libcli/auth Move PAC parsing and verification in common.

This uses the source3 PAC code (originally from Samba4) with some
small changes to restore functionality needed by the torture tests,
and to have a common API.

Andrew Bartlett

3 files changed, 375 insertions, 2 deletions

diff --git a/libcli/auth/kerberos_pac.c b/libcli/auth/kerberos_pac.c
new file mode 100644
index 0000000000..6a41eb1ace
--- /dev/null
+++ b/libcli/auth/kerberos_pac.c
@@ -0,0 +1,358 @@
+/*
+   Unix SMB/CIFS implementation.
+   kerberos authorization data (PAC) utility library
+   Copyright (C) Jim McDonough <jmcd@us.ibm.com> 2003
+   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2004-2005
+   Copyright (C) Andrew Tridgell 2001
+   Copyright (C) Luke Howard 2002-2003
+   Copyright (C) Stefan Metzmacher 2004-2005
+   Copyright (C) Guenther Deschner 2005,2007,2008
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#ifdef HAVE_KRB5
+
+#include "librpc/gen_ndr/ndr_krb5pac.h"
+#include "libcli/auth/krb5_wrap.h"
+
+krb5_error_code check_pac_checksum(TALLOC_CTX *mem_ctx,
+					  DATA_BLOB pac_data,
+					  struct PAC_SIGNATURE_DATA *sig,
+					  krb5_context context,
+					  const krb5_keyblock *keyblock)
+{
+	krb5_error_code ret;
+	krb5_checksum cksum;
+	krb5_keyusage usage = 0;
+
+	smb_krb5_checksum_from_pac_sig(&cksum, sig);
+
+#ifdef HAVE_KRB5_KU_OTHER_CKSUM /* Heimdal */
+	usage = KRB5_KU_OTHER_CKSUM;
+#elif defined(HAVE_KRB5_KEYUSAGE_APP_DATA_CKSUM) /* MIT */
+	usage = KRB5_KEYUSAGE_APP_DATA_CKSUM;
+#else
+#error UNKNOWN_KRB5_KEYUSAGE
+#endif
+
+	ret = smb_krb5_verify_checksum(context,
+				       keyblock,
+				       usage,
+				       &cksum,
+				       pac_data.data,
+				       pac_data.length);
+
+	if (ret) {
+		DEBUG(2,("check_pac_checksum: PAC Verification failed: %s (%d)\n",
+			error_message(ret), ret));
+		return ret;
+	}
+
+	return ret;
+}
+
+/**
+* @brief Decode a blob containing a NDR envoded PAC structure
+*
+* @param mem_ctx	  - The memory context
+* @param pac_data_blob	  - The data blob containing the NDR encoded data
+* @param context	  - The Kerberos Context
+* @param service_keyblock - The Service Key used to verify the checksum
+* @param client_principal - The client principal
+* @param tgs_authtime     - The ticket timestamp
+* @param pac_data_out	  - [out] The decoded PAC
+*
+* @return - A NTSTATUS error code
+*/
+NTSTATUS kerberos_decode_pac(TALLOC_CTX *mem_ctx,
+			     DATA_BLOB pac_data_blob,
+			     krb5_context context,
+			     const krb5_keyblock *krbtgt_keyblock,
+			     const krb5_keyblock *service_keyblock,
+			     krb5_const_principal client_principal,
+			     time_t tgs_authtime,
+			     struct PAC_DATA **pac_data_out)
+{
+	NTSTATUS status;
+	enum ndr_err_code ndr_err;
+	krb5_error_code ret;
+	DATA_BLOB modified_pac_blob;
+
+	NTTIME tgs_authtime_nttime;
+	krb5_principal client_principal_pac = NULL;
+	int i;
+
+	struct PAC_SIGNATURE_DATA *srv_sig_ptr = NULL;
+	struct PAC_SIGNATURE_DATA *kdc_sig_ptr = NULL;
+	struct PAC_SIGNATURE_DATA *srv_sig_wipe = NULL;
+	struct PAC_SIGNATURE_DATA *kdc_sig_wipe = NULL;
+	struct PAC_LOGON_NAME *logon_name = NULL;
+	struct PAC_LOGON_INFO *logon_info = NULL;
+	struct PAC_DATA *pac_data = NULL;
+	struct PAC_DATA_RAW *pac_data_raw = NULL;
+
+	DATA_BLOB *srv_sig_blob = NULL;
+	DATA_BLOB *kdc_sig_blob = NULL;
+
+	bool bool_ret;
+
+	*pac_data_out = NULL;
+
+	pac_data = talloc(mem_ctx, struct PAC_DATA);
+	pac_data_raw = talloc(mem_ctx, struct PAC_DATA_RAW);
+	kdc_sig_wipe = talloc(mem_ctx, struct PAC_SIGNATURE_DATA);
+	srv_sig_wipe = talloc(mem_ctx, struct PAC_SIGNATURE_DATA);
+	if (!pac_data_raw || !pac_data || !kdc_sig_wipe || !srv_sig_wipe) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	ndr_err = ndr_pull_struct_blob(&pac_data_blob, pac_data, pac_data,
+		       (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		status = ndr_map_error2ntstatus(ndr_err);
+		DEBUG(0,("can't parse the PAC: %s\n",
+			nt_errstr(status)));
+		return status;
+	}
+
+	if (pac_data->num_buffers < 4) {
+		/* we need logon_ingo, service_key and kdc_key */
+		DEBUG(0,("less than 4 PAC buffers\n"));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	ndr_err = ndr_pull_struct_blob(
+				&pac_data_blob, pac_data_raw, pac_data_raw,
+				(ndr_pull_flags_fn_t)ndr_pull_PAC_DATA_RAW);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		status = ndr_map_error2ntstatus(ndr_err);
+		DEBUG(0,("can't parse the PAC: %s\n",
+			nt_errstr(status)));
+		return status;
+	}
+
+	if (pac_data_raw->num_buffers < 4) {
+		/* we need logon_ingo, service_key and kdc_key */
+		DEBUG(0,("less than 4 PAC buffers\n"));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	if (pac_data->num_buffers != pac_data_raw->num_buffers) {
+		/* we need logon_ingo, service_key and kdc_key */
+		DEBUG(0, ("misparse! PAC_DATA has %d buffers while "
+			  "PAC_DATA_RAW has %d\n", pac_data->num_buffers,
+			  pac_data_raw->num_buffers));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	for (i=0; i < pac_data->num_buffers; i++) {
+		struct PAC_BUFFER *data_buf = &pac_data->buffers[i];
+		struct PAC_BUFFER_RAW *raw_buf = &pac_data_raw->buffers[i];
+
+		if (data_buf->type != raw_buf->type) {
+			DEBUG(0, ("misparse! PAC_DATA buffer %d has type "
+				  "%d while PAC_DATA_RAW has %d\n", i,
+				  data_buf->type, raw_buf->type));
+			return NT_STATUS_INVALID_PARAMETER;
+		}
+		switch (data_buf->type) {
+		case PAC_TYPE_LOGON_INFO:
+			if (!data_buf->info) {
+				break;
+			}
+			logon_info = data_buf->info->logon_info.info;
+			break;
+		case PAC_TYPE_SRV_CHECKSUM:
+			if (!data_buf->info) {
+				break;
+			}
+			srv_sig_ptr = &data_buf->info->srv_cksum;
+			srv_sig_blob = &raw_buf->info->remaining;
+			break;
+		case PAC_TYPE_KDC_CHECKSUM:
+			if (!data_buf->info) {
+				break;
+			}
+			kdc_sig_ptr = &data_buf->info->kdc_cksum;
+			kdc_sig_blob = &raw_buf->info->remaining;
+			break;
+		case PAC_TYPE_LOGON_NAME:
+			logon_name = &data_buf->info->logon_name;
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (!logon_info) {
+		DEBUG(0,("PAC no logon_info\n"));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	if (!logon_name) {
+		DEBUG(0,("PAC no logon_name\n"));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	if (!srv_sig_ptr || !srv_sig_blob) {
+		DEBUG(0,("PAC no srv_key\n"));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	if (!kdc_sig_ptr || !kdc_sig_blob) {
+		DEBUG(0,("PAC no kdc_key\n"));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	/* Find and zero out the signatures,
+	 * as required by the signing algorithm */
+
+	/* We find the data blobs above,
+	 * now we parse them to get at the exact portion we should zero */
+	ndr_err = ndr_pull_struct_blob(
+			kdc_sig_blob, kdc_sig_wipe, kdc_sig_wipe,
+			(ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		status = ndr_map_error2ntstatus(ndr_err);
+		DEBUG(0,("can't parse the KDC signature: %s\n",
+			nt_errstr(status)));
+		return status;
+	}
+
+	ndr_err = ndr_pull_struct_blob(
+			srv_sig_blob, srv_sig_wipe, srv_sig_wipe,
+			(ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		status = ndr_map_error2ntstatus(ndr_err);
+		DEBUG(0,("can't parse the SRV signature: %s\n",
+			nt_errstr(status)));
+		return status;
+	}
+
+	/* Now zero the decoded structure */
+	memset(kdc_sig_wipe->signature.data,
+		'\0', kdc_sig_wipe->signature.length);
+	memset(srv_sig_wipe->signature.data,
+		'\0', srv_sig_wipe->signature.length);
+
+	/* and reencode, back into the same place it came from */
+	ndr_err = ndr_push_struct_blob(
+			kdc_sig_blob, pac_data_raw, kdc_sig_wipe,
+			(ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		status = ndr_map_error2ntstatus(ndr_err);
+		DEBUG(0,("can't repack the KDC signature: %s\n",
+			nt_errstr(status)));
+		return status;
+	}
+	ndr_err = ndr_push_struct_blob(
+			srv_sig_blob, pac_data_raw, srv_sig_wipe,
+			(ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		status = ndr_map_error2ntstatus(ndr_err);
+		DEBUG(0,("can't repack the SRV signature: %s\n",
+			nt_errstr(status)));
+		return status;
+	}
+
+	/* push out the whole structure, but now with zero'ed signatures */
+	ndr_err = ndr_push_struct_blob(
+			&modified_pac_blob, pac_data_raw, pac_data_raw,
+			(ndr_push_flags_fn_t)ndr_push_PAC_DATA_RAW);
+	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
+		status = ndr_map_error2ntstatus(ndr_err);
+		DEBUG(0,("can't repack the RAW PAC: %s\n",
+			nt_errstr(status)));
+		return status;
+	}
+
+	/* verify by service_key */
+	ret = check_pac_checksum(mem_ctx,
+				 modified_pac_blob, srv_sig_ptr,
+				 context,
+				 service_keyblock);
+	if (ret) {
+		DEBUG(1, ("PAC Decode: Failed to verify the service "
+			  "signature: %s\n", error_message(ret)));
+		return NT_STATUS_ACCESS_DENIED;
+	}
+
+	if (krbtgt_keyblock) {
+		/* verify the service key checksum by krbtgt_key */
+		ret = check_pac_checksum(mem_ctx,
+					 srv_sig_ptr->signature, kdc_sig_ptr,
+					 context, krbtgt_keyblock);
+		if (ret) {
+			DEBUG(1, ("PAC Decode: Failed to verify the KDC signature: %s\n",
+				  smb_get_krb5_error_message(context, ret, mem_ctx)));
+			return NT_STATUS_ACCESS_DENIED;
+		}
+	}
+
+	/* Convert to NT time, so as not to loose accuracy in comparison */
+	unix_to_nt_time(&tgs_authtime_nttime, tgs_authtime);
+
+	if (tgs_authtime_nttime != logon_name->logon_time) {
+		DEBUG(2, ("PAC Decode: "
+			  "Logon time mismatch between ticket and PAC!\n"));
+		DEBUG(2, ("PAC Decode: PAC: %s\n",
+			  nt_time_string(mem_ctx, logon_name->logon_time)));
+		DEBUG(2, ("PAC Decode: Ticket: %s\n",
+			  nt_time_string(mem_ctx, tgs_authtime_nttime)));
+		return NT_STATUS_ACCESS_DENIED;
+	}
+
+	ret = smb_krb5_parse_name_norealm(context,
+					  logon_name->account_name,
+					  &client_principal_pac);
+	if (ret) {
+		DEBUG(2, ("Could not parse name from PAC: [%s]:%s\n",
+			  logon_name->account_name, error_message(ret)));
+		return NT_STATUS_INVALID_PARAMETER;
+	}
+
+	bool_ret = smb_krb5_principal_compare_any_realm(context,
+							client_principal,
+							client_principal_pac);
+
+	krb5_free_principal(context, client_principal_pac);
+
+	if (!bool_ret) {
+		DEBUG(2, ("Name in PAC [%s] does not match principal name "
+			  "in ticket\n", logon_name->account_name));
+		return NT_STATUS_ACCESS_DENIED;
+	}
+
+	DEBUG(3,("Found account name from PAC: %s [%s]\n",
+		 logon_info->info3.base.account_name.string,
+		 logon_info->info3.base.full_name.string));
+
+	DEBUG(10,("Successfully validated Kerberos PAC\n"));
+
+	if (DEBUGLEVEL >= 10) {
+		const char *s;
+		s = NDR_PRINT_STRUCT_STRING(mem_ctx, PAC_DATA, pac_data);
+		if (s) {
+			DEBUGADD(10,("%s\n", s));
+		}
+	}
+
+	*pac_data_out = pac_data;
+
+	return NT_STATUS_OK;
+}
+
+#endif
diff --git a/libcli/auth/krb5_wrap.h b/libcli/auth/krb5_wrap.h
index 3cdcedc971..4f333cc4b0 100644
--- a/libcli/auth/krb5_wrap.h
+++ b/libcli/auth/krb5_wrap.h
@@ -54,3 +54,18 @@ krb5_error_code smb_krb5_unparse_name(TALLOC_CTX *mem_ctx,
 					 krb5_checksum *cksum,
 					 uint8_t *data,
 					  size_t length);
+
+krb5_error_code check_pac_checksum(TALLOC_CTX *mem_ctx,
+				   DATA_BLOB pac_data,
+				   struct PAC_SIGNATURE_DATA *sig,
+				   krb5_context context,
+				   const krb5_keyblock *keyblock);
+
+NTSTATUS kerberos_decode_pac(TALLOC_CTX *mem_ctx,
+			     DATA_BLOB pac_data_blob,
+			     krb5_context context,
+			     const krb5_keyblock *krbtgt_keyblock,
+			     const krb5_keyblock *service_keyblock,
+			     krb5_const_principal client_principal,
+			     time_t tgs_authtime,
+			     struct PAC_DATA **pac_data_out);
diff --git a/libcli/auth/wscript_build b/libcli/auth/wscript_build
index 6f5483f48b..e7d8b5660f 100644
--- a/libcli/auth/wscript_build
+++ b/libcli/auth/wscript_build
@@ -40,5 +40,5 @@ bld.SAMBA_SUBSYSTEM('SPNEGO_PARSE',
                     deps='asn1util')
 
 bld.SAMBA_SUBSYSTEM('KRB5_WRAP',
-                    source='krb5_wrap.c',
-                    deps='krb5')
+                    source='krb5_wrap.c kerberos_pac.c',
+                    deps='krb5 ndr-krb5pac')