tpm2-store/src/main.rs

// Copyright 2020 Patrick Uiterwijk
//
// Licensed under the MIT license

use std::convert::{TryFrom, TryInto};
use std::env;
use std::io::{self, Read, Write};

use anyhow::{bail, Context, Error, Result};
use josekit::jwe::{alg::direct::DirectJweAlgorithm::Dir, enc::A256GCM};
use serde::{Deserialize, Serialize};
use tpm2_policy::TPMPolicyStep;
use tss_esapi::structures::SensitiveData;

mod cli;
mod tpm_objects;
mod utils;

use cli::TPM2Config;

fn perform_encrypt(cfg: TPM2Config, input: Vec<u8>) -> Result<()> {
    let key_type = match &cfg.key {
        None => "ecc",
        Some(key_type) => key_type,
    };
    let key_public = tpm_objects::get_key_public(key_type, cfg.get_name_hash_alg())?;

    let mut ctx = utils::get_tpm2_ctx()?;
    let key_handle = utils::get_tpm2_primary_key(&mut ctx, key_public)?;

    let policy_runner: TPMPolicyStep = TPMPolicyStep::try_from(&cfg)?;

    let pin_type = match policy_runner {
        TPMPolicyStep::NoStep => "tpm2",
        TPMPolicyStep::PCRs(_, _, _) => "tpm2",
        _ => "tpm2plus",
    };

    let (_, policy_digest) = policy_runner.send_policy(&mut ctx, true)?;

    let mut jwk = josekit::jwk::Jwk::generate_oct_key(32).context("Error generating random JWK")?;
    jwk.set_key_operations(vec!["encrypt", "decrypt"]);
    let jwk_str = serde_json::to_string(&jwk.as_ref())?;

    let public = tpm_objects::create_tpm2b_public_sealed_object(policy_digest)?.try_into()?;
    let jwk_str = SensitiveData::try_from(jwk_str.as_bytes().to_vec())?;
    let jwk_result = ctx.execute_with_nullauth_session(|ctx| {
        ctx.create(key_handle, public, None, Some(jwk_str), None, None)
    })?;

    let jwk_priv = tpm_objects::get_tpm2b_private(jwk_result.out_private.into())?;

    let jwk_pub = tpm_objects::get_tpm2b_public(jwk_result.out_public.try_into()?)?;

    let private_hdr = ClevisInner {
        pin: pin_type.to_string(),
        tpm2: Tpm2Inner {
            hash: cfg.hash.as_ref().unwrap_or(&"sha256".to_string()).clone(),
            key: key_type.to_string(),
            jwk_pub,
            jwk_priv,
            pcr_bank: cfg.pcr_bank.clone(),
            pcr_ids: cfg.get_pcr_ids_str(),
            policy_pubkey_path: cfg.policy_pubkey_path,
            policy_ref: cfg.policy_ref,
            policy_path: cfg.policy_path,
        },
    };

    let mut hdr = josekit::jwe::JweHeader::new();
    hdr.set_algorithm(Dir.name());
    hdr.set_content_encryption(A256GCM.name());
    hdr.set_claim(
        "clevis",
        Some(serde_json::value::to_value(private_hdr).context("Error serializing private header")?),
    )
    .context("Error adding clevis claim")?;

    let encrypter = Dir
        .encrypter_from_jwk(&jwk)
        .context("Error creating direct encrypter")?;
    let jwe_token = josekit::jwe::serialize_compact(&input, &hdr, &encrypter)
        .context("Error serializing JWE token")?;

    io::stdout().write_all(jwe_token.as_bytes())?;

    Ok(())
}

#[derive(Debug, Serialize, Deserialize, Clone)]
struct Tpm2Inner {
    hash: String,
    #[serde(
        deserialize_with = "utils::deserialize_as_base64_url_no_pad",
        serialize_with = "utils::serialize_as_base64_url_no_pad"
    )]
    jwk_priv: Vec<u8>,
    #[serde(
        deserialize_with = "utils::deserialize_as_base64_url_no_pad",
        serialize_with = "utils::serialize_as_base64_url_no_pad"
    )]
    jwk_pub: Vec<u8>,
    key: String,

    // PCR Binding may be specified, may not
    #[serde(skip_serializing_if = "Option::is_none")]
    pcr_bank: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pcr_ids: Option<String>,

    // Public key (in PEM format) for a wildcard policy that's OR'd with the PCR one
    #[serde(skip_serializing_if = "Option::is_none")]
    policy_pubkey_path: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    policy_ref: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    policy_path: Option<String>,
}

impl Tpm2Inner {
    fn get_pcr_ids(&self) -> Option<Vec<u64>> {
        Some(
            self.pcr_ids
                .as_ref()?
                .split(',')
                .map(|x| x.parse::<u64>().unwrap())
                .collect(),
        )
    }
}

impl TryFrom<&Tpm2Inner> for TPMPolicyStep {
    type Error = Error;

    fn try_from(cfg: &Tpm2Inner) -> Result<Self> {
        if cfg.pcr_ids.is_some() && cfg.policy_pubkey_path.is_some() {
            Ok(TPMPolicyStep::Or([
                Box::new(TPMPolicyStep::PCRs(
                    utils::get_hash_alg_from_name(cfg.pcr_bank.as_ref()),
                    cfg.get_pcr_ids().unwrap(),
                    Box::new(TPMPolicyStep::NoStep),
                )),
                Box::new(utils::get_authorized_policy_step(
                    cfg.policy_pubkey_path.as_ref().unwrap(),
                    &cfg.policy_path,
                    &cfg.policy_ref,
                )?),
                Box::new(TPMPolicyStep::NoStep),
                Box::new(TPMPolicyStep::NoStep),
                Box::new(TPMPolicyStep::NoStep),
                Box::new(TPMPolicyStep::NoStep),
                Box::new(TPMPolicyStep::NoStep),
                Box::new(TPMPolicyStep::NoStep),
            ]))
        } else if cfg.pcr_ids.is_some() {
            Ok(TPMPolicyStep::PCRs(
                utils::get_hash_alg_from_name(cfg.pcr_bank.as_ref()),
                cfg.get_pcr_ids().unwrap(),
                Box::new(TPMPolicyStep::NoStep),
            ))
        } else if cfg.policy_pubkey_path.is_some() {
            utils::get_authorized_policy_step(
                cfg.policy_pubkey_path.as_ref().unwrap(),
                &cfg.policy_path,
                &cfg.policy_ref,
            )
        } else {
            Ok(TPMPolicyStep::NoStep)
        }
    }
}

#[derive(Debug, Serialize, Deserialize, Clone)]
struct ClevisInner {
    pin: String,
    tpm2: Tpm2Inner,
}

fn perform_decrypt(input: Vec<u8>) -> Result<()> {
    let input = String::from_utf8(input).context("Error reading input")?;
    let hdr = josekit::jwt::decode_header(&input).context("Error decoding header")?;
    let hdr_clevis = hdr.claim("clevis").context("Error getting clevis claim")?;
    let hdr_clevis: ClevisInner =
        serde_json::from_value(hdr_clevis.clone()).context("Error deserializing clevis header")?;

    if hdr_clevis.pin != "tpm2" && hdr_clevis.pin != "tpm2plus" {
        bail!("JWE pin mismatch");
    }

    let jwkpub = tpm_objects::build_tpm2b_public(&hdr_clevis.tpm2.jwk_pub)?.try_into()?;
    let jwkpriv = tpm_objects::build_tpm2b_private(&hdr_clevis.tpm2.jwk_priv)?;

    let policy = TPMPolicyStep::try_from(&hdr_clevis.tpm2)?;

    let name_alg = crate::utils::get_hash_alg_from_name(Some(&hdr_clevis.tpm2.hash));
    let key_public = tpm_objects::get_key_public(hdr_clevis.tpm2.key.as_str(), name_alg)?;

    let mut ctx = utils::get_tpm2_ctx()?;
    let key_handle = utils::get_tpm2_primary_key(&mut ctx, key_public)?;

    let key =
        ctx.execute_with_nullauth_session(|ctx| ctx.load(key_handle, jwkpriv.try_into()?, jwkpub))?;

    let (policy_session, _) = policy.send_policy(&mut ctx, false)?;

    let unsealed = ctx.execute_with_session(policy_session, |ctx| ctx.unseal(key.into()))?;
    let unsealed = &unsealed.value();
    let mut jwk = josekit::jwk::Jwk::from_bytes(unsealed).context("Error unmarshaling JWK")?;
    jwk.set_parameter("alg", None)
        .context("Error removing the alg parameter")?;
    let decrypter = Dir
        .decrypter_from_jwk(&jwk)
        .context("Error creating decrypter")?;

    let (payload, _) =
        josekit::jwe::deserialize_compact(&input, &decrypter).context("Error decrypting JWE")?;

    io::stdout().write_all(&payload)?;

    Ok(())
}

fn print_summary() {
    println!("Encrypts using a TPM2.0 chip binding policy");
}

fn print_help() {
    eprintln!(
        "
Usage (encryption): clevis encrypt tpm2 CONFIG < PLAINTEXT > JWE
Usage (decryption): clevis decrypt tpm2 CONFIG < JWE > PLAINTEXT

Encrypts or decrypts using a TPM2.0 chip binding policy

This command uses the following configuration properties:

  hash: <string>  Hash algorithm used in the computation of the object name (default: sha256)

  key: <string>  Algorithm type for the generated key (options: ecc, rsa; default: ecc)

  pcr_bank: <string>  PCR algorithm bank to use for policy (default: sha256)

  pcr_ids: <string>  PCR list used for policy. If not present, no PCR policy is used

  use_policy: <bool>  Whether to use a policy

  policy_ref: <string>  Reference to search for in signed policy file (default: {})

  > For policies, the path is {}, and the public key is at {}
",
        cli::DEFAULT_POLICY_REF,
        cli::DEFAULT_POLICY_PATH,
        cli::DEFAULT_PUBKEY_PATH,
    );

    std::process::exit(2);
}

fn main() -> Result<()> {
    let args: Vec<String> = env::args().collect();
    let (mode, cfg) = match cli::get_mode_and_cfg(&args) {
        Err(e) => {
            eprintln!("Error during parsing operation: {}", e);
            std::process::exit(1);
        }
        Ok((mode, cfg)) => (mode, cfg),
    };

    match mode {
        cli::ActionMode::Summary => {
            print_summary();
            return Ok(());
        }
        cli::ActionMode::Help => {
            print_help();
            return Ok(());
        }
        _ => {}
    };

    let mut input = Vec::new();
    if let Err(e) = io::stdin().read_to_end(&mut input) {
        eprintln!("Error getting input token: {}", e);
        std::process::exit(1);
    }

    match mode {
        cli::ActionMode::Encrypt => perform_encrypt(cfg.unwrap(), input),
        cli::ActionMode::Decrypt => perform_decrypt(input),
        cli::ActionMode::Summary => unreachable!(),
        cli::ActionMode::Help => unreachable!(),
    }
}