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engine: add magic numbers to verify struct integrity

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The main focus of this commit is 'bal_safety.h'. This header file
adds magic numbers to prevent Undefined Behavior. Right now this
has only been added to 'bal_assembler_t'.

This introduces 3 magic numbers:

#define BAL_MAGIC_UNINITIALIZED 0x00000000U
#define BAL_ASSEMBLER_MAGIC_ALIVE 0xBA11A550U
#define BAL_ASSEMBLER_MAGIC_DEAD  0xDEADBA11U

'ALIVE' magic numbers will be set only if the struct has been
initialized properly. Every function should check a struct's magic
number to make sure it's not operating on a memory corrupted struct.

'DEAD' magic numbers should be set on a struct's 'destory()' function.
This is done to prevent Double Free and Use-After-Free scenarios.

Convenience macro 'BAL_CHECK_MAGIC' and 'BAL_CHECK_MAGIC_VOID' have
been added to easily validate struct integrity.

Signed-off-by: Ronald Caesar <github43132@proton.me>
This commit is contained in:
Ronald Caesar
2026-06-17 03:20:17 -04:00
parent 2e7240e9d4
commit 35ef021fc9
3 changed files with 147 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/bal_assembler.h
+5 -2
View File
@@ -55,7 +55,8 @@ extern "C"
/// be ignored until the assembler is reset.
bal_error_t status;
uint32_t pad;
/// Integrity check.
uint32_t magic;
} bal_assembler_t;
/// Initializes the assembler with a specific memory buffer and the size of the buffer in
@@ -64,8 +65,10 @@ extern "C"
/// # Returns
///
/// * [`BAL_SUCCESS`] on success.
/// * [`BAL_ERROR_INVALID_ARGUMENT`] if `assembler` or `buffer` is NULL.
/// * [`BAL_ERROR_INVALID_ARGUMENT`] if `assembler` or `buffer` is NULL, or if `size` is `0`.
/// * [`BAL_ERROR_MEMORY_ALIGNMENT`] if `buffer` is not 4-byte aligned.
/// * [`BAL_ERROR_CAPACITY_TOO_BIG`] if `size` is large enough to cause a `size_t` integer
/// overflow.
bal_error_t bal_assembler_init(bal_assembler_t *assembler,
void *buffer,
size_t size,
include/bal_safety.h
+92
View File
@@ -0,0 +1,92 @@
#ifndef BALLISTIC_SAFETY_H
#define BALLISTIC_SAFETY_H
#ifdef __cplusplus
extern "C"
{
#endif // __cplusplus
#define BAL_MAGIC_UNINITIALIZED 0x00000000U
#define BAL_ASSEMBLER_MAGIC_ALIVE 0xBA11A550U // BALLISTO
#define BAL_ASSEMBLER_MAGIC_DEAD 0xDEADBA11U // DEADBALL
static const char *bal_decode_magic(uint32_t magic)
{
switch (magic)
{
case BAL_MAGIC_UNINITIALIZED:
return "Uninitialized Memory";
case BAL_ASSEMBLER_MAGIC_ALIVE:
return "BALLISTO";
case BAL_ASSEMBLER_MAGIC_DEAD:
return "DEADBALL";
default:
return "Unknown (Likely Buffer Overflow)";
}
}
static inline const char *bal_diagnose_magic_failure(uint32_t actual_magic, uint32_t dead_magic)
{
if (actual_magic == BAL_MAGIC_UNINITIALIZED)
{
return "Struct was never initialized.";
}
if (actual_magic == dead_magic)
{
return "Struct was explicitly destroyed (Double Free?).";
}
return "Memory corruption or wrong struct type passed.";
}
#define BAL_CHECK_MAGIC(ptr, alive_magic, dead_magic, struct_name_str, logger) \
do \
{ \
if (BAL_UNLIKELY((ptr)->magic != (alive_magic))) \
{ \
BAL_LOG_ERROR(&logger, \
"\n================================================================\n" \
"%s INTEGRITY CHECK FAILED!\n" \
" Expected : 0x%08X (%s)\n" \
" Actual : 0x%08X (%s)\n" \
" Reason: %s\n" \
"================================================================\n", \
(struct_name_str), \
(alive_magic), \
bal_decode_magic(alive_magic), \
(ptr)->magic, \
bal_decode_magic((ptr)->magic), \
bal_diagnose_magic_failure((ptr)->magic, (dead_magic))); \
(ptr)->status = BAL_ERROR_STRUCT_CORRUPTED; \
return (BAL_ERROR_STRUCT_CORRUPTED); \
} \
} while (0)
#define BAL_CHECK_MAGIC_VOID(ptr, alive_magic, dead_magic, struct_name_str, logger) \
do \
{ \
if (BAL_UNLIKELY((ptr)->magic != (alive_magic))) \
{ \
BAL_LOG_ERROR(&logger, \
"\n================================================================\n" \
"%s INTEGRITY CHECK FAILED!\n" \
" Expected : 0x%08X (%s)\n" \
" Actual : 0x%08X (%s)\n" \
" Reason: %s\n" \
"================================================================\n", \
(struct_name_str), \
(alive_magic), \
bal_decode_magic(alive_magic), \
(ptr)->magic, \
bal_decode_magic((ptr)->magic), \
bal_diagnose_magic_failure((ptr)->magic, (dead_magic))); \
(ptr)->status = BAL_ERROR_STRUCT_CORRUPTED; \
return; \
} \
} while (0)
#ifdef __cplusplus
}
#endif // __cplusplus
#endif // BALLISTIC_SAFETY_H
src/bal_assembler.c
+50 -4
View File
@@ -1,4 +1,5 @@
#include "bal_assembler.h"
#include "bal_safety.h"
#include <stdbool.h>
#include <string.h>
@@ -17,16 +18,40 @@ bal_assembler_init(bal_assembler_t *assembler,
return BAL_ERROR_INVALID_ARGUMENT;
}
assembler->buffer = NULL;
assembler->capacity = 0;
assembler->offset = 0;
assembler->logger = logger;
assembler->status = BAL_ERROR_INVALID_ARGUMENT;
assembler->magic = 0;
if (NULL == buffer)
{
BAL_LOG_ERROR(&logger, "Buffer is NULL.");
return BAL_ERROR_INVALID_ARGUMENT;
BAL_LOG_ERROR(&logger, "Aborting function: Buffer is NULL.");
return assembler->status;
}
if (0 == size)
{
BAL_LOG_ERROR(&logger, "Aborting function: Buffer capacity is 0.");
return assembler->status;
}
if ((uintptr_t)buffer % 4 != 0)
{
BAL_LOG_ERROR(&logger, "Buffer %p is not 4-byte aligned.", buffer);
return BAL_ERROR_MEMORY_ALIGNMENT;
BAL_LOG_ERROR(&logger, "Aborting function: Buffer %p is not 4-byte aligned.", buffer);
assembler->status = BAL_ERROR_MEMORY_ALIGNMENT;
return assembler->status;
}
if (size > (SIZE_MAX / sizeof(uint32_t)))
{
BAL_LOG_ERROR(&logger,
"Aborting function: Buffer capacity %zu is too large and would "
"cause integer overflow.",
size);
assembler->status = BAL_ERROR_CAPACITY_TOO_BIG;
return assembler->status;
}
assembler->buffer = (uint32_t *)buffer;
@@ -34,6 +59,7 @@ bal_assembler_init(bal_assembler_t *assembler,
assembler->offset = 0;
assembler->logger = logger;
assembler->status = BAL_SUCCESS;
assembler->magic = BAL_ASSEMBLER_MAGIC_ALIVE;
BAL_LOG_INFO(
&logger, "Assembler initialized. Buffer: %p, Capacity: %zu instructions.", buffer, size);
@@ -48,6 +74,26 @@ bal_assembler_reset(bal_assembler_t *assembler)
return;
}
BAL_CHECK_MAGIC_VOID(assembler,
BAL_ASSEMBLER_MAGIC_ALIVE,
BAL_ASSEMBLER_MAGIC_DEAD,
"bal_assembler_t",
assembler->logger);
if (BAL_UNLIKELY(NULL == assembler->buffer))
{
BAL_LOG_ERROR(&assembler->logger, "Aborting function: assembler->buffer == NULL");
assembler->status = BAL_ERROR_INVALID_ARGUMENT;
return;
}
if (BAL_UNLIKELY(0 == assembler->capacity))
{
BAL_LOG_ERROR(&assembler->logger, "Aborting function: assembler->capacity == 0");
assembler->status = BAL_ERROR_INVALID_ARGUMENT;
return;
}
assembler->offset = 0;
assembler->status = BAL_SUCCESS;
(void)memset(assembler->buffer, 0, assembler->capacity * sizeof(uint32_t));