From dc2895812a8e5bca344a48b3523a7f60d25a3ebb Mon Sep 17 00:00:00 2001
From: Stefan Berger <stefanb@linux.vnet.ibm.com>
Date: Fri, 5 Jul 2019 16:43:50 -0400
Subject: [PATCH] swtpm: Have SWTPM_IO_Read read at least the 10 bytes from the
 TPM header

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>
---
 src/swtpm/swtpm_io.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/swtpm/swtpm_io.c b/src/swtpm/swtpm_io.c
index 77dcf2b..1318477 100644
--- a/src/swtpm/swtpm_io.c
+++ b/src/swtpm/swtpm_io.c
@@ -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;