Keep log directory open, use mkdirat(2) and openat(2)

chat.c

@@ -144,6 +144,7 @@ int main(int argc, char *argv[]) {
 	const char *cert = NULL;
 	const char *priv = NULL;
 
+	bool log = false;
 	bool sasl = false;
 	const char *pass = NULL;
 	const char *nick = NULL;
@@ -212,7 +213,7 @@ int main(int argc, char *argv[]) {
 			break; case 'i': filterAdd(Ice, optarg);
 			break; case 'j': self.join = optarg;
 			break; case 'k': priv = optarg;
-			break; case 'l': logEnable = true;
+			break; case 'l': log = true; logOpen();
 			break; case 'm': self.mode = optarg;
 			break; case 'n': nick = optarg;
 			break; case 'o': insecure = true; printCert = true;
@@ -277,7 +278,7 @@ int main(int argc, char *argv[]) {
 	}
 
 #ifdef __OpenBSD__
-	if (self.restricted && logEnable) {
+	if (self.restricted && log) {
 		const char *logdir = dataMkdir("");
 		int error = unveil(logdir, "wc");
 		if (error) err(EX_OSERR, "unveil");
@@ -285,7 +286,7 @@ int main(int argc, char *argv[]) {
 
 	char promises[64] = "stdio tty";
 	char *ptr = &promises[strlen(promises)], *end = &promises[sizeof(promises)];
-	if (logEnable) ptr = seprintf(ptr, end, " wpath cpath");
+	if (log) ptr = seprintf(ptr, end, " wpath cpath");
 	if (!self.restricted) ptr = seprintf(ptr, end, " proc exec");
 
 	char *promisesInitial = ptr;

chat.h

@@ -394,7 +394,7 @@ struct Filter filterAdd(enum Heat heat, const char *pattern);
 bool filterRemove(struct Filter filter);
 enum Heat filterCheck(enum Heat heat, uint id, const struct Message *msg);
 
-extern bool logEnable;
+void logOpen(void);
 void logFormat(uint id, const time_t *time, const char *format, ...)
 	__attribute__((format(printf, 3, 4)));
 void logClose(void);

log.c

@@ -27,16 +27,32 @@
 
 #include <assert.h>
 #include <err.h>
+#include <errno.h>
+#include <fcntl.h>
 #include <limits.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <sys/stat.h>
 #include <sysexits.h>
 #include <time.h>
+#include <unistd.h>
 
 #include "chat.h"
 
-bool logEnable;
+static int logDir = -1;
+
+void logOpen(void) {
+	dataMkdir("");
+	const char *path = dataMkdir("log");
+	logDir = open(path, O_RDONLY | O_CLOEXEC);
+	if (logDir < 0) err(EX_CANTCREAT, "%s", path);
+}
+
+static void logMkdir(const char *path) {
+	int error = mkdirat(logDir, path, S_IRWXU);
+	if (error && errno != EEXIST) err(EX_CANTCREAT, "log/%s", path);
+}
 
 static struct {
 	int year;
@@ -62,44 +78,47 @@ static FILE *logFile(uint id, const struct tm *tm) {
 	logs[id].month = tm->tm_mon;
 	logs[id].day = tm->tm_mday;
 
-	char path[PATH_MAX] = "log";
-	size_t len = strlen(path);
-	dataMkdir("");
-	dataMkdir(path);
-
-	path[len++] = '/';
+	size_t len = 0;
+	char path[PATH_MAX];
 	for (const char *ch = network.name; *ch; ++ch) {
 		path[len++] = (*ch == '/' ? '_' : *ch);
 	}
 	path[len] = '\0';
-	dataMkdir(path);
+	logMkdir(path);
 
 	path[len++] = '/';
 	for (const char *ch = idNames[id]; *ch; ++ch) {
 		path[len++] = (*ch == '/' ? '_' : *ch);
 	}
 	path[len] = '\0';
-	dataMkdir(path);
+	logMkdir(path);
 
 	strftime(&path[len], sizeof(path) - len, "/%F.log", tm);
-	logs[id].file = dataOpen(path, "ae");
-	if (!logs[id].file) exit(EX_CANTCREAT);
+	int fd = openat(
+		logDir, path,
+		O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC,
+		S_IRUSR | S_IWUSR
+	);
+	if (fd < 0) err(EX_CANTCREAT, "log/%s", path);
+	logs[id].file = fdopen(fd, "a");
+	if (!logs[id].file) err(EX_OSERR, "fdopen");
 
 	setlinebuf(logs[id].file);
 	return logs[id].file;
 }
 
 void logClose(void) {
-	if (!logEnable) return;
+	if (logDir < 0) return;
 	for (uint id = 0; id < IDCap; ++id) {
 		if (!logs[id].file) continue;
 		int error = fclose(logs[id].file);
 		if (error) err(EX_IOERR, "%s", idNames[id]);
 	}
+	close(logDir);
 }
 
 void logFormat(uint id, const time_t *src, const char *format, ...) {
-	if (!logEnable) return;
+	if (logDir < 0) return;
 
 	time_t ts = (src ? *src : time(NULL));
 	struct tm *tm = localtime(&ts);