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-rw-r--r--libc/inet/resolv.c189
1 files changed, 69 insertions, 120 deletions
diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
index ed2e0d2fa..8bbd7c7cd 100644
--- a/libc/inet/resolv.c
+++ b/libc/inet/resolv.c
@@ -11,6 +11,7 @@
/*
* Portions Copyright (c) 1985, 1993
* The Regents of the University of California. All rights reserved.
+ * Portions Copyright © 2021 mirabilos <m@mirbsd.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@@ -395,14 +396,6 @@ extern int __dns_lookup(const char *name,
int type,
unsigned char **outpacket,
struct resolv_answer *a) attribute_hidden;
-extern int __encode_dotted(const char *dotted,
- unsigned char *dest,
- int maxlen) attribute_hidden;
-extern int __decode_dotted(const unsigned char *packet,
- int offset,
- int packet_len,
- char *dest,
- int dest_len) attribute_hidden;
extern int __encode_header(struct resolv_header *h,
unsigned char *dest,
int maxlen) attribute_hidden;
@@ -416,6 +409,13 @@ extern int __encode_answer(struct resolv_answer *a,
int maxlen) attribute_hidden;
extern void __open_nameservers(void) attribute_hidden;
extern void __close_nameservers(void) attribute_hidden;
+extern int __hnbad(const char *dotted) attribute_hidden;
+
+#define __encode_dotted(dotted,dest,maxlen) \
+ dn_comp((dotted), (dest), (maxlen), NULL, NULL)
+#define __decode_dotted(packet,offset,packet_len,dest,dest_len) \
+ dn_expand((packet), (packet) + (packet_len), (packet) + (offset), \
+ (dest), (dest_len))
/*
* Theory of operation.
@@ -552,116 +552,6 @@ void __decode_header(unsigned char *data,
#endif /* L_decodeh */
-#ifdef L_encoded
-
-/* Encode a dotted string into nameserver transport-level encoding.
- This routine is fairly dumb, and doesn't attempt to compress
- the data */
-int __encode_dotted(const char *dotted, unsigned char *dest, int maxlen)
-{
- unsigned used = 0;
-
- while (dotted && *dotted) {
- char *c = strchr(dotted, '.');
- int l = c ? c - dotted : strlen(dotted);
-
- /* two consecutive dots are not valid */
- if (l == 0)
- return -1;
-
- if (l >= (maxlen - used - 1))
- return -1;
-
- dest[used++] = l;
- memcpy(dest + used, dotted, l);
- used += l;
-
- if (!c)
- break;
- dotted = c + 1;
- }
-
- if (maxlen < 1)
- return -1;
-
- dest[used++] = 0;
-
- return used;
-}
-#endif /* L_encoded */
-
-
-#ifdef L_decoded
-
-/* Decode a dotted string from nameserver transport-level encoding.
- This routine understands compressed data. */
-int __decode_dotted(const unsigned char *packet,
- int offset,
- int packet_len,
- char *dest,
- int dest_len)
-{
- unsigned b;
- bool measure = 1;
- unsigned total = 0;
- unsigned used = 0;
- unsigned maxiter = 256;
-
- if (!packet)
- return -1;
-
- dest[0] = '\0';
- while (--maxiter) {
- if (offset >= packet_len)
- return -1;
- b = packet[offset++];
- if (b == 0)
- break;
-
- if (measure)
- total++;
-
- if ((b & 0xc0) == 0xc0) {
- if (offset >= packet_len)
- return -1;
- if (measure)
- total++;
- /* compressed item, redirect */
- offset = ((b & 0x3f) << 8) | packet[offset];
- measure = 0;
- continue;
- }
-
- if (used + b + 1 >= dest_len)
- return -1;
- if (offset + b >= packet_len)
- return -1;
- memcpy(dest + used, packet + offset, b);
- offset += b;
- used += b;
-
- if (measure)
- total += b;
-
- if (packet[offset] != 0)
- dest[used++] = '.';
- else
- dest[used++] = '\0';
- }
- if (!maxiter)
- return -1;
-
- /* The null byte must be counted too */
- if (measure)
- total++;
-
- DPRINTF("Total decode len = %d\n", total);
-
- return total;
-}
-#endif /* L_decoded */
-
-
#ifdef L_encodeq
int __encode_question(const struct resolv_question *q,
@@ -1204,6 +1094,7 @@ int __dns_lookup(const char *name,
bool ends_with_dot;
bool contains_dot;
sockaddr46_t sa;
+ int num_answers;
fd = -1;
lookup = NULL;
@@ -1446,6 +1337,7 @@ int __dns_lookup(const char *name,
goto fail1;
}
pos = HFIXEDSZ;
+ /*XXX TODO: check that question matches query (and qdcount==1?) */
for (j = 0; j < h.qdcount; j++) {
DPRINTF("Skipping question %d at %d\n", j, pos);
i = __length_question(packet + pos, packet_len - pos);
@@ -1460,6 +1352,7 @@ int __dns_lookup(const char *name,
DPRINTF("Decoding answer at pos %d\n", pos);
first_answer = 1;
+ num_answers = 0;
a->dotted = NULL;
for (j = 0; j < h.ancount; j++) {
i = __decode_answer(packet, pos, packet_len, &ma);
@@ -1467,12 +1360,15 @@ int __dns_lookup(const char *name,
DPRINTF("failed decode %d\n", i);
/* If the message was truncated but we have
* decoded some answers, pretend it's OK */
- if (j && h.tc)
+ if (num_answers && h.tc)
break;
goto try_next_server;
}
pos += i;
+ if (__hnbad(ma.dotted))
+ break;
+ ++num_answers;
if (first_answer) {
ma.buf = a->buf;
ma.buflen = a->buflen;
@@ -1502,6 +1398,10 @@ int __dns_lookup(const char *name,
++a->add_count;
}
}
+ if (!num_answers) {
+ h_errno = NO_RECOVERY;
+ goto fail1;
+ }
/* Success! */
DPRINTF("Answer name = |%s|\n", a->dotted);
@@ -2468,7 +2368,7 @@ int gethostbyaddr_r(const void *addr, socklen_t addrlen,
/* Decode CNAME into buf, feed it to __dns_lookup() again */
i = __decode_dotted(packet, a.rdoffset, packet_len, buf, buflen);
free(packet);
- if (i < 0) {
+ if (i < 0 || __hnbad(buf)) {
*h_errnop = NO_RECOVERY;
return -1;
}
@@ -2477,6 +2377,10 @@ int gethostbyaddr_r(const void *addr, socklen_t addrlen,
if (a.atype == T_PTR) { /* ADDRESS */
i = __decode_dotted(packet, a.rdoffset, packet_len, buf, buflen);
free(packet);
+ if (__hnbad(buf)) {
+ *h_errnop = NO_RECOVERY;
+ return -1;
+ }
result_buf->h_name = buf;
result_buf->h_addrtype = type;
result_buf->h_length = addrlen;
@@ -3042,6 +2946,51 @@ int ns_name_pton(const char *src, u_char *dst, size_t dstsiz)
libc_hidden_def(ns_name_pton)
/*
+ * __hnbad(dotted)
+ * Check whether a name is valid enough for DNS. The rules, as
+ * laid down by glibc, are:
+ * - printable input string
+ * - converts to label notation
+ * - each label only contains [0-9a-zA-Z_-], up to 63 octets
+ * - first label doesn’t begin with ‘-’
+ * This both is weaker than Unix hostnames (e.g. it allows
+ * underscores and leading/trailing hyphen-minus) and stronger
+ * than general (e.g. a leading “*.” is valid sometimes), take care.
+ * return:
+ * 0 if the name is ok
+ */
+int __hnbad(const char *dotted)
+{
+ unsigned char c, n, *cp;
+ unsigned char buf[NS_MAXCDNAME];
+
+ cp = (unsigned char *)dotted;
+ while ((c = *cp++))
+ if (c < 0x21 || c > 0x7E)
+ return (1);
+ if (ns_name_pton(dotted, buf, sizeof(buf)) < 0)
+ return (2);
+ if (buf[0] > 0 && buf[1] == '-')
+ return (3);
+ cp = buf;
+ while ((n = *cp++)) {
+ if (n > 63)
+ return (4);
+ while (n--) {
+ c = *cp++;
+ if (c < '-' ||
+ (c > '-' && c < '0') ||
+ (c > '9' && c < 'A') ||
+ (c > 'Z' && c < '_') ||
+ (c > '_' && c < 'a') ||
+ c > 'z')
+ return (5);
+ }
+ }
+ return (0);
+}
+
+/*
* ns_name_unpack(msg, eom, src, dst, dstsiz)
* Unpack a domain name from a message, source may be compressed.
* return:
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-18 00:37:22 +0000