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HTTP proxy used for ipv6 addresses which have equivalent (but not exact) no_proxy matches #5745

andrewflbarnes opened this issue Jul 29, 2020 · 2 comments


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andrewflbarnes commented Jul 29, 2020

I did this

Set http_proxy and include ::1 in the no_proxy variable or --noproxy option. Perform a curl command to a URL with an ipv6 IP equivalent to ::1 but not an exact match. e.g.

$ export http_proxy="some.proxy"
$ export no_proxy="::1"

$ curl [0:0:0:0:0:0:0:1]:5672 -s -v >/dev/null
* Uses proxy env variable no_proxy == '::1'
* Uses proxy env variable http_proxy == 'some.proxy'
* Could not resolve proxy: some.proxy
* Closing connection 0
# or
# curl -v -s --no-proxy="::1" http://[0:0:0:0:0:0:0:1]:5672 >/dev/null

Appears to break when equivalent addresses have truncation, trailing 0s and dual addresses. Other examples:

 curl --noproxy "0:0:0:0:0:0:7f00:1" [::7f00:1]:5672 -s -v >/dev/null
 curl --noproxy "::7f00:1" [0:0:0:0:0:0:7f00:1]:5672 -s -v >/dev/null
 curl --noproxy "0:0:0:0:0:0:7f00:1" [0:0:0:0:0:0:7f00:0001]:5672 -s -v >/dev/null
 curl --noproxy "0:0:0:0:0:0:7f00:0001" [0:0:0:0:0:0:7f00:1]:5672 -s -v >/dev/null
 curl --noproxy "::7f00:1" [::]:5672 -s -v >/dev/null

I expected the following

curl doesn't use a proxy and attempts to connect to the host directly as it does in an exact match e.g.

$  curl --noproxy "::1" [::1]:5672 -s -v >/dev/null
*   Trying ::1:5672...
* Connected to ::1 (::1) port 5672 (#0)
> GET / HTTP/1.1
> Host: [::1]:5672
> User-Agent: curl/7.71.1
> Accept: */*

# etc.

Side note: curl appears to have the ability to resolve/convert ipv6 elsewhere for verbose output e.g.

$ curl --noproxy "0:0:0:0:0:0:7f00:1" [0:0:0:0:0:0:7f00:1]:5672 -s -v >/dev/null 
*   Trying ::

$ curl --noproxy "0:0:0:0:0:f:ff00:1" [0:0:0:0:0:f:ff00:1]:5672 -s -v >/dev/null 
*   Trying ::f:ff00:1:5672...

curl/libcurl version

$ curl -V
curl 7.71.1 (x86_64-apple-darwin18.7.0) libcurl/7.71.1 SecureTransport zlib/1.2.11
Release-Date: 2020-07-01
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp 
Features: AsynchDNS IPv6 Largefile libz NTLM NTLM_WB SSL UnixSockets

operating system

Darwin MacBook-Pro.local 18.7.0 Darwin Kernel Version 18.7.0: Tue Aug 20 16:57:14 PDT 2019; root:xnu-4903.271.2~2/RELEASE_X86_64 x86_64

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bagder commented Jul 29, 2020

Confirmed, the noproxy matching is done on the plain string.

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bagder commented Aug 12, 2020

I'm leaning towards just documenting this behavior for now. I feel no personal urge to work on it.

bagder added a commit that referenced this issue Aug 22, 2020
Also: the current behavior is now documented in the curl.1 and
CURLOPT_NOPROXY.3 man pages.

Reported-by: Andrew Barnes
Closes #5745
@bagder bagder closed this as completed in 712d16c Aug 22, 2020
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2 participants