krb5_const_principal pac_client;
krb5_error_code code;
krb5_pac pac = NULL;
krb5_data pac_data;
@@ -330,11 +342,6 @@ krb5_error_code kdb_samba_db_sign_auth_data(krb5_context context,
krbtgt = krbtgt == NULL ? local_krbtgt : krbtgt;
krbtgt_key = krbtgt_key == NULL ? local_krbtgt_key : krbtgt_key;
- /* FIXME: We don't support S4U yet */
- if (flags & KRB5_KDB_FLAGS_S4U) {
- return KRB5_KDB_DBTYPE_NOSUP;
- }
-
is_as_req = ((flags & KRB5_KDB_FLAG_CLIENT_REFERRALS_ONLY) != 0);
/*
@@ -395,6 +402,16 @@ krb5_error_code kdb_samba_db_sign_auth_data(krb5_context context,
ks_client_princ = client->princ;
}
+ /* In protocol transition, we are currently not provided with the tgt
+ * client name to verify the PAC, we could probably skip the name
+ * verification and just verify the signatures, but since we don't
+ * support cross-realm nor aliases, we can just use server->princ */
+ if (flags & KRB5_KDB_FLAG_PROTOCOL_TRANSITION) {
+ pac_client = server->princ;
+ } else {
+ pac_client = ks_client_princ;
+ }
+
if (client_entry == NULL) {
client_entry = client;
}
@@ -469,7 +486,7 @@ krb5_error_code kdb_samba_db_sign_auth_data(krb5_context context,
code = ks_verify_pac(context,
flags,
- ks_client_princ,
+ pac_client,
client_entry,
server,
krbtgt,
@@ -515,7 +532,7 @@ krb5_error_code kdb_samba_db_sign_auth_data(krb5_context context,
is_as_req ? "AS-REQ" : "TGS-REQ",
client_name);
code = krb5_pac_sign(context, pac, authtime, ks_client_princ,
- server_key, krbtgt_key, &pac_data);
+ server_key, krbtgt_key, &pac_data);
if (code != 0) {
DBG_ERR("krb5_pac_sign failed: %d\n", code);
goto done;
@@ -541,12 +558,6 @@ krb5_error_code kdb_samba_db_sign_auth_data(krb5_context context,
KRB5_AUTHDATA_IF_RELEVANT,
authdata,
signed_auth_data);
- if (code != 0) {
- goto done;
- }
-
- code = 0;
-
done:
if (client_entry != NULL && client_entry != client) {
ks_free_principal(context, client_entry);
@@ -572,32 +583,13 @@ krb5_error_code kdb_samba_db_check_allowed_to_delegate(krb5_context context,
* server; -> delegating service
* proxy; -> target principal
*/
- krb5_db_entry *delegating_service = discard_const_p(krb5_db_entry, server);
-
- char *target_name = NULL;
- bool is_enterprise;
- krb5_error_code code;
mit_ctx = ks_get_context(context);
if (mit_ctx == NULL) {
return KRB5_KDB_DBNOTINITED;
}
- code = krb5_unparse_name(context, proxy, &target_name);
- if (code) {
- goto done;
- }
-
- is_enterprise = (proxy->type == KRB5_NT_ENTERPRISE_PRINCIPAL);
-
- code = mit_samba_check_s4u2proxy(mit_ctx,
- delegating_service,
- target_name,
- is_enterprise);
-
-done:
- free(target_name);
- return code;
+ return mit_samba_check_s4u2proxy(mit_ctx, server, proxy);
}
diff --git a/source4/kdc/mit_samba.c b/source4/kdc/mit_samba.c
index cb72b5de294..03c2c2ea1de 100644
--- a/source4/kdc/mit_samba.c
+++ b/source4/kdc/mit_samba.c
@@ -517,7 +517,6 @@ int mit_samba_get_pac(struct mit_samba_context *smb_ctx,
krb5_error_code mit_samba_reget_pac(struct mit_samba_context *ctx,
krb5_context context,
int flags,
- krb5_const_principal client_principal,
krb5_db_entry *client,
krb5_db_entry *server,
krb5_db_entry *krbtgt,
@@ -689,7 +688,7 @@ krb5_error_code mit_samba_reget_pac(struct mit_samba_context *ctx,
context,
*pac,
server->princ,
- discard_const(client_principal),
+ client->princ,
deleg_blob);
if (!NT_STATUS_IS_OK(nt_status)) {
DEBUG(0, ("Update delegation info failed: %s\n",
@@ -1081,41 +1080,17 @@ int mit_samba_check_client_access(struct mit_samba_context *ctx,
}
int mit_samba_check_s4u2proxy(struct mit_samba_context *ctx,
- krb5_db_entry *kentry,
- const char *target_name,
- bool is_nt_enterprise_name)
+ const krb5_db_entry *server,
+ krb5_const_principal target_principal)
{
-#if 1
- /*
- * This is disabled because mit_samba_update_pac_data() does not handle
- * S4U_DELEGATION_INFO
- */
-
- return KRB5KDC_ERR_BADOPTION;
-#else
- krb5_principal target_principal;
- int flags = 0;
- int ret;
-
- if (is_nt_enterprise_name) {
- flags = KRB5_PRINCIPAL_PARSE_ENTERPRISE;
- }
-
- ret = krb5_parse_name_flags(ctx->context, target_name,
- flags, &target_principal);
- if (ret) {
- return ret;
- }
-
- ret = samba_kdc_check_s4u2proxy(ctx->context,
- ctx->db_ctx,
- skdc_entry,
- target_principal);
-
- krb5_free_principal(ctx->context, target_principal);
-
- return ret;
-#endif
+ struct samba_kdc_entry *server_skdc_entry =
+ talloc_get_type_abort(server->e_data,
+ struct samba_kdc_entry);
+
+ return samba_kdc_check_s4u2proxy(ctx->context,
+ ctx->db_ctx,
+ server_skdc_entry,
+ target_principal);
}
static krb5_error_code mit_samba_change_pwd_error(krb5_context context,
diff --git a/source4/kdc/mit_samba.h b/source4/kdc/mit_samba.h
index 4431e82a1b2..9370ab533af 100644
--- a/source4/kdc/mit_samba.h
+++ b/source4/kdc/mit_samba.h
@@ -57,7 +57,6 @@ int mit_samba_get_pac(struct mit_samba_context *smb_ctx,
krb5_error_code mit_samba_reget_pac(struct mit_samba_context *ctx,
krb5_context context,
int flags,
- krb5_const_principal client_principal,
krb5_db_entry *client,
krb5_db_entry *server,
krb5_db_entry *krbtgt,
@@ -74,9 +73,8 @@ int mit_samba_check_client_access(struct mit_samba_context *ctx,
DATA_BLOB *e_data);
int mit_samba_check_s4u2proxy(struct mit_samba_context *ctx,
- krb5_db_entry *kentry,
- const char *target_name,
- bool is_nt_enterprise_name);
+ const krb5_db_entry *server,
+ krb5_const_principal target_principal);
int mit_samba_kpasswd_change_password(struct mit_samba_context *ctx,
char *pwd,
--
2.37.1
From 325912375cf54743ab8ea557172a72b870002e9f Mon Sep 17 00:00:00 2001
From: Isaac Boukris <iboukris@gmail.com>
Date: Fri, 27 Sep 2019 18:35:30 +0300
Subject: [PATCH 2/3] krb5-mit: enable S4U client support for MIT build
Signed-off-by: Isaac Boukris <iboukris@gmail.com>
Pair-Programmed-With: Andreas Schneider <asn@samba.org>
---
lib/krb5_wrap/krb5_samba.c | 185 ++++++++++++++++++++++++++
lib/krb5_wrap/krb5_samba.h | 2 -
source4/auth/kerberos/kerberos_util.c | 11 --
3 files changed, 185 insertions(+), 13 deletions(-)
diff --git a/lib/krb5_wrap/krb5_samba.c b/lib/krb5_wrap/krb5_samba.c
index 4321f07ca09..3fd95e47fca 100644
--- a/lib/krb5_wrap/krb5_samba.c
+++ b/lib/krb5_wrap/krb5_samba.c
@@ -2702,6 +2702,191 @@ krb5_error_code smb_krb5_kinit_s4u2_ccache(krb5_context ctx,
return 0;
}
+
+#else /* MIT */
+
+static bool princ_compare_no_dollar(krb5_context ctx,
+ krb5_principal a,
+ krb5_principal b)
+{
+ bool cmp;
+ krb5_principal mod = NULL;
+
+ if (a->length == 1 && b->length == 1 &&
+ a->data[0].length != 0 && b->data[0].length != 0 &&
+ a->data[0].data[a->data[0].length -1] !=
+ b->data[0].data[b->data[0].length -1]) {
+ if (a->data[0].data[a->data[0].length -1] == '$') {
+ mod = a;
+ mod->data[0].length--;
+ } else if (b->data[0].data[b->data[0].length -1] == '$') {
+ mod = b;
+ mod->data[0].length--;
+ }
+ }
+
+ cmp = krb5_principal_compare_flags(ctx, a, b,
+ KRB5_PRINCIPAL_COMPARE_CASEFOLD);
+
+ if (mod != NULL) {
+ mod->data[0].length++;
+ }
+
+ return cmp;
+}
+
+krb5_error_code smb_krb5_kinit_s4u2_ccache(krb5_context ctx,
+ krb5_ccache store_cc,
+ krb5_principal init_principal,
+ const char *init_password,
+ krb5_principal impersonate_principal,
+ const char *self_service,
+ const char *target_service,
+ krb5_get_init_creds_opt *krb_options,
+ time_t *expire_time,
+ time_t *kdc_time)
+{
+ krb5_error_code code;
+ krb5_principal self_princ = NULL;
+ krb5_principal target_princ = NULL;
+ krb5_creds *store_creds;
+ krb5_creds *s4u2self_creds = NULL;
+ krb5_creds *s4u2proxy_creds = NULL;
+ krb5_creds init_creds = {0};
+ krb5_creds mcreds = {0};
+ krb5_flags options = KRB5_GC_NO_STORE;
+ krb5_ccache tmp_cc;
+ bool s4u2proxy;
+
+ code = krb5_cc_new_unique(ctx, "MEMORY", NULL, &tmp_cc);
+ if (code != 0) {
+ return code;
+ }
+
+ code = krb5_get_init_creds_password(ctx, &init_creds,
+ init_principal,
+ init_password,
+ NULL, NULL,
+ 0,
+ NULL,
+ krb_options);
+ if (code != 0) {
+ goto done;
+ }
+
+ code = krb5_cc_initialize(ctx, tmp_cc, init_creds.client);
+ if (code != 0) {
+ goto done;
+ }
+
+ code = krb5_cc_store_cred(ctx, tmp_cc, &init_creds);
+ if (code != 0) {
+ goto done;
+ }
+
+ /*
+ * Check if we also need S4U2Proxy or if S4U2Self is
+ * enough in order to get a ticket for the target.
+ */
+ if (target_service == NULL) {
+ s4u2proxy = false;
+ } else if (strcmp(target_service, self_service) == 0) {
+ s4u2proxy = false;
+ } else {
+ s4u2proxy = true;
+ }
+
+ code = krb5_parse_name(ctx, self_service, &self_princ);
+ if (code != 0) {
+ goto done;
+ }
+
+ /* MIT lacks aliases support in S4U, for S4U2Self we require the tgt
+ * client and the request server to be the same principal name. */
+ if (!princ_compare_no_dollar(ctx, init_creds.client, self_princ)) {
+ code = KRB5KDC_ERR_PADATA_TYPE_NOSUPP;
+ goto done;
+ }
+
+ mcreds.client = impersonate_principal;
+ mcreds.server = init_creds.client;
+
+ code = krb5_get_credentials_for_user(ctx, options, tmp_cc, &mcreds,
+ NULL, &s4u2self_creds);
+ if (code != 0) {
+ goto done;
+ }
+
+ if (s4u2proxy) {
+ code = krb5_parse_name(ctx, target_service, &target_princ);
+ if (code != 0) {
+ goto done;
+ }
+
+ mcreds.client = init_creds.client;
+ mcreds.server = target_princ;
+ mcreds.second_ticket = s4u2self_creds->ticket;
+
+ code = krb5_get_credentials(ctx, options |
+ KRB5_GC_CONSTRAINED_DELEGATION,
+ tmp_cc, &mcreds, &s4u2proxy_creds);
+ if (code != 0) {
+ goto done;
+ }
+
+ /* Check KDC support of S4U2Proxy extension */
+ if (!krb5_principal_compare(ctx, s4u2self_creds->client,
+ s4u2proxy_creds->client)) {
+ code = KRB5KDC_ERR_PADATA_TYPE_NOSUPP;
+ goto done;
+ }
+
+ store_creds = s4u2proxy_creds;
+ } else {
+ store_creds = s4u2self_creds;;
+
+ /* We need to save the ticket with the requested server name
+ * or the caller won't be able to find it in cache. */
+ if (!krb5_principal_compare(ctx, self_princ,
+ store_creds->server)) {
+ krb5_free_principal(ctx, store_creds->server);
+ store_creds->server = NULL;
+ code = krb5_copy_principal(ctx, self_princ,
+ &store_creds->server);
+ if (code != 0) {
+ goto done;
+ }
+ }
+ }
+
+ code = krb5_cc_initialize(ctx, store_cc, store_creds->client);
+ if (code != 0) {
+ goto done;
+ }
+
+ code = krb5_cc_store_cred(ctx, store_cc, store_creds);
+ if (code != 0) {
+ goto done;
+ }
+
+ if (expire_time) {
+ *expire_time = (time_t) store_creds->times.endtime;
+ }
+
+ if (kdc_time) {
+ *kdc_time = (time_t) store_creds->times.starttime;
+ }
+
+done:
+ krb5_cc_destroy(ctx, tmp_cc);
+ krb5_free_cred_contents(ctx, &init_creds);
+ krb5_free_creds(ctx, s4u2self_creds);
+ krb5_free_creds(ctx, s4u2proxy_creds);
+ krb5_free_principal(ctx, self_princ);
+ krb5_free_principal(ctx, target_princ);
+
+ return code;
+}
#endif
#if !defined(HAVE_KRB5_MAKE_PRINCIPAL) && defined(HAVE_KRB5_BUILD_PRINCIPAL_ALLOC_VA)
diff --git a/lib/krb5_wrap/krb5_samba.h b/lib/krb5_wrap/krb5_samba.h
index a66b7465530..c8573f52bd9 100644
--- a/lib/krb5_wrap/krb5_samba.h
+++ b/lib/krb5_wrap/krb5_samba.h
@@ -252,7 +252,6 @@ krb5_error_code smb_krb5_kinit_password_ccache(krb5_context ctx,
krb5_get_init_creds_opt *krb_options,
time_t *expire_time,
time_t *kdc_time);
-#ifdef SAMBA4_USES_HEIMDAL
krb5_error_code smb_krb5_kinit_s4u2_ccache(krb5_context ctx,
krb5_ccache store_cc,
krb5_principal init_principal,
@@ -263,7 +262,6 @@ krb5_error_code smb_krb5_kinit_s4u2_ccache(krb5_context ctx,
krb5_get_init_creds_opt *krb_options,
time_t *expire_time,
time_t *kdc_time);
-#endif
#if defined(HAVE_KRB5_MAKE_PRINCIPAL)
#define smb_krb5_make_principal krb5_make_principal
diff --git a/source4/auth/kerberos/kerberos_util.c b/source4/auth/kerberos/kerberos_util.c
index 544d9d853cc..c14d8c72d8c 100644
--- a/source4/auth/kerberos/kerberos_util.c
+++ b/source4/auth/kerberos/kerberos_util.c
@@ -234,9 +234,7 @@ done:
{
krb5_error_code ret;
const char *password;
-#ifdef SAMBA4_USES_HEIMDAL
const char *self_service;
-#endif
const char *target_service;
time_t kdc_time = 0;
krb5_principal princ;
@@ -268,9 +266,7 @@ done:
return ret;
}
-#ifdef SAMBA4_USES_HEIMDAL
self_service = cli_credentials_get_self_service(credentials);
-#endif
target_service = cli_credentials_get_target_service(credentials);
password = cli_credentials_get_password(credentials);
@@ -331,7 +327,6 @@ done:
#endif
if (password) {
if (impersonate_principal) {
-#ifdef SAMBA4_USES_HEIMDAL
ret = smb_krb5_kinit_s4u2_ccache(smb_krb5_context->krb5_context,
ccache,
princ,
@@ -342,12 +337,6 @@ done:
krb_options,
NULL,
&kdc_time);
-#else
- talloc_free(mem_ctx);
- (*error_string) = "INTERNAL error: s4u2 ops "
- "are not supported with MIT build yet";
- return EINVAL;
-#endif
} else {
ret = smb_krb5_kinit_password_ccache(smb_krb5_context->krb5_context,
ccache,
--
2.37.1
From a5713b1558192f24348f7794da84bf65cf78e6ec Mon Sep 17 00:00:00 2001
From: Isaac Boukris <iboukris@gmail.com>
Date: Sat, 19 Sep 2020 14:16:20 +0200
Subject: [PATCH 3/3] wip: for canonicalization with new MIT kdc code
---
source4/kdc/mit_samba.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/source4/kdc/mit_samba.c b/source4/kdc/mit_samba.c
index 03c2c2ea1de..30fade56531 100644
--- a/source4/kdc/mit_samba.c
+++ b/source4/kdc/mit_samba.c
@@ -232,6 +232,9 @@ int mit_samba_get_principal(struct mit_samba_context *ctx,
if (kflags & KRB5_KDB_FLAG_CANONICALIZE) {
sflags |= SDB_F_CANON;
}
+#if KRB5_KDB_API_VERSION >= 10
+ sflags |= SDB_F_FORCE_CANON;
+#endif
if (kflags & (KRB5_KDB_FLAG_CLIENT_REFERRALS_ONLY |
KRB5_KDB_FLAG_INCLUDE_PAC)) {
/*
--
2.37.1
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