[PATCH v2 18/21] tpm: Pass migration key passphrase via fd to swtpm

[Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx>]

This patch now passes the passphrase as a migration key to swtpm.
This now encrypts the state of the TPM while a VM is migrated between
hosts or when suspended into a file. Since the migration key secret
is the same as the state encryption secret, this now requires that
the migration destination host has the same secret value.

Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
---
 src/qemu/qemu_tpm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_tpm.c b/src/qemu/qemu_tpm.c
index a8cec0d873..7362df8b4d 100644
--- a/src/qemu/qemu_tpm.c
+++ b/src/qemu/qemu_tpm.c
@@ -576,6 +576,7 @@ qemuTPMEmulatorBuildCommand(virDomainTPMDefPtr tpm,
     bool created = false;
     char *pidfile;
     VIR_AUTOCLOSE pwdfile_fd = -1;
+    VIR_AUTOCLOSE migpwdfile_fd = -1;
 
     if (qemuTPMCreateEmulatorStorage(tpm->data.emulator.storagepath,
                                      &created, swtpm_user, swtpm_group) < 0)
@@ -637,7 +638,9 @@ qemuTPMEmulatorBuildCommand(virDomainTPMDefPtr tpm,
         }
 
         pwdfile_fd = qemuTPMSetupEncryption(tpm->data.emulator.encryption, cmd);
-        if (pwdfile_fd < 0)
+        migpwdfile_fd = qemuTPMSetupEncryption(tpm->data.emulator.encryption,
+                                               cmd);
+        if (pwdfile_fd < 0 || migpwdfile_fd < 0)
             goto error;
 
         virCommandAddArg(cmd, "--key");
@@ -645,6 +648,12 @@ qemuTPMEmulatorBuildCommand(virDomainTPMDefPtr tpm,
                                pwdfile_fd);
         virCommandPassFD(cmd, pwdfile_fd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
         pwdfile_fd = -1;
+
+        virCommandAddArg(cmd, "--migration-key");
+        virCommandAddArgFormat(cmd, "pwdfd=%d,mode=aes-256-cbc,kdf=pbkdf2",
+                               migpwdfile_fd);
+        virCommandPassFD(cmd, migpwdfile_fd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+        migpwdfile_fd = -1;
     }
 
     return cmd;
-- 
2.20.1

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