[Xen-devel] [PATCH 9/9] stubdom/vtpm: Add PCR pass-through to hardware TPM

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

This allows the hardware TPM's PCRs to be accessed from a vTPM for
debugging and as a simple alternative to a deep quote in situations
where the integrity of the vTPM's own TCB is not in question.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 stubdom/Makefile                   |  1 +
 stubdom/vtpm-pcr-passthrough.patch | 73 ++++++++++++++++++++++++++++++++++++++
 stubdom/vtpm/vtpm_cmd.c            | 38 ++++++++++++++++++++
 3 files changed, 112 insertions(+)
 create mode 100644 stubdom/vtpm-pcr-passthrough.patch

diff --git a/stubdom/Makefile b/stubdom/Makefile
index 790b547..03ec07e 100644
--- a/stubdom/Makefile
+++ b/stubdom/Makefile
@@ -210,6 +210,7 @@ tpm_emulator-$(XEN_TARGET_ARCH): 
tpm_emulator-$(TPMEMU_VERSION).tar.gz
        patch -d $@ -p1 < vtpm-locality.patch
        patch -d $@ -p1 < vtpm-bufsize.patch
        patch -d $@ -p1 < vtpm-locality5-pcrs.patch
+       patch -d $@ -p1 < vtpm-pcr-passthrough.patch
        mkdir $@/build
        cd $@/build; $(CMAKE) .. -DCMAKE_C_COMPILER=${CC} 
-DCMAKE_C_FLAGS="-std=c99 -DTPM_NO_EXTERN $(TARGET_CPPFLAGS) $(TARGET_CFLAGS) 
-Wno-declaration-after-statement"
        touch $@
diff --git a/stubdom/vtpm-pcr-passthrough.patch 
b/stubdom/vtpm-pcr-passthrough.patch
new file mode 100644
index 0000000..4e898a5
--- /dev/null
+++ b/stubdom/vtpm-pcr-passthrough.patch
@@ -0,0 +1,73 @@
+diff --git a/tpm/tpm_capability.c b/tpm/tpm_capability.c
+index f8f7f0f..885af52 100644
+--- a/tpm/tpm_capability.c
++++ b/tpm/tpm_capability.c
+@@ -72,7 +72,7 @@ static TPM_RESULT cap_property(UINT32 subCapSize, BYTE 
*subCap,
+   switch (property) {
+     case TPM_CAP_PROP_PCR:
+       debug("[TPM_CAP_PROP_PCR]");
+-      return return_UINT32(respSize, resp, TPM_NUM_PCR);
++      return return_UINT32(respSize, resp, TPM_NUM_PCR_V);
+ 
+     case TPM_CAP_PROP_DIR:
+       debug("[TPM_CAP_PROP_DIR]");
+diff --git a/tpm/tpm_emulator_extern.h b/tpm/tpm_emulator_extern.h
+index 36a32dd..77ed595 100644
+--- a/tpm/tpm_emulator_extern.h
++++ b/tpm/tpm_emulator_extern.h
+@@ -56,6 +56,7 @@ void (*tpm_free)(/*const*/ void *ptr);
+ /* random numbers */
+ 
+ void (*tpm_get_extern_random_bytes)(void *buf, size_t nbytes);
++void tpm_get_extern_pcr(int index, void *buf);
+ 
+ /* usec since last call */
+ 
+diff --git a/tpm/tpm_integrity.c b/tpm/tpm_integrity.c
+index 66ece83..f3c4196 100644
+--- a/tpm/tpm_integrity.c
++++ b/tpm/tpm_integrity.c
+@@ -56,8 +56,11 @@ TPM_RESULT TPM_Extend(TPM_PCRINDEX pcrNum, TPM_DIGEST 
*inDigest,
+ TPM_RESULT TPM_PCRRead(TPM_PCRINDEX pcrIndex, TPM_PCRVALUE *outDigest)
+ {
+   info("TPM_PCRRead()");
+-  if (pcrIndex >= TPM_NUM_PCR) return TPM_BADINDEX;
+-  memcpy(outDigest, &PCR_VALUE[pcrIndex], sizeof(TPM_PCRVALUE));
++  if (pcrIndex >= TPM_NUM_PCR_V) return TPM_BADINDEX;
++  if (pcrIndex >= TPM_NUM_PCR)
++      tpm_get_extern_pcr(pcrIndex - TPM_NUM_PCR, outDigest);
++  else
++    memcpy(outDigest, &PCR_VALUE[pcrIndex], sizeof(TPM_PCRVALUE));
+   return TPM_SUCCESS;
+ }
+ 
+@@ -138,12 +141,15 @@ TPM_RESULT tpm_compute_pcr_digest(TPM_PCR_SELECTION 
*pcrSelection,
+   BYTE *buf, *ptr;
+   info("tpm_compute_pcr_digest()");
+   /* create PCR composite */
+-  if ((pcrSelection->sizeOfSelect * 8) > TPM_NUM_PCR
++  if ((pcrSelection->sizeOfSelect * 8) > TPM_NUM_PCR_V
+       || pcrSelection->sizeOfSelect == 0) return TPM_INVALID_PCR_INFO;
+   for (i = 0, j = 0; i < pcrSelection->sizeOfSelect * 8; i++) {
+     /* is PCR number i selected ? */
+     if (pcrSelection->pcrSelect[i >> 3] & (1 << (i & 7))) {
+-      memcpy(&comp.pcrValue[j++], &PCR_VALUE[i], sizeof(TPM_PCRVALUE));
++      if (i >= TPM_NUM_PCR)
++        tpm_get_extern_pcr(i - TPM_NUM_PCR, &comp.pcrValue[j++]);
++      else
++        memcpy(&comp.pcrValue[j++], &PCR_VALUE[i], sizeof(TPM_PCRVALUE));
+     }
+   }
+   memcpy(&comp.select, pcrSelection, sizeof(TPM_PCR_SELECTION));
+diff --git a/tpm/tpm_structures.h b/tpm/tpm_structures.h
+index 08cef1e..8c97fc5 100644
+--- a/tpm/tpm_structures.h
++++ b/tpm/tpm_structures.h
+@@ -677,6 +677,7 @@ typedef struct tdTPM_CMK_MA_APPROVAL {
+  * Number of PCRs of the TPM (must be a multiple of eight)
+  */
+ #define TPM_NUM_PCR 32
++#define TPM_NUM_PCR_V (TPM_NUM_PCR + 24)
+ 
+ /*
+  * TPM_PCR_SELECTION ([TPM_Part2], Section 8.1)
diff --git a/stubdom/vtpm/vtpm_cmd.c b/stubdom/vtpm/vtpm_cmd.c
index 7eae98b..ed058fb 100644
--- a/stubdom/vtpm/vtpm_cmd.c
+++ b/stubdom/vtpm/vtpm_cmd.c
@@ -134,6 +134,44 @@ egress:
 
 }
 
+extern struct tpmfront_dev* tpmfront_dev;
+void tpm_get_extern_pcr(int index, void *buf) {
+   TPM_RESULT status = TPM_SUCCESS;
+   uint8_t* cmdbuf, *resp, *bptr;
+   size_t resplen = 0;
+   UINT32 len;
+
+   /*Ask the real tpm for the PCR value */
+   TPM_TAG tag = TPM_TAG_RQU_COMMAND;
+   UINT32 size;
+   TPM_COMMAND_CODE ord = TPM_ORD_PCRRead;
+   len = size = sizeof(TPM_TAG) + sizeof(UINT32) + sizeof(TPM_COMMAND_CODE) + 
sizeof(UINT32);
+
+   /*Create the raw tpm command */
+   bptr = cmdbuf = malloc(size);
+   TRYFAILGOTO(pack_header(&bptr, &len, tag, size, ord));
+   TRYFAILGOTO(tpm_marshal_UINT32(&bptr, &len, index));
+
+   /* Send cmd, wait for response */
+   TRYFAILGOTOMSG(tpmfront_cmd(tpmfront_dev, cmdbuf, size, &resp, &resplen),
+      ERR_TPMFRONT);
+
+   bptr = resp; len = resplen;
+   TRYFAILGOTOMSG(unpack_header(&bptr, &len, &tag, &size, &ord), 
ERR_MALFORMED);
+
+   //Check return status of command
+   CHECKSTATUSGOTO(ord, "TPM_PCRRead()");
+
+   //Get the PCR value out
+   TRYFAILGOTOMSG(tpm_unmarshal_BYTE_ARRAY(&bptr, &len, buf, 20), 
ERR_MALFORMED);
+
+   goto egress;
+abort_egress:
+   memset(buf, 0x20, 20);
+egress:
+   free(cmdbuf);
+}
+
 TPM_RESULT VTPM_LoadHashKey(struct tpmfront_dev* tpmfront_dev, uint8_t** data, 
size_t* data_length)
 {
    TPM_RESULT status = TPM_SUCCESS;
-- 
1.7.11.7


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