This is a proof-of-concept implementation of the "Challenge/Response Remote Attestation" interaction model of the IETF RATS Reference Interaction Models for Remote Attestation Procedures using TPM 2.0. The IETF Remote ATtestation ProcedureS (RATS) working group standardizes formats for describing assertions/claims about system components and associated evidence; and procedures and protocols to convey these assertions/claims to relying parties. Given the security and privacy sensitive nature of these assertions/claims, the working group specifies approaches to protect this exchanged data.
This proof-of-concept implementation realizes the Attesting Computing Environment—a Computing Environment capable of monitoring and attesting a target Computing Environment—as well as the target Computing Environment itself, as described in the RATS Architecture.
Next steps:
- Block-wise CoAP data transfers
- Verify TPM Quote with mbedtls using TPM public key
- Use non-zero reference PCRs
- Introduce a Make flag which disables console output (useful for embedded systems and firmware)
- "Extended" TPM Quote using TPM audit session(s) and TPM PCR Read operations
- Make CHARRA a library (
libcharra
) and make attester and verifier example code inexample
folder
The following diagram shows the protocol flow of the CHARRA attestation process.
.----------. .----------.
| Attester | | Verifier |
'----------' '----------'
| |
| <---------- requestAttestation(nonce, keyID, pcrSelection) |
| |
tpmQuote(nonce, pcrSelection) |
| => evidence |
| |
| evidence ------------------------------------------------> |
| |
| appraiseEvidence(evidence, nonce, referencePcrs)
| attestationResult <= |
| |
CHARRA comes with a Docker test environment and Docker helper scripts to build and run it in Docker. It is also possible to build and run CHARRA manually.
-
Install Docker.
-
Build Docker image:
./docker/build.sh
-
Run Docker image:
./docker/run.sh
-
Compile CHARRA (inside container):
cd charra/ make -j
-
Run CHARRA (inside container):
(bin/attester &); sleep .2 ; bin/verifier ; sleep 1 ; pkill attester
If you see "ATTESTATION SUCCESSFUL" you're done. Congratz :-D
The Dockerfile
provides details on installing all dependencies and should be considered authoritative over this.
-
Install all dependencies that are needed for the TPM2-TSS.
-
Install libCoAP:
git clone --depth=1 --recursive -b 'develop' \ 'https://github.com/obgm/libcoap.git' /tmp/libcoap cd /tmp/libcoap ./autogen.sh ./configure --disable-tests --disable-documentation --disable-manpages --disable-dtls --disable-shared --enable-fast-install make -j make install
Make sure that you do not have
libcoap-1-0-dev
installed, as the headers might conflict. -
Install mbedtls:
git clone --depth=1 --recursive -b 'development' \ 'https://github.com/ARMmbed/mbedtls.git' /tmp/mbedtls cd /tmp/mbedtls make -j lib SHARED=true make install
-
Install QCBOR:
git clone --depth=1 --recursive -b 'master' \ 'https://github.com/laurencelundblade/QCBOR.git' /tmp/qcbor cd /tmp/qcbor make -j all so make install install_so
-
Install t_cose:
git clone --depth=1 --recursive -b 'master' \ 'https://github.com/laurencelundblade/t_cose.git' /tmp/t_cose cd /tmp/t_cose make -j -f Makefile.psa libt_cose.a libt_cose.so make -f Makefile.psa install install_so
-
Compile programs:
make -j
-
Download and install IBM's TPM 2.0 Simulator.
-
Download and install the TPM2 Tools.
-
Start the TPM Simulator (and remove the state file
NVChip
):(cd /tmp ; pkill tpm_server ; rm -f NVChip; /usr/local/bin/tpm_server > /dev/null &)
-
Send TPM startup command:
/usr/local/bin/tpm2_startup -Tmssim --clear
-
Run Attester and Verifier:
(bin/attester &); sleep .2 ; bin/verifier ; sleep 1 ; pkill -f bin/attester
If you see "ATTESTATION SUCCESSFUL" you're done. Congratz :-D
-
Clang
scan-build
:make clean ; scan-build make
-
Valgrind:
(valgrind --leak-check=full \ --show-leak-kinds=all -v \ bin/attester \ 2> attester-valgrind-stderr.log &); \ sleep .2 ; \ (valgrind --leak-check=full \ --show-leak-kinds=all -v \ bin/verifier\ 2> verifier-valgrind-stderr.log) ;\ sleep 1 ; \ pkill bin/attester