1 files changed, 58 insertions, 0 deletions
diff --git a/src/auths/xtextdecode.c b/src/auths/xtextdecode.c
new file mode 100644
index 0000000..746dfbd
--- /dev/null
+++ b/src/auths/xtextdecode.c
@@ -0,0 +1,58 @@
+/*************************************************
+*     Exim - an Internet mail transport agent    *
+*************************************************/
+
+/* Copyright (c) The Exim Maintainers 2022 */
+/* Copyright (c) University of Cambridge 1995 - 2009 */
+/* See the file NOTICE for conditions of use and distribution. */
+
+#include "../exim.h"
+
+
+/*************************************************
+*          Decode byte-string in xtext           *
+*************************************************/
+
+/* This function decodes a string in xtextformat as defined in RFC 1891 and
+required by the SMTP AUTH extension (RFC 2554). We put the result in a piece of
+store of equal length - it cannot be longer than this. Although in general the
+result of decoding an xtext may be binary, in the context in which it is used
+by Exim (for decoding the value of AUTH on a MAIL command), the result is
+expected to be an addr-spec. We therefore add on a terminating zero, for
+convenience.
+
+Arguments:
+  code        points to the coded string, zero-terminated
+  ptr         where to put the pointer to the result, which is in
+              dynamic store
+
+Returns:      the number of bytes in the result, excluding the final zero;
+              -1 if the input is malformed
+*/
+
+int
+auth_xtextdecode(uschar *code, uschar **ptr)
+{
+register int x;
+uschar * result = store_get(Ustrlen(code) + 1, code);
+*ptr = result;
+
+while ((x = (*code++)) != 0)
+  {
+  if (x < 33 || x > 127 || x == '=') return -1;
+  if (x == '+')
+    {
+    register int y;
+    if (!isxdigit((x = (*code++)))) return -1;
+    y = ((isdigit(x))? x - '0' : (tolower(x) - 'a' + 10)) << 4;
+    if (!isxdigit((x = (*code++)))) return -1;
+    *result++ = y | ((isdigit(x))? x - '0' : (tolower(x) - 'a' + 10));
+    }
+  else *result++ = x;
+  }
+
+*result = 0;
+return result - *ptr;
+}
+
+/* End of xtextdecode.c */