X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/5f17d2f09733cc77355841fbf095a95186cc9fe5..65fe780259d0009354b5dfc9a4f1b48ad6513db2:/src/src/pdkim/pdkim.c

diff --git a/src/src/pdkim/pdkim.c b/src/src/pdkim/pdkim.c
index 7712409b5..3a6ca4e91 100644
--- a/src/src/pdkim/pdkim.c
+++ b/src/src/pdkim/pdkim.c
@@ -1111,14 +1111,14 @@ return string_catn(str, US"\r\n\t", 3);
 
 /*
  * RFC 5322 specifies that header line length SHOULD be no more than 78
- * lets make it so!
  *  pdkim_headcat
  *
- * returns uschar * (not nul-terminated)
+ * Returns gstring (not nul-terminated) appending to one supplied
  *
  * col: this int holds and receives column number (octets since last '\n')
  * str: partial string to append to
- * pad: padding, split line or space after before or after eg: ";"
+ * pad: padding, split line or space after before or after eg: ";".
+ *               Only the initial charater is used.
  * intro: - must join to payload eg "h=", usually the tag name
  * payload: eg base64 data - long data can be split arbitrarily.
  *
@@ -1127,7 +1127,7 @@ return string_catn(str, US"\r\n\t", 3);
  * pairs and inside long values. it also always spaces or breaks after the
  * "pad"
  *
- * no guarantees are made for output given out-of range input. like tag
+ * No guarantees are made for output given out-of range input. like tag
  * names longer than 78, or bogus col. Input is assumed to be free of line breaks.
  */
 
@@ -1135,92 +1135,64 @@ static gstring *
 pdkim_headcat(int * col, gstring * str,
   const uschar * pad, const uschar * intro, const uschar * payload)
 {
-size_t l;
+int len, chomp, padded = 0;
 
-if (pad)
-  {
-  l = Ustrlen(pad);
-  if (*col + l > 78)
-    str = pdkim_hdr_cont(str, col);
-  str = string_catn(str, pad, l);
-  *col += l;
-  }
-
-l = (pad?1:0) + (intro?Ustrlen(intro):0);
+/* If we can fit at least the pad at the end of current line, do it now.
+Otherwise, wrap if there is a pad. */
 
-if (*col + l > 78)
-  { /*can't fit intro - start a new line to make room.*/
-  str = pdkim_hdr_cont(str, col);
-  l = intro?Ustrlen(intro):0;
-  }
-
-l += payload ? Ustrlen(payload):0 ;
-
-while (l>77)
-  { /* this fragment will not fit on a single line */
-  if (pad)
-    {
-    str = string_catn(str, US" ", 1);
-    *col += 1;
-    pad = NULL; /* only want this once */
-    l--;
-    }
-
-  if (intro)
-    {
-    size_t sl = Ustrlen(intro);
-
-    str = string_catn(str, intro, sl);
-    *col += sl;
-    l -= sl;
-    intro = NULL; /* only want this once */
-    }
-
-  if (payload)
+if (pad)
+  if (*col + 1 <= 78)
     {
-    size_t sl = Ustrlen(payload);
-    size_t chomp = *col+sl < 77 ? sl : 78-*col;
-
-    str = string_catn(str, payload, chomp);
-    *col += chomp;
-    payload += chomp;
-    l -= chomp-1;
+    str = string_catn(str, pad, 1);
+    (*col)++;
+    pad = NULL;
+    padded = 1;
     }
+  else
+    str = pdkim_hdr_cont(str, col);
 
-  /* the while precondition tells us it didn't fit. */
-  str = pdkim_hdr_cont(str, col);
-  }
+/* Special case: if the whole addition does not fit at the end of the current
+line, but could fit on a new line, wrap to give it its full, dedicated line.  */
 
-if (*col + l > 78)
+len = (pad ? 2 : padded)
+    + (intro ? Ustrlen(intro) : 0)
+    + (payload ? Ustrlen(payload) : 0);
+if (len <= 77 && *col+len > 78)
   {
   str = pdkim_hdr_cont(str, col);
-  pad = NULL;
+  padded = 0;
   }
 
+/* Either we already dealt with the pad or we know there is room */
+
 if (pad)
   {
+  str = string_catn(str, pad, 1);
   str = string_catn(str, US" ", 1);
-  *col += 1;
-  pad = NULL;
+  *col += 2;
   }
-
-if (intro)
+else if (padded && *col < 78)
   {
-  size_t sl = Ustrlen(intro);
-
-  str = string_catn(str, intro, sl);
-  *col += sl;
-  l -= sl;
-  intro = NULL;
+  str = string_catn(str, US" ", 1);
+  (*col)++;
   }
 
-if (payload)
-  {
-  size_t sl = Ustrlen(payload);
+/* Call recursively with intro as payload: it gets the same, special treatment
+(that is, not split if < 78).  */
 
-  str = string_catn(str, payload, sl);
-  *col += sl;
-  }
+if (intro)
+  str = pdkim_headcat(col, str, NULL, NULL, intro);
+
+if (payload)
+  for (len = Ustrlen(payload); len; len -= chomp)
+    {
+    if (*col >= 78)
+      str = pdkim_hdr_cont(str, col);
+    chomp = *col+len > 78 ? 78 - *col : len;
+    str = string_catn(str, payload, chomp);
+    *col += chomp;
+    payload += chomp;
+    }
 
 return str;
 }