parsedate: offer a getdate_capped() alternative

... and use internally. This function will return TIME_T_MAX instead of
failure if the parsed data is found to be larger than what can be
represented. TIME_T_MAX being the largest value curl can represent.

Reviewed-by: Daniel Gustafsson
Reported-by: JanB on github
Fixes #4152
Closes #4651

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/parsedate.c b/lib/parsedate.c
index f4b18d091..585d7ea40 100644
--- a/lib/parsedate.c
+++ b/lib/parsedate.c
@@ -587,6 +587,30 @@ time_t curl_getdate(const char *p, const time_t *now)
   return -1;
 }
 
+/* Curl_getdate_capped() differs from curl_getdate() in that this will return
+   TIME_T_MAX in case the parsed time value was too big, instead of an
+   error. */
+
+time_t Curl_getdate_capped(const char *p)
+{
+  time_t parsed = -1;
+  int rc = parsedate(p, &parsed);
+
+  switch(rc) {
+  case PARSEDATE_OK:
+    if(parsed == -1)
+      /* avoid returning -1 for a working scenario */
+      parsed++;
+    return parsed;
+  case PARSEDATE_LATER:
+    /* this returns the maximum time value */
+    return parsed;
+  default:
+    return -1; /* everything else is fail */
+  }
+  /* UNREACHABLE */
+}
+
 /*
  * Curl_gmtime() is a gmtime() replacement for portability. Do not use the
  * gmtime_r() or gmtime() functions anywhere else but here.