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From 31f0c1b06bfd90d52009b59b9a4bf26c297790a7 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Mon, 14 Nov 2022 17:26:49 +0100
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Subject: [PATCH] tpm2-util: force default TCTI to be "device" with parameter
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 "/dev/tpmrm0"
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Apparently some distros default to tss-abmrd. Let's bypass that and
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always go to the kernel resource manager.
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abmrd cannot really work for us, since we want to access the TPM already
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in earliest boot i.e. in environments the abmrd service is not available
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in.
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Fixes: #25352
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(cherry picked from commit 34906680afe60d724ea435b79b9b830a4bf2e7e9)
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Related: #2138081
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---
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 src/shared/tpm2-util.c | 13 ++++++++++++-
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 1 file changed, 12 insertions(+), 1 deletion(-)
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diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
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index 65e8d48347..9d73316146 100644
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--- a/src/shared/tpm2-util.c
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+++ b/src/shared/tpm2-util.c
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@@ -152,8 +152,19 @@ int tpm2_context_init(const char *device, struct tpm2_context *ret) {
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         if (r < 0)
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                 return log_error_errno(r, "TPM2 support not installed: %m");
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-        if (!device)
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+        if (!device) {
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                 device = secure_getenv("SYSTEMD_TPM2_DEVICE");
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+                if (device)
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+                        /* Setting the env var to an empty string forces tpm2-tss' own device picking
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+                         * logic to be used. */
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+                        device = empty_to_null(device);
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+                else
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+                        /* If nothing was specified explicitly, we'll use a hardcoded default: the "device" tcti
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+                         * driver and the "/dev/tpmrm0" device. We do this since on some distributions the tpm2-abrmd
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+                         * might be used and we really don't want that, since it is a system service and that creates
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+                         * various ordering issues/deadlocks during early boot. */
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+                        device = "device:/dev/tpmrm0";
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+        }
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         if (device) {
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                 const char *param, *driver, *fn;