- 0002-kdfa-use-openssl-for-hmac-not-tpm.patch: fixed unexpected leak of
cleartext password into the tpm when generating an HMAC in the context of tpm_kdfa() (key derivation function). OBS-URL: https://build.opensuse.org/package/show/security/tpm2.0-tools?expand=0&rev=23
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Matthias Gerstner
Git OBS Bridge
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207
0002-kdfa-use-openssl-for-hmac-not-tpm.patch
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207
0002-kdfa-use-openssl-for-hmac-not-tpm.patch
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@ -0,0 +1,207 @@
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From c5d72beaab1cbbbe68271f4bc4b6670d69985157 Mon Sep 17 00:00:00 2001
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From: William Roberts <william.c.roberts@intel.com>
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Date: Wed, 21 Jun 2017 09:32:32 -0700
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Subject: [PATCH] kdfa: use openssl for hmac not tpm
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While not reachable in the current code base tools, a potential
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security bug lurked in tpm_kdfa().
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If using that routine for an hmac authorization, the hmac was
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calculated using the tpm. A user of an object wishing to
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authenticate via hmac, would expect that the password is never
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sent to the tpm. However, since the hmac calculation relies on
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password, and is performed by the tpm, the password ends up
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being sent in plain text to the tpm.
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The fix is to use openssl to generate the hmac on the host.
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Fixes: CVE-2017-7524
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Signed-off-by: William Roberts <william.c.roberts@intel.com>
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---
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Makefile.am | 4 +--
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configure.ac | 3 ++-
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lib/tpm_kdfa.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++--------
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lib/tpm_kdfa.h | 2 +-
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lib/tpm_session.c | 2 +-
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5 files changed, 72 insertions(+), 15 deletions(-)
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Index: tpm2.0-tools-2.0.0/Makefile.am
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===================================================================
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--- tpm2.0-tools-2.0.0.orig/Makefile.am
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+++ tpm2.0-tools-2.0.0/Makefile.am
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@@ -35,10 +35,10 @@ ACLOCAL_AMFLAGS = -I m4
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INCLUDE_DIRS = -I$(srcdir)/src -I$(srcdir)/lib
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LIB_COMMON := lib/libcommon.a
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-AM_CFLAGS := $(INCLUDE_DIRS) $(TPM20_TSS_CFLAGS) $(EXTRA_CFLAGS)
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+AM_CFLAGS := $(INCLUDE_DIRS) $(TPM20_TSS_CFLAGS) $(EXTRA_CFLAGS) $(CRYPTO_FLAGS)
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AM_LDFLAGS := $(EXTRA_LDFLAGS)
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-LDADD = $(LIB_COMMON) $(TPM20_TSS_LIBS) $(TCTI_SOCK_LIBS) $(TCTI_DEV_LIBS)
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+LDADD = $(LIB_COMMON) $(TPM20_TSS_LIBS) $(TCTI_SOCK_LIBS) $(TCTI_DEV_LIBS) $(CRYPTO_LIBS)
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sbin_PROGRAMS = \
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tools/tpm2_create \
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Index: tpm2.0-tools-2.0.0/configure.ac
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===================================================================
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--- tpm2.0-tools-2.0.0.orig/configure.ac
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+++ tpm2.0-tools-2.0.0/configure.ac
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@@ -49,7 +49,8 @@ AS_IF(
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[AC_MSG_ERROR(
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[no TCTIs: at least one TCTI library must be enabled],
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[1])])
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-PKG_CHECK_MODULES([CURL],[libcurl libcrypto])
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+PKG_CHECK_MODULES([CRYPTO],[libcrypto])
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+PKG_CHECK_MODULES([CURL],[libcurl])
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AC_ARG_ENABLE([unit],
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[AS_HELP_STRING([--enable-unit],
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[build cmocka unit tests (default is no)])],
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Index: tpm2.0-tools-2.0.0/lib/tpm_kdfa.c
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===================================================================
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--- tpm2.0-tools-2.0.0.orig/lib/tpm_kdfa.c
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+++ tpm2.0-tools-2.0.0/lib/tpm_kdfa.c
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@@ -27,20 +27,40 @@
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#include <sapi/tpm20.h>
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+ #include <openssl/err.h>
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+#include <openssl/hmac.h>
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+
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#include "string-bytes.h"
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#include "tpm_hmac.h"
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+#include "log.h"
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+
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+static const EVP_MD *tpm_algorithm_to_openssl_digest(TPMI_ALG_HASH algorithm) {
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-TPM_RC tpm_kdfa(TSS2_SYS_CONTEXT *sapi_context, TPMI_ALG_HASH hashAlg,
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+ switch(algorithm) {
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+ case TPM_ALG_SHA1:
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+ return EVP_sha1();
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+ case ALG_SHA256_VALUE:
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+ return EVP_sha256();
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+ case TPM_ALG_SHA384:
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+ return EVP_sha384();
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+ case TPM_ALG_SHA512:
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+ return EVP_sha512();
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+ default:
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+ return NULL;
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+ }
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+ /* no return, not possible */
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+}
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+
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+TPM_RC tpm_kdfa(TPMI_ALG_HASH hashAlg,
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TPM2B *key, char *label, TPM2B *contextU, TPM2B *contextV, UINT16 bits,
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TPM2B_MAX_BUFFER *resultKey )
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{
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- TPM2B_DIGEST tmpResult;
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TPM2B_DIGEST tpm2bLabel, tpm2bBits, tpm2b_i_2;
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UINT8 *tpm2bBitsPtr = &tpm2bBits.t.buffer[0];
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UINT8 *tpm2b_i_2Ptr = &tpm2b_i_2.t.buffer[0];
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TPM2B_DIGEST *bufferList[8];
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UINT32 bitsSwizzled, i_Swizzled;
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- TPM_RC rval;
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+ TPM_RC rval = TPM_RC_SUCCESS;
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int i, j;
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UINT16 bytes = bits / 8;
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@@ -64,8 +84,24 @@ TPM_RC tpm_kdfa(TSS2_SYS_CONTEXT *sapi_c
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i = 1;
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+ const EVP_MD *md = tpm_algorithm_to_openssl_digest(hashAlg);
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+ if (!md) {
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+ LOG_ERR("Algorithm not supported for hmac: %x", hashAlg);
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+ return TPM_RC_HASH;
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+ }
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+
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+ HMAC_CTX ctx;
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+ HMAC_CTX_init(&ctx);
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+ int rc = HMAC_Init_ex(&ctx, key->buffer, key->size, md, NULL);
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+ if (!rc) {
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+ LOG_ERR("HMAC Init failed: %s", ERR_error_string(rc, NULL));
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+ return TPM_RC_MEMORY;
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+ }
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+
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+ // TODO Why is this a loop? It appears to only execute once.
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while( resultKey->t.size < bytes )
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{
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+ TPM2B_DIGEST tmpResult;
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// Inner loop
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i_Swizzled = string_bytes_endian_convert_32( i );
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@@ -77,21 +113,41 @@ TPM_RC tpm_kdfa(TSS2_SYS_CONTEXT *sapi_c
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bufferList[j++] = (TPM2B_DIGEST *)contextU;
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bufferList[j++] = (TPM2B_DIGEST *)contextV;
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bufferList[j++] = (TPM2B_DIGEST *)&(tpm2bBits.b);
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- bufferList[j++] = (TPM2B_DIGEST *)0;
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- rval = tpm_hmac(sapi_context, hashAlg, key, (TPM2B **)&( bufferList[0] ), &tmpResult );
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- if( rval != TPM_RC_SUCCESS )
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- {
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- return( rval );
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+ bufferList[j] = (TPM2B_DIGEST *)0;
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+
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+ int c;
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+ for(c=0; c < j; c++) {
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+ TPM2B_DIGEST *digest = bufferList[c];
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+ int rc = HMAC_Update(&ctx, digest->b.buffer, digest->b.size);
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+ if (!rc) {
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+ LOG_ERR("HMAC Update failed: %s", ERR_error_string(rc, NULL));
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+ rval = TPM_RC_MEMORY;
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+ goto err;
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+ }
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}
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+ unsigned size = sizeof(tmpResult.t.buffer);
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+ int rc = HMAC_Final(&ctx, tmpResult.t.buffer, &size);
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+ if (!rc) {
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+ LOG_ERR("HMAC Final failed: %s", ERR_error_string(rc, NULL));
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+ rval = TPM_RC_MEMORY;
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+ goto err;
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+ }
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+
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+ tmpResult.t.size = size;
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+
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bool res = string_bytes_concat_buffer(resultKey, &(tmpResult.b));
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if (!res) {
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- return TSS2_SYS_RC_BAD_VALUE;
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+ rval = TSS2_SYS_RC_BAD_VALUE;
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+ goto err;
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}
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}
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// Truncate the result to the desired size.
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resultKey->t.size = bytes;
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- return TPM_RC_SUCCESS;
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+err:
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+ HMAC_CTX_cleanup(&ctx);
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+
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+ return rval;
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}
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Index: tpm2.0-tools-2.0.0/lib/tpm_kdfa.h
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===================================================================
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--- tpm2.0-tools-2.0.0.orig/lib/tpm_kdfa.h
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+++ tpm2.0-tools-2.0.0/lib/tpm_kdfa.h
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@@ -42,7 +42,7 @@
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* @param resultKey
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* @return
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*/
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-TPM_RC tpm_kdfa(TSS2_SYS_CONTEXT *sapi_context, TPMI_ALG_HASH hashAlg,
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+TPM_RC tpm_kdfa(TPMI_ALG_HASH hashAlg,
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TPM2B *key, char *label, TPM2B *contextU, TPM2B *contextV,
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UINT16 bits, TPM2B_MAX_BUFFER *resultKey );
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Index: tpm2.0-tools-2.0.0/lib/tpm_session.c
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===================================================================
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--- tpm2.0-tools-2.0.0.orig/lib/tpm_session.c
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+++ tpm2.0-tools-2.0.0/lib/tpm_session.c
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@@ -198,7 +198,7 @@ static TPM_RC StartAuthSession(TSS2_SYS_
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}
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else
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{
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- rval = tpm_kdfa(sapi_context, session->authHash, &(key.b), label, &( session->nonceNewer.b ),
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+ rval = tpm_kdfa(session->authHash, &(key.b), label, &( session->nonceNewer.b ),
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&( session->nonceOlder.b ), bytes * 8, (TPM2B_MAX_BUFFER *)&( session->sessionKey ) );
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}
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@ -1,3 +1,10 @@
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-------------------------------------------------------------------
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Thu Jun 29 09:45:45 UTC 2017 - matthias.gerstner@suse.com
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- 0002-kdfa-use-openssl-for-hmac-not-tpm.patch: fixed unexpected leak of
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cleartext password into the tpm when generating an HMAC in the context of
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tpm_kdfa() (key derivation function).
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-------------------------------------------------------------------
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Tue Jun 20 08:35:29 UTC 2017 - matthias.gerstner@suse.com
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@ -29,6 +29,7 @@ Patch1: tpm2.0-tools-fix-gcc7.patch
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# this fixes an error with an unexpectedly large number of PCRS (bnc#1044419)
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# there's no release containing this fix yet
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Patch2: 0001-tpm2_listpcrs-use-TPM2_GetCapability-to-determine-PC.patch
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Patch3: 0002-kdfa-use-openssl-for-hmac-not-tpm.patch
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BuildRequires: autoconf-archive
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BuildRequires: automake
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BuildRequires: gcc-c++
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@ -52,6 +53,7 @@ associated interfaces.
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%patch0 -p1
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%patch1 -p1
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%patch2 -p1
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%patch3 -p1
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%build
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bash ./bootstrap
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