Make sure that input file name and output file name are distinct (to the extent possible).

frontend/src/main.c

@@ -147,6 +147,7 @@ int MAIN(const int argc, CHR *const argv[])
 	init_terminal();
 	setup_signal_handler(SIGINT, sigint_handler);
 	int result = EXIT_FAILURE;
+	CHR *input_file = NULL, *output_file = NULL;
 	char *passphrase_buffer = NULL;
 
 	FPRINTF(stderr, T("SlunkCrypt Utility (%") T(PRIstr) T("-%") T(PRIstr) T("), by LoRd_MuldeR <MuldeR2@GMX.de>\n"), OS_TYPE, CPU_ARCH);
@@ -203,8 +204,6 @@ int MAIN(const int argc, CHR *const argv[])
 	check_excess_arguments(argc, 5);
 
 	const CHR *const passphrase = PW_FROM_ENV ? GETENV(ENV_PASSWORD) : argv[2U];
-	const CHR *const input_file = argv[PW_FROM_ENV ? 2U : 3U], *const output_file = argv[PW_FROM_ENV ? 3U : 4U];
-
 	if ((!passphrase) || (!passphrase[0U]))
 	{
 		FPUTS(T("Error: The passphrase must be specified, directly or indirectly!\n\n"), stderr);
@@ -220,9 +219,23 @@ int MAIN(const int argc, CHR *const argv[])
 		}
 	}
 
-	if ((!input_file[0U]) || (!output_file[0U]))
+	input_file = absolute_path(argv[PW_FROM_ENV ? 2U : 3U]);
+	if ((!input_file) || (!input_file[0U]))
 	{
-		FPUTS(T("Error: The input file and/or output file must not be empty!\n\n"), stderr);
+		FPUTS(T("Error: Input file path could not be resolved!\n\n"), stderr);
+		goto clean_up;
+	}
+
+	output_file = absolute_path(argv[PW_FROM_ENV ? 3U : 4U]);
+	if ((!output_file) || (!output_file[0U]))
+	{
+		FPUTS(T("Error: Output file path could not be resolved!\n\n"), stderr);
+		goto clean_up;
+	}
+
+	if (!path_compare(input_file, output_file))
+	{
+		FPUTS(T("Error: Input and output files must not be the same path! (effectively)\n\n"), stderr);
 		goto clean_up;
 	}
 
@@ -303,6 +316,16 @@ clean_up:
 		free(passphrase_buffer);
 	}
 
+	if (input_file)
+	{
+		free(input_file);
+	}
+
+	if (output_file)
+	{
+		free(output_file);
+	}
+
 	return result;
 }
 

frontend/src/platform.h

@@ -58,6 +58,7 @@
 #	define STRNICMP(X,Y,Z) _wcsnicmp((X),(Y),(Z))
 #	define STRRCHR(X,Y) wcsrchr((X),(Y))
 #	define STRTOUL(X) wcstoul((X), NULL, 0)
+#	define STRDUP(X) _wcsdup((X))
 #	define FPUTS(X,Y) fputws((X),(Y))
 #	define FPRINTF(X,Y,...) fwprintf((X),(Y),__VA_ARGS__)
 #	define REMOVE(X) _wremove((X))
@@ -81,6 +82,7 @@
 #	define STRNICMP(X,Y,Z) strncasecmp((X),(Y),(Z))
 #	define STRRCHR(X,Y) strrchr((X),(Y))
 #	define STRTOUL(X) strtoul((X), NULL, 0)
+#	define STRDUP(X) strdup((X))
 #	define FPUTS(X,Y) fputs((X),(Y))
 #	define FPRINTF(X,Y,...) fprintf((X),(Y),__VA_ARGS__)
 #	define REMOVE(X) remove((X))

frontend/src/utils.c

@@ -19,6 +19,7 @@
 #include <sys/types.h>
 #include <time.h>
 #include <signal.h>
+#include <stdarg.h>
 
 /* Platform support */
 #ifdef _WIN32
@@ -35,6 +36,7 @@
 #		define _O_U8TEXT 0x40000
 #	endif
 #else
+#	include <unistd.h>
 #	if defined(__USE_LARGEFILE64) && (__USE_LARGEFILE64)
 #		define STAT_T struct stat64
 #		define FSTAT(X,Y) fstat64((X),(Y))
@@ -105,6 +107,65 @@ void setup_signal_handler(const int signo, signal_handler_t* const handler)
 #endif
 }
 
+// ==========================================================================
+// String functions
+// ==========================================================================
+
+char *concat_str(const char *const str, ...)
+{
+	const char *ptr;
+	char *buffer;
+	size_t buff_size = 1U;
+	va_list arg;
+	va_start(arg, str);
+	for (ptr = str; ptr != NULL; ptr = va_arg(arg, const char*))
+	{
+		buff_size += strlen(ptr);
+	}
+	if ((buffer = (char*)calloc(buff_size, sizeof(char))))
+	{
+		va_end(arg);
+		va_start(arg, str);
+		for (ptr = str; ptr != NULL; ptr = va_arg(arg, const char*))
+		{
+			strcat(buffer, ptr);
+		}
+	}
+	va_end(arg);
+	return buffer;
+}
+
+char* CHR_to_utf8(const CHR *const input)
+{
+#ifdef _WIN32
+	char *buffer = NULL;
+	DWORD buffer_size = 0U, result = 0U;
+
+	buffer_size = input ? WideCharToMultiByte(CP_UTF8, 0, input, -1, NULL, 0, NULL, NULL) : 0U;
+	if (buffer_size < 1U)
+	{
+		return NULL;
+	}
+
+	buffer = (char*)malloc(sizeof(char) * buffer_size);
+	if (!buffer)
+	{
+		return NULL;
+	}
+
+	result = WideCharToMultiByte(CP_UTF8, 0, input, -1, (LPSTR)buffer, buffer_size, NULL, NULL);
+	if ((result > 0U) && (result <= buffer_size))
+	{
+		return buffer;
+	}
+
+	free(buffer);
+	return NULL;
+#else
+	return strdup(input); /*simple string copy*/
+#endif
+}
+
 // ==========================================================================
 // Time functions
 // ==========================================================================
@@ -149,41 +210,6 @@ uint64_t clock_read(void)
 	return 0U;
 }
 
-// ==========================================================================
-// Character set conversion
-// ==========================================================================
-
-char* CHR_to_utf8(const CHR *const input)
-{
-#ifdef _WIN32
-	char *buffer = NULL;
-	DWORD buffer_size = 0U, result = 0U;
-
-	buffer_size = input ? WideCharToMultiByte(CP_UTF8, 0, input, -1, NULL, 0, NULL, NULL) : 0U;
-	if (buffer_size < 1U)
-	{
-		return NULL;
-	}
-
-	buffer = (char*) malloc(sizeof(char) * buffer_size);
-	if (!buffer)
-	{
-		return NULL;
-	}
-
-	result = WideCharToMultiByte(CP_UTF8, 0, input, -1, (LPSTR)buffer, buffer_size, NULL, NULL);
-	if ((result > 0U) && (result <= buffer_size))
-	{
-		return buffer;
-	}
-
-	free(buffer);
-	return NULL;
-#else
-	return strdup(input); /*simple string copy*/
-#endif
-}
-
 // ==========================================================================
 // Byte-order support
 // ==========================================================================
@@ -233,6 +259,42 @@ size_t fread_ui64(uint64_t *const value, FILE *const stream)
 // File functions
 // ==========================================================================
 
+#define JOIN_PATHS(X,Y) concat_str((X), "/", (Y), NULL)
+
+CHR *absolute_path(const CHR *const path)
+{
+#ifdef _WIN32
+	wchar_t *const result = _wfullpath(NULL, path, 0U);
+#else
+	char *result = realpath(path, NULL);
+	if ((!result) && path[0U] && (path[0U] != '/'))
+	{
+		char *const cwd = getcwd(NULL, 0U);
+		if (cwd)
+		{
+			const char *path_off = path;
+			while ((path_off[0U] == '.') && (path_off[1U] == '/'))
+			{
+				path_off += 2U;
+				while (path_off[0U] == '/') ++path_off;
+			}
+			result = JOIN_PATHS(cwd, path_off);
+			free(cwd);
+		}
+	}
+#endif
+	return result ? result : STRDUP(path);
+}
+
+int path_compare(const CHR *const path0, const CHR *const path1)
+{
+#ifdef _WIN32
+	return _wcsicmp(path0, path1);
+#else
+	return strcmp(path0, path1);
+#endif
+}
+
 uint64_t get_file_size(FILE* const file)
 {
 	STAT_T stat;

frontend/src/utils.h

@@ -23,8 +23,11 @@ size_t fwrite_ui64(const uint64_t value, FILE *const stream);
 size_t fread_ui64(uint64_t *const value, FILE *const stream);
 
 char* CHR_to_utf8(const CHR *const input);
-uint64_t get_file_size(FILE* const file);
+
+CHR *absolute_path(const CHR *const path);
+int path_compare(const CHR *const path0, const CHR *const path1);
 const CHR *get_file_name(const CHR *path);
+uint64_t get_file_size(FILE* const file);
 
 uint64_t round_down(const uint64_t value, const uint64_t base);