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systemd/SOURCES/0545-tpm2-cache-the-TPM-sup...

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From b5409900792af67d30b80d8088a853c01fdfdc5f Mon Sep 17 00:00:00 2001
From: Dan Streetman <ddstreet@ieee.org>
Date: Fri, 17 Feb 2023 12:59:18 -0500
Subject: [PATCH] tpm2: cache the TPM supported commands, add
tpm2_supports_command()
Cache the TPM's supported commands and provide a function to check if a command
is supported.
(cherry picked from commit adbf0c8cfb5d8635133ce9e2be088f9489b54694)
Related: RHEL-16182
---
src/shared/tpm2-util.c | 60 ++++++++++++++++++++++++++++++++++++++++++
src/shared/tpm2-util.h | 3 +++
src/test/test-tpm2.c | 9 +++++++
3 files changed, 72 insertions(+)
diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
index cbdae73759..d38e260f9a 100644
--- a/src/shared/tpm2-util.c
+++ b/src/shared/tpm2-util.c
@@ -191,12 +191,47 @@ static int tpm2_get_capability(
return more == TPM2_YES;
}
+#define TPMA_CC_TO_TPM2_CC(cca) (((cca) & TPMA_CC_COMMANDINDEX_MASK) >> TPMA_CC_COMMANDINDEX_SHIFT)
+
static int tpm2_cache_capabilities(Tpm2Context *c) {
TPMU_CAPABILITIES capability;
int r;
assert(c);
+ /* Cache the command capabilities. The spec isn't actually clear if commands can be added/removed
+ * while running, but that would be crazy, so let's hope it is not possbile. */
+ TPM2_CC current_cc = TPM2_CC_FIRST;
+ for (;;) {
+ r = tpm2_get_capability(
+ c,
+ TPM2_CAP_COMMANDS,
+ current_cc,
+ TPM2_MAX_CAP_CC,
+ &capability);
+ if (r < 0)
+ return r;
+
+ TPML_CCA commands = capability.command;
+
+ /* We should never get 0; the TPM must support some commands, and it must not set 'more' if
+ * there are no more. */
+ assert(commands.count > 0);
+
+ if (!GREEDY_REALLOC_APPEND(
+ c->capability_commands,
+ c->n_capability_commands,
+ commands.commandAttributes,
+ commands.count))
+ return log_oom();
+
+ if (r == 0)
+ break;
+
+ /* Set current_cc to index after last cc the TPM provided */
+ current_cc = TPMA_CC_TO_TPM2_CC(commands.commandAttributes[commands.count - 1]) + 1;
+ }
+
/* Cache the PCR capabilities, which are safe to cache, as the only way they can change is
* TPM2_PCR_Allocate(), which changes the allocation after the next _TPM_Init(). If the TPM is
* reinitialized while we are using it, all our context and sessions will be invalid, so we can
@@ -252,6 +287,29 @@ int tpm2_supports_alg(Tpm2Context *c, TPM2_ALG_ID alg) {
return tpm2_get_capability_alg(c, alg, NULL);
}
+/* Get the TPMA_CC for a TPM2_CC. Returns true if the TPM supports the command and the TPMA_CC is provided,
+ * otherwise false. */
+static bool tpm2_get_capability_command(Tpm2Context *c, TPM2_CC command, TPMA_CC *ret) {
+ assert(c);
+
+ FOREACH_ARRAY(cca, c->capability_commands, c->n_capability_commands)
+ if (TPMA_CC_TO_TPM2_CC(*cca) == command) {
+ if (ret)
+ *ret = *cca;
+ return true;
+ }
+
+ log_debug("TPM does not support command 0x%04" PRIx32 ".", command);
+ if (ret)
+ *ret = 0;
+
+ return false;
+}
+
+bool tpm2_supports_command(Tpm2Context *c, TPM2_CC command) {
+ return tpm2_get_capability_command(c, command, NULL);
+}
+
/* Returns 1 if the TPM supports the ECC curve, 0 if not, or < 0 for any error. */
static int tpm2_supports_ecc_curve(Tpm2Context *c, TPM2_ECC_CURVE curve) {
TPMU_CAPABILITIES capability;
@@ -415,6 +473,8 @@ static Tpm2Context *tpm2_context_free(Tpm2Context *c) {
c->tcti_context = mfree(c->tcti_context);
c->tcti_dl = safe_dlclose(c->tcti_dl);
+ c->capability_commands = mfree(c->capability_commands);
+
return mfree(c);
}
diff --git a/src/shared/tpm2-util.h b/src/shared/tpm2-util.h
index 1f20aadc98..1ca1a2e503 100644
--- a/src/shared/tpm2-util.h
+++ b/src/shared/tpm2-util.h
@@ -62,6 +62,8 @@ typedef struct {
ESYS_CONTEXT *esys_context;
/* Some selected cached capabilities of the TPM */
+ TPMA_CC *capability_commands;
+ size_t n_capability_commands;
TPML_PCR_SELECTION capability_pcrs;
} Tpm2Context;
@@ -85,6 +87,7 @@ Tpm2Handle *tpm2_handle_free(Tpm2Handle *handle);
DEFINE_TRIVIAL_CLEANUP_FUNC(Tpm2Handle*, tpm2_handle_free);
int tpm2_supports_alg(Tpm2Context *c, TPM2_ALG_ID alg);
+bool tpm2_supports_command(Tpm2Context *c, TPM2_CC command);
bool tpm2_test_parms(Tpm2Context *c, TPMI_ALG_PUBLIC alg, const TPMU_PUBLIC_PARMS *parms);
diff --git a/src/test/test-tpm2.c b/src/test/test-tpm2.c
index af06085af6..dfc8b98e08 100644
--- a/src/test/test-tpm2.c
+++ b/src/test/test-tpm2.c
@@ -658,6 +658,15 @@ TEST(tpm_required_tests) {
assert_se(tpm2_supports_alg(c, TPM2_ALG_RSA) == 1);
assert_se(tpm2_supports_alg(c, TPM2_ALG_AES) == 1);
assert_se(tpm2_supports_alg(c, TPM2_ALG_CFB) == 1);
+
+ /* Test invalid commands */
+ assert_se(!tpm2_supports_command(c, TPM2_CC_FIRST - 1));
+ assert_se(!tpm2_supports_command(c, TPM2_CC_LAST + 1));
+
+ /* Test valid commands */
+ assert_se(tpm2_supports_command(c, TPM2_CC_Create));
+ assert_se(tpm2_supports_command(c, TPM2_CC_CreatePrimary));
+ assert_se(tpm2_supports_command(c, TPM2_CC_Unseal));
}
#endif /* HAVE_TPM2 */