Header-wrap expansion. Bug 2843

4 files changed, 118 insertions, 66 deletions

diff --git a/src/src/deliver.c b/src/src/deliver.c
index 9b77b3619..e2994b116 100644
--- a/src/src/deliver.c
+++ b/src/src/deliver.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) The Exim Maintainers 2020 - 2022 */
+/* Copyright (c) The Exim Maintainers 2020 - 2023 */
 /* Copyright (c) University of Cambridge 1995 - 2018 */
 /* See the file NOTICE for conditions of use and distribution. */
 /* SPDX-License-Identifier: GPL-2.0-or-later */
@@ -5566,69 +5566,14 @@ Limit to about 1024 chars total. */
 static void
 dsn_put_wrapped(FILE * fp, const uschar * header, const uschar * s)
 {
-const uschar * t;
-int llen = fprintf(fp, "%s", CS header), sleft = Ustrlen(s);
-int remain = 1022 - llen;
+gstring * g = string_cat(NULL, header);
 
-if (*s && remain > 0)
-  {
-  for(;;)
-    {
-    unsigned ltail;	/* source chars to skip */
-
-    /* Chop at a newline, or end of string */
-
-    if ((t = Ustrchr(s, '\\')) && t[1] == 'n')
-      ltail = 2;
-    else if ((t = Ustrchr(s, '\n')))
-      ltail = 1;
-    else
-      {
-      t = s + sleft;
-      ltail = 0;
-      }
-
-    /* If that is too long, search backward for a space */
-
-    if ((llen + t - s) > 78)
-      {
-      const uschar * u;
-      for (u = s + 78 - llen; u > s + 10; --u) if (*u == ' ') break;
-      if (u > s + 10)
-	{				/* found a space to linebreak at */
-	llen = u - s;
-	remain -= fprintf(fp, "%.*s", (int)llen, s);
-	s += ++llen;			/* skip the space also */
-	}
-      else if (llen < 78)
-	{				/* just linebreak at 78 */
-	llen = 78 - llen;
-	remain -= fprintf(fp, "%.*s", llen, s);
-	s += llen;
-	}
-      else				/* header rather long */
-	llen = 0;
-      }
-    else
-      {
-      llen = t - s;
-      remain -= fprintf(fp, "%.*s", llen, s);
-      s = t + ltail;
-      }
+g = string_cat(g, s);
+gstring_release_unused(g);
+fprintf(fp, "%s\n", wrap_header(string_from_gstring(g), 79, 1023, US" ", 1));
+}
 
-    sleft -= llen;
-    remain -= 2;
-    if (!*s || remain <= 0)
-      break;
-    fputs("\n ", fp);
-    llen = 1;		/* one for the leading space output above */
-    }
 
-  if (s[-1] != '\n') fputs("\n", fp);
-  }
-else
-  fputs("\n", fp);
-}
 
 
 /*************************************************
diff --git a/src/src/expand.c b/src/src/expand.c
index baf7134cd..6dcd45062 100644
--- a/src/src/expand.c
+++ b/src/src/expand.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) The Exim Maintainers 2020 - 2022 */
+/* Copyright (c) The Exim Maintainers 2020 - 2023 */
 /* Copyright (c) University of Cambridge 1995 - 2018 */
 /* See the file NOTICE for conditions of use and distribution. */
 /* SPDX-License-Identifier: GPL-2.0-or-later */
@@ -237,6 +237,7 @@ static uschar *op_table_main[] = {
   US"expand",
   US"h",
   US"hash",
+  US"headerwrap",
   US"hex2b64",
   US"hexquote",
   US"ipv6denorm",
@@ -284,6 +285,7 @@ enum {
   EOP_EXPAND,
   EOP_H,
   EOP_HASH,
+  EOP_HEADERWRAP,
   EOP_HEX2B64,
   EOP_HEXQUOTE,
   EOP_IPV6DENORM,
@@ -7262,7 +7264,7 @@ NOT_ITEM: ;
 	{
 	uschar *t;
 	unsigned long int n = Ustrtoul(sub, &t, 10);
-	if (*t != 0)
+	if (*t)
 	  {
 	  expand_string_message = string_sprintf("argument for base62 "
 	    "operator is \"%s\", which is not a decimal number", sub);
@@ -7278,7 +7280,7 @@ NOT_ITEM: ;
 	{
 	uschar *tt = sub;
 	unsigned long int n = 0;
-	while (*tt != 0)
+	while (*tt)
 	  {
 	  uschar *t = Ustrchr(base62_chars, *tt++);
 	  if (!t)
@@ -7428,6 +7430,29 @@ NOT_ITEM: ;
 	goto EXPAND_FAILED;
 #endif
 
+      /* Line-wrap a string as if it is a header line */
+
+      case EOP_HEADERWRAP:
+	{
+	unsigned col = 80, lim = 998;
+	uschar * s;
+
+	if (arg)
+	  {
+	  const uschar * list = arg;
+	  int sep = '_';
+	  if ((s = string_nextinlist(&list, &sep, NULL, 0)))
+	    {
+	    col = atoi(CS s);
+	    if ((s = string_nextinlist(&list, &sep, NULL, 0)))
+	      lim = atoi(CS s);
+	    }
+	  }
+	  if ((s =  wrap_header(sub, col, lim, US"\t", 8)))
+	    yield = string_cat(yield, s);
+	}
+	break;
+
       /* Convert hex encoding to base64 encoding */
 
       case EOP_HEX2B64:
diff --git a/src/src/functions.h b/src/src/functions.h
index 37f0a57bc..5fbb426ec 100644
--- a/src/src/functions.h
+++ b/src/src/functions.h
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) The Exim Maintainers 2020 - 2022 */
+/* Copyright (c) The Exim Maintainers 2020 - 2023 */
 /* Copyright (c) University of Cambridge 1995 - 2018 */
 /* See the file NOTICE for conditions of use and distribution. */
 /* SPDX-License-Identifier: GPL-2.0-or-later */
@@ -678,6 +678,7 @@ extern void    version_init(void);
 
 extern BOOL    write_chunk(transport_ctx *, uschar *, int);
 extern ssize_t write_to_fd_buf(int, const uschar *, size_t);
+extern uschar *wrap_header(const uschar *, unsigned, unsigned, const uschar *, unsigned);
 
 
 /******************************************************************************/
diff --git a/src/src/header.c b/src/src/header.c
index a4dd6e72e..e2b3d8a9c 100644
--- a/src/src/header.c
+++ b/src/src/header.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) The Exim Maintainers 2020 - 2022 */
+/* Copyright (c) The Exim Maintainers 2020 - 2023 */
 /* Copyright (c) University of Cambridge 1995 - 2016 */
 /* See the file NOTICE for conditions of use and distribution. */
 /* SPDX-License-Identifier: GPL-2.0-or-later */
@@ -466,4 +466,85 @@ va_end(ap);
 return !cond;
 }
 
+
+
+/* Wrap and truncate a string for use as a header.
+Convert either the sequence "\n" or a real newline into newline plus indent.
+If that still takes us past the column limit, look for the last space
+and split there too.
+Limit to the given max total char count.
+
+Return: string or NULL */
+
+uschar *
+wrap_header(const uschar * s, unsigned cols, unsigned maxchars,
+  const uschar * indent, unsigned indent_cols)
+{
+gstring * g = NULL;
+
+if (maxchars == 0) maxchars = INT_MAX;
+if (cols == 0) cols = INT_MAX;
+
+if (s && *s)
+  {
+  int sleft = Ustrlen(s);
+  for(unsigned llen = 0; ; llen = indent_cols)
+    {
+    const uschar * t;
+    unsigned ltail = 0, glen;
+
+    if ((t = Ustrchr(s, '\\')) && t[1] == 'n')
+      ltail = 2;
+    else if ((t = Ustrchr(s, '\n')))
+      ltail = 1;
+    else
+      t = s + sleft;
+
+    if ((llen + t - s) > cols)		/* more than a linesworth of s */
+      {					/* look backward for whitespace */
+      for (const uschar * u = s + cols - llen; u > s + 10; --u) if (isspace(*u))
+	{
+	llen = u - s;
+	while (u > s+1 && isspace(u[-1])) --u;	/* find start of whitespace */
+	g = string_catn(g, s, u - s);
+	s += ++llen;				/* skip the space */
+	while (*s && isspace(*s))		/* and any trailing */
+	  s++, llen++;
+	goto LDONE;
+	}
+					/* no whitespace */
+      if (llen < cols)
+	{					/* just linebreak at 80 */
+	llen = cols - llen;
+	g = string_catn(g, s, llen);
+	s += llen;
+	}
+      else
+        llen = 0;
+      LDONE:
+      }
+    else				/* rest of s fits in line */
+      {
+      llen = t - s;
+      g = string_catn(g, s, llen);
+      s = t + ltail;
+      }
+
+    if (!*s)
+      break;				/* no trailing linebreak */
+    if ((glen = gstring_length(g)) >= maxchars)
+      {
+      gstring_trim(g, glen - maxchars);
+      break;				/* no trailing linebreak */
+      }
+    sleft -= llen;
+    g = string_catn(g, US"\n", 1);
+    g = string_catn(g, indent, 1);
+    }
+  }
+gstring_release_unused(g);
+return string_from_gstring(g);
+}
+
+
 /* End of header.c */