mda_expand_format: simplify token name extraction for %{name}

It is simpler to compute the length based on the start and end
pointers and pass that value to memcpy(), adding an explicit NUL
terminator after copying.  OK op@

diff --git a/usr.sbin/smtpd/mda_variables.c b/usr.sbin/smtpd/mda_variables.c
index 7c14d2e..0f2be77 100644 (file)
--- a/usr.sbin/smtpd/mda_variables.c
+++ b/usr.sbin/smtpd/mda_variables.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: mda_variables.c,v 1.8 2023/03/19 01:43:11 millert Exp $       */
+/*     $OpenBSD: mda_variables.c,v 1.9 2023/03/19 16:43:44 millert Exp $       */
 
 /*
  * Copyright (c) 2011-2017 Gilles Chehade <gilles@poolp.org>
@@ -243,7 +243,7 @@ mda_expand_format(char *buf, size_t len, const struct deliver *dlv,
        char            exptok[EXPAND_BUFFER];
        ssize_t         exptoklen;
        char            token[MAXTOKENLEN];
-       size_t          ret, tmpret;
+       size_t          ret, tmpret, toklen;
 
        if (len < sizeof tmpbuf) {
                log_warnx("mda_expand_format: tmp buffer < rule buffer");
@@ -268,7 +268,6 @@ mda_expand_format(char *buf, size_t len, const struct deliver *dlv,
                pbuf += 2;
        }
 
-
        /* expansion loop */
        for (; *pbuf && ret < sizeof tmpbuf; ret += tmpret) {
                if (*pbuf == '%' && *(pbuf + 1) == '%') {
@@ -285,17 +284,16 @@ mda_expand_format(char *buf, size_t len, const struct deliver *dlv,
                }
 
                /* %{...} otherwise fail */
-               if (*(pbuf+1) != '{' || (ebuf = strchr(pbuf+1, '}')) == NULL)
+               if ((ebuf = strchr(pbuf+2, '}')) == NULL)
                        return 0;
 
                /* extract token from %{token} */
-               if ((size_t)(ebuf - pbuf) - 1 >= sizeof token)
+               toklen = ebuf - (pbuf+2);
+               if (toklen >= sizeof token)
                        return 0;
 
-               memcpy(token, pbuf+2, ebuf-pbuf-1);
-               if (strchr(token, '}') == NULL)
-                       return 0;
-               *strchr(token, '}') = '\0';
+               memcpy(token, pbuf+2, toklen);
+               token[toklen] = '\0';
 
                exptoklen = mda_expand_token(exptok, sizeof exptok, token, dlv,
                    ui, mda_command);