RCurl getURL with FTP over proxy - r

Question

In R I'm trying to get data from a ftp server using RCurl. The server has explicit encryption activated. Below one of the many attempts to make this work but I always get 530 Login or password incorrect! Still the username / password works when using another client like WinSCP. Any help is welcome!
library(RCurl)
# CURL_SSLVERSION_TLSv1_1 <- 5L
# CURL_SSLVERSION_TLSv1_2 <- 6L
opts <- curlOptions(
proxy = "http://my.proxy/",
proxyport = 8080,
dirlistonly = TRUE,
sslversion = 6L,
ftp.use.epsv = FALSE,
ssl.verifypeer=TRUE
)
dat <- getURL("ftp://myUser:myPaas#ftps.myServer.com/", .opts = opts )
Here some screenshots of the winscp setup (only German OS available)
Connection screen:
Protocol screen:
WinSCP connection string:
Here is the output having verbose = TRUE added
* Trying 10.x.x.x...
* Connected to 10.x.x.x (10.x.x.x) port 8080 (#0)
> GET ftp://User:Pass#ftp.myserver.com/ HTTP/1.1
Host: ftp.myserver.com:21
Accept: */*
Proxy-Connection: Keep-Alive
< HTTP/1.1 403 Forbidden
< Server: squid/3.5.20
< Mime-Version: 1.0
< Date: Thu, 15 Nov 2018 11:12:24 GMT
< Content-Type: text/html;charset=utf-8
< Content-Length: 3898
< X-Squid-Error: ERR_FTP_FORBIDDEN 530
< Vary: Accept-Language
< Content-Language: en
< WWW-Authenticate: Basic realm="FTP ftp.myserver.com"
< X-Cache: MISS from Proxy-xxxxxx
< X-Cache-Lookup: MISS from Proxy-xxxxx:8080
< Via: 1.1 Proxy-xxxxxx (squid/3.5.20)
< Connection: keep-alive
<
* Connection #0 to host 10.x.x.x left intact
Here is the WinSCP log:
. 2018-11-15 17:09:15.999 Verbinde mit ftp.MyServer.com ...
. 2018-11-15 17:09:15.999 HTTP proxy command: CONNECT ftp.MyServer.com:21 HTTP/1.1
. 2018-11-15 17:09:15.999 Host: ftp.MyServer.com:21
. 2018-11-15 17:09:16.014 Verbindung mit dem Proxy hergestellt, führe Handshakes aus ...
. 2018-11-15 17:09:16.039 HTTP proxy response: HTTP/1.1 200 Connection established
. 2018-11-15 17:09:16.039 HTTP proxy headers:
. 2018-11-15 17:09:16.039
. 2018-11-15 17:09:16.039 Verbunden mit ftp.MyServer.com, TLS Verbindung wird ausgehandelt...
< 2018-11-15 17:09:16.059 220 Welcome to FTP MyServer
> 2018-11-15 17:09:16.059 AUTH TLS
< 2018-11-15 17:09:16.093 234 Using authentication type TLS
. 2018-11-15 17:09:16.179 Verifying certificate for "MY Server" with fingerprint xx:yy:zz.............. and 18 failures
. 2018-11-15 17:09:16.179 Certificate common name "ftp.MyServer.com" matches hostname
. 2018-11-15 17:09:16.179 Certificate for "MY Server" matches cached fingerprint and failures
. 2018-11-15 17:09:16.179 Using TLSv1.2, cipher TLSv1/SSLv3: ECDHE-RSA-AES256-GCM-SHA384, 2048 bit RSA, ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=RSA Enc=AESGCM(256) Mac=AEAD
. 2018-11-15 17:09:16.216 TLS Verbindung hergestellt. Warte auf die Willkommensnachricht...
> 2018-11-15 17:09:16.216 USER MyUser
< 2018-11-15 17:09:16.216 331 Password required for MyUser
> 2018-11-15 17:09:16.216 PASS **********
< 2018-11-15 17:09:16.236 230 Logged on
Here is the R console log with more info:
* Trying 10.101.0.32...
* Connected to 10.101.0.32 (10.x.x.x) port 8080 (#0)
> GET ftp://MyUser:#ftp.MyServer.com/ HTTP/1.1
Host: ftp.MyServer.com:21
Accept: */*
Proxy-Connection: Keep-Alive
< HTTP/1.1 401 Unauthorized
< Server: squid/3.5.20
< Mime-Version: 1.0
< Date: Fri, 16 Nov 2018 08:25:46 GMT
< Content-Type: text/html;charset=utf-8
< Content-Length: 3898
< X-Squid-Error: ERR_FTP_FORBIDDEN 530
< Vary: Accept-Language
< Content-Language: en
< WWW-Authenticate: Basic realm="FTP MyServer ftp.MyServer.com"
< X-Cache: MISS from Proxy-xxxx
< X-Cache-Lookup: MISS from Proxy-xxxx:8080
< Via: 1.1 Proxy-xxxx (squid/3.5.20)
< Connection: keep-alive
<
* Ignoring the response-body
* Connection #0 to host 10.x.x.x left intact
* Issue another request to this URL: 'ftp://ftp.MyServer.com'
* Found bundle for host ftp.MyServer.com: 0xafea17a
* Re-using existing connection! (#0) with host 10.x.x.x
* Connected to 10.x.x.x (10.x.x.x) port 8080 (#0)
* Server auth using Basic with user 'Nordex'
> GET ftp://MyUser:#ftp.MyServer.com/ HTTP/1.1
Authorization: Basic Tm9yZGV50g==
Host: ftp.MyServer.com:21
Accept: */*
Proxy-Connection: Keep-Alive
< HTTP/1.1 401 Unauthorized
< Server: squid/3.5.20
< Mime-Version: 1.0
< Date: Fri, 16 Nov 2018 08:25:46 GMT
< Content-Type: text/html;charset=utf-8
< Content-Length: 3947
< X-Squid-Error: ERR_FTP_FORBIDDEN 530
< Vary: Accept-Language
< Content-Language: en
* Authentication problem. Ignoring this.
< WWW-Authenticate: Basic realm="FTP MyServer ftp.MyServer.com"
< X-Cache: MISS from Proxy-xxxx
< X-Cache-Lookup: MISS from Proxy-xxxx:8080
< Via: 1.1 Proxy-xxxx (squid/3.5.20)
< Connection: keep-alive
<
* Connection #0 to host 10.x.x.x left intact

Answer 1

WinSCP sends CONNECT command to proxy:
. 2018-11-15 17:09:15.999 HTTP proxy command: CONNECT ftp.MyServer.com:21 HTTP/1.1
While RCurl sends GET command:
> GET ftp://User:Pass#ftp.myserver.com/ HTTP/1.1
In cURL, you use CURLOPT_HTTPPROXYTUNNEL option to make it use CONNECT:
make libcurl tunnel all operations through the HTTP proxy (set with CURLOPT_PROXY). There is a big difference between using a proxy and to tunnel through it.
Tunneling means that an HTTP CONNECT request is sent to the proxy, asking it to connect to a remote host on a specific port number and then the traffic is just passed through the proxy.
In RCurl, that corresponds to httpproxytunnel. So this should do:
opts <- curlOptions(
proxy = "http://my.proxy/",
proxyport = 8080,
httpproxytunnel = 1,
...
)