Description of problem:

Recently librepo introduced new option librepo.LRO_PROXYAUTHMETHODS (see link [1]) and deprecated the librepo.LRO_PROXYAUTH option (see link [2]).

Still, dnf uses [3] the LRO_PROXYAUTH=True, which does not work for me.
Even with configured proxy settings, dnf sends first request without auth header, receives "407 Proxy Authentication Required" response from the proxy server and closes connection.

For some reason, dnf/librepo/curl do not retry with any of the auth methods suggested by the proxy server.

It may be also an issue of librepo or curl, not sure. The very same symptoms were reported on Bluecoat proxy server and PHP: https://core.trac.wordpress.org/ticket/31232

I'm posting the bug against dnf, because I was able to fix auth with one line in dnf code, and this dirty fix can be used by anyone else struggling to connect behind similar proxy.
But apparently the root cause lies far beyond dnf, somewhere in between curl and the proxy server implementation. Any suggestions?

An obvious solution would be to add a new dnf option "proxy_auth_method", to allow direct configuration of LRO_PROXYAUTHMETHODS through dnf.conf.


Version-Release number of selected component (if applicable):
The issue is reproducible in fedora-24 (dnf-1.1.9-2.fc24) and fedora-rawhide (dnf-1.1.10-1.fc26).

How reproducible:
Always reproducible.

Steps to Reproduce:
1. Add proxy configuration in dnf config:
  # cat /etc/dnf/dnf.conf
  [main]
  gpgcheck=1
  installonly_limit=3
  clean_requirements_on_remove=True
  # proxy server IP = 10.11.12.13
  proxy=http://cisco-wsa.internal.net:3128
  proxy_username=myusername
  proxy_password=VeryStrongPassword

2. Run dnf under strace:
  # strace -s2000 dnf install vim > dnf-out-1 2>&1

3. Search ip address of the proxy server and find that unauthenticated CONNECT request is sent:
  # less dnf-out-1
connect(11, {sa_family=AF_INET, sin_port=htons(3128), sin_addr=inet_addr("10.11.12.13")}, 16) = -1 EINPROGRESS (Operation now in progress)
sendto(11, "CONNECT mirrors.fedoraproject.org:443 HTTP/1.1\r\nHost: mirrors.fedoraproject.org:443\r\nUser-Agent: dnf/1.1.10\r\n\r\n", 111, MSG_NOSIGNAL, NULL, 0) = 111
recvfrom(11, "HTTP/1.1 407 Proxy Authentication Required\r\nMime-Version: 1.0\r\nDate: Fri, 21 Oct 2016 08:34:02 GMT\r\nVia: 1.1 cisco-wsa.internal.net:80 (Cisco-WSA/9.1.1-074)\r\nContent-Type: text/html\r\nProxy-Authenticate: Negotiate\r\nProxy-Authenticate: NTLM\r\nProxy-Authenticate: Basic realm=\"Cisco IronPort Web Security Appliance\"\r\nConnection: close\r\nProxy-Connection: close\r\nContent-Length: 2088\r\n\r\nHere goes HTML error message"..., 16384, 0, NULL, NULL) = 2477
close(11)                               = 0


Actual results: authentication header is not sent, authentication is not even attempted.

Expected results: authenticated connection is attempted.

Now, let's specify explicitly in dnf code that we want to use Basic Auth.
The value of LRO_PROXYAUTHMETHODS is described in link [1].

[root@localhost ~]# diff -U3 /usr/lib/python3.5/site-packages/dnf/repo_orig.py /usr/lib/python3.5/site-packages/dnf/repo.py
--- /usr/lib/python3.5/site-packages/dnf/repo_orig.py   2016-10-21 08:42:45.261000000 +0000
+++ /usr/lib/python3.5/site-packages/dnf/repo.py        2016-10-21 08:47:07.186000000 +0000
@@ -664,7 +664,8 @@
         # apply repo options
         h.maxspeed = self.throttle if type(self.throttle) is int \
                      else int(self.bandwidth * self.throttle)
-        h.setopt(librepo.LRO_PROXYAUTH, True)
+        # h.setopt(librepo.LRO_PROXYAUTH, True)
+        h.setopt(librepo.LRO_PROXYAUTHMETHODS, 1)
         h.proxy = self.proxy
         h.lowspeedlimit = self.minrate
         if self.timeout > 0:

with the same proxy configuration in /etc/dnf/dnf.conf,
runnig dnf under strace is successful:
  # strace -s2000 dnf install vim > dnf-out-2 2>&1
  # less dnf-out-2
connect(10, {sa_family=AF_INET, sin_port=htons(3128), sin_addr=inet_addr("10.11.12.13")}, 16) = -1 EINPROGRESS (Operation now in progress)
sendto(10, "CONNECT alt.fedoraproject.org:443 HTTP/1.1\r\nHost: alt.fedoraproject.org:443\r\nProxy-Authorization: Basic BASE64-encoded-myusername:VeryStrongPassword\r\nUser-Agent: dnf/1.1.10\r\n\r\n", 180, MSG_NOSIGNAL, NULL, 0) = 180
recvfrom(10, "HTTP/1.1 200 Connection established\r\nDate: Fri, 21 Oct 2016 08:40:17 GMT\r\nVia: 1.1 cisco-wsa.internal.net:80 (Cisco-WSA/9.1.1-074)\r\n\r\n", 16384, 0, NULL, NULL) = 142

It works!

Now, let's try to use NTLM auth:

[root@localhost ~]# cat /etc/dnf/dnf.conf
[main]
gpgcheck=1
installonly_limit=3
clean_requirements_on_remove=True
proxy=http://cisco-wsa.internal.net:3128
proxy_username=windowsdomain\myusername
proxy_password=VeryStrongPassword

[root@localhost ~]# diff -U3 /usr/lib/python3.5/site-packages/dnf/repo_orig.py /usr/lib/python3.5/site-packages/dnf/repo.py
--- /usr/lib/python3.5/site-packages/dnf/repo_orig.py   2016-10-21 08:42:45.261000000 +0000
+++ /usr/lib/python3.5/site-packages/dnf/repo.py        2016-10-21 08:47:07.186000000 +0000
@@ -664,7 +664,8 @@
         # apply repo options
         h.maxspeed = self.throttle if type(self.throttle) is int \
                      else int(self.bandwidth * self.throttle)
-        h.setopt(librepo.LRO_PROXYAUTH, True)
+        # h.setopt(librepo.LRO_PROXYAUTH, True)
+        h.setopt(librepo.LRO_PROXYAUTHMETHODS, 8)
         h.proxy = self.proxy
         h.lowspeedlimit = self.minrate
         if self.timeout > 0:

[root@localhost ~]# strace -s2000 dnf -y install vim > dnf-out-3 2>&1
connect(10, {sa_family=AF_INET, sin_port=htons(3128), sin_addr=inet_addr("10.11.12.13")}, 16) = -1 EINPROGRESS (Operation now in progress)
sendto(10, "CONNECT alt.fedoraproject.org:443 HTTP/1.1\r\nHost: alt.fedoraproject.org:443\r\nProxy-Authorization: NTLM TlRMTVNTUAABAAAABoIIAAAAAAAAAAAAAAAAAAAAAAA=\r\nUser-Agent: dnf/1.1.10\r\n\r\n", 175, MSG_NOSIGNAL, NULL, 0) = 175
recvfrom(10, "HTTP/1.1 407 Proxy Authentication Required\r\nMime-Version: 1.0\r\nDate: Fri, 21 Oct 2016 08:50:18 GMT\r\nVia: 1.1 cisco-wsa.internal.net:80 (Cisco-WSA/9.1.1-074)\r\nContent-Type: text/html\r\nProxy-Authenticate: NTLM BASE64-encoded-challange\r\nConnection: keep-alive\r\nProxy-Connection: keep-alive\r\nContent-Length: 0\r\n\r\n", 16384, 0, NULL, NULL) = 557
uname({sysname="Linux", nodename="localhost.localdomain", ...}) = 0
sendto(10, "CONNECT alt.fedoraproject.org:443 HTTP/1.1\r\nHost: alt.fedoraproject.org:443\r\nProxy-Authorization: NTLM BASE64-encoded-response\r\nUser-Agent: dnf/1.1.10\r\n\r\n", 543, MSG_NOSIGNAL, NULL, 0) = 543
recvfrom(10, "HTTP/1.1 200 Connection established\r\nDate: Fri, 21 Oct 2016 08:50:18 GMT\r\nVia: 1.1 cisco-wsa.internal.net:80 (Cisco-WSA/9.1.1-074)\r\n\r\n", 16384, 0, NULL, NULL) = 142

Works again!

To sum up,
  * dnf does not authenticate against proxy, even if auth options are set;
  * it would be nice to add new dnf.conf option to be able to specify explicitly the proxy auth method.


Additional info:
[1] https://github.com/rpm-software-management/librepo/commit/bfc05df2f74ad7038977ce4c6b1fd367ec1da430#diff-963eed69ec97dd555106594053f52cf2R69

[2] https://github.com/rpm-software-management/librepo/commit/bfc05df2f74ad7038977ce4c6b1fd367ec1da430#diff-9cff5beb4a457ecb5636a70db528d172R159

[3] https://github.com/rpm-software-management/dnf/blob/0c1908cfafa5961924e48dc66225b31cdc34186e/dnf/repo.py#L668