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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 6/9] vtpm: add ordinal for obtaining an EK signature
For a vTPM to be useful for remote attestation, proof that the vTPM's EK
was generated and held within a secure vTPM implementation is necessary.
This patch adds an ordinal to the vTPM which will request a quote
providing this evidence from the TPM Manager; it only functions during
the first startup of a given vTPM in order to provide proof that the EK
was freshly generated (and not a key whose private part is available
elsewhere).
Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
stubdom/Makefile | 1 +
stubdom/vtpm-parent-sign-ek.patch | 196 ++++++++++++++++++++++++++++++++++++++
stubdom/vtpm/vtpm_cmd.c | 45 +++++++++
3 files changed, 242 insertions(+)
create mode 100644 stubdom/vtpm-parent-sign-ek.patch
diff --git a/stubdom/Makefile b/stubdom/Makefile
index b1822b7..3e5f054 100644
--- a/stubdom/Makefile
+++ b/stubdom/Makefile
@@ -208,6 +208,7 @@ tpm_emulator-$(XEN_TARGET_ARCH):
tpm_emulator-$(TPMEMU_VERSION).tar.gz
patch -d $@ -p1 < tpmemu-$(TPMEMU_VERSION).patch;
patch -d $@ -p1 < vtpm-bufsize.patch
patch -d $@ -p1 < vtpm-locality.patch
+ patch -d $@ -p1 < vtpm-parent-sign-ek.patch
mkdir $@/build
cd $@/build; CC=${CC} $(CMAKE) .. -DCMAKE_C_FLAGS:STRING="-std=c99
-DTPM_NO_EXTERN $(TARGET_CPPFLAGS) $(TARGET_CFLAGS)
-Wno-declaration-after-statement"
touch $@
diff --git a/stubdom/vtpm-parent-sign-ek.patch
b/stubdom/vtpm-parent-sign-ek.patch
new file mode 100644
index 0000000..14e66ee
--- /dev/null
+++ b/stubdom/vtpm-parent-sign-ek.patch
@@ -0,0 +1,196 @@
+diff --git a/tpm/tpm_cmd_handler.c b/tpm/tpm_cmd_handler.c
+index 9e1cfb4..0fabf98 100644
+--- a/tpm/tpm_cmd_handler.c
++++ b/tpm/tpm_cmd_handler.c
+@@ -3312,6 +3312,37 @@ static TPM_RESULT
execute_TPM_OwnerReadPubek(TPM_REQUEST *req, TPM_RESPONSE *rsp
+ return res;
+ }
+
++static TPM_RESULT execute_TPM_ParentSignEK(TPM_REQUEST *req, TPM_RESPONSE
*rsp)
++{
++ TPM_NONCE nonce;
++ TPM_RESULT res;
++ UINT32 sigSize;
++ BYTE *sig;
++ BYTE *ptr;
++ UINT32 len;
++ TPM_PCR_SELECTION targetPCR;
++
++ tpm_compute_in_param_digest(req);
++
++ ptr = req->param;
++ len = req->paramSize;
++ if (tpm_unmarshal_TPM_NONCE(&ptr, &len, &nonce)
++ || tpm_unmarshal_TPM_PCR_SELECTION(&ptr, &len, &targetPCR)
++ || len != 0) return TPM_BAD_PARAMETER;
++
++ res = TPM_ParentSignEK(&nonce, &targetPCR, &req->auth1, &sigSize, &sig);
++ if (res != TPM_SUCCESS) return res;
++ rsp->paramSize = len = sigSize;
++ rsp->param = ptr = tpm_malloc(len);
++ if (ptr == NULL || tpm_marshal_BLOB(&ptr, &len, sig, sigSize)) {
++ tpm_free(rsp->param);
++ res = TPM_FAIL;
++ }
++ tpm_free(sig);
++
++ return res;
++}
++
+ static void tpm_setup_rsp_auth(TPM_COMMAND_CODE ordinal, TPM_RESPONSE *rsp)
+ {
+ tpm_hmac_ctx_t hmac;
+@@ -4062,6 +4093,11 @@ void tpm_execute_command(TPM_REQUEST *req, TPM_RESPONSE
*rsp)
+ res = execute_TPM_OwnerReadPubek(req, rsp);
+ break;
+
++ case TPM_ORD_ParentSignEK:
++ debug("[TPM_ORD_ParentSignEK]");
++ res = execute_TPM_ParentSignEK(req, rsp);
++ break;
++
+ default:
+ #ifdef MTM_EMULATOR
+ res = mtm_execute_command(req, rsp);
+diff --git a/tpm/tpm_commands.h b/tpm/tpm_commands.h
+index a7666f6..7fef934 100644
+--- a/tpm/tpm_commands.h
++++ b/tpm/tpm_commands.h
+@@ -3054,6 +3054,23 @@ TPM_RESULT TPM_OwnerReadPubek(
+ TPM_PUBKEY *pubEndorsementKey
+ );
+
++/**
++ * TPM_ParentSignEK - gets a hardware TPM quote of a vTPM's EK
++ * @externalData: [in] AntiReplay nonce to prevent replay of messages
++ * @sel: [in] PCR selection for the hardware TPM's quote
++ * @auth1: [in, out] Authorization protocol parameters
++ * @sigSize: [out] The length of the returned digital signature
++ * @sig: [out] The resulting digital signature and PCR values
++ * Returns: TPM_SUCCESS on success, a TPM error code otherwise.
++ */
++TPM_RESULT TPM_ParentSignEK(
++ TPM_NONCE *externalData,
++ TPM_PCR_SELECTION *sel,
++ TPM_AUTH *auth1,
++ UINT32 *sigSize,
++ BYTE **sig
++);
++
+ /*
+ * Error handling
+ * [tpm_error.c]
+diff --git a/tpm/tpm_credentials.c b/tpm/tpm_credentials.c
+index 9cd64af..01f29e6 100644
+--- a/tpm/tpm_credentials.c
++++ b/tpm/tpm_credentials.c
+@@ -180,3 +180,34 @@ TPM_RESULT TPM_OwnerReadInternalPub(TPM_KEY_HANDLE
keyHandle, TPM_AUTH *auth1,
+ return TPM_BAD_PARAMETER;
+ }
+ }
++
++int endorsementKeyFresh = 0;
++
++TPM_RESULT VTPM_GetParentQuote(TPM_DIGEST* data, TPM_PCR_SELECTION *sel,
UINT32 *sigSize, BYTE **sig);
++
++TPM_RESULT TPM_ParentSignEK(TPM_NONCE *externalData, TPM_PCR_SELECTION *sel,
++ TPM_AUTH *auth1, UINT32 *sigSize, BYTE **sig)
++{
++ TPM_PUBKEY pubKey;
++ TPM_RESULT res;
++ TPM_DIGEST hres;
++
++ info("TPM_ParentSignEK()");
++
++ res = tpm_verify_auth(auth1, tpmData.permanent.data.ownerAuth,
TPM_KH_OWNER);
++ if (res != TPM_SUCCESS) return res;
++
++ if (!endorsementKeyFresh) return TPM_DISABLED_CMD;
++
++ res = tpm_get_pubek(&pubKey);
++ if (res != TPM_SUCCESS) return res;
++
++ if (tpm_compute_pubkey_checksum(externalData, &pubKey, &hres))
++ res = TPM_FAIL;
++
++ if (res == TPM_SUCCESS)
++ res = VTPM_GetParentQuote(&hres, sel, sigSize, sig);
++
++ free_TPM_PUBKEY(pubKey);
++ return res;
++}
+diff --git a/tpm/tpm_data.c b/tpm/tpm_data.c
+index 50c9697..6a0c499 100644
+--- a/tpm/tpm_data.c
++++ b/tpm/tpm_data.c
+@@ -76,6 +76,8 @@ static void init_timeouts(void)
+ tpmData.permanent.data.cmd_durations[2] = 1000;
+ }
+
++extern int endorsementKeyFresh;
++
+ void tpm_init_data(void)
+ {
+ /* endorsement key */
+@@ -157,6 +159,7 @@ void tpm_init_data(void)
+ if (tpmConf & TPM_CONF_GENERATE_EK) {
+ /* generate a new endorsement key */
+ tpm_rsa_generate_key(&tpmData.permanent.data.endorsementKey, 2048);
++ endorsementKeyFresh = 1;
+ } else {
+ /* setup endorsement key */
+ tpm_rsa_import_key(&tpmData.permanent.data.endorsementKey,
+diff --git a/tpm/tpm_structures.h b/tpm/tpm_structures.h
+index f746c05..b0f4625 100644
+--- a/tpm/tpm_structures.h
++++ b/tpm/tpm_structures.h
+@@ -658,6 +658,49 @@ typedef struct tdTPM_CMK_MA_APPROVAL {
+ #define TPM_ORD_TickStampBlob 242
+ #define TPM_ORD_MAX 256
+
++/* VTPM-only commands: */
++/*
++ * ParentSignEK - Proof of fresh provisioning and EK value
++ *
++ * Input:
++ * TPM_TAG tag TPM_TAG_RQU_AUTH1_COMMAND
++ * UINT32 paramSize Total size of request
++ * TPM_COMMAND_CODE ordinal TPM_ORD_ParentSignEK
++ * TPM_NONCE externData 20 bytes of external data
++ * TPM_PCR_SELECTION ptSel PCR selection for physical TPM
++ * ---
++ * UINT32 authHandle Owner authorization session (OIAP)
++ * TPM_NONCE nonceOdd Nonce for authHandle
++ * BOOL continueAuth Continue flag for authHandle
++ * TPM_AUTHDATA privAuth Authorization digest for command
++ *
++ * Output:
++ * TPM_TAG tag TPM_TAG_RSP_AUTH1_COMMAND
++ * UINT32 paramSize Total size of response
++ * TPM_RESULT returnCode Return code of the operation
++ * BYTE[] sig Signature provided by physical TPM
++ * TPM_PCRVALUE[] pcrValue Values of hardware PCRs used in the
quote
++ * ---
++ * TPM_NONCE nonceEven Nonce for authHandle
++ * BOOL continueAuth Continue flag for authHandle
++ * TPM_AUTHDATA resAuth Authorization digest for response
++ *
++ * This command is only valid on the first boot of a vTPM; on any subsequent
++ * boot, the command returns TPM_DISABLED_CMD. It is intended to be used to
++ * provide evidence of proper platform configuration to the verifier/CA which
is
++ * responsible for the creation of the vTPM's endorsement credential, which
will
++ * be used on subsequent boots to certify AIKs via the usual Privacy CA
protocol.
++ *
++ * The values of the virtual TPM's PCRs are not included in the response.
++ * The signature is a standard TPM_Quote response from the physical TPM; its
++ * externalData is the SHA1 hash of the following structure:
++ * TPM_PUBKEY pubEK The vTPM's public EK
++ * TPM_NONCE externData From input to the deep quote
++ *
++ * This structure was chosen to match the return of TPM_ReadPubek
++ */
++#define TPM_ORD_ParentSignEK (TPM_VENDOR_COMMAND |
TPM_ORD_ReadPubek)
++
+ /*
+ * TCS Ordinals ([TPM_Part2], Section 17.1)
+ *
diff --git a/stubdom/vtpm/vtpm_cmd.c b/stubdom/vtpm/vtpm_cmd.c
index 7eae98b..6fda456 100644
--- a/stubdom/vtpm/vtpm_cmd.c
+++ b/stubdom/vtpm/vtpm_cmd.c
@@ -217,6 +217,51 @@ egress:
return status;
}
+extern struct tpmfront_dev* tpmfront_dev;
+TPM_RESULT VTPM_GetParentQuote(TPM_NONCE *data, TPM_PCR_SELECTION *sel, UINT32
*sigSize, BYTE **sig)
+{
+ TPM_RESULT status = TPM_SUCCESS;
+ uint8_t* bptr, *resp;
+ uint8_t* cmdbuf = NULL;
+ size_t resplen = 0;
+ UINT32 len;
+
+ TPM_TAG tag = VTPM_TAG_REQ;
+ UINT32 size;
+ TPM_COMMAND_CODE ord = VTPM_ORD_GET_QUOTE;
+
+ /*Create the command*/
+ len = size = VTPM_COMMAND_HEADER_SIZE + 25;
+ bptr = cmdbuf = malloc(size);
+ TRYFAILGOTO(pack_header(&bptr, &len, tag, size, ord));
+ TRYFAILGOTO(tpm_marshal_TPM_NONCE(&bptr, &len, data));
+ TRYFAILGOTO(tpm_marshal_TPM_PCR_SELECTION(&bptr, &len, sel));
+
+ /* Send the command to vtpm_manager */
+ info("Requesting Quote from backend");
+ TRYFAILGOTOMSG(tpmfront_cmd(tpmfront_dev, cmdbuf, size, &resp, &resplen),
ERR_TPMFRONT);
+
+ /* Unpack response header */
+ bptr = resp;
+ len = resplen;
+ TRYFAILGOTOMSG(unpack_header(&bptr, &len, &tag, &size, &ord),
ERR_MALFORMED);
+
+ /* Check return code */
+ CHECKSTATUSGOTO(ord, "VTPM_GetParentQuote()");
+
+ /* Copy out the value */
+ *sigSize = len;
+ *sig = tpm_malloc(*sigSize);
+ TRYFAILGOTOMSG(tpm_unmarshal_BYTE_ARRAY(&bptr, &len, *sig, *sigSize),
ERR_MALFORMED);
+
+ goto egress;
+abort_egress:
+ error("VTPM_GetParentQuote failed");
+egress:
+ free(cmdbuf);
+ return status;
+}
+
TPM_RESULT VTPM_PCRRead(struct tpmfront_dev* tpmfront_dev, UINT32 pcrIndex,
BYTE* outDigest)
{
TPM_RESULT status = TPM_SUCCESS;
--
1.9.0
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