Have a common routine for converting dates and times to strings.

Have a routine that takes a buffer, a strftime format, and a struct tm *
as arguments, and:

* checks whether the struct tm * is null and, if so, returns a string
indicating that the date and time couldn't be converted;

* otherwise, passes it to strftime(), along with the buffer and the
format argument and, if strftime() returns 0, meaning the string didn't
fit into the buffer and thus that the buffer's contents are undefined,
returns a string indicating that the date and time didn't fit into the
buffer;

* otherwise, returns a pointer to the buffer.

Call that routine instead of directly calling strftime() in printers;
that prevents printing a buffer with undefined data if the buffer isn't
big enough for the string.

Also, when generating file names using an strftime format, check the
return value of strftime() to make sure the buffer didn't overflow.

diff --git a/netdissect.h b/netdissect.h
index 5c16be660cd3e185f5d6de411e0d3ca42c15fed7..b1074ef72bc921fdd7dbcf4d6d59445e11561de9 100644 (file)
--- a/netdissect.h
+++ b/netdissect.h
@@ -423,6 +423,9 @@ extern void ts_print(netdissect_options *, const struct timeval *);
 extern void signed_relts_print(netdissect_options *, int32_t);
 extern void unsigned_relts_print(netdissect_options *, uint32_t);
 
+extern const char *nd_format_time(char *buf, size_t bufsize,
+    const char *format, const struct tm *timeptr);
+
 extern void fn_print_char(netdissect_options *, u_char);
 extern void fn_print_str(netdissect_options *, const u_char *);
 extern u_int nd_printztn(netdissect_options *, const u_char *, u_int, const u_char *);

diff --git a/ntp.c b/ntp.c
index 10fabe4b6d13575b4578f78ec33cfb1497cb8ea2..ec8f659a4eb020b6232458226268676f3582654c 100644 (file)
--- a/ntp.c
+++ b/ntp.c
@@ -54,8 +54,8 @@ p_ntp_time(netdissect_options *ndo,
        if (i) {
            int64_t seconds_64bit = (int64_t)i - JAN_1970;
            time_t seconds;
-           struct tm *tm;
            char time_buf[128];
+           const char *time_string;
 
            seconds = (time_t)seconds_64bit;
            if (seconds != seconds_64bit) {
@@ -63,21 +63,12 @@ p_ntp_time(netdissect_options *ndo,
                 * It doesn't fit into a time_t, so we can't hand it
                 * to gmtime.
                 */
-               ND_PRINT(" (unrepresentable)");
+               time_string = "[Time is too large to fit into a time_t]";
            } else {
-               tm = gmtime(&seconds);
-               if (tm == NULL) {
-                   /*
-                    * gmtime() can't handle it.
-                    * (Yes, that might happen with some version of
-                    * Microsoft's C library.)
-                    */
-                   ND_PRINT(" (unrepresentable)");
-               } else {
-                   /* use ISO 8601 (RFC3339) format */
-                   strftime(time_buf, sizeof (time_buf), "%Y-%m-%dT%H:%M:%SZ", tm);
-                   ND_PRINT(" (%s)", time_buf);
-               }
+               /* use ISO 8601 (RFC3339) format */
+               time_string = nd_format_time(time_buf, sizeof (time_buf),
+                 "%Y-%m-%dT%H:%M:%SZ", gmtime(&seconds));
            }
+           ND_PRINT(" (%s)", time_string);
        }
 }

diff --git a/print-ahcp.c b/print-ahcp.c
index 9859f76009d5953efffb8a0d9c2c60d4bcd23879..d57edda9e090f280c214de3a45e057d962461a7a 100644 (file)
--- a/print-ahcp.c
+++ b/print-ahcp.c
@@ -102,18 +102,14 @@ ahcp_time_print(netdissect_options *ndo,
                 const u_char *cp, uint8_t len)
 {
        time_t t;
-       struct tm *tm;
-       char buf[BUFSIZE];
+       char buf[sizeof("-yyyyyyyyyy-mm-dd hh:mm:ss UTC")];
 
        if (len != 4)
                goto invalid;
        t = GET_BE_U_4(cp);
-       if (NULL == (tm = gmtime(&t)))
-               ND_PRINT(": gmtime() error");
-       else if (0 == strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", tm))
-               ND_PRINT(": strftime() error");
-       else
-               ND_PRINT(": %s UTC", buf);
+       ND_PRINT(": %s",
+           nd_format_time(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S UTC",
+             gmtime(&t)));
        return;
 
 invalid:

diff --git a/print-arista.c b/print-arista.c
index 039a1ffd1e89bbea87e23918d98ffa12b8a530a6..079ad684bc1145dfb6e3264cc8b671474569f180 100644 (file)
--- a/print-arista.c
+++ b/print-arista.c
@@ -10,7 +10,6 @@
 
 #include "netdissect.h"
 #include "extract.h"
-#include "addrtoname.h"
 
 /*
 
@@ -93,17 +92,13 @@ arista_print_date_hms_time(netdissect_options *ndo, uint32_t seconds,
                uint32_t nanoseconds)
 {
        time_t ts;
-       struct tm *tm;
-       char buf[BUFSIZE];
+       char buf[sizeof("-yyyyyyyyyy-mm-dd hh:mm:ss")];
 
        ts = seconds + (nanoseconds / 1000000000);
        nanoseconds %= 1000000000;
-       if (NULL == (tm = gmtime(&ts)))
-               ND_PRINT("gmtime() error");
-       else if (0 == strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", tm))
-               ND_PRINT("strftime() error");
-       else
-               ND_PRINT("%s.%09u", buf, nanoseconds);
+       ND_PRINT("%s.%09u",
+           nd_format_time(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S",
+              gmtime(&ts)), nanoseconds);
 }
 
 int

diff --git a/print-rx.c b/print-rx.c
index 26b51c19d881965370c5c49d3075f405f80248a3..0a1a8d12d40d167b3fc518184b0506a2f14da78d 100644 (file)
--- a/print-rx.c
+++ b/print-rx.c
@@ -794,12 +794,12 @@ rx_cache_find(netdissect_options *ndo, const struct rx_header *rxh,
                        ND_PRINT(" %" PRIu64, _i); \
                }
 
-#define DATEOUT() { time_t _t; struct tm *tm; char str[256]; \
+#define DATEOUT() { time_t _t; char str[256]; \
                        _t = (time_t) GET_BE_S_4(bp); \
                        bp += sizeof(int32_t); \
-                       tm = localtime(&_t); \
-                       strftime(str, 256, "%Y/%m/%d %H:%M:%S", tm); \
-                       ND_PRINT(" %s", str); \
+                       ND_PRINT(" %s", \
+                           nd_format_time(str, sizeof(str), \
+                             "%Y/%m/%d %H:%M:%S", localtime(&_t))); \
                }
 
 #define STOREATTROUT() { uint32_t mask, _i; \

diff --git a/print-zep.c b/print-zep.c
index 8119a19e9a7bba6a2774f689522e93b13091dd3d..52901e789b1ddfc89fd3aafc30f588ebd562bfca 100644 (file)
--- a/print-zep.c
+++ b/print-zep.c
@@ -82,12 +82,11 @@ static void zep_print_ts(netdissect_options *ndo, const u_char *p)
         */
        if (i) {
                time_t seconds = i - JAN_1970;
-               struct tm *tm;
                char time_buf[128];
 
-               tm = localtime(&seconds);
-               strftime(time_buf, sizeof (time_buf), "%Y/%m/%d %H:%M:%S", tm);
-               ND_PRINT(" (%s)", time_buf);
+               ND_PRINT(" (%s)",
+                   nd_format_time(time_buf, sizeof (time_buf), "%Y/%m/%d %H:%M:%S",
+                     localtime(&seconds)));
        }
 }
 

diff --git a/smbutil.c b/smbutil.c
index 9e19909a29703d66f03a3dae68e9ae4a799a1ba8..97217a8d9fc6a8a4def9fbd160b9217e37cd2d92 100644 (file)
--- a/smbutil.c
+++ b/smbutil.c
@@ -768,9 +768,8 @@ smb_fdata1(netdissect_options *ndo,
        case 'T':
          {
            time_t t;
-           struct tm *lt;
            const char *tstring;
-           char buffer[sizeof("Www Mmm dd hh:mm:ss yyyyy\n")];
+           char buffer[sizeof("Www Mmm dd hh:mm:ss yyyyy")];
            uint32_t x;
 
            switch (atoi(fmt + 1)) {
@@ -800,16 +799,11 @@ smb_fdata1(netdissect_options *ndo,
                break;
            }
            if (t != 0) {
-               lt = localtime(&t);
-               if (lt != NULL) {
-                   strftime(buffer, sizeof(buffer), "%a %b %e %T %Y%n", lt);
-                   tstring = buffer;
-               }
-               else
-                   tstring = "(Can't convert time)\n";
+                   tstring = nd_format_time(buffer, sizeof(buffer), "%a %b %e %T %Y",
+                   localtime(&t));
            } else
-               tstring = "NULL\n";
-           ND_PRINT("%s", tstring);
+               tstring = "NULL";
+           ND_PRINT("%s\n", tstring);
            fmt++;
            while (ND_ASCII_ISDIGIT(*fmt))
                fmt++;

diff --git a/tcpdump.c b/tcpdump.c
index 78d0871a567685b1d11ebf867c4a27f4c5281f91..0b6541589f018fd61121bcb66a9fd6262d44346d 100644 (file)
--- a/tcpdump.c
+++ b/tcpdump.c
@@ -843,6 +843,8 @@ MakeFilename(char *buffer, char *orig_name, int cnt, int max_chars)
         char *filename = malloc(PATH_MAX + 1);
         if (filename == NULL)
             error("%s: malloc", __func__);
+        if (strlen(orig_name) == 0)
+            error("an empty string is not a valid file name");
 
         /* Process with strftime if Gflag is set. */
         if (Gflag != 0) {
@@ -854,9 +856,25 @@ MakeFilename(char *buffer, char *orig_name, int cnt, int max_chars)
           }
 
           /* There's no good way to detect an error in strftime since a return
-           * value of 0 isn't necessarily failure.
+           * value of 0 isn't necessarily failure; if orig_name is an empty
+           * string, the formatted string will be empty.
+           *
+           * However, the C90 standard says that, if there *is* a
+           * buffer overflow, the content of the buffer is undefined,
+           * so we must check for a buffer overflow.
+           *
+           * So we check above for an empty orig_name, and only call
+           * strftime() if it's non-empty, in which case the return
+           * value will only be 0 if the formatted date doesn't fit
+           * in the buffer.
+           *
+           * (We check above because, even if we don't use -G, we
+           * want a better error message than "tcpdump: : No such
+           * file or directory" for this case.)
            */
-          strftime(filename, PATH_MAX, orig_name, local_tm);
+          if (strftime(filename, PATH_MAX, orig_name, local_tm) == 0) {
+            error("%s: strftime", __func__);
+          }
         } else {
           strncpy(filename, orig_name, PATH_MAX);
         }

diff --git a/util-print.c b/util-print.c
index 8b20649729122b286dcfb01a62f495c4b51b8e27..0548337860eee16e7666150390076c0b3295b156 100644 (file)
--- a/util-print.c
+++ b/util-print.c
@@ -230,7 +230,8 @@ ts_date_hmsfrac_print(netdissect_options *ndo, long sec, long usec,
 {
        time_t Time = sec;
        struct tm *tm;
-       char timestr[32];
+       char timebuf[32];
+       const char *timestr;
 
        if ((unsigned)sec & 0x80000000) {
                ND_PRINT("[Error converting time]");
@@ -242,14 +243,13 @@ ts_date_hmsfrac_print(netdissect_options *ndo, long sec, long usec,
        else
                tm = gmtime(&Time);
 
-       if (!tm) {
-               ND_PRINT("[Error converting time]");
-               return;
+       if (date_flag == WITH_DATE) {
+               timestr = nd_format_time(timebuf, sizeof(timebuf),
+                   "%Y-%m-%d %H:%M:%S", tm);
+       } else {
+               timestr = nd_format_time(timebuf, sizeof(timebuf),
+                   "%H:%M:%S", tm);
        }
-       if (date_flag == WITH_DATE)
-               strftime(timestr, sizeof(timestr), "%Y-%m-%d %H:%M:%S", tm);
-       else
-               strftime(timestr, sizeof(timestr), "%H:%M:%S", tm);
        ND_PRINT("%s", timestr);
 
        ts_frac_print(ndo, usec);
@@ -405,6 +405,26 @@ signed_relts_print(netdissect_options *ndo,
        unsigned_relts_print(ndo, secs);
 }
 
+/*
+ * Format a struct tm with strftime().
+ * If the pointer to the struct tm is null, that means that the
+ * routine to convert a time_t to a struct tm failed; the localtime()
+ * and gmtime() in the Microsoft Visual Studio C library will fail,
+ * returning null, if the value is before the UNIX Epoch.
+ */
+const char *
+nd_format_time(char *buf, size_t bufsize, const char *format,
+         const struct tm *timeptr)
+{
+       if (timeptr != NULL) {
+               if (strftime(buf, bufsize, format, timeptr) != 0)
+                       return (buf);
+               else
+                       return ("[nd_format_time() buffer is too small]");
+       } else
+               return ("[localtime() or gmtime() couldn't convert the date and time]");
+}
+
 /* Print the truncated string */
 void nd_print_trunc(netdissect_options *ndo)
 {