Add a snprinf wrapper which checks that the buffer was big enough

If we scale our buffer to be wide enough for the format string, we
should expect that the calculation was correct.

char_array_0() invocations are removed, since snprintf nul-terminates
the output in any case.

A similar wrapper is used for strftime calls, but only in timedatectl.c.

1 files changed, 28 insertions, 39 deletions

diff --git a/src/timedate/timedatectl.c b/src/timedate/timedatectl.c
index 74f40b9c80..1f85536cf2 100644
--- a/src/timedate/timedatectl.c
+++ b/src/timedate/timedatectl.c
@@ -38,6 +38,8 @@
 #include "pager.h"
 #include "time-dst.h"
 
+#define xstrftime(buf, fmt, tm) assert_se(strftime(buf, sizeof(buf), fmt, tm) > 0)
+
 static bool arg_no_pager = false;
 static bool arg_ask_password = true;
 static BusTransport arg_transport = BUS_TRANSPORT_LOCAL;
@@ -123,15 +125,11 @@ static void print_status_info(const StatusInfo *i) {
                 fprintf(stderr, "Warning: Could not get time from timedated and not operating locally.\n\n");
 
         if (have_time) {
-                zero(tm);
-                assert_se(strftime(a, sizeof(a), "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&sec, &tm)) > 0);
-                char_array_0(a);
-                printf("      Local time: %s\n", a);
-
-                zero(tm);
-                assert_se(strftime(a, sizeof(a), "%a %Y-%m-%d %H:%M:%S UTC", gmtime_r(&sec, &tm)) > 0);
-                char_array_0(a);
-                printf("  Universal time: %s\n", a);
+                xstrftime(a, "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&sec, &tm));
+                printf("      Local time: %.*s\n", (int) sizeof(a), a);
+
+                xstrftime(a, "%a %Y-%m-%d %H:%M:%S UTC", gmtime_r(&sec, &tm));
+                printf("  Universal time: %.*s\n", (int) sizeof(a), a);
         } else {
                 printf("      Local time: %s\n", "n/a");
                 printf("  Universal time: %s\n", "n/a");
@@ -141,24 +139,19 @@ static void print_status_info(const StatusInfo *i) {
                 time_t rtc_sec;
 
                 rtc_sec = (time_t)(i->rtc_time / USEC_PER_SEC);
-                zero(tm);
-                assert_se(strftime(a, sizeof(a), "%a %Y-%m-%d %H:%M:%S", gmtime_r(&rtc_sec, &tm)) > 0);
-                char_array_0(a);
-                printf("        RTC time: %s\n", a);
+                xstrftime(a, "%a %Y-%m-%d %H:%M:%S", gmtime_r(&rtc_sec, &tm));
+                printf("        RTC time: %.*s\n", (int) sizeof(a), a);
         } else
                 printf("        RTC time: %s\n", "n/a");
 
-        if (have_time) {
-                zero(tm);
-                assert_se(strftime(a, sizeof(a), "%Z, %z", localtime_r(&sec, &tm)) > 0);
-                char_array_0(a);
-        }
+        if (have_time)
+                xstrftime(a, "%Z, %z", localtime_r(&sec, &tm));
 
-        printf("       Time zone: %s (%s)\n"
+        printf("       Time zone: %s (%.*s)\n"
                "     NTP enabled: %s\n"
                "NTP synchronized: %s\n"
                " RTC in local TZ: %s\n",
-               strna(i->timezone), have_time ? a : "n/a",
+               strna(i->timezone), (int) sizeof(a), have_time ? a : "n/a",
                i->ntp_capable ? yes_no(i->ntp_enabled) : "n/a",
                yes_no(i->ntp_synced),
                yes_no(i->rtc_local));
@@ -173,30 +166,26 @@ static void print_status_info(const StatusInfo *i) {
                         printf("      DST active: %s\n", yes_no(is_dstc));
 
                         t = tc - 1;
-                        zero(tm);
-                        assert_se(strftime(a, sizeof(a), "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&t, &tm)) > 0);
-                        char_array_0(a);
+                        xstrftime(a, "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&t, &tm));
 
-                        zero(tm);
-                        assert_se(strftime(b, sizeof(b), "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&tc, &tm)) > 0);
-                        char_array_0(b);
+                        xstrftime(b, "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&tc, &tm));
                         printf(" Last DST change: DST %s at\n"
-                               "                  %s\n"
-                               "                  %s\n",
-                               is_dstc ? "began" : "ended", a, b);
+                               "                  %.*s\n"
+                               "                  %.*s\n",
+                               is_dstc ? "began" : "ended",
+                               (int) sizeof(a), a,
+                               (int) sizeof(b), b);
 
                         t = tn - 1;
-                        zero(tm);
-                        assert_se(strftime(a, sizeof(a), "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&t, &tm)) > 0);
-                        char_array_0(a);
-
-                        zero(tm);
-                        assert_se(strftime(b, sizeof(b), "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&tn, &tm)) > 0);
-                        char_array_0(b);
+                        xstrftime(a, "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&t, &tm));
+                        xstrftime(b, "%a %Y-%m-%d %H:%M:%S %Z", localtime_r(&tn, &tm));
                         printf(" Next DST change: DST %s (the clock jumps %s) at\n"
-                               "                  %s\n"
-                               "                  %s\n",
-                               is_dstn ? "begins" : "ends", jump_str(dn, s, sizeof(s)), a, b);
+                               "                  %.*s\n"
+                               "                  %.*s\n",
+                               is_dstn ? "begins" : "ends",
+                               jump_str(dn, s, sizeof(s)),
+                               (int) sizeof(a), a,
+                               (int) sizeof(b), b);
                 }
         } else
                 printf("      DST active: %s\n", yes_no(is_dstc));