tpm2: Add utilities for debugging of constant time issues

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>

diff --git a/src/Makefile.am b/src/Makefile.am
index 888b17464742b34345d3987bb005e13aa6b48f01..37d3fdac121f4c620a3df7aa1434dfb31e3216ec 100644 (file)
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -539,6 +539,7 @@ libtpms_tpm2_la_SOURCES += \
        tpm2/crypto/openssl/TpmToOsslSupport.c
 
 noinst_HEADERS += \
+       tpm2/crypto/openssl/ConsttimeUtils.h \
        tpm2/crypto/openssl/BnConvert_fp.h \
        tpm2/crypto/openssl/BnMath_fp.h \
        tpm2/crypto/openssl/BnMemory_fp.h \

diff --git a/src/tpm2/crypto/openssl/ConsttimeUtils.h b/src/tpm2/crypto/openssl/ConsttimeUtils.h
new file mode 100644 (file)
index 0000000..3364bee
--- /dev/null
+++ b/src/tpm2/crypto/openssl/ConsttimeUtils.h
@@ -0,0 +1,117 @@
+/********************************************************************************/
+/*                                                                             */
+/*                      Constant time debugging helper functions               */
+/*                          Written by Stefan Berger                           */
+/*                    IBM Thomas J. Watson Research Center                     */
+/*                                                                             */
+/*  Licenses and Notices                                                       */
+/*                                                                             */
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+/*                                                                             */
+/*  (c) Copyright IBM Corp. and others, 2020                                   */
+/*                                                                             */
+/********************************************************************************/
+
+#ifndef CONSTTIME_UTILS_H
+#define CONSTTIME_UTILS_H
+
+#include <assert.h>
+#include <stdio.h>
+
+#include "BnValues.h"
+
+#include <openssl/bn.h>
+
+static __inline__ unsigned long long rdtsc() {
+    unsigned long h, l;
+
+    __asm__ __volatile__ ("rdtsc" : "=a"(l), "=d"(h));
+
+    return  (unsigned long long)l |
+           ((unsigned long long)h << 32 );
+}
+
+// Make sure that the given BIGNUM has the given number of expected bytes.
+// Skip over any leading zeros the BIGNUM may have.
+static inline void assert_ossl_num_bytes(const BIGNUM *a,
+                                         unsigned int num_bytes,
+                                         int verbose,
+                                         const char *caller) {
+    unsigned char buffer[LARGEST_NUMBER] = { 0, };
+    int len, i;
+
+    len = BN_bn2bin(a, buffer);
+    for (i = 0; i < len; i++) {
+        if (buffer[i])
+            break;
+    }
+    len -= i;
+    if (num_bytes != (unsigned int)len) {
+        printf("%s: Expected %u bytes but found %d (caller: %s)\n", __func__, num_bytes, len, caller);
+    } else {
+        if (verbose)
+            printf("%s: check passed; num_bytes = %d (caller: %s)\n",__func__, num_bytes, caller);
+    }
+    assert(num_bytes == (unsigned int)len);
+}
+
+// Make sure that the bigNum has the expected number of bytes after it was
+// converted to an OpenSSL BIGNUM.
+static inline void assert_bn_ossl_num_bytes(bigNum tpmb,
+                                            unsigned int num_bytes,
+                                            int verbose,
+                                            const char *caller) {
+    BIG_INITIALIZED(osslb, tpmb);
+
+    assert_ossl_num_bytes(osslb, num_bytes, verbose, caller);
+
+    BN_free(osslb);
+}
+
+#endif /* CONSTTIME_UTILS_H */