dissect-image: Various fixes w.r.t verity signature checking (#44386)

src/shared/dissect-image.c

@@ -1062,7 +1062,7 @@ static int dissect_image_from_unpartitioned(
         m->verity_ready = verity_settings_data_covers(verity, PARTITION_ROOT);
 
         m->has_verity_sig = false; /* signature not embedded, must be specified */
-        m->verity_sig_ready = m->verity_ready && iovec_is_set(&verity->root_hash);
+        m->verity_sig_ready = m->verity_ready && iovec_is_set(&verity->root_hash_sig);
 
         if (uuid)
                 m->image_uuid = *uuid;
@@ -3549,13 +3549,11 @@ static int do_crypt_activate_verity(
                                 return r < 0 ? r : -EDESTADDRREQ;
 
                         log_debug("Activation of signed Verity volume without validating signature is permitted by policy. Continuing.");
-                } else
+                        measure_signature = false;
+                } else {
                         log_debug("Verity activation via userspace signature logic worked, activating by root hash.");
-
-                /* Otherwise let's see what signature-less activation results in. */
-
-                measure_signature = true;
-
+                        measure_signature = true;
+                }
         } else if (!FLAGS_SET(policy_flags, PARTITION_POLICY_VERITY))
                 return log_debug_errno(SYNTHETIC_ERRNO(ERFKILL),
                                        "No-signature activation of Verity volume not allowed by policy, refusing.");
@@ -5487,7 +5485,6 @@ int mountfsd_mount_image_fd(
         _cleanup_(dissected_image_unrefp) DissectedImage *di = NULL;
         _cleanup_close_ int verity_data_fd = -EBADF;
         _cleanup_free_ char *ps = NULL;
-        const char *error_id;
         int r;
 
         assert(image_fd >= 0);
@@ -5567,7 +5564,8 @@ int mountfsd_mount_image_fd(
         }
 
         sd_json_variant *reply = NULL;
-        r = varlink_callbo_and_log(
+        const char *error_id = NULL;
+        r = sd_varlink_callbo(
                         vl,
                         "io.systemd.MountFileSystem.MountImage",
                         &reply,
@@ -5585,7 +5583,23 @@ int mountfsd_mount_image_fd(
                         SD_JSON_BUILD_PAIR_CONDITION(verity && iovec_is_set(&verity->root_hash_sig), "verityRootHashSignature", JSON_BUILD_IOVEC_BASE64(&verity->root_hash_sig)),
                         SD_JSON_BUILD_PAIR_BOOLEAN("allowInteractiveAuthentication", FLAGS_SET(flags, DISSECT_IMAGE_ALLOW_INTERACTIVE_AUTH)));
         if (r < 0)
-                return r;
+                return log_error_errno(r, "Failed to issue MountImage() varlink call: %m");
+        if (error_id) {
+                /* Return the same errors as dissected_image_decrypt(), so that callers can report them the
+                 * same way, whether they mount the image themselves or through mountfsd. */
+                if (streq(error_id, "io.systemd.MountFileSystem.KeyNotFound"))
+                        return log_error_errno(SYNTHETIC_ERRNO(EDESTADDRREQ),
+                                               "mountfsd refused the image, because no trusted key validates its signature.");
+                if (streq(error_id, "io.systemd.MountFileSystem.DeniedByImagePolicy"))
+                        return log_error_errno(SYNTHETIC_ERRNO(ERFKILL),
+                                               "mountfsd refused the image, because the image policy doesn't permit it.");
+
+                r = sd_varlink_error_to_errno(error_id, reply);
+                if (r != -EBADR)
+                        return log_error_errno(r, "Failed to issue MountImage() varlink call: %m");
+
+                return log_error_errno(r, "Failed to issue MountImage() varlink call: %s", error_id);
+        }
 
         r = sd_json_dispatch(reply, dispatch_table, SD_JSON_ALLOW_EXTENSIONS, &p);
         if (r < 0)
@@ -5741,12 +5755,10 @@ int mountfsd_mount_directory_fd(
         }
 
         sd_json_variant *reply = NULL;
-        const char *error_id = NULL;
         r = varlink_callbo_and_log(
                         vl,
                         "io.systemd.MountFileSystem.MountDirectory",
                         &reply,
-                        &error_id,
                         SD_JSON_BUILD_PAIR_UNSIGNED("directoryFileDescriptor", 0),
                         SD_JSON_BUILD_PAIR_CONDITION(userns_fd >= 0, "userNamespaceFileDescriptor", SD_JSON_BUILD_UNSIGNED(1)),
                         SD_JSON_BUILD_PAIR_BOOLEAN("readOnly", FLAGS_SET(flags, DISSECT_IMAGE_MOUNT_READ_ONLY)),

src/shared/pcrextend-util.c

@@ -75,7 +75,7 @@ int pcrextend_pcr_now(unsigned pcr, const char *word, const struct iovec *secret
         log_debug("Measurement of '%s' into PCR %u completed.", word, pcr);
         return 1;
 #else
-        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "TPM2 support disabled, not measuring.");
+        return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "TPM2 support disabled, not measuring.");
 #endif
 }
 
@@ -116,7 +116,7 @@ int pcrextend_nvpcr_now(const char *nvpcr, const char *word, const char *event)
         log_debug("Measurement of '%s' into NvPCR '%s' completed.", word, nvpcr);
         return 1;
 #else
-        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "TPM2 support disabled, not measuring.");
+        return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "TPM2 support disabled, not measuring.");
 #endif
 }
 

test/units/TEST-70-TPM2.nvpcr.sh

@@ -26,7 +26,7 @@ at_exit() {
     mv -f /run/systemd/tpm2-pcr-signature.json.bak /run/systemd/tpm2-pcr-signature.json
     rm -f /tmp/tpm2-pcr-private-key.pem /tmp/tpm2-pcr-public-key.pem /tmp/tpm2-pcr-signature.json.valid
     rm -rf /run/nvpcr /tmp/nvpcr
-    rm -f /var/tmp/nvpcr.raw /run/verity.d/test-70-nvpcr.crt
+    rm -f /var/tmp/nvpcr.raw /var/tmp/nvpcr-untrusted.raw /run/verity.d/test-70-nvpcr.crt
     rm -f /run/systemd/nvpcr/test.auth /run/systemd/nvpcr/test2.auth /run/systemd/nvpcr/aaa.auth /run/systemd/nvpcr/zzz.auth /run/systemd/nvpcr/unauth.auth /run/systemd/nvpcr/unauth2.auth
     rm -f /tmp/test.policy
     rm -f /run/systemd/tpm2-nv-space-exhausted-orderly
@@ -368,17 +368,9 @@ fi
 mkdir -p /tmp/nvpcr/tree
 touch /tmp/nvpcr/tree/file
 
-if machine_supports_verity_keyring; then
-    SYSTEMD_REPART_OVERRIDE_FSTYPE=squashfs \
-        systemd-repart -P \
-                    -s /tmp/nvpcr/tree \
-                    --certificate=/usr/share/mkosi.crt \
-                    --private-key=/usr/share/mkosi.key \
-                    /var/tmp/nvpcr.raw
-else
-    OPENSSL_CONFIG="/tmp/nvpcr/opensslconfig"
-    # Unfortunately OpenSSL insists on reading some config file, hence provide one with mostly placeholder contents
-    cat >"${OPENSSL_CONFIG:?}" <<EOF
+OPENSSL_CONFIG="/tmp/nvpcr/opensslconfig"
+# Unfortunately OpenSSL insists on reading some config file, hence provide one with mostly placeholder contents
+cat >"${OPENSSL_CONFIG:?}" <<EOF
 [ req ]
 prompt = no
 distinguished_name = req_distinguished_name
@@ -393,6 +385,14 @@ CN = Common Name
 emailAddress = test@email.com
 EOF
 
+if machine_supports_verity_keyring; then
+    SYSTEMD_REPART_OVERRIDE_FSTYPE=squashfs \
+        systemd-repart -P \
+                    -s /tmp/nvpcr/tree \
+                    --certificate=/usr/share/mkosi.crt \
+                    --private-key=/usr/share/mkosi.key \
+                    /var/tmp/nvpcr.raw
+else
     openssl req -config "$OPENSSL_CONFIG" -subj="/CN=waldo" \
                 -x509 -sha256 -nodes -days 365 -newkey rsa:4096 \
                 -keyout /tmp/nvpcr/test-70-nvpcr.key -out /tmp/nvpcr/test-70-nvpcr.crt
@@ -412,5 +412,23 @@ cp /run/log/systemd/tpm2-measure.log /tmp/nvpcr/log-before
 
 systemd-dissect --image-policy='root=signed:=absent+unused' --mtree /var/tmp/nvpcr.raw
 
+# The record of a validated signature ends with the serial and the issuer of the signer.
 set +o pipefail
-diff /tmp/nvpcr/log-before /run/log/systemd/tpm2-measure.log | grep -F '"content":{"nvIndexName":"verity","string":"verity:'
+diff /tmp/nvpcr/log-before /run/log/systemd/tpm2-measure.log | grep -E '"content":\{"nvIndexName":"verity","string":"verity:[^"]*:[0-9a-f]+:[0-9a-f]+/[^"]+"'
+
+# If neither the kernel nor userspace can validate the signature, only the root hash is measured, without
+# the signer. Neither the kernel keyring nor /run/verity.d/ contains the certificate of the untrusted key.
+openssl req -config "$OPENSSL_CONFIG" -subj="/CN=untrusted" \
+            -x509 -sha256 -nodes -days 365 -newkey rsa:4096 \
+            -keyout /tmp/nvpcr/untrusted.key -out /tmp/nvpcr/untrusted.crt
+
+SYSTEMD_REPART_OVERRIDE_FSTYPE=squashfs \
+    systemd-repart -P \
+                -s /tmp/nvpcr/tree \
+                --certificate=/tmp/nvpcr/untrusted.crt \
+                --private-key=/tmp/nvpcr/untrusted.key \
+                /var/tmp/nvpcr-untrusted.raw
+
+cp /run/log/systemd/tpm2-measure.log /tmp/nvpcr/log-before
+systemd-dissect --image-policy='root=verity+signed:=absent+unused' --mtree /var/tmp/nvpcr-untrusted.raw
+diff /tmp/nvpcr/log-before /run/log/systemd/tpm2-measure.log | grep -E '"content":\{"nvIndexName":"verity","string":"verity:[^"]*:"'