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tpm2: add some extra validation of device string before using it

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Let's add some extra validation before constructing and using the .so
name to load. This isn't really security sensitive, given that we
used secure_getenv() to get the device string (and it thus should have
been come from a trusted source) but let's better be safe than sorry.

(cherry picked from commit 50a085143fa8f5dd6b6b3cef8a6ea2ec7c53ed0d)
(cherry picked from commit 542dbc623e00d55224db30280d90f48d51cdf8f8)
This commit is contained in:
Lennart Poettering 2022-11-15 23:01:04 +01:00 committed by Zbigniew Jędrzejewski-Szmek
parent e1248c8474
commit ca5b66b5a3
1 changed files with 14 additions and 2 deletions
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16
src/shared/tpm2-util.c
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@ -172,15 +172,27 @@ static int tpm2_init(const char *device, struct tpm2_context *ret) {
param = strchr(device, ':');
if (param) {
/* Syntax #1: Pair of driver string and arbitrary parameter */
driver = strndupa_safe(device, param - device);
if (isempty(driver))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "TPM2 driver name is empty, refusing.");
param++;
} else {
} else if (path_is_absolute(device) && path_is_valid(device)) {
/* Syntax #2: TPM device node */
driver = "device";
param = device;
}
} else
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid TPM2 driver string, refusing.");
log_debug("Using TPM2 TCTI driver '%s' with device '%s'.", driver, param);
fn = strjoina("libtss2-tcti-", driver, ".so.0");
/* Better safe than sorry, let's refuse strings that cannot possibly be valid driver early, before going to disk. */
if (!filename_is_valid(fn))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "TPM2 driver name '%s' not valid, refusing.", driver);
dl = dlopen(fn, RTLD_NOW);
if (!dl)
return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "Failed to load %s: %s", fn, dlerror());