Support for sealing/unseal a secret based on an externally signed PCR…

… policy.

* Added new `WOLFBOOT_TPM_SEAL` and `WOLFBOOT_TPM_SEAL_NV_BASE` config options.
* Added new `tools/tpm/policy_create` tool for assisting with creation of a policy digest. The sign keytool `--policy=file` signs the policy.
* Added new `WOLFBOOT_TPM_VERIFY` option to enable offloading of the asymmetric verification to the TPM. By default wolfCrypt will be used.
* Added example seal/unseal to update_flash for ARCH_SIM.
* Renamed `WOLFBOOT_TPM_KEYSTORE_NV_INDEX` to `WOLFBOOT_TPM_KEYSTORE_NV_BASE` to support multiple public keys.
* Refactored most TPM code into tpm.c.
* Refactored the keystore ROT to use new `wolfBoot_check_rot` API.
* Refactored the sign keytool to have a sign_digest function to allow signing firmware and policy for sealing/unsealing.
* Fix for make distclean && make using the wrong key tools.

.github/workflows/test-build-sim-tpm.yml

@@ -53,9 +53,10 @@ jobs:
         run: |
           make -C tools/keytools && make -C tools/bin-assemble
 
-      - name: Build wolfboot
+      # needed for tpm tools
+      - name: Build keystore.c
         run: |
-          make ${{inputs.make-args}} WOLFBOOT_TPM_KEYSTORE_AUTH="${{inputs.authstr}}"
+          make keys ${{inputs.make-args}}
 
       - name: Build TPM tools
         run: |
@@ -65,6 +66,16 @@ jobs:
         run: |
           ./tools/tpm/rot -write ${{inputs.rot-args}} -auth="${{inputs.authstr}}"
 
+      - name: Create a PCR Policy
+        run: |
+          echo aaa > aaa.bin
+          ./tools/tpm/pcr_extend 0 aaa.bin
+          ./tools/tpm/policy_create -pcr=0 -out=policy.bin
+
+      - name: Build wolfboot
+        run: |
+          make ${{inputs.make-args}} WOLFBOOT_TPM_KEYSTORE_AUTH="${{inputs.authstr}}"
+
       - name: Run wolfBoot
         run: |
           ./wolfboot.elf get_version

.github/workflows/test-tpm.yml

@@ -36,6 +36,7 @@ jobs:
       config-file: ./config/examples/sim-tpm.config
       make-args: SIGN=RSA2048 HASH=SHA256
 
+
   sim_tpm_measured_ecc256:
     uses: ./.github/workflows/test-build-sim-tpm.yml
     with:
@@ -82,3 +83,29 @@ jobs:
       config-file: ./config/examples/sim-tpm-keystore.config
       make-args: SIGN=RSA2048 HASH=SHA256
       authstr: TestAuth
+
+
+  sim_tpm_seal_ecc256:
+    uses: ./.github/workflows/test-build-sim-tpm.yml
+    with:
+      arch: host
+      config-file: ./config/examples/sim-tpm-seal.config
+      make-args: SIGN=ECC256 HASH=SHA256 POLICY_FILE=policy.bin
+      authstr: TestAuth
+
+  sim_tpm_seal_ecc384:
+    uses: ./.github/workflows/test-build-sim-tpm.yml
+    with:
+      arch: host
+      config-file: ./config/examples/sim-tpm-seal.config
+      make-args: SIGN=ECC384 HASH=SHA384 POLICY_FILE=policy.bin
+      rot-args: -sha384
+      authstr: TestAuth
+
+  sim_tpm_seal_rsa2048:
+    uses: ./.github/workflows/test-build-sim-tpm.yml
+    with:
+      arch: host
+      config-file: ./config/examples/sim-tpm-seal.config
+      make-args: SIGN=RSA2048 HASH=SHA256 POLICY_FILE=policy.bin
+      authstr: TestAuth

.gitignore

@@ -101,6 +101,10 @@ tools/unit-tests/unit-parser
 tools/bin-assemble/bin-assemble
 tools/elf-parser/elf-parser
 tools/tpm/rot
+tools/tpm/pcr_read
+tools/tpm/pcr_reset
+tools/tpm/pcr_extend
+tools/tpm/policy_create
 config/*.ld
 
 # Generated confiuguration file

IDE/XilinxSDK/README.md

@@ -37,7 +37,8 @@ Note: If not using Position Independent Code (PIC) the linker script `ldscript.l
 ## Signing Example
 
 ```sh
-python3 ./tools/keytools/sign.py --rsa4096 --sha3 ../helloworld/Debug/helloworld.elf ./rsa4096.der 1
+make keytools
+./tools/keytools/sign --rsa4096 --sha3 ../helloworld/Debug/helloworld.elf ./rsa4096.der 1
 ```
 
 ## Bootgen

Makefile

@@ -154,10 +154,8 @@ include tools/test-enc.mk
 include tools/test-delta.mk
 include tools/test-renode.mk
 
-PYTHON?=python3
 keytools_check: keytools FORCE
 
-
 $(PRIVATE_KEY):
 	$(Q)$(MAKE) keytools_check
 	$(Q)(test $(SIGN) = NONE) || ("$(KEYGEN_TOOL)" $(KEYGEN_OPTIONS) -g $(PRIVATE_KEY)) || true

config/examples/sim-tpm-keystore.config

@@ -19,7 +19,7 @@ WOLFBOOT_FIXED_PARTITIONS=1
 
 # Use NV for TPM based Root of Trust
 WOLFBOOT_TPM_KEYSTORE?=1
-WOLFBOOT_TPM_KEYSTORE_NV_INDEX?=0x01400200
+WOLFBOOT_TPM_KEYSTORE_NV_BASE?=0x01400200
 #WOLFBOOT_TPM_KEYSTORE_AUTH?=TestAuth
 
 # TPM Logging

config/examples/sim-tpm-seal.config

@@ -0,0 +1,35 @@
+ARCH=sim
+TARGET=sim
+SIGN?=ECC256
+HASH?=SHA256
+SPI_FLASH=0
+DEBUG=0
+WOLFTPM=1
+
+# sizes should be multiple of system page size
+WOLFBOOT_PARTITION_SIZE=0x40000
+WOLFBOOT_SECTOR_SIZE=0x1000
+WOLFBOOT_PARTITION_BOOT_ADDRESS=0x80000
+# if on external flash, it should be multiple of system page size
+WOLFBOOT_PARTITION_UPDATE_ADDRESS=0x100000
+WOLFBOOT_PARTITION_SWAP_ADDRESS=0x180000
+
+# required for keytools
+WOLFBOOT_FIXED_PARTITIONS=1
+
+# Use NV for TPM based Root of Trust
+WOLFBOOT_TPM_KEYSTORE?=1
+WOLFBOOT_TPM_KEYSTORE_NV_BASE?=0x01400200
+#WOLFBOOT_TPM_KEYSTORE_AUTH?=TestAuth
+
+# Measured boot at test PCR index 16
+MEASURED_BOOT?=1
+MEASURED_PCR_A?=16
+
+# Sealing a secret into TPM based on external PCR policy signed by the sign tool
+WOLFBOOT_TPM_SEAL?=1
+WOLFBOOT_TPM_SEAL_NV_BASE=0x01400300
+
+# TPM Logging
+#CFLAGS_EXTRA+=-DDEBUG_WOLFTPM
+#CFLAGS_EXTRA+=-DWOLFTPM_DEBUG_VERBOSE

config/examples/sim-tpm.config

@@ -5,6 +5,8 @@ HASH?=SHA256
 SPI_FLASH=0
 DEBUG=0
 WOLFTPM=1
+# enable offloading of asymmetric verify to TPM
+WOLFBOOT_TPM_VERIFY?=1
 
 # sizes should be multiple of system page size
 WOLFBOOT_PARTITION_SIZE=0x40000

config/examples/x86_fsp_qemu.config

@@ -13,7 +13,7 @@ WOLFTPM=0
 
 # TPM Keystore options
 #WOLFBOOT_TPM_KEYSTORE?=1
-#WOLFBOOT_TPM_KEYSTORE_NV_INDEX?=0x01800200
+#WOLFBOOT_TPM_KEYSTORE_NV_BASE?=0x01800200
 #WOLFBOOT_TPM_POLICY_NV_INDEX?=0x01800201
 
 # 4gb - 8mb

config/examples/x86_fsp_qemu_stage1_auth.config

@@ -13,7 +13,7 @@ WOLFTPM=0
 
 # TPM Keystore options
 #WOLFBOOT_TPM_KEYSTORE?=1
-#WOLFBOOT_TPM_KEYSTORE_NV_INDEX?=0x01800200
+#WOLFBOOT_TPM_KEYSTORE_NV_BASE?=0x01800200
 #WOLFBOOT_TPM_POLICY_NV_INDEX?=0x01800201
 
 # 4gb - 8mb

config/examples/x86_fsp_qemu_tpm.config

@@ -13,7 +13,7 @@ WOLFTPM=1
 
 # TPM Keystore options
 #WOLFBOOT_TPM_KEYSTORE?=1
-#WOLFBOOT_TPM_KEYSTORE_NV_INDEX?=0x01800200
+#WOLFBOOT_TPM_KEYSTORE_NV_BASE?=0x01800200
 #WOLFBOOT_TPM_POLICY_NV_INDEX?=0x01800201
 
 # 4gb - 8mb

config/examples/x86_fsp_qemu_tpm_keystore.config

@@ -13,7 +13,7 @@ WOLFTPM=1
 
 # TPM Keystore options
 WOLFBOOT_TPM_KEYSTORE?=1
-WOLFBOOT_TPM_KEYSTORE_NV_INDEX?=0x01800200
+WOLFBOOT_TPM_KEYSTORE_NV_BASE?=0x01800200
 WOLFBOOT_TPM_POLICY_NV_INDEX?=0x01800201
 
 # 4gb - 8mb

docs/Signing.md

@@ -157,7 +157,6 @@ be used for the key, 16 for the initialization of the IV.
     SHAREDKEY.BIN is expected to be exactly 48 bytes in size, of which 32 will
 be used for the key, 16 for the initialization of the IV.
 
-
 #### Delta updates (incremental updates from a known version)
 
 An incremental update is created using the sign tool when the following option
@@ -167,6 +166,16 @@ is provided:
     `BASE_SIGNED_IMG.BIN` and the new image signed starting from `IMAGE.BIN`. The
 result is stored in a file ending in `_signed_diff.bin`.
 
+#### Policy signing (for sealing/unsealing with a TPM)
+
+Provides a PCR mask and digest to be signed and included in the header. The signing key is used to sign the digest.
+
+  * `--policy policy.bin`: This argument is multi-purpose.
+  By default the file should contain a 4-byte PCR mask and SHA2-256 PCR digest to be signed.
+  If using `--manual-sign` then the file should contain the 4-byte PCR mask and signature.
+  The PCR mask and signature will be included in the `HDR_POLICY_SIGNATURE` header tag.
+  Note: This may require increasing the `IMAGE_HEADER_SIZE` as two signatures will be stored in the header.
+
 #### Three-steps signing using external provisioning tools
 
 If the private key is not accessible, while it's possible to sign payloads using
@@ -222,13 +231,13 @@ openssl rsa -inform DER -outform DER -in my_key.der -out rsa2048_pub.der -pubout
 ./tools/keytools/keygen --rsa2048 -i rsa2048_pub.der
 
 # Generate Hash to Sign
-./tools/keytools/sign            --rsa2048 --sha-only --sha256 test-app/image.bin rsa2048_pub.der 1
+./tools/keytools/sign --rsa2048 --sha-only --sha256 test-app/image.bin rsa2048_pub.der 1
 
 # Sign hash Example (here is where you would use an HSM)
 openssl pkeyutl -sign -keyform der -inkey my_key.der -in test-app/image_v1_digest.bin > test-app/image_v1.sig
 
 # Generate final signed binary
-./tools/keytools/sign            --rsa2048 --sha256 --manual-sign test-app/image.bin rsa2048_pub.der 1 test-app/image_v1.sig
+./tools/keytools/sign --rsa2048 --sha256 --manual-sign test-app/image.bin rsa2048_pub.der 1 test-app/image_v1.sig
 
 # Combine into factory image (0xc0000 is the WOLFBOOT_PARTITION_BOOT_ADDRESS)
 tools/bin-assemble/bin-assemble factory.bin 0x0 wolfboot.bin \

docs/TPM.md

@@ -6,11 +6,14 @@ In wolfBoot we support TPM based root of trust, sealing/unsealing, cryptographic
 
 | Config Option | Preprocessor Macro | Description                         |
 | ------------- | ------------------ | ----------------------------------- |
-| `WOLFTPM=1`   | `WOLFBOOT_TPM`     | Enables wolfTPM support and cryptographic offloading for RSA2048 and ECC256/384 |
+| `WOLFTPM=1`   | `WOLFBOOT_TPM`     | Enables wolfTPM support |
+| `WOLFBOOT_TPM_VERIFY=1` | `WOLFBOOT_TPM_VERIFY` | Enables cryptographic offloading for RSA2048 and ECC256/384 to the TPM. |
 | `WOLFBOOT_TPM_KEYSTORE=1` | `WOLFBOOT_TPM_KEYSTORE` | Enables TPM based root of trust. NV Index must store a hash of the trusted public key. |
-| `WOLFBOOT_TPM_KEYSTORE_NV_INDEX=0x` | `WOLFBOOT_TPM_KEYSTORE_NV_INDEX=0x` | NV index in platform range 0x1400000 - 0x17FFFFF |
+| `WOLFBOOT_TPM_KEYSTORE_NV_BASE=0x` | `WOLFBOOT_TPM_KEYSTORE_NV_BASE=0x` | NV index in platform range 0x1400000 - 0x17FFFFF. |
 | `MEASURED_BOOT=1` | `WOLFBOOT_MEASURED_BOOT` | Enable measured boot. Extend PCR with wolfBoot hash. |
-| `MEASURED_PCR_A=16` | `WOLFBOOT_MEASURED_PCR_A=16` | The PCR index to use. See [docs/measured_boot.md](/docs/measured_boot.md) |
+| `MEASURED_PCR_A=16` | `WOLFBOOT_MEASURED_PCR_A=16` | The PCR index to use. See [docs/measured_boot.md](/docs/measured_boot.md). |
+| `WOLFBOOT_TPM_SEAL=1` | `WOLFBOOT_TPM_SEAL` | Enables support for sealing/unsealing based on PCR policy signed externally. |
+| `WOLFBOOT_TPM_SEAL_NV_BASE=0x01400300` | `WOLFBOOT_TPM_SEAL_NV_BASE` | To override the default sealed blob storage location in the platform hierarchy. |
 
 ## Root of Trust (ROT)
 
@@ -20,12 +23,140 @@ The design uses a platform NV handle that has been locked. The NV stores a hash
 
 ## Cryptographic offloading
 
-The RSA2048 and ECC256/384 bit verification can be offloaded to a TPM for code size reduction or performance improvement.
+The RSA2048 and ECC256/384 bit verification can be offloaded to a TPM for code size reduction or performance improvement. Enabled using `WOLFBOOT_TPM_VERIFY`
 
 ## Measured Boot
 
-The wolfBoot image is hashed and extended to the indicated PCR. This can be used later in the application to prove the boot process was not tampered with.
+The wolfBoot image is hashed and extended to the indicated PCR. This can be used later in the application to prove the boot process was not tampered with. Enabled with `WOLFBOOT_MEASURED_BOOT` and exposes API `wolfBoot_tpm2_extend`.
 
 ## Sealing and Unsealing a secret
 
-API's for this will be available soon.
+See the wolfTPM Sealing/Unsealing example [here](https://github.com/wolfSSL/wolfTPM/tree/secret_seal/examples/boot#secure-boot-encryption-key-storage)
+
+Known PCR values must be signed to seal/unseal a secret. The signature for the authorization policy resides in the signed header using the `--policy` argument.
+If a signed policy is not in the header then a value cannot be sealed. Instead the PCR(s) and a digest to sign will be printed for use with the sign tool.
+
+This exposes two new wolfBoot API's for sealing and unsealing data with blob stored to NV index:
+```c
+int wolfBoot_seal(struct wolfBoot_image* img, int index, const uint8_t* secret, int secret_sz);
+int wolfBoot_unseal(struct wolfBoot_image* img, int index, uint8_t* secret, int* secret_sz);
+```
+
+By default this index will be based on an NV Index at `(0x01400300 + index)`.
+The default NV base can be overridden with `WOLFBOOT_TPM_SEAL_NV_BASE`.
+
+
+### Testing seal/unseal with simulator
+
+```sh
+cp config/examples/sim-tpm-seal.config .config
+make keytools
+make tpmtools
+echo aaa > aaa.bin
+./tools/tpm/pcr_extend 0 aaa.bin
+./tools/tpm/policy_create -pcr=0
+# if ROT enabled
+./tools/tpm/rot -write
+make clean && make POLICY_FILE=policy.bin
+./wolfboot.elf get_version
+Simulator assigned ./internal_flash.dd to base 0x103797000
+Mfg IBM  (0), Vendor SW   TPM, Fw 8217.4131 (0x163636), FIPS 140-2 1, CC-EAL4 0
+Unlocking disk...
+Boot partition: 0x103817000
+Image size 54400
+Sealing 32 bytes
+11c6ac0ec972ae567c541750c6ecccd426f131dad3eeca5e6540d901d9f0c336
+Unsealed 32 bytes
+11c6ac0ec972ae567c541750c6ecccd426f131dad3eeca5e6540d901d9f0c336
+Boot partition: 0x103817000
+Image size 54400
+TPM Root of Trust valid (id 0)
+Simulator assigned ./internal_flash.dd to base 0x103962000
+1
+```
+
+### Testing seal/unseal on actual hardware
+
+1) Get the actual PCR digest for policy.
+2) Sign policy and include in firmware image header.
+
+
+#### Getting PCR values
+
+If no signed policy exists, then the seal function will generate and display the active PCR's, PCR digest and policy digest (to sign)
+
+```sh
+% make tpmtools
+% ./tools/tpm/rot -write
+% ./tools/tpm/pcr_reset 16
+% ./wolfboot.elf get_version
+Simulator assigned ./internal_flash.dd to base 0x101a64000
+Mfg IBM  (0), Vendor SW   TPM, Fw 8217.4131 (0x163636), FIPS 140-2 1, CC-EAL4 0
+Boot partition: 0x101ae4000
+Image size 57192
+Policy header not found!
+Generating policy based on active PCR's!
+Getting active PCR's (0-16)
+PCR 16 (counter 20)
+8f7ac1d5a5eac58a2305ca459f27c35705a9212c0fb2a9088b1df761f3d5f842
+Found 1 active PCR's (mask 0x00010000)
+PCR Digest (32 bytes):
+f84085631f85333ad0338b06c82f16888b7923abaccffb881d5416e389be256c
+PCR Mask (0x00010000) and PCR Policy Digest (36 bytes):
+0000010034ba061436aba2e9a167a1ee46af4a9578a8c6b9f71fdece21607a0cb40468ec
+Use this policy with the sign tool (--policy arg) or POLICY_FILE config
+Image policy signature missing!
+Boot partition: 0x101ae4000
+Image size 57192
+TPM Root of Trust valid (id 0)
+Simulator assigned ./internal_flash.dd to base 0x101c2f000
+1
+```
+
+The `0000010034ba061436aba2e9a167a1ee46af4a9578a8c6b9f71fdece21607a0cb40468ec` above can be directly used by the keytool. The
+
+`echo "0000010034ba061436aba2e9a167a1ee46af4a9578a8c6b9f71fdece21607a0cb40468ec" | xxd -r -p > policy.bin`
+
+OR use the `tools/tpm/policy_create` tool to generate a digest to be signed. The used PCR(s) must be set using "-pcr=#". The PCR digest can be supplied using "-pcrdigest=" or if not supplied will be read from the TPM directly.
+
+```sh
+% ./tools/tpm/policy_create -pcr=16 -pcrdigest=f84085631f85333ad0338b06c82f16888b7923abaccffb881d5416e389be256c -out=policy.bin
+# OR
+% ./tools/tpm/policy_create -pcrmask=0x00010000 -pcrdigest=f84085631f85333ad0338b06c82f16888b7923abaccffb881d5416e389be256c -out=policy.bin
+Policy Create Tool
+PCR Index(s) (SHA256): 16  (mask 0x00010000)
+PCR Digest (32 bytes):
+	f84085631f85333ad0338b06c82f16888b7923abaccffb881d5416e389be256c
+PCR Mask (0x00010000) and PCR Policy Digest (36 bytes):
+	0000010034ba061436aba2e9a167a1ee46af4a9578a8c6b9f71fdece21607a0cb40468ec
+Wrote 36 bytes to policy.bin
+```
+
+#### Signing Policy
+
+Building firmware with the policy digest to sign:
+
+```sh
+% make POLICY_FILE=policy.bin
+```
+
+OR manually using:
+
+```sh
+% ./tools/keytools/sign --ecc256 --policy policy.bin test-app/image.elf wolfboot_signing_private_key.der 1
+wolfBoot KeyTools (Compiled C version)
+wolfBoot version 1100000
+Update type:          Firmware
+Input image:          test-app/image.elf
+Selected cipher:      ECC256
+Selected hash  :      SHA256
+Public key:           wolfboot_signing_private_key.der
+Output  image:        test-app/image_v1_signed.bin
+Target partition id : 1
+image header size calculated at runtime (256 bytes)
+Calculating SHA256 digest...
+Signing the digest...
+Opening policy file policy.bin
+Signing the policy digest...
+Output image(s) successfully created.
+```