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Fix handling of string-typed address from SOCKS5 server.

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In the variable-length address slot, the main SOCKS5 reply packet can
contain a binary IP address (4- or 16-byte for v4/v6 respectively), or
a string intended to be interpreted as a domain name.

I was trying out the Python SOCKS5 proxy 'pproxy' today, which sends a
string-typed reply if you send it a string-typed domain name to
connect to. This caused me to notice that PuTTY mishandles the latter
case, by failing to account for the prefix length byte of that string
when computing the total size of the reply packet. So we would
misinterpret the final byte of its reply packet as the initial byte of
the actual connection, causing us to fail to recognise the SSH greeting.
This commit is contained in:
Simon Tatham 2019-10-01 19:31:37 +01:00
parent 745ed3ad3b
commit 283bd541a6
1 changed files with 1 additions and 1 deletions
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2
proxy.c
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@ -1178,7 +1178,7 @@ int proxy_socks5_negotiate (ProxySocket *p, int change)
switch (data[3]) { switch (data[3]) {
case 1: len += 4; break; /* IPv4 address */ case 1: len += 4; break; /* IPv4 address */
case 4: len += 16; break;/* IPv6 address */ case 4: len += 16; break;/* IPv6 address */
case 3: len += (unsigned char)data[4]; break; /* domain name */ case 3: len += 1+(unsigned char)data[4]; break; /* domain name */
default: default:
plug_closing(p->plug, "Proxy error: SOCKS proxy returned " plug_closing(p->plug, "Proxy error: SOCKS proxy returned "
"unrecognised address format", "unrecognised address format",