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Fix: ringbuffer: Add file header version field and detect reading corrupted blackbox files using hash value

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In the future, if something changes in the file header we can
increment the version and split up the parsing into separate functions
for backwards compatibility.
This commit is contained in:
David Vossel 2013-06-26 17:41:48 -05:00
parent 11b18cced4
commit a2bdeed3cc
1 changed files with 79 additions and 4 deletions
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83
lib/ringbuffer.c
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@ -22,6 +22,8 @@
#include <qb/qbdefs.h>
#include "atomic_int.h"
#define QB_RB_FILE_HEADER_VERSION 1
/*
* #define CRAZY_DEBUG_PRINTFS 1
*/
@ -717,17 +719,33 @@ print_header(struct qb_ringbuffer_s * rb)
#endif /* S_SPLINT_S */
}
/*
* FILE HEADER ORDER
* 1. word_size
* 2. write_pt
* 3. read_pt
* 4. version
* 5. header_hash
*
* 6. data
*/
ssize_t
qb_rb_write_to_file(struct qb_ringbuffer_s * rb, int32_t fd)
{
ssize_t result;
ssize_t written_size = 0;
uint32_t hash = 0;
uint32_t version = QB_RB_FILE_HEADER_VERSION;
if (rb == NULL) {
return -EINVAL;
}
print_header(rb);
/*
* 1. word_size
*/
result = write(fd, &rb->shared_hdr->word_size, sizeof(uint32_t));
if (result != sizeof(uint32_t)) {
return -errno;
@ -735,7 +753,7 @@ qb_rb_write_to_file(struct qb_ringbuffer_s * rb, int32_t fd)
written_size += result;
/*
* store the read & write pointers
* 2. 3. store the read & write pointers
*/
result = write(fd, (void *)&rb->shared_hdr->write_pt, sizeof(uint32_t));
if (result != sizeof(uint32_t)) {
@ -748,6 +766,25 @@ qb_rb_write_to_file(struct qb_ringbuffer_s * rb, int32_t fd)
}
written_size += result;
/*
* 4. version used
*/
result = write(fd, &version, sizeof(uint32_t));
if (result != sizeof(uint32_t)) {
return -errno;
}
written_size += result;
/*
* 5. hash helps us verify header is not corrupted on file read
*/
hash = rb->shared_hdr->word_size + rb->shared_hdr->write_pt + rb->shared_hdr->read_pt + QB_RB_FILE_HEADER_VERSION;
result = write(fd, &hash, sizeof(uint32_t));
if (result != sizeof(uint32_t)) {
return -errno;
}
written_size += result;
result = write(fd, rb->shared_data,
rb->shared_hdr->word_size * sizeof(uint32_t));
if (result != rb->shared_hdr->word_size * sizeof(uint32_t)) {
@ -770,11 +807,17 @@ qb_rb_create_from_file(int32_t fd, uint32_t flags)
uint32_t write_pt;
struct qb_ringbuffer_s *rb;
uint32_t word_size = 0;
uint32_t version = 0;
uint32_t hash = 0;
uint32_t calculated_hash = 0;
if (fd < 0) {
return NULL;
}
/*
* 1. word size
*/
n_required = sizeof(uint32_t);
n_read = read(fd, &word_size, n_required);
if (n_read != n_required) {
@ -783,6 +826,9 @@ qb_rb_create_from_file(int32_t fd, uint32_t flags)
}
total_read += n_read;
/*
* 2. 3. read & write pointers
*/
n_read = read(fd, &write_pt, sizeof(uint32_t));
assert(n_read == sizeof(uint32_t));
total_read += n_read;
@ -791,12 +837,41 @@ qb_rb_create_from_file(int32_t fd, uint32_t flags)
assert(n_read == sizeof(uint32_t));
total_read += n_read;
if (write_pt > word_size || read_pt > word_size) {
qb_util_log(LOG_ERR, "Corrupt blackbox: read_pt:%d, write_pt:%d, word_size:%d",
read_pt, write_pt, word_size);
/*
* 4. version
*/
n_required = sizeof(uint32_t);
n_read = read(fd, &version, n_required);
if (n_read != n_required) {
qb_util_perror(LOG_ERR, "Unable to read blackbox file header");
return NULL;
}
total_read += n_read;
/*
* 5. Hash
*/
n_required = sizeof(uint32_t);
n_read = read(fd, &hash, n_required);
if (n_read != n_required) {
qb_util_perror(LOG_ERR, "Unable to read blackbox file header");
return NULL;
}
total_read += n_read;
calculated_hash = word_size + write_pt + read_pt + version;
if (hash != calculated_hash) {
qb_util_log(LOG_ERR, "Corrupt blackbox: File header hash (%d) does not match calculated hash (%d)", hash, calculated_hash);
return NULL;
} else if (version != QB_RB_FILE_HEADER_VERSION) {
qb_util_log(LOG_ERR, "Wrong file header version. Expected %d got %d",
QB_RB_FILE_HEADER_VERSION, version);
return NULL;
}
/*
* 6. data
*/
n_required = (word_size * sizeof(uint32_t));
rb = qb_rb_open("create_from_file", n_required,
QB_RB_FLAG_CREATE | QB_RB_FLAG_NO_SEMAPHORE, 0);