Re: [tpm2] NVRAM_write, BUFFER_SIZE is 0

[Duncan.Palmer at data61.csiro.au]

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We see the same behaviour on an Intel NUC5i7. I haven't looked at the capabilities reported by the TPM device on that platform. The attached patch (setting max_data_size = MAX_NV_BUFFER_SIZE when max_data_size is reported as 0), sorts the problem out.


Dunk


Duncan Palmer
Senior Software Engineer | Autonomous Systems
Data61 | CSIRO

E duncan.palmer(a)csiro.au

Queensland Centre for Advanced Technologies (QCAT),

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________________________________
From: tpm2 <tpm2-bounces(a)lists.01.org> on behalf of Ian Oliver <ian.justin.oliver(a)gmail.com>
Sent: 17 April 2018 21:10
To: tpm2(a)lists.01.org
Subject: [tpm2] NVRAM_write, BUFFER_SIZE is 0

Hi,

we're having problems writing to NV_RAM with tpm2_nvwrite. We can define areas but not write


$ tpm2_nvlist
0x1800005:
  hash algorithm:
    friendly: sha256
    value: 0xB
  attributes:
    friendly: ownerwrite|policywrite|ownerread|written
    value: 0xA000220
  size: 32




$ echo -n "hello" | tpm2_nvwrite -x 0x1800005 -a 0x40000001 -V
INFO on line: "135" in file: "tools/tpm2_nvwrite.c": The data(size=0) to be written:
INFO on line: "149" in file: "tools/tpm2_nvwrite.c": Success to write NV area at index 0x1800005 (25165829) offset 0x0.
INFO on line: "135" in file: "tools/tpm2_nvwrite.c": The data(size=0) to be written:
INFO on line: "149" in file: "tools/tpm2_nvwrite.c": Success to write NV area at index 0x1800005 (25165829) offset 0x0.
INFO on line: "135" in file: "tools/tpm2_nvwrite.c": The data(size=0) to be written:
INFO on line: "149" in file: "tools/tpm2_nvwrite.c": Success to write NV area at index 0x1800005 (25165829) offset 0x0.
INFO on line: "135" in file: "tools/tpm2_nvwrite.c": The data(size=0) to be written:
INFO on line: "149" in file: "tools/tpm2_nvwrite.c": Success to write NV area at index 0x1800005 (25165829) offset 0x0.
INFO on line: "135" in file: "tools/tpm2_nvwrite.c": The data(size=0) to be written:
INFO on line: "149" in file: "tools/tpm2_nvwrite.c": Success to write NV area at index 0x1800005 (25165829) offset 0x0.
...
Which loops infinitely


Relevant parts of the tpm2-tools and tpm2-tss code:
file: tpm2_nvwrite.c
113     res = tpm2_util_nv_max_buffer_size(sapi_context, &max_data_size);
The call to tpm2_nv_read_public should get the TPM_PT_NV_BUFFER_MAX capability but and store it to max_data_size.
In that part of the code max_data_size gets set to 0 and that causes the loop above.


The TPM_PT_NV_BUFFER_MAX seems not to be defined in the capabilities for this device: Infineon TPM 2.0 9665  as reported by tpm2_cap.

t.

Ian


--
Dr. Ian Oliver
===============================
Privacy Engineering:  via Amazon<http://www.amazon.co.uk/dp/1497569710>
Twitter: @i_j_oliver

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commit c60f3528a1d4d147f45cb73b3698f1395b67a647
Author: Duncan Palmer <duncan.palmer@csiro.au>
Date:   Fri Feb 9 10:01:36 2018 +1000

    tpm2_nv(read|write): use a default buffer size if TPM reports 0.
    
    On a NUC5i7RYH, the TPM reports it's max NV buffer size as 0, which
    means we can neither read nor write. In this case, default to
    MAX_NV_BUFFER_SIZE.

diff --git a/tools/tpm2_nvread.c b/tools/tpm2_nvread.c
index 9d71fd4..251eb5b 100644
--- a/tools/tpm2_nvread.c
+++ b/tools/tpm2_nvread.c
@@ -123,6 +123,9 @@ static bool nv_read(TSS2_SYS_CONTEXT *sapi_context, tpm2_option_flags flags) {
     if (max_data_size > MAX_NV_BUFFER_SIZE) {
         max_data_size = MAX_NV_BUFFER_SIZE;
     }
+    if (max_data_size == 0) {
+        max_data_size = MAX_NV_BUFFER_SIZE;
+    }
 
     UINT8 *data_buffer = malloc(data_size);
     if (!data_buffer) {
diff --git a/tools/tpm2_nvwrite.c b/tools/tpm2_nvwrite.c
index 278e733..14c0b0d 100644
--- a/tools/tpm2_nvwrite.c
+++ b/tools/tpm2_nvwrite.c
@@ -119,6 +119,9 @@ static bool nv_write(TSS2_SYS_CONTEXT *sapi_context) {
     if (max_data_size > MAX_NV_BUFFER_SIZE) {
         max_data_size = MAX_NV_BUFFER_SIZE;
     }
+    if (max_data_size == 0) {
+        max_data_size = MAX_NV_BUFFER_SIZE;
+    }
 
     UINT16 data_offset = 0;
     UINT16 bytes_left = ctx.nv_buffer.t.size;