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-rw-r--r--networking/parse_pasv_epsv.c66
1 files changed, 66 insertions, 0 deletions
diff --git a/networking/parse_pasv_epsv.c b/networking/parse_pasv_epsv.c
new file mode 100644
index 000000000..14f4d4258
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+++ b/networking/parse_pasv_epsv.c
@@ -0,0 +1,66 @@
1/*
2 * Utility routines.
3 *
4 * Copyright (C) 2018 Denys Vlasenko
5 *
6 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
7 */
8//kbuild:lib-$(CONFIG_FTPGET) += parse_pasv_epsv.o
9//kbuild:lib-$(CONFIG_FTPPUT) += parse_pasv_epsv.o
10//kbuild:lib-$(CONFIG_WGET) += parse_pasv_epsv.o
11
12#include "libbb.h"
13
14int FAST_FUNC parse_pasv_epsv(char *buf)
15{
16/*
17 * PASV command will not work for IPv6. RFC2428 describes
18 * IPv6-capable "extended PASV" - EPSV.
19 *
20 * "EPSV [protocol]" asks server to bind to and listen on a data port
21 * in specified protocol. Protocol is 1 for IPv4, 2 for IPv6.
22 * If not specified, defaults to "same as used for control connection".
23 * If server understood you, it should answer "229 <some text>(|||port|)"
24 * where "|" are literal pipe chars and "port" is ASCII decimal port#.
25 *
26 * There is also an IPv6-capable replacement for PORT (EPRT),
27 * but we don't need that.
28 *
29 * NB: PASV may still work for some servers even over IPv6.
30 * For example, vsftp happily answers
31 * "227 Entering Passive Mode (0,0,0,0,n,n)" and proceeds as usual.
32 */
33 char *ptr;
34 int port;
35
36 if (!ENABLE_FEATURE_IPV6 || buf[2] == '7' /* "227" */) {
37 /* Response is "227 garbageN1,N2,N3,N4,P1,P2[)garbage]"
38 * Server's IP is N1.N2.N3.N4 (we ignore it)
39 * Server's port for data connection is P1*256+P2 */
40 ptr = strrchr(buf, ')');
41 if (ptr) *ptr = '\0';
42
43 ptr = strrchr(buf, ',');
44 if (!ptr) return -1;
45 *ptr = '\0';
46 port = xatou_range(ptr + 1, 0, 255);
47
48 ptr = strrchr(buf, ',');
49 if (!ptr) return -1;
50 *ptr = '\0';
51 port += xatou_range(ptr + 1, 0, 255) * 256;
52 } else {
53 /* Response is "229 garbage(|||P1|)"
54 * Server's port for data connection is P1 */
55 ptr = strrchr(buf, '|');
56 if (!ptr) return -1;
57 *ptr = '\0';
58
59 ptr = strrchr(buf, '|');
60 if (!ptr) return -1;
61 *ptr = '\0';
62 port = xatou_range(ptr + 1, 0, 65535);
63 }
64
65 return port;
66}