+
+
+/*
+ * Detects, using heuristics, if an SMTP server or client response string
+ * contains a base64-encoded portion. If it does, decodes it and replaces
+ * any non-printable characters with a hex representation. Caller is
+ * responsible for free'ing return value. If the decode fails, a copy of
+ * the input string is returned.
+ */
+static
+char *
+prepare_for_display (const char *string, int *next_line_encoded) {
+ const char *start = NULL;
+ const char *decoded;
+ size_t decoded_len;
+ int prefix_len = -1;
+
+ if (strncmp (string, "AUTH ", 5) == 0) {
+ /* AUTH line: the mechanism isn't encoded. If there's an initial
+ response, it must be base64 encoded.. */
+ char *mechanism = strchr (string + 5, ' ');
+
+ if (mechanism != NULL) {
+ prefix_len = (int) (mechanism - string + 1);
+ } /* else no space following the mechanism, so no initial response */
+ *next_line_encoded = 0;
+ } else if (strncmp (string, "334 ", 4) == 0) {
+ /* 334 is the server's request for user or password. */
+ prefix_len = 4;
+ /* The next (client response) line must be base64 encoded. */
+ *next_line_encoded = 1;
+ } else if (*next_line_encoded) {
+ /* "next" line now refers to this line, which is a base64-encoded
+ client response. */
+ prefix_len = 0;
+ *next_line_encoded = 0;
+ } else {
+ *next_line_encoded = 0;
+ }
+
+ /* Don't attempt to decoded unencoded initial response ('=') or cancel
+ response ('*'). */
+ if (prefix_len > -1 &&
+ string[prefix_len] != '=' && string[prefix_len] != '*') {
+ start = string + prefix_len;
+ }
+
+ if (start && decodeBase64 (start, &decoded, &decoded_len, 1, NULL) == OK) {
+ char *hexified;
+ char *prefix = mh_xmalloc(prefix_len + 1);
+ char *display_string;
+
+ /* prefix is the beginning portion, which isn't base64 encoded. */
+ snprintf (prefix, prefix_len + 1, "%*s", prefix_len, string);
+ hexify ((const unsigned char *) decoded, decoded_len, &hexified);
+ /* Wrap the decoded portion in "b64<>". */
+ display_string = concat (prefix, "b64<", hexified, ">", NULL);
+ free (hexified);
+ free (prefix);
+ free ((char *) decoded);
+
+ return display_string;
+ } else {
+ return getcpy (string);
+ }
+}