refactor(download): remove curl backend

Cargo.toml

@@ -11,8 +11,7 @@ repository = "https://github.com/rust-lang/rustup"
 build = "build.rs"
 
 [features]
-curl-backend = ["dep:curl"]
-default = ["curl-backend", "reqwest-native-tls", "reqwest-rustls-tls"]
+default = ["reqwest-native-tls", "reqwest-rustls-tls"]
 
 vendored-openssl = ['openssl/vendored']
 
@@ -50,7 +49,6 @@ clap = { version = "4", features = ["derive", "wrap_help", "string"] }
 clap-cargo = "0.18.3"
 clap_complete = "4"
 console = "0.16"
-curl = { version = "0.4.44", optional = true }
 effective-limits = "0.5.5"
 enum-map = "2.5.0"
 env_proxy = { version = "0.4.1", optional = true }
@@ -63,8 +61,9 @@ indicatif = "0.18"
 itertools = "0.14"
 libc = "0.2"
 opener = "0.8.0"
-# `openssl` is used by `curl` or `reqwest` backend although it isn't imported by rustup: this
-# allows controlling the vendoring status without exposing the presence of the download crate.
+# `openssl` is used by the `reqwest` backend although it isn't imported by
+# rustup: this allows controlling the vendoring status without exposing the
+# presence of the download crate.
 openssl = { version = "0.10", optional = true }
 # HACK: Temporarily pinned due to ppc64 ELFv1/v2 ABI issue in 300.5.5, to be
 # removed when <https://github.com/openssl/openssl/issues/29815> lands.

build.rs

@@ -66,7 +66,7 @@ fn main() {
     // This will work on all supported Windows versions but it relies on
     // us using `SetDefaultDllDirectories` before any libraries are loaded.
     // See also: src/bin/rustup-init.rs
-    let delay_load_dlls = ["bcrypt", "api-ms-win-core-synch-l1-2-0"];
+    let delay_load_dlls = ["api-ms-win-core-synch-l1-2-0"];
     for dll in delay_load_dlls {
         println!("cargo::rustc-link-arg-bin=rustup-init=/delayload:{dll}.dll");
     }

ci/run.bash

@@ -19,8 +19,7 @@ if [ -n "$INSTALL_BINDGEN" ]; then
   export PATH="$CARGO_HOME/bin/bindgen-cli:$PATH"
 fi
 
-
-FEATURES=('--no-default-features' '--features' 'curl-backend,reqwest-native-tls')
+FEATURES=('--no-default-features' '--features' 'reqwest-native-tls')
 case "$(uname -s)" in
   *NT* ) ;; # Windows NT
   * ) FEATURES+=('--features' 'vendored-openssl') ;;
@@ -60,7 +59,7 @@ build_test() {
   cmd="$1"
   shift
 
-  features=('--features' 'curl-backend,reqwest-native-tls')
+  features=('--features' 'reqwest-native-tls')
   case "$TARGET" in
     # these platforms aren't supported by aws-lc-rs:
     powerpc* ) ;;

doc/user-guide/src/network-proxies.md

@@ -6,38 +6,25 @@ uses a proxy by setting its URL in the environment. In most cases, setting
 `https_proxy` should be sufficient. Commands may differ between different
 systems and shells:
 
- - On a Unix-like system with a shell like __bash__ or __zsh__:  
-   ```bash
-   export https_proxy=socks5://proxy.example.com:1080
-   ```
- - On Windows [__Command Prompt (cmd)__][cmd]:  
-   ```cmd
-   set https_proxy=socks5://proxy.example.com:1080
-   ```
- - On Windows [__PowerShell__][ps] (or __PowerShell Core__):  
-   ```cmd
-   $env:https_proxy="socks5://proxy.example.com:1080"
-   ```
- - Replace `socks5://proxy.example.com:1080` with 
+- On a Unix-like system with a shell like **bash** or **zsh**:
+  ```bash
+  export https_proxy=socks5://proxy.example.com:1080
+  ```
+- On Windows [**Command Prompt (cmd)**][cmd]:
+  ```cmd
+  set https_proxy=socks5://proxy.example.com:1080
+  ```
+- On Windows [**PowerShell**][ps] (or **PowerShell Core**):
+  ```cmd
+  $env:https_proxy="socks5://proxy.example.com:1080"
+  ```
+- Replace `socks5://proxy.example.com:1080` with
   `http://proxy.example.com:8080` when an HTTP proxy is used instead.
 
 If you need a more complex setup, `rustup` supports the convention used by the
-__curl__ program, documented in the ENVIRONMENT section of [its manual
+**curl** program, documented in the ENVIRONMENT section of [its manual
 page][curlman].
 
-The use of `curl` is presently **deprecated**, however it can still be used by
-providing the `RUSTUP_USE_CURL` environment variable, for example:
-
-```bash
-RUSTUP_USE_CURL=1 rustup update
-```
-
-Note that some versions of `libcurl` apparently require you to drop the
-`http://` or `https://` prefix in environment variables. For example, `export
-http_proxy=proxy.example.com:1080` (and likewise for HTTPS). If you are
-getting an SSL `unknown protocol` error from `rustup` via `libcurl` but the
-command-line `curl` command works fine, this may be the problem.
-
 [curlman]: https://curl.se/docs/manpage.html#:~:text=Environment,-The%20environment%20variables
 [cmd]: https://en.wikipedia.org/wiki/Cmd.exe
 [ps]: https://en.wikipedia.org/wiki/PowerShell