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From 5b20ba25259da453a2aac5e65978a11bc2d048ed Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Tue, 15 Nov 2022 23:01:04 +0100
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Subject: [PATCH] tpm2: add some extra validation of device string before using
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it
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Let's add some extra validation before constructing and using the .so
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name to load. This isn't really security sensitive, given that we
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used secure_getenv() to get the device string (and it thus should have
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been come from a trusted source) but let's better be safe than sorry.
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(cherry picked from commit 50a085143fa8f5dd6b6b3cef8a6ea2ec7c53ed0d)
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Related: #2138081
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---
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src/shared/tpm2-util.c | 16 ++++++++++++++--
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1 file changed, 14 insertions(+), 2 deletions(-)
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diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
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index 9d73316146..4d0df944a9 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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@@ -174,15 +174,27 @@ int tpm2_context_init(const char *device, struct tpm2_context *ret) {
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param = strchr(device, ':');
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if (param) {
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+ /* Syntax #1: Pair of driver string and arbitrary parameter */
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driver = strndupa_safe(device, param - device);
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+ if (isempty(driver))
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+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "TPM2 driver name is empty, refusing.");
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+
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param++;
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- } else {
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+ } else if (path_is_absolute(device) && path_is_valid(device)) {
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+ /* Syntax #2: TPM device node */
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driver = "device";
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param = device;
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- }
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+ } else
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+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid TPM2 driver string, refusing.");
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+
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+ log_debug("Using TPM2 TCTI driver '%s' with device '%s'.", driver, param);
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fn = strjoina("libtss2-tcti-", driver, ".so.0");
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+ /* Better safe than sorry, let's refuse strings that cannot possibly be valid driver early, before going to disk. */
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+ if (!filename_is_valid(fn))
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+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "TPM2 driver name '%s' not valid, refusing.", driver);
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+
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dl = dlopen(fn, RTLD_NOW);
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if (!dl)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "Failed to load %s: %s", fn, dlerror());
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