CVE-2020-28009: Integer overflow in get_stdinput()

[exim.git] / src / src / string.c

diff --git a/src/src/string.c b/src/src/string.c
index 80cf49fdf1b297d14f0d25d43708b98c92e20660..27e030bd8e4575d211caf48cc8bc8cd4ba0ade64 100644 (file)
--- a/src/src/string.c
+++ b/src/src/string.c
@@ -3,6 +3,7 @@
 *************************************************/
 
 /* Copyright (c) University of Cambridge 1995 - 2018 */
+/* Copyright (c) The Exim Maintainers 2020 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Miscellaneous string-handling functions. Some are not required for
@@ -280,17 +281,17 @@ return ch;
 /* This function is called for critical strings. It checks for any
 non-printing characters, and if any are found, it makes a new copy
 of the string with suitable escape sequences. It is most often called by the
-macro string_printing(), which sets allow_tab TRUE.
+macro string_printing(), which sets flags to 0.
 
 Arguments:
   s             the input string
-  allow_tab     TRUE to allow tab as a printing character
+  flags                Bit 0: convert tabs.  Bit 1: convert spaces.
 
 Returns:        string with non-printers encoded as printing sequences
 */
 
 const uschar *
-string_printing2(const uschar *s, BOOL allow_tab)
+string_printing2(const uschar *s, int flags)
 {
 int nonprintcount = 0;
 int length = 0;
@@ -300,7 +301,10 @@ uschar *ss, *tt;
 while (*t != 0)
   {
   int c = *t++;
-  if (!mac_isprint(c) || (!allow_tab && c == '\t')) nonprintcount++;
+  if (  !mac_isprint(c)
+     || flags & SP_TAB && c == '\t'
+     || flags & SP_SPACE && c == ' '
+     ) nonprintcount++;
   length++;
   }
 
@@ -309,17 +313,19 @@ if (nonprintcount == 0) return s;
 /* Get a new block of store guaranteed big enough to hold the
 expanded string. */
 
-ss = store_get(length + nonprintcount * 3 + 1, is_tainted(s));
+tt = ss = store_get(length + nonprintcount * 3 + 1, is_tainted(s));
 
 /* Copy everything, escaping non printers. */
 
-t = s;
-tt = ss;
-
-while (*t != 0)
+for (t = s; *t; )
   {
   int c = *t;
-  if (mac_isprint(c) && (allow_tab || c != '\t')) *tt++ = *t++; else
+  if (  mac_isprint(c)
+     && (!(flags & SP_TAB) || c != '\t')
+     && (!(flags & SP_SPACE) || c != ' ')
+     )
+    *tt++ = *t++;
+  else
     {
     *tt++ = '\\';
     switch (*t)
@@ -574,18 +580,14 @@ uschar *ss = yield = store_get(Ustrlen(s) + 1, is_tainted(s));
 while (*s != 0)
   {
   if (*s != '\\')
-    {
     *ss++ = *s++;
-    }
   else if (isdigit(s[1]))
     {
     *ss++ = (s[1] - '0')*100 + (s[2] - '0')*10 + s[3] - '0';
     s += 4;
     }
   else if (*(++s) != 0)
-    {
     *ss++ = *s++;
-    }
   }
 
 *ss = 0;
@@ -950,7 +952,10 @@ else
     s = ss;
     if (!*s || *++s != sep || sep_is_special) break;
     }
-  while (g->ptr > 0 && isspace(g->s[g->ptr-1])) g->ptr--;
+  /* while (g->ptr > 0 && isspace(g->s[g->ptr-1])) g->ptr--; */
+  while (  g->ptr > 0 && isspace(g->s[g->ptr-1])
+       && (g->ptr == 1 || g->s[g->ptr-2] != '\\') )
+    g->ptr--;
   buffer = string_from_gstring(g);
   gstring_release_unused(g);
   }
@@ -1086,7 +1091,16 @@ existing length of the string. */
 
 unsigned inc = oldsize < 4096 ? 127 : 1023;
 
+if (g->ptr < 0 || g->ptr > g->size || g->size >= INT_MAX/2)
+  log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+    "internal error in gstring_grow (ptr %d size %d)", g->ptr, g->size);
+
 if (count <= 0) return;
+
+if (count >= INT_MAX/2 - g->ptr)
+  log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+    "internal error in gstring_grow (ptr %d count %d)", g->ptr, count);
+
 g->size = (p + count + inc + 1) & ~inc;                /* one for a NUL */
 
 /* Try to extend an existing allocation. If the result of calling
@@ -1135,6 +1149,10 @@ string_catn(gstring * g, const uschar *s, int count)
 int p;
 BOOL srctaint = is_tainted(s);
 
+if (count < 0)
+  log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+    "internal error in string_catn (count %d)", count);
+
 if (!g)
   {
   unsigned inc = count < 4096 ? 127 : 1023;
@@ -1144,8 +1162,12 @@ if (!g)
 else if (srctaint && !is_tainted(g->s))
   gstring_rebuffer(g);
 
+if (g->ptr < 0 || g->ptr > g->size)
+  log_write(0, LOG_MAIN|LOG_PANIC_DIE,
+    "internal error in string_catn (ptr %d size %d)", g->ptr, g->size);
+
 p = g->ptr;
-if (p + count >= g->size)
+if (count >= g->size - p)
   gstring_grow(g, count);
 
 /* Because we always specify the exact number of characters to copy, we can