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Work better with tools that resist DNS poisoning by using the 0x20 hack: make DNSPort replies perserve case.

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svn:r17170
This commit is contained in:
Nick Mathewson 2008-10-29 15:31:26 +00:00
parent 361086005c
commit c8a5e2d588
2 changed files with 38 additions and 2 deletions
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2
ChangeLog
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@ -10,6 +10,8 @@ Changes in version 0.2.1.7-alpha - 2008-10-xx
- Now NodeFamily and MyFamily config options allow spaces in
identity fingerprints, so it's easier to paste them in.
Suggested by Lucky Green.
- Preserve case in replies to DNSPort requests in order to support
the 0x20 hack for resisting DNS poisoning attacks.
o Hidden service performance improvements:
- When the client launches an introduction circuit, retry with a

38
src/or/dnsserv.c
View File

@ -207,6 +207,38 @@ dnsserv_reject_request(edge_connection_t *conn)
}
}
/** Look up the original name that corresponds to 'addr' in req. We use this
* to preserve case in order to facilitate people using 0x20-hacks to avoid
* DNS poisoning. */
static const char *
evdns_get_orig_address(const struct evdns_server_request *req,
int rtype, const char *addr)
{
int i, type;
switch (rtype) {
case RESOLVED_TYPE_IPV4:
type = EVDNS_TYPE_A;
break;
case RESOLVED_TYPE_HOSTNAME:
type = EVDNS_TYPE_PTR;
break;
case RESOLVED_TYPE_IPV6:
type = EVDNS_TYPE_AAAA;
break;
default:
tor_fragile_assert();
return addr;
}
for (i = 0; i < req->nquestions; ++i) {
const struct evdns_server_question *q = req->questions[i];
if (q->type == type && !strcasecmp(q->name, addr))
return q->name;
}
return addr;
}
/** Tell the dns request waiting for an answer on <b>conn</b> that we have an
* answer of type <b>answer_type</b> (RESOLVE_TYPE_IPV4/IPV6/ERR), of length
* <b>answer_len</b>, in <b>answer</b>, with TTL <b>ttl</b>. Doesn't do
@ -219,9 +251,11 @@ dnsserv_resolved(edge_connection_t *conn,
int ttl)
{
struct evdns_server_request *req = conn->dns_server_request;
const char *name;
int err = DNS_ERR_NONE;
if (!req)
return;
name = evdns_get_orig_address(req, answer_type, conn->socks_request->address);
/* XXXX021 Re-do; this is dumb. */
if (ttl < 60)
@ -236,13 +270,13 @@ dnsserv_resolved(edge_connection_t *conn,
} else if (answer_type == RESOLVED_TYPE_IPV4 && answer_len == 4 &&
conn->socks_request->command == SOCKS_COMMAND_RESOLVE) {
evdns_server_request_add_a_reply(req,
conn->socks_request->address,
name,
1, (char*)answer, ttl);
} else if (answer_type == RESOLVED_TYPE_HOSTNAME &&
conn->socks_request->command == SOCKS_COMMAND_RESOLVE_PTR) {
char *ans = tor_strndup(answer, answer_len);
evdns_server_request_add_ptr_reply(req, NULL,
conn->socks_request->address,
name,
(char*)answer, ttl);
tor_free(ans);
} else if (answer_type == RESOLVED_TYPE_ERROR) {