libtpmtss: Query maximum TPM data transmission size

diff --git a/src/libtpmtss/tpm_tss_tss2.c b/src/libtpmtss/tpm_tss_tss2.c
index 90a16c103ed86d018cce546e0c1986e594f2e165..1b24a42d059980c409775f34d5cec9a81a6562d3 100644 (file)
--- a/src/libtpmtss/tpm_tss_tss2.c
+++ b/src/libtpmtss/tpm_tss_tss2.c
@@ -1046,12 +1046,14 @@ METHOD(tpm_tss_t, get_data, bool,
        private_tpm_tss_tss2_t *this, uint32_t hierarchy, uint32_t handle,
        chunk_t pin, chunk_t *data)
 {
-       uint16_t nv_size, nv_offset = 0;
+       uint16_t max_data_size, nv_size, nv_offset = 0;
        uint32_t rval;
 
+       TPMS_CAPABILITY_DATA cap_data;
+       TPMI_YES_NO more_data;
        TPM2B_NAME nv_name = { { sizeof(TPM2B_NAME)-2, } };
        TPM2B_NV_PUBLIC nv_public = { { 0, } };
-       TPM2B_MAX_NV_BUFFER nv_data = { { sizeof(TPM2B_MAX_NV_BUFFER)-2, } };
+       TPM2B_MAX_NV_BUFFER nv_data = { { MAX_NV_BUFFER_SIZE, } };
        TPMS_AUTH_COMMAND  session_data_cmd;
        TPMS_AUTH_RESPONSE session_data_rsp;
        TSS2_SYS_CMD_AUTHS sessions_data_cmd;
@@ -1059,6 +1061,18 @@ METHOD(tpm_tss_t, get_data, bool,
        TPMS_AUTH_COMMAND  *session_data_cmd_array[1];
        TPMS_AUTH_RESPONSE *session_data_rsp_array[1];
 
+       /* query maximum TPM data transmission size */
+       rval = Tss2_Sys_GetCapability(this->sys_context, 0, TPM_CAP_TPM_PROPERTIES,
+                               TPM_PT_NV_BUFFER_MAX, 1, &more_data, &cap_data, 0);
+       if (rval != TPM_RC_SUCCESS)
+       {
+               DBG1(DBG_PTS,"%s Tss2_Sys_GetCapability failed for "
+                                        "TPM_CAP_TPM_PROPERTIES: 0x%06x", LABEL, rval);
+               return FALSE;
+       }
+       max_data_size = min(cap_data.data.tpmProperties.tpmProperty[0].value,
+                                               MAX_NV_BUFFER_SIZE);
+
        /* get size of NV object */
        rval = Tss2_Sys_NV_ReadPublic(this->sys_context, handle, 0, &nv_public,
                                                                                                                                &nv_name, 0);
@@ -1093,11 +1107,11 @@ METHOD(tpm_tss_t, get_data, bool,
        }
        *( (uint8_t *)((void *)&session_data_cmd.sessionAttributes ) ) = 0;
 
-       /* read NV data an NV buffer block at a time */
+       /* read NV data a maximum data size block at a time */
        while (nv_size > 0)
        {
                rval = Tss2_Sys_NV_Read(this->sys_context, hierarchy, handle,
-                                       &sessions_data_cmd, min(nv_size, MAX_NV_BUFFER_SIZE),
+                                       &sessions_data_cmd, min(nv_size, max_data_size),
                                        nv_offset, &nv_data, &sessions_data_rsp);
 
                if (rval != TPM_RC_SUCCESS)