Make the demo directory check more robust

This is how it should've been to begin with, but I was lazy.

3 files changed, 28 insertions, 4 deletions

diff --git a/src/demorec.c b/src/demorec.c
index 2108436..c8871bd 100644
--- a/src/demorec.c
+++ b/src/demorec.c
@@ -88,7 +88,8 @@ static void hook_record_cb(const struct con_cmdargs *args) {
 	bool was = *recording;
 	if (!was && args->argc == 2 || args->argc == 3) {
 		// safety check: make sure a directory exists, otherwise recording
-		// silently fails
+		// silently fails. this is necessarily TOCTOU, but in practice it's
+		// way better than not doing it - just to have a sanity check.
 		const char *arg = args->argv[1];
 		const char *lastslash = 0;
 		for (const char *p = arg; *p; ++p) {
@@ -111,9 +112,28 @@ static void hook_record_cb(const struct con_cmdargs *args) {
 					*q = (uchar)*p;
 				}
 				q[argdirlen] = OS_LIT('\0');
-				if (os_access(dir, X_OK) == -1) {
-					con_warn("ERROR: can't record demo: subdirectory %.*s "
-							"doesn't exist\n", argdirlen, arg);
+				// this is pretty ugly. the error cases would be way tidier if
+				// we could use open(O_DIRECTORY), but that's not a thing on
+				// windows, of course.
+				struct os_stat s;
+				if (os_stat(dir, &s) == -1) {
+					con_warn("ERROR: can't record demo: ");
+					if (errno == ENOENT) {
+						con_warn("subdirectory %.*s doesn't exist\n",
+								argdirlen, arg);
+					}
+					else {
+						con_warn("%s\n", strerror(errno)); // guess this'll do.
+					}
+					return;
+				}
+				if (!S_ISDIR(s.st_mode)) {
+					// duping this warning call to avoid duping the string data,
+					// very stupid, oh well. if/when we have New And Improved
+					// Logging this can be tidied up...
+					con_warn("ERROR: can't record demo: ");
+					con_warn("the path %.*s is not a directory\n",
+							argdirlen, arg);
 					return;
 				}
 			}
diff --git a/src/os-win32.h b/src/os-win32.h
index 8aeb93a..12720a9 100644
--- a/src/os-win32.h
+++ b/src/os-win32.h
@@ -109,6 +109,9 @@ static inline void os_randombytes(void *buf, int sz) {
 #define W_OK 2
 #define X_OK R_OK // there's no actual X bit, just pretend
 
+// windows doesn't define this for some reason!? note: add others as needed...
+#define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
+
 // just dump this boilerplate here as well, I spose
 #define OS_WINDOWS_ERROR(arrayname) \
 	FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM, 0, GetLastError(), \
diff --git a/src/os.h b/src/os.h
index c00eaf3..3d3ab00 100644
--- a/src/os.h
+++ b/src/os.h
@@ -46,6 +46,7 @@
 #include <string.h>
 #include <strings.h>
 #include <sys/mman.h>
+#include <sys/stat.h>
 #include <unistd.h>
 #endif