IMA currently extends the different TPM banks by padding/truncating the
SHA1 template digest. Although the IMA measurement list only includes
the SHA1 template digest, the template digest could be re-calculated
properly for each bank.
This patch adds support for properly calculating the template hash for
multiple TPM banks - "sha1" and "sha256".
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
---
src/evmctl.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 162 insertions(+)
diff --git a/src/evmctl.c b/src/evmctl.c
index 9c8544a95b6a..61a0e15c8dd7 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -63,6 +63,7 @@
#include <openssl/err.h>
#include <openssl/rsa.h>
#include <openssl/engine.h>
+#include "hash_info.h"
#ifndef XATTR_APPAARMOR_SUFFIX
#define XATTR_APPARMOR_SUFFIX "apparmor"
@@ -1647,8 +1648,165 @@ void ima_ng_show(struct template_entry *entry)
}
}
+struct tpm_bank_info {
+ int digest_size;
+ int supported;
+ const char *algo_name;
+ uint8_t digest[MAX_DIGEST_SIZE];
+ uint8_t pcr[NUM_PCRS][MAX_DIGEST_SIZE];
+};
+
+static void set_bank_info(struct tpm_bank_info *bank, const char *algo_name)
+{
+ const EVP_MD *md;
+
+ bank->algo_name = algo_name;
+ md = EVP_get_digestbyname(bank->algo_name);
+ if (!md)
+ return;
+
+ bank->supported = 1;
+ bank->digest_size = EVP_MD_size(md);
+}
+
+static struct tpm_bank_info *init_tpm_banks(int *num_banks)
+{
+ struct tpm_bank_info *banks = NULL;
+ const char *default_algos[] = {"sha1", "sha256"};
+ int num_algos = sizeof(default_algos) / sizeof(default_algos[0]);
+ int i, j;
+
+ banks = calloc(num_algos, sizeof(struct tpm_bank_info));
+ if (!banks)
+ return banks;
+
+ /* re-calculate the PCRs digests for only known algorithms */
+ *num_banks = num_algos;
+ for (i = 0; i < num_algos; i++) {
+ for (j = 0; j < HASH_ALGO__LAST; j++) {
+ if (!strcmp(default_algos[i], hash_algo_name[j]))
+ set_bank_info(&banks[i], hash_algo_name[j]);
+ }
+ }
+ return banks;
+}
+
+/* Calculate the template hash for a particular hash algorithm */
+static int calculate_template_digest(EVP_MD_CTX *pctx, const EVP_MD *md,
+ struct template_entry *entry,
+ struct tpm_bank_info *bank)
+{
+ unsigned int mdlen;
+ int err;
+
+ err = EVP_DigestInit(pctx, md);
+ if (!err) {
+ printf("EVP_DigestInit() failed\n");
+ goto out;
+ }
+
+ err = EVP_DigestUpdate(pctx, entry->template, entry->template_len);
+ if (!err) {
+ printf("EVP_DigestUpdate() failed\n");
+ goto out;
+ }
+
+ err = EVP_DigestFinal(pctx, bank->digest, &mdlen);
+ if (!err)
+ printf("EVP_DigestUpdate() failed\n");
+out:
+ if (!err)
+ err = 1;
+ return err;
+}
+
+/* Extend a specific TPM bank with the template hash */
+static int extend_tpm_bank(EVP_MD_CTX *pctx, const EVP_MD *md,
+ struct template_entry *entry,
+ struct tpm_bank_info *bank)
+{
+ unsigned int mdlen;
+ int err;
+
+ err = EVP_DigestInit(pctx, md);
+ if (!err) {
+ printf("EVP_DigestInit() failed\n");
+ goto out;
+ }
+
+ err = EVP_DigestUpdate(pctx, bank->pcr[entry->header.pcr],
+ bank->digest_size);
+ if (!err) {
+ printf("EVP_DigestUpdate() failed\n");
+ goto out;
+ }
+
+ if (validate && !memcmp(entry->header.digest, zero, SHA_DIGEST_LENGTH))
+ err = EVP_DigestUpdate(pctx, fox, bank->digest_size);
+ else
+ err = EVP_DigestUpdate(pctx, bank->digest, bank->digest_size);
+ if (!err) {
+ printf("EVP_DigestUpdate() failed\n");
+ goto out;
+ }
+
+ err = EVP_DigestFinal(pctx, bank->pcr[entry->header.pcr], &mdlen);
+ if (!err)
+ printf("EVP_DigestFinal() failed\n");
+
+out:
+ if (!err)
+ err = 1;
+ return err;
+}
+
+/* Calculate and extend the template hash for multiple hash algorithms */
+static void extend_tpm_banks(struct template_entry *entry, int num_banks,
+ struct tpm_bank_info *bank)
+{
+ EVP_MD_CTX *pctx;
+ const EVP_MD *md;
+#if OPENSSL_VERSION_NUMBER < 0x10100000
+ EVP_MD_CTX ctx;
+ pctx = &ctx;
+#else
+ pctx = EVP_MD_CTX_new();
+#endif
+ int err;
+ int i;
+
+ for (i = 0; i < num_banks; i++) {
+ if (!bank[i].supported)
+ continue;
+ md = EVP_get_digestbyname(bank[i].algo_name);
+ if (!md) {
+ printf("EVP_get_digestbyname(%s) failed\n",
+ bank[i].algo_name);
+ bank[i].supported = 0;
+ continue;
+ }
+
+ err = calculate_template_digest(pctx, md, entry, &bank[i]);
+ if (!err) {
+ bank[i].supported = 0;
+ continue;
+ }
+
+ /* extend TPM BANK with template digest */
+ err = extend_tpm_bank(pctx, md, entry, &bank[i]);
+ if (!err)
+ bank[i].supported = 0;
+ }
+#if OPENSSL_VERSION_NUMBER >= 0x10100000
+ EVP_MD_CTX_free(pctx);
+#endif
+}
+
static int ima_measurement(const char *file)
{
+ struct tpm_bank_info *pseudo_banks;
+ int num_banks = 0;
+
uint8_t pcr[NUM_PCRS][SHA_DIGEST_LENGTH] = {{0}};
uint8_t hwpcr[SHA_DIGEST_LENGTH];
struct template_entry entry = { .template = 0 };
@@ -1664,6 +1822,8 @@ static int ima_measurement(const char *file)
log_debug("Initial PCR value: ");
log_debug_dump(pcr, sizeof(pcr));
+ pseudo_banks = init_tpm_banks(&num_banks);
+
fp = fopen(file, "rb");
if (!fp) {
log_err("Failed to open measurement file: %s\n", file);
@@ -1702,6 +1862,8 @@ static int ima_measurement(const char *file)
goto out;
}
+ extend_tpm_banks(&entry, num_banks, pseudo_banks);
+
if (validate)
ima_verify_template_hash(&entry);
--
2.7.5
