Detect IDevID/IAK template from certificates

keylime-agent.conf

@@ -228,19 +228,21 @@ tpm_signing_alg = "rsassa"
 ek_handle = "generate"
 
 # Enable IDevID and IAK usage and set their algorithms.
-# Choosing a template will override the name and asymmetric algorithm choices.
+# By default the template will be detected automatically from the certificates. This will happen if iak_idevid_template is left empty or set as "default" or "detect".
+# Choosing a template will override the name and asymmetric algorithm choices. To use these choices, set iak_idevid_template to "manual"
 # Templates are specified in the TCG document found here, section 7.3.4: 
 # https://trustedcomputinggroup.org/wp-content/uploads/TPM-2p0-Keys-for-Device-Identity-and-Attestation_v1_r12_pub10082021.pdf
 #
 # Accepted values:
+# iak_idevid_template:        default, detect, H-1, H-2, H-3, H-4, H-5, manual
 # iak_idevid_asymmetric_alg:   rsa, ecc
 # iak_idevid_name_alg:        sha256, sm3_256, sha384, sha512
-# iak_idevid_template:        H-1, H-2, H-3, H-4, H-5
-# Leave template as "" in order to use asymmetric and name algorithm options
 enable_iak_idevid = false
+iak_idevid_template = "detect"
+# In order for these values to be used, set the iak_idevid_template option to manual
 iak_idevid_asymmetric_alg = "rsa"
 iak_idevid_name_alg = "sha256"
-iak_idevid_template = "H-1"
+
 
 # The name of the file containing the X509 IAK certificate.
 # If set as "default", the "iak-cert.crt" value is used

keylime-agent/src/crypto.rs

@@ -137,6 +137,36 @@
     }
 }
 
+/// Detect a template from a certificate
+/// Templates defined in: TPM 2.0 Keys for Device Identity and Attestation at https://trustedcomputinggroup.org/wp-content/uploads/TPM-2p0-Keys-for-Device-Identity-and-Attestation_v1_r12_pub10082021.pdf
+pub(crate) fn match_cert_to_template(cert: &X509) -> Result<String> {
+    // Id:RSA_PSS only added in rust-openssl from v0.10.59; remove this let and use Id::RSA_PSS after update
+    // Id taken from https://boringssl.googlesource.com/boringssl/+/refs/heads/master/include/openssl/nid.h#4039
+    let id_rsa_pss: Id = Id::from_raw(912);
+    match cert.public_key()?.id() {
+        Id::RSA => match cert.public_key()?.bits() {
+            2048 => Ok("H-1".to_string()),
+            _ => Ok("".to_string()),
+        },
+        cert_id if cert_id == id_rsa_pss => match cert.public_key()?.bits() {
+            2048 => Ok("H-1".to_string()),
+            _ => Ok("".to_string()),
+        },
+        Id::EC => match cert.public_key()?.bits() {
+            256 => match cert.public_key()?.ec_key()?.group().curve_name() {
+                Some(Nid::SECP256K1) => Ok("H-2".to_string()),
+                _ => Ok("H-5".to_string()),
+            },
+            384 => Ok("H-3".to_string()),
+            521 => Ok("H-4".to_string()),
+            _ => Ok("".to_string()),
+        },
+        _ => Err(Error::Other(
+            "Certificate does not seem to have an RSA or EC key".to_string(),
+        )),
+    }
+}
+
 /// Read a PEM file and returns the public and private keys
 pub(crate) fn load_key_pair(
     key_path: &Path,

keylime-agent/src/main.rs

@@ -277,29 +277,9 @@ async fn main() -> Result<()> {
         config.agent.tpm_signing_alg.as_ref(),
     )?;
 
-    let (asym_alg, name_alg) = tpm::get_idevid_template(
-        config.agent.iak_idevid_template.as_str(),
-        config.agent.iak_idevid_asymmetric_alg.as_str(),
-        config.agent.iak_idevid_name_alg.as_str(),
-    )?;
-
-    let (iak, idevid) = if config.agent.enable_iak_idevid {
-        let idevid = ctx.create_idevid(asym_alg, name_alg)?;
-        info!("IDevID created.");
-        // Flush after creating to make room for AK and EK and IAK
-        ctx.as_mut().flush_context(idevid.handle.into())?;
-        let iak = ctx.create_iak(asym_alg, name_alg)?;
-        info!("IAK created.");
-        (Some(iak), Some(idevid))
-    } else {
-        (None, None)
-    };
-
     let iak_cert: Option<X509>;
     let idevid_cert: Option<X509>;
     // Attempt to load the IAK and IDevID certificates
-    // Check the certificates contain the keys that have been regenerated by the TPM
-    // If they do not there is likely a configuration issue where the template has been set to the wrong value
     if config.agent.enable_iak_idevid {
         iak_cert = match config.agent.iak_cert.as_ref() {
             "" => {
@@ -317,19 +297,7 @@ async fn main() -> Result<()> {
                         Ok(cert) => cert,
                         Err(error) => crypto::load_x509_pem(iak_path)?,
                     };
-                    if crypto::check_x509_key(
-                        &iakcert,
-                        iak.clone()
-                            .expect(
-                                "IAK could not be used in cert key check.",
-                            )
-                            .public,
-                    )? {
-                        Some(iakcert)
-                    } else {
-                        error!("IAK template does not match certificate. Check template in configuration.");
-                        return Err(Error::Configuration("IAK template does not match certificate. Check template in configuration.".to_string()));
-                    }
+                    Some(iakcert)
                 } else {
                     debug!("Can not find IAK certificate");
                     None
@@ -352,20 +320,7 @@ async fn main() -> Result<()> {
                         Ok(cert) => cert,
                         Err(error) => crypto::load_x509_pem(idevid_path)?,
                     };
-                    if crypto::check_x509_key(
-                        &idevcert,
-                        idevid
-                            .clone()
-                            .expect(
-                                "IDevID could not be used in cert key check.",
-                            )
-                            .public,
-                    )? {
-                        Some(idevcert)
-                    } else {
-                        error!("IDevID template does not match certificate. Check template in configuration.");
-                        return Err(Error::Configuration("IDevID template does not match certificate. Check template in configuration.".to_string()));
-                    }
+                    Some(idevcert)
                 } else {
                     debug!("Can not find IDevID certificate");
                     None
@@ -376,6 +331,54 @@ async fn main() -> Result<()> {
         iak_cert = None;
         idevid_cert = None;
     }
+    /// Regenerate the IAK and IDevID and check that the keys match the certificates that have been loaded
+    let (iak, idevid) = if config.agent.enable_iak_idevid {
+        let (asym_alg, name_alg) = tpm::get_idevid_template(
+            &crypto::match_cert_to_template(
+                &iak_cert.clone().ok_or(Error::Other(
+                    "IAK/IDevID enabled but cert could not be used"
+                        .to_string(),
+                ))?,
+            )?,
+            config.agent.iak_idevid_template.as_str(),
+            config.agent.iak_idevid_asymmetric_alg.as_str(),
+            config.agent.iak_idevid_name_alg.as_str(),
+        )?;
+
+        let idevid = ctx.create_idevid(asym_alg, name_alg)?;
+        info!("IDevID created.");
+        // Flush after creating to make room for AK and EK and IAK
+        ctx.as_mut().flush_context(idevid.handle.into())?;
+        if crypto::check_x509_key(
+            &idevid_cert.clone().ok_or(Error::Other(
+                "IAK/IDevID enabled but cert could not be used".to_string(),
+            ))?,
+            idevid.clone().public,
+        )? {
+            info!("Regenerated IDevID matches certificate.");
+        } else {
+            error!("IDevID template does not match certificate. Check template in configuration.");
+            return Err(Error::Configuration("IDevID template does not match certificate. Check template in configuration.".to_string()));
+        }
+
+        let iak = ctx.create_iak(asym_alg, name_alg)?;
+        info!("IAK created.");
+        if crypto::check_x509_key(
+            &iak_cert.clone().ok_or(Error::Other(
+                "IAK/IDevID enabled but cert could not be used".to_string(),
+            ))?,
+            iak.clone().public,
+        )? {
+            info!("Regenerated IAK matches certificate.");
+        } else {
+            error!("IAK template does not match certificate. Check template in configuration.");
+            return Err(Error::Configuration("IAK template does not match certificate. Check template in configuration.".to_string()));
+        }
+
+        (Some(iak), Some(idevid))
+    } else {
+        (None, None)
+    };
 
     // Gather EK values and certs
     let ek_result = match config.agent.ek_handle.as_ref() {

keylime/src/tpm.rs

@@ -105,15 +105,24 @@
 ];
 const UNIQUE_IAK: [u8; 3] = [0x49, 0x41, 0x4b];
 
-/// Return the asymmetric and name algorithms, either by matching to a template or using the user specified algorithms if no template is set
+/// Return the asymmetric and name algorithms, either by matching to a template or using the user specified algorithms
+/// If the template config option is set to "", "detect" or "default", the template will be matched to the certs
+/// If a template has been specified, that will be used
+/// If the option has been set to "manual", or some other not-empty string, the user specified algorithms will be used
 pub fn get_idevid_template(
+    detect_str: &str,
     template_str: &str,
     asym_alg_str: &str,
     name_alg_str: &str,
 ) -> std::result::Result<
     (AsymmetricAlgorithm, HashingAlgorithm),
     AlgorithmError,
 > {
+    let template_str = if ["", "detect", "default"].contains(&template_str) {
+        detect_str
+    } else {
+        template_str
+    };
     let (asym_alg, name_alg) = match template_str {
         "H-1" => (AsymmetricAlgorithm::Rsa, HashingAlgorithm::Sha256),
         "H-2" => (AsymmetricAlgorithm::Ecc, HashingAlgorithm::Sha256),