MINOR: resolvers: fix the resolv_str_to_dn_label() API about trailing zero

This function is bogus at the API level: it demands that the input string
is zero-terminated *and* that its length *including* the trailing zero is
passed on input. While that already looks smelly, the trailing zero is
copied as-is, and is then explicitly replaced with a zero... Not only
all callers have to pass hostname_len+1 everywhere to work around this
absurdity, but this requirement causes a bug in the do-resolve() action
that passes random string lengths on input, and that will be fixed on a
subsequent patch.

Let's fix this API issue for now.

This patch will have to be backported, and in versions 2.3 and older,
the function is in dns.c and is called dns_str_to_dn_label().

diff --git a/src/resolvers.c b/src/resolvers.c
index fe7b6a81edd68f869f0be964435d420dd8b3b265..66c787eb340834cff58140d5ef11d90d776e1fc9 100644 (file)
--- a/src/resolvers.c
+++ b/src/resolvers.c
@@ -190,7 +190,7 @@ struct resolv_srvrq *new_resolv_srvrq(struct server *srv, char *fqdn)
        int fqdn_len, hostname_dn_len;
 
        fqdn_len = strlen(fqdn);
-       hostname_dn_len = resolv_str_to_dn_label(fqdn, fqdn_len + 1, trash.area,
+       hostname_dn_len = resolv_str_to_dn_label(fqdn, fqdn_len, trash.area,
                                              trash.size);
        if (hostname_dn_len == -1) {
                ha_alert("%s '%s', server '%s': failed to parse FQDN '%s'\n",
@@ -1651,18 +1651,19 @@ int resolv_dn_label_to_str(const char *dn, int dn_len, char *str, int str_len)
 
 /* Turns a string into domain name label: www.haproxy.org into 3www7haproxy3org
  *
- * <str> must be a null-terminated string. <str_len> must include the
- * terminating null byte. <dn> buffer must be allocated and its size must be
- * passed in <dn_len>.
+ * <str> contains the input string that is <str_len> bytes long (trailing zero
+ * not needed). <dn> buffer must be allocated large enough to contain the
+ * encoded string and a trailing zero, so it must be at least str_len+2, and
+ * this allocated buffer size must be passed in <dn_len>.
  *
- *  In case of error, -1 is returned, otherwise, the number of bytes copied in
+ * In case of error, -1 is returned, otherwise, the number of bytes copied in
  * <dn> (excluding the terminating null byte).
  */
 int resolv_str_to_dn_label(const char *str, int str_len, char *dn, int dn_len)
 {
        int i, offset;
 
-       if (dn_len < str_len + 1)
+       if (dn_len < str_len + 2)
                return -1;
 
        /* First byte of dn will be used to store the length of the first
@@ -1675,7 +1676,7 @@ int resolv_str_to_dn_label(const char *str, int str_len, char *dn, int dn_len)
                                return -1;
 
                        /* ignore trailing dot */
-                       if (i + 2 == str_len) {
+                       if (i + 1 == str_len) {
                                i++;
                                break;
                        }
@@ -1686,7 +1687,7 @@ int resolv_str_to_dn_label(const char *str, int str_len, char *dn, int dn_len)
                }
                dn[i+1] = str[i];
        }
-       dn[offset] = (i - offset - 1);
+       dn[offset] = i - offset;
        dn[i] = '\0';
        return i;
 }
@@ -2734,7 +2735,7 @@ static int action_prepare_for_resolution(struct stream *stream, const char *host
 
        hostname_len    = strlen(hostname);
        hostname_dn     = tmp->area;
-       hostname_dn_len = resolv_str_to_dn_label(hostname, hostname_len + 1,
+       hostname_dn_len = resolv_str_to_dn_label(hostname, hostname_len,
                                                 hostname_dn, tmp->size);
        if (hostname_dn_len == -1)
                goto err;

diff --git a/src/server.c b/src/server.c
index 49cd7e2522f73cb3635e246892a94e9c671355aa..ca9a59363c78a707ec96edcb90f09bf6ad70129a 100644 (file)
--- a/src/server.c
+++ b/src/server.c
@@ -2013,7 +2013,7 @@ int srv_prepare_for_resolution(struct server *srv, const char *hostname)
 
        hostname_len    = strlen(hostname);
        hostname_dn     = trash.area;
-       hostname_dn_len = resolv_str_to_dn_label(hostname, hostname_len + 1,
+       hostname_dn_len = resolv_str_to_dn_label(hostname, hostname_len,
                                                 hostname_dn, trash.size);
        if (hostname_dn_len == -1)
                goto err;
@@ -3710,7 +3710,7 @@ int srv_set_fqdn(struct server *srv, const char *hostname, int resolv_locked)
        chunk_reset(&trash);
        hostname_len    = strlen(hostname);
        hostname_dn     = trash.area;
-       hostname_dn_len = resolv_str_to_dn_label(hostname, hostname_len + 1,
+       hostname_dn_len = resolv_str_to_dn_label(hostname, hostname_len,
                                                 hostname_dn, trash.size);
        if (hostname_dn_len == -1)
                goto err;