docs/frontends/FTP-and-SFTP.txt: warn users about connecting to the FTP and SFTP...

diff --git a/docs/frontends/FTP-and-SFTP.txt b/docs/frontends/FTP-and-SFTP.txt
index 41ee8fa566e1ead40bb57b63f22877c0193cdb7b..883e660e78e7f007ba7460111c9c9a0037518295 100644 (file)
--- a/docs/frontends/FTP-and-SFTP.txt
+++ b/docs/frontends/FTP-and-SFTP.txt
@@ -95,6 +95,11 @@ that server in an "accounts.url" directive:
 You can provide both accounts.file and accounts.url, although it probably
 isn't very useful except for testing.
 
+FTP provides no security, and so your password or caps could be eavesdropped
+if you connect to the FTP server remotely. The examples above include
+":interface=127.0.0.1" in the "port" option, which causes the server to only
+accept connections from localhost.
+
 
 == Configuring SFTP Access ==
 
@@ -105,6 +110,17 @@ program talks to a given server, it will store the host key it receives, and
 will complain if a subsequent connection uses a different key. This reduces
 the opportunity for man-in-the-middle attacks to just the first connection.
 
+Exercise caution when connecting to the SFTP server remotely. The AES
+implementation used by the SFTP code does not have defenses against timing
+attacks. The code for encrypting the SFTP connection was not written by the
+Tahoe-LAFS team, and we have not reviewed it as carefully as we have reviewed
+the code for encrypting files and directories in Tahoe-LAFS itself. If you
+can connect to the SFTP server (which is provided by the Tahoe-LAFS gateway)
+only from a client on the same host, then you would be safe from any problem
+with the SFTP connection security. The examples given below enforce this
+policy by including ":interface=127.0.0.1" in the "port" option, which
+causes the server to only accept connections from localhost.
+
 You will use directives in the tahoe.cfg file to tell the SFTP code where to
 find these keys. To create one, use the ssh-keygen tool (which comes with the
 standard openssh client distribution):
@@ -119,7 +135,7 @@ lines to the BASEDIR/tahoe.cfg file:
 
  [sftpd]
  enabled = true
- port = tcp:8022:interface=127.0.0.1 
+ port = tcp:8022:interface=127.0.0.1
  host_pubkey_file = private/ssh_host_rsa_key.pub
  host_privkey_file = private/ssh_host_rsa_key
  accounts.file = private/ftp.accounts