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swtpm: Have SWTPM_IO_Read read at least the 10 bytes from the TPM header

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Have SWTPM_IO_Read() read at leat the 10 bytes from the (regular) TPM
header. This solves a particular problem with the TPM 2 header prefix for
which we will add support in the subsequent patch. In the prefix case the IBM
TSS 2 stack sends 4 bytes for the command, then 1 byte for the locality, and then
4 bytes for the length indicator followed by the command. If we just read once
we would only then get 4 bytes. Reading 10 bytes gets all of these plus the sub-
sequent TPM command or the whole TPM command in case this prefix header is
missing.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
This commit is contained in:
Stefan Berger 2019-07-05 16:43:50 -04:00 committed by Stefan Berger
parent 71beceeda4
commit dc2895812a
1 changed files with 7 additions and 3 deletions
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10
src/swtpm/swtpm_io.c
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@ -64,7 +64,7 @@
#include "logging.h"
#include "swtpm_debug.h"
#include "swtpm_io.h"
#include "tpmlib.h"
/*
global variables
@ -90,6 +90,7 @@ TPM_RESULT SWTPM_IO_Read(TPM_CONNECTION_FD *connection_fd, /* read/write file
size_t bufferSize) /* input: max size of output buffer */
{
ssize_t n;
size_t offset = 0;
if (connection_fd->fd < 0) {
TPM_DEBUG("SWTPM_IO_Read: Passed file descriptor is invalid\n");
@ -97,17 +98,20 @@ TPM_RESULT SWTPM_IO_Read(TPM_CONNECTION_FD *connection_fd, /* read/write file
}
while (true) {
n = read(connection_fd->fd, buffer, bufferSize);
n = read(connection_fd->fd, &buffer[offset], bufferSize - offset);
if (n < 0 && errno == EINTR)
continue;
if (n > 0) {
*bufferLength = n;
offset += n;
if (offset < sizeof(struct tpm_req_header))
continue;
break;
} else {
return TPM_IOERROR;
}
}
*bufferLength = offset;
TPM_PrintAll(" SWTPM_IO_Read:", " ", buffer, *bufferLength);
return 0;