From b95e41bccc64e488ca9c824e632b8ca5bc87db55 Mon Sep 17 00:00:00 2001
From: Alberto Planas <aplanas@suse.com>
Date: Fri, 18 Jun 2021 15:54:22 +0200
Subject: [PATCH] tpm2_eventlog: read eventlog file in chunks

The eventlog file lives is securityfs, that do not return the file size.
The current implementation first try to do a "fseek(fp, 0, SEEK_END)"
for this file, and this will always return 0.

This generate an error, and tpm2_eventlog exit with:

ERROR: Unable to run tpm2_eventlog

This patch replace the reading logic, now reading in chunks of 16KB and
reallocating the buffer if needed. Also introduces a new function in
files.c ("files_read_bytes_chunk") that helps counting the total read
size, that now is different from the ammount of allocated memory.

Fixes #2775

Signed-off-by: Alberto Planas <aplanas@suse.com>
---
 lib/files.c                |  9 +++++++++
 lib/files.h                | 15 ++++++++++++++
 tools/misc/tpm2_eventlog.c | 40 +++++++++++++++++++-------------------
 3 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/lib/files.c b/lib/files.c
index 884dd23c..7f0fb39f 100644
--- a/lib/files.c
+++ b/lib/files.c
@@ -564,6 +564,15 @@ bool files_read_bytes(FILE *out, UINT8 bytes[], size_t len) {
     return (readx(out, bytes, len) == len);
 }
 
+bool files_read_bytes_chunk(FILE *out, UINT8 bytes[], size_t len, size_t *read_len) {
+
+    BAIL_ON_NULL("FILE", out);
+    BAIL_ON_NULL("bytes", bytes);
+    size_t chunk_len = readx(out, bytes, len);
+    *read_len += chunk_len;
+    return (chunk_len == len);
+}
+
 bool files_write_bytes(FILE *out, uint8_t bytes[], size_t len) {
 
     BAIL_ON_NULL("FILE", out);
diff --git a/lib/files.h b/lib/files.h
index 33022cbd..684b7eef 100644
--- a/lib/files.h
+++ b/lib/files.h
@@ -571,6 +571,21 @@ bool files_read_64(FILE *out, UINT64 *data);
  */
 bool files_read_bytes(FILE *out, UINT8 data[], size_t size);
 
+/**
+ * Reads len bytes from a file and set the read length.
+ * @param out
+ *  The file to read from.
+ * @param data
+ *  The buffer to read into, only valid on a True return.
+ * @param size
+ *  The number of bytes to read.
+ * @param read_size
+ *  Total number of bytes readed.
+ * @return
+ *  True on success, False otherwise.
+ */
+bool files_read_bytes_chunk(FILE *out, UINT8 data[], size_t size, size_t *read_size);
+
 /**
  * Converts a TPM2B_ATTEST to a TPMS_ATTEST using libmu.
  * @param quoted
diff --git a/tools/misc/tpm2_eventlog.c b/tools/misc/tpm2_eventlog.c
index b51089bd..64ce6add 100644
--- a/tools/misc/tpm2_eventlog.c
+++ b/tools/misc/tpm2_eventlog.c
@@ -12,6 +12,8 @@
 #include "tpm2_eventlog_yaml.h"
 #include "tpm2_tool.h"
 
+#define CHUNK_SIZE 16384
+
 static char *filename = NULL;
 
 /* Set the default YAML version */
@@ -72,37 +74,35 @@ static tool_rc tpm2_tool_onrun(ESYS_CONTEXT *ectx, tpm2_option_flags flags) {
         return tool_rc_option_error;
     }
 
-    /* Get file size */
-    unsigned long size = 0;
-    bool ret = files_get_file_size_path(filename, &size);
-    if (!ret || !size) {
+    /* Read the file in chunks.  Usually the file will reside in
+       securityfs, and those files do not have a public file size */
+    tool_rc rc = tool_rc_success;
+    FILE *fileptr = fopen(filename, "rb");
+    if (!fileptr) {
         return tool_rc_general_error;
     }
 
-    /* Allocate buffer to read file data */
-    UINT8 *eventlog = calloc(1, size);
+    /* Reserve the buffer for the first chunk */
+    UINT8 *eventlog = calloc(1, CHUNK_SIZE);
     if (eventlog == NULL){
-        LOG_ERR("failed to allocate %lu bytes: %s", size, strerror(errno));
+        LOG_ERR("failed to allocate %d bytes: %s", CHUNK_SIZE, strerror(errno));
         return tool_rc_general_error;
     }
 
-    /* Load buffer with file data */
-    tool_rc rc = tool_rc_success;
-    FILE *fileptr = fopen(filename, "rb");
-    if (!fileptr) {
-        rc = tool_rc_general_error;
-        goto out;
+    unsigned long size = 0;
+    while (files_read_bytes_chunk(fileptr, eventlog, CHUNK_SIZE, &size)) {
+        UINT8 *eventlog_tmp = realloc(eventlog, size + CHUNK_SIZE);
+        if (eventlog_tmp == NULL){
+            LOG_ERR("failed to allocate %lu bytes: %s", size + CHUNK_SIZE, strerror(errno));
+            rc = tool_rc_general_error;
+            goto out;
+        }
+        eventlog = eventlog_tmp;
     }
-
-    ret = files_read_bytes(fileptr, eventlog, size);
     fclose(fileptr);
-    if (!ret) {
-        rc = tool_rc_general_error;
-        goto out;
-    }
 
     /* Parse eventlog data */
-    ret = yaml_eventlog(eventlog, size, eventlog_version);
+    bool ret = yaml_eventlog(eventlog, size, eventlog_version);
     if (!ret) {
         LOG_ERR("failed to parse tpm2 eventlog");
         rc = tool_rc_general_error;
-- 
2.32.0