r10174: This patch implements generic PAC verification, without assumptions

about the size of the signature.  In particular, this works with AES,
which was previously broken Samba4/Samba4.

Reviewed by metze (and thanks for help with the previous IDL commit).
(This used to be commit 3c8be196cce3bf275a0bf8d0cf127df570b560d3)

diff --git a/source4/auth/kerberos/kerberos_pac.c b/source4/auth/kerberos/kerberos_pac.c
index df1a871f8581f91776d8db40a35e85a678d3782f..dede5e8430db270d67538e94b40e9ca7e1f8174a 100644 (file)
--- a/source4/auth/kerberos/kerberos_pac.c
+++ b/source4/auth/kerberos/kerberos_pac.c
@@ -78,38 +78,70 @@ static krb5_error_code check_pac_checksum(TALLOC_CTX *mem_ctx,
 {
        krb5_error_code ret;
        NTSTATUS status;
-       struct PAC_SIGNATURE_DATA srv_sig;
        struct PAC_SIGNATURE_DATA *srv_sig_ptr = NULL;
-       struct PAC_SIGNATURE_DATA kdc_sig;
        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_INFO *logon_info = NULL;
        struct PAC_LOGON_NAME *logon_name = NULL;
        struct PAC_DATA *pac_data;
+       struct PAC_DATA_RAW *pac_data_raw;
 
-       DATA_BLOB modified_pac_blob = data_blob_talloc(mem_ctx, blob.data, blob.length);
+       DATA_BLOB *srv_sig_blob;
+       DATA_BLOB *kdc_sig_blob;
+
+       DATA_BLOB modified_pac_blob;
        NTTIME tgs_authtime_nttime;
        krb5_principal client_principal_pac;
        int i;
 
        pac_data = talloc(mem_ctx, struct PAC_DATA);
-       if (!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;
        }
 
-       status = ndr_pull_struct_blob(&blob, mem_ctx, pac_data,
+       status = ndr_pull_struct_blob(&blob, pac_data, pac_data,
                                      (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA);
        if (!NT_STATUS_IS_OK(status)) {
                DEBUG(0,("can't parse the PAC\n"));
                return status;
        }
 
-       if (pac_data->num_buffers < 3) {
+       if (pac_data->num_buffers < 4) {
                /* we need logon_ingo, service_key and kdc_key */
-               DEBUG(0,("less than 3 PAC buffers\n"));
-               return NT_STATUS_FOOBAR;
+               DEBUG(0,("less than 4 PAC buffers\n"));
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       status = ndr_pull_struct_blob(&blob, pac_data_raw, pac_data_raw,
+                                     (ndr_pull_flags_fn_t)ndr_pull_PAC_DATA_RAW);
+       if (!NT_STATUS_IS_OK(status)) {
+               DEBUG(0,("can't parse the PAC\n"));
+               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++) {
+               if (pac_data->buffers[i].type != pac_data_raw->buffers[i].type) {
+                       DEBUG(0,("misparse!  PAC_DATA buffer %d has type %d while PAC_DATA_RAW has %d\n",
+                                i, pac_data->buffers[i].type, pac_data->buffers[i].type));
+                       return NT_STATUS_INVALID_PARAMETER;
+               }
                switch (pac_data->buffers[i].type) {
                        case PAC_TYPE_LOGON_INFO:
                                if (!pac_data->buffers[i].info) {
@@ -122,14 +154,14 @@ static krb5_error_code check_pac_checksum(TALLOC_CTX *mem_ctx,
                                        break;
                                }
                                srv_sig_ptr = &pac_data->buffers[i].info->srv_cksum;
-                               srv_sig = pac_data->buffers[i].info->srv_cksum;
+                               srv_sig_blob = &pac_data_raw->buffers[i].info->remaining;
                                break;
                        case PAC_TYPE_KDC_CHECKSUM:
                                if (!pac_data->buffers[i].info) {
                                        break;
                                }
                                kdc_sig_ptr = &pac_data->buffers[i].info->kdc_cksum;
-                               kdc_sig = pac_data->buffers[i].info->kdc_cksum;
+                               kdc_sig_blob = &pac_data_raw->buffers[i].info->remaining;
                                break;
                        case PAC_TYPE_LOGON_NAME:
                                logon_name = &pac_data->buffers[i].info->logon_name;
@@ -141,29 +173,72 @@ static krb5_error_code check_pac_checksum(TALLOC_CTX *mem_ctx,
 
        if (!logon_info) {
                DEBUG(0,("PAC no logon_info\n"));
-               return NT_STATUS_FOOBAR;
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       if (!logon_name) {
+               DEBUG(0,("PAC no logon_name\n"));
+               return NT_STATUS_INVALID_PARAMETER;
        }
 
-       if (!srv_sig_ptr) {
+       if (!srv_sig_ptr || !srv_sig_blob) {
                DEBUG(0,("PAC no srv_key\n"));
-               return NT_STATUS_FOOBAR;
+               return NT_STATUS_INVALID_PARAMETER;
        }
 
-       if (!kdc_sig_ptr) {
+       if (!kdc_sig_ptr || !kdc_sig_blob) {
                DEBUG(0,("PAC no kdc_key\n"));
-               return NT_STATUS_FOOBAR;
+               return NT_STATUS_INVALID_PARAMETER;
        }
 
-       memset(&modified_pac_blob.data[modified_pac_blob.length - 20],
-              '\0', 16);
-       memset(&modified_pac_blob.data[modified_pac_blob.length - 44],
-              '\0', 16);
+       /* 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 */
+       status = ndr_pull_struct_blob(kdc_sig_blob, kdc_sig_wipe, kdc_sig_wipe,
+                                     (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
+       if (!NT_STATUS_IS_OK(status)) {
+               DEBUG(0,("can't parse the KDC signature\n"));
+               return status;
+       }
+       
+       status = ndr_pull_struct_blob(srv_sig_blob, srv_sig_wipe, srv_sig_wipe,
+                                     (ndr_pull_flags_fn_t)ndr_pull_PAC_SIGNATURE_DATA);
+       if (!NT_STATUS_IS_OK(status)) {
+               DEBUG(0,("can't parse the SRV signature\n"));
+               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 */
+       status = ndr_push_struct_blob(kdc_sig_blob, pac_data_raw, kdc_sig_wipe,
+                                     (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
+       if (!NT_STATUS_IS_OK(status)) {
+               DEBUG(0,("can't repack the KDC signature\n"));
+               return status;
+       }       
+       status = ndr_push_struct_blob(srv_sig_blob, pac_data_raw, srv_sig_wipe,
+                                     (ndr_push_flags_fn_t)ndr_push_PAC_SIGNATURE_DATA);
+       if (!NT_STATUS_IS_OK(status)) {
+               DEBUG(0,("can't repack the SRV signature\n"));
+               return status;
+       }
+
+       /* push out the whole structure, but now with zero'ed signatures */
+       status = ndr_push_struct_blob(&modified_pac_blob, pac_data_raw, pac_data_raw,
+                                        (ndr_push_flags_fn_t)ndr_push_PAC_DATA_RAW);
+       if (!NT_STATUS_IS_OK(status)) {
+               DEBUG(0,("can't repack the RAW PAC\n"));
+               return status;
+       }
 
        /* verify by service_key */
        ret = check_pac_checksum(mem_ctx, 
-                                   modified_pac_blob, &srv_sig, 
-                                   context, 
-                                   service_keyblock);
+                                modified_pac_blob, srv_sig_ptr, 
+                                context, 
+                                service_keyblock);
        if (ret) {
                DEBUG(1, ("PAC Decode: Failed to verify the service signature: %s\n",
                          smb_get_krb5_error_message(context, ret, mem_ctx)));
@@ -172,7 +247,7 @@ static krb5_error_code check_pac_checksum(TALLOC_CTX *mem_ctx,
 
        if (krbtgt_keyblock) {
                ret = check_pac_checksum(mem_ctx, 
-                                           srv_sig_ptr->signature, &kdc_sig, 
+                                           srv_sig_ptr->signature, kdc_sig_ptr, 
                                            context, krbtgt_keyblock);
                if (ret) {
                        DEBUG(1, ("PAC Decode: Failed to verify the KDC signature: %s\n",