wget: add EPSV support

function                                             old     new   delta
parse_pasv_epsv                                        -     151    +151
wget_main                                           2440    2382     -58
xconnect_ftpdata                                     223      94    -129
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/2 up/down: 151/-187)          Total: -36 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

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..f32087152
--- /dev/null
+++ b/networking/parse_pasv_epsv.c
@@ -0,0 +1,66 @@
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 2018 Denys Vlasenko
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+//kbuild:lib-$(CONFIG_FTPGET) += ftpgetput.o
+//kbuild:lib-$(CONFIG_FTPPUT) += ftpgetput.o
+//kbuild:lib-$(CONFIG_WGET) += parse_pasv_epsv.o
+
+#include "libbb.h"
+
+int FAST_FUNC parse_pasv_epsv(char *buf)
+{
+/*
+ * PASV command will not work for IPv6. RFC2428 describes
+ * IPv6-capable "extended PASV" - EPSV.
+ *
+ * "EPSV [protocol]" asks server to bind to and listen on a data port
+ * in specified protocol. Protocol is 1 for IPv4, 2 for IPv6.
+ * If not specified, defaults to "same as used for control connection".
+ * If server understood you, it should answer "229 <some text>(|||port|)"
+ * where "|" are literal pipe chars and "port" is ASCII decimal port#.
+ *
+ * There is also an IPv6-capable replacement for PORT (EPRT),
+ * but we don't need that.
+ *
+ * NB: PASV may still work for some servers even over IPv6.
+ * For example, vsftp happily answers
+ * "227 Entering Passive Mode (0,0,0,0,n,n)" and proceeds as usual.
+ */
+	char *ptr;
+	int port;
+
+	if (!ENABLE_FEATURE_IPV6 || buf[2] == '7' /* "227" */) {
+		/* Response is "227 garbageN1,N2,N3,N4,P1,P2[)garbage]"
+		 * Server's IP is N1.N2.N3.N4 (we ignore it)
+		 * Server's port for data connection is P1*256+P2 */
+		ptr = strrchr(buf, ')');
+		if (ptr) *ptr = '\0';
+
+		ptr = strrchr(buf, ',');
+		if (!ptr) return -1;
+		*ptr = '\0';
+		port = xatou_range(ptr + 1, 0, 255);
+
+		ptr = strrchr(buf, ',');
+		if (!ptr) return -1;
+		*ptr = '\0';
+		port += xatou_range(ptr + 1, 0, 255) * 256;
+	} else {
+		/* Response is "229 garbage(|||P1|)"
+		 * Server's port for data connection is P1 */
+		ptr = strrchr(buf, '|');
+		if (!ptr) return -1;
+		*ptr = '\0';
+
+		ptr = strrchr(buf, '|');
+		if (!ptr) return -1;
+		*ptr = '\0';
+		port = xatou_range(ptr + 1, 0, 65535);
+	}
+
+	return port;
+}