>Number: 184507
>Category: bin
>Synopsis: [patch] libfetch: allow hiding User-Agent with empty string
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Thu Dec 05 00:00:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator: Jan Beich
>Release:
>Organization:
>Environment:
>Description:
In some situations it may be desirable to completely hide User-Agent field
when fetching a file e.g., when using over Tor.
>How-To-Repeat:
$ sudo nc -kl 0 80 &
# before
$ HTTP_USER_AGENT= fetch http://0
GET / HTTP/1.1
Host: 0
Accept: */*
User-Agent: fetch libfetch/2.0
Connection: close
^C
# after
$ HTTP_USER_AGENT= fetch http://0
GET / HTTP/1.1
Host: 0
Accept: */*
Connection: close
^C
# other download tools
$ curl -A "" http://0
GET / HTTP/1.1
Host: 0
Accept: */*
^C
$ wget -U "" http://0 2>/dev/null
GET / HTTP/1.1
Accept: */*
Host: 0
Connection: Keep-Alive
^C
>Fix:
--- noua.diff begins here ---
Index: lib/libfetch/fetch.3
===================================================================
--- lib/libfetch/fetch.3 (revision 258921)
+++ lib/libfetch/fetch.3 (working copy)
@@ -627,6 +627,7 @@ the document URL will be used as referrer URL.
Specifies the User-Agent string to use for HTTP requests.
This can be useful when working with HTTP origin or proxy servers that
differentiate between user agents.
+If used with an empty string no User-Agent is sent.
.It Ev NETRC
Specifies a file to use instead of
.Pa ~/.netrc
Index: lib/libfetch/http.c
===================================================================
--- lib/libfetch/http.c (revision 258921)
+++ lib/libfetch/http.c (working copy)
@@ -1679,9 +1679,10 @@ http_request(struct url *URL, const char *op, stru
else
http_cmd(conn, "Referer: %s", p);
}
- if ((p = getenv("HTTP_USER_AGENT")) != NULL && *p != '\0')
- http_cmd(conn, "User-Agent: %s", p);
- else
+ if ((p = getenv("HTTP_USER_AGENT")) != NULL) {
+ if (*p != '\0')
+ http_cmd(conn, "User-Agent: %s", p);
+ } else
http_cmd(conn, "User-Agent: %s " _LIBFETCH_VER,
getprogname());
if (url->offset > 0)
http_cmd(conn, "Range: bytes=%lld-", (long
long)url->offset);
--- noua.diff ends here ---
>Release-Note:
>Audit-Trail:
>Unformatted:
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