Cargo proxy authentication methods: rust-lang#7330

This commit adds support for HTTP proxy authentication methods in cargo as suggested by rust-lang#7330.

The added authentication methods added are supported by `libcurl`:
* NTLM
* NTLM_WB
* GSSNEGOTIATE
* BASIC
* DIGEST
* DIGEST_IE

The authentication methods suggest user credentials to be provided as well - and their support will be added in future commits.

src/cargo/ops/registry.rs

@@ -7,7 +7,7 @@ use std::time::Duration;
 use std::{cmp, env};
 
 use crates_io::{NewCrate, NewCrateDependency, Registry};
-use curl::easy::{Easy, InfoType, SslOpt};
+use curl::easy::{Easy, InfoType, SslOpt, Auth};
 use failure::{bail, format_err};
 use log::{log, Level};
 use percent_encoding::{percent_encode, NON_ALPHANUMERIC};
@@ -409,12 +409,14 @@ pub fn http_handle_and_timeout(config: &Config) -> CargoResult<(Easy, HttpTimeou
 
 pub fn needs_custom_http_transport(config: &Config) -> CargoResult<bool> {
     let proxy_exists = http_proxy_exists(config)?;
+    let proxy_auth_exists = http_proxy_auth_exists(config)?;
     let timeout = HttpTimeout::new(config)?.is_non_default();
     let cainfo = config.get_path("http.cainfo")?;
     let check_revoke = config.get_bool("http.check-revoke")?;
     let user_agent = config.get_string("http.user-agent")?;
 
     Ok(proxy_exists
+        || proxy_auth_exists
         || timeout
         || cainfo.is_some()
         || check_revoke.is_some()
@@ -426,6 +428,9 @@ pub fn configure_http_handle(config: &Config, handle: &mut Easy) -> CargoResult<
     if let Some(proxy) = http_proxy(config)? {
         handle.proxy(&proxy)?;
     }
+    if let Some(proxy_auth) = http_proxy_auth(config)? {
+        handle.proxy_auth(&proxy_auth)?;
+    }
     if let Some(cainfo) = config.get_path("http.cainfo")? {
         handle.cainfo(&cainfo.val)?;
     }
@@ -545,6 +550,34 @@ fn http_proxy_exists(config: &Config) -> CargoResult<bool> {
     }
 }
 
+/// Finds an explicit HTTP proxy authentication method if one is available.
+///
+/// Checks cargo's `http.proxy-auth`. This will be passed on
+/// to libcurl via respective `Auth` parameter.
+fn http_proxy_auth(config: &Config) -> CargoResult<Option<&Auth>> {
+    if let Some(s) = config.get_string("http.proxy-auth")? {
+        let val = match s {
+            Some("ntlm")         => Some(Auth::new().ntlm(true)),
+            Some("ntlm_wb")      => Some(Auth::new().ntlm_wb(true)),
+            Some("gssnegotiate") => Some(Auth::new().gssnegotiate(true)),
+            Some("basic")        => Some(Auth::new().basic(true)),
+            Some("digest")       => Some(Auth::new().digest(true)),
+            Some("digest_ie")    => Some(Auth::new().digest_ie(true)),
+            _ => Ok(None)
+        };
+        return Ok(&*val);
+    }
+    Ok(None)
+}
+
+/// Determine if HTTP proxy authentication method is provided.
+fn http_proxy_auth_exists(config: &Config) -> CargoResult<bool> {
+    if http_proxy_auth(config)?.is_some() {
+        return Ok(true)
+    }
+    Ok(false)
+}
+
 pub fn registry_login(
     config: &Config,
     token: Option<String>,