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tpmlib: Introduce TPMPROP_TPM2_BUFFER_MAX and set it to 4096 for now #583

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Merged
stefanberger merged 1 commit into from
May 7, 2026
Merged

tpmlib: Introduce TPMPROP_TPM2_BUFFER_MAX and set it to 4096 for now #583

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3 changes: 2 additions & 1 deletion include/libtpms/tpm_library.h.in
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
/* IBM Thomas J. Watson Research Center */
/* $Id: tpm_library.h 4623 2011-09-28 15:15:09Z kgoldman $ */
/* */
/* (c) Copyright IBM Corporation 2010. */
/* (c) Copyright IBM Corporation 2010-2026. */
/* */
/* All rights reserved. */
/* */
Expand Down Expand Up @@ -98,6 +98,7 @@ enum TPMLIB_TPMProperty {
TPMPROP_TPM_MAX_NV_SPACE,
TPMPROP_TPM_MAX_SAVESTATE_SPACE,
TPMPROP_TPM_MAX_VOLATILESTATE_SPACE,
TPMPROP_TPM2_BUFFER_MAX,
};

TPM_RESULT TPMLIB_GetTPMProperty(enum TPMLIB_TPMProperty prop, int *result);
Expand Down
4 changes: 4 additions & 0 deletions man/man3/TPMLIB_GetTPMProperty.pod
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Expand Up @@ -94,6 +94,10 @@ The maximum size of the savestate blob (includes the space safety margin).
The maximum size of the volatile state blob (includes the space saferty
margin).

=item B<TPMPROP_TPM2_BUFFER_MAX> (since v0.11)

The maximum sizes of the TPM2 command and result buffers.

=back

=head1 ERRORS
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2 changes: 2 additions & 0 deletions src/tpm_library_conf.h
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Expand Up @@ -53,6 +53,8 @@
/* maximum size of the IO buffer used for requests and responses */
#define TPM_BUFFER_MAX 4096

#define TPM2_BUFFER_MAX 4096

/*
* Below the following acronyms are used to identify what
* #define influences which one of the state blobs the TPM
Expand Down
20 changes: 12 additions & 8 deletions src/tpm_tpm2_interface.c
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Expand Up @@ -199,15 +199,15 @@ static TPM_RESULT TPM2_Process(unsigned char **respbuffer, uint32_t *resp_size,
req.Buffer = command;

/* have the TPM 2 write directly into the response buffer */
if (*respbufsize < TPM_BUFFER_MAX || !*respbuffer) {
tmp = realloc(*respbuffer, TPM_BUFFER_MAX);
if (*respbufsize < TPM2_BUFFER_MAX || !*respbuffer) {
tmp = realloc(*respbuffer, TPM2_BUFFER_MAX);
if (!tmp) {
TPMLIB_LogTPM2Error("Could not allocated %u bytes.\n",
TPM_BUFFER_MAX);
TPM2_BUFFER_MAX);
return TPM_SIZE;
}
*respbuffer = tmp;
*respbufsize = TPM_BUFFER_MAX;
*respbufsize = TPM2_BUFFER_MAX;
}
resp.BufferSize = *respbufsize;
resp.Buffer = *respbuffer;
Expand Down Expand Up @@ -321,14 +321,18 @@ static TPM_RESULT TPM2_GetTPMProperty(enum TPMLIB_TPMProperty prop,
int *result)
{
switch (prop) {
case TPMPROP_TPM_RSA_KEY_LENGTH_MAX:
case TPMPROP_TPM_RSA_KEY_LENGTH_MAX:
*result = MAX_RSA_KEY_BITS;
break;

case TPMPROP_TPM_KEY_HANDLES:
case TPMPROP_TPM_KEY_HANDLES:
*result = MAX_HANDLE_NUM;
break;

case TPMPROP_TPM2_BUFFER_MAX: /* v0.11 */
*result = TPM2_BUFFER_MAX;
break;

/* not supported for TPM 2 */
case TPMPROP_TPM_OWNER_EVICT_KEY_HANDLES:
case TPMPROP_TPM_MIN_AUTH_SESSIONS:
Expand Down Expand Up @@ -629,7 +633,7 @@ static char *TPM2_GetInfo(enum TPMLIB_InfoFlags flags)
goto exit;
}

static uint32_t tpm2_buffersize = TPM_BUFFER_MAX;
static uint32_t tpm2_buffersize = TPM2_BUFFER_MAX;

static uint32_t TPM2_SetBufferSize(uint32_t wanted_size,
uint32_t *min_size,
Expand All @@ -643,7 +647,7 @@ static uint32_t TPM2_SetBufferSize(uint32_t wanted_size,
* (plus a generous 128 bytes) and the TPM_ContextLoad/Save commands.
*/
const uint32_t min = sizeof(TPMS_CONTEXT) + 128;
const uint32_t max = TPM_BUFFER_MAX;
const uint32_t max = TPM2_BUFFER_MAX;

if (min_size)
*min_size = min;
Expand Down
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