[Xen-devel] [PATCH 12/13] stubdom/vtpm: constrain locality by XSM label

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

This adds the ability for a vTPM to constrain what localities a given
client domain can use based on its XSM label. For example:

  locality=user_1:vm_r:domU_t=0,1,2 locality=user_1:vm_r:watcher_t=5

An arbitrary prefix can be matched by using a '*'.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 stubdom/vtpm/vtpm.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 74 insertions(+), 2 deletions(-)

diff --git a/stubdom/vtpm/vtpm.c b/stubdom/vtpm/vtpm.c
index feb8aa3..01dc90b 100644
--- a/stubdom/vtpm/vtpm.c
+++ b/stubdom/vtpm/vtpm.c
@@ -139,6 +139,35 @@ int check_ordinal(tpmcmd_t* tpmcmd) {
    return true;
 }
 
+struct locality_item {
+       char* lbl;
+       uint8_t mask[32];
+};
+#define MAX_CLIENT_LOCALITIES 16
+static struct locality_item client_locality[MAX_CLIENT_LOCALITIES];
+static int nr_client_localities = 0;
+
+static void *generate_locality_mask(domid_t domid, unsigned int handle)
+{
+   char label[512];
+   int i;
+   if (tpmback_get_peercontext(domid, handle, label, sizeof(label)))
+      BUG();
+   for(i=0; i < nr_client_localities; i++) {
+      if (!strcmp(client_locality[i].lbl, label))
+         goto found;
+      if (client_locality[i].lbl[0] == '*') {
+        char * f = strstr(label, 1 + client_locality[i].lbl);
+        if (!strcmp(f, 1 + client_locality[i].lbl))
+           goto found;
+      }
+   }
+   return NULL;
+ found:
+   tpmback_set_opaque(domid, handle, client_locality[i].mask);
+   return client_locality[i].mask;
+}
+
 static void main_loop(void) {
    tpmcmd_t* tpmcmd = NULL;
    int res = -1;
@@ -164,11 +193,24 @@ static void main_loop(void) {
    while(tpmcmd) {
       /* Handle the request */
       if(tpmcmd->req_len) {
+        uint8_t* locality_mask = tpmcmd->opaque;
+        uint8_t locality_bit = (1 << (tpmcmd->locality & 7));
+        int locality_byte = tpmcmd->locality >> 3;
         tpmcmd->resp = NULL;
         tpmcmd->resp_len = 0;
 
-         /* First check for disabled ordinals */
-         if(!check_ordinal(tpmcmd)) {
+        if (nr_client_localities && !locality_mask)
+           locality_mask = generate_locality_mask(tpmcmd->domid, 
tpmcmd->handle);
+        if (nr_client_localities && !locality_mask) {
+            error("Unknown client label in tpm_handle_command");
+            create_error_response(tpmcmd, TPM_FAIL);
+        }
+        else if (nr_client_localities && !(locality_mask[locality_byte] & 
locality_bit)) {
+            error("Invalid locality (%d) for client in tpm_handle_command", 
tpmcmd->locality);
+            create_error_response(tpmcmd, TPM_FAIL);
+        }
+         /* Check for disabled ordinals */
+         else if(!check_ordinal(tpmcmd)) {
             create_error_response(tpmcmd, TPM_BAD_ORDINAL);
          }
          /* If not disabled, do the command */
@@ -273,6 +315,36 @@ int parse_cmd_line(int argc, char** argv)
             pch = strtok(NULL, ",");
          }
       }
+      else if(!strncmp(argv[i], "locality=", 9)) {
+        char *lbl = argv[i] + 9;
+       char *pch = strchr(lbl, '=');
+       uint8_t* locality_mask = client_locality[nr_client_localities].mask;
+       if (pch == NULL) {
+                error("Invalid locality specification: %s", lbl);
+                return -1;
+       }
+       if (nr_client_localities == MAX_CLIENT_LOCALITIES) {
+               error("Too many locality specifications");
+               return -1;
+       }
+       client_locality[nr_client_localities].lbl = lbl;
+       memset(locality_mask, 0, 32);
+       nr_client_localities++;
+       *pch = 0;
+       pch = strtok(pch + 1, ",");
+       while (pch != NULL) {
+               unsigned int loc;
+               if (sscanf(pch, "%u", &loc) == 1 && loc < 256) {
+                       uint8_t locality_bit = (1 << (loc & 7));
+                       int locality_byte = loc >> 3;
+                       locality_mask[locality_byte] |= locality_bit;
+               } else {
+                       error("Invalid locality item: %s", pch);
+                       return -1;
+               }
+               pch = strtok(NULL, ",");
+       }
+      }
       else {
         error("Invalid command line option `%s'", argv[i]);
       }
-- 
1.8.1


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