Use GIT_CREDENTIAL_CALLBACK=0 to disable use of credential callback

Author: ianthomas23

docs/env_vars.md

@@ -19,6 +19,12 @@ time.
 `GIT_COMMITTER_NAME`
 : The human-readable name for the "committer" field.
 
+`GIT_CREDENTIAL_CALLBACK`
+: By default, `git2cpp` will prompt the user to enter a username and password if they are required
+  for remote authentication, using a
+  [libgit2 credential callback](https://libgit2.org/docs/reference/main/credential/git_credential_acquire_cb.html).
+  To disable the callback use `export GIT_CREDENTIAL_CALLBACK=0`.
+
 
 ## In WebAssembly build only
 

src/subcommand/clone_subcommand.cpp

@@ -53,7 +53,10 @@ void clone_subcommand::run()
     checkout_opts.progress_cb = checkout_progress;
     checkout_opts.progress_payload = &pd;
     clone_opts.checkout_opts = checkout_opts;
-    clone_opts.fetch_opts.callbacks.credentials = user_credentials;
+    if (want_user_credentials())
+    {
+        clone_opts.fetch_opts.callbacks.credentials = user_credentials;
+    }
     clone_opts.fetch_opts.callbacks.sideband_progress = sideband_progress;
     clone_opts.fetch_opts.callbacks.transfer_progress = fetch_progress;
     clone_opts.fetch_opts.callbacks.payload = &pd;

src/subcommand/fetch_subcommand.cpp

@@ -44,7 +44,10 @@ void fetch_subcommand::run()
 
     git_indexer_progress pd = {0};
     git_fetch_options fetch_opts = GIT_FETCH_OPTIONS_INIT;
-    fetch_opts.callbacks.credentials = user_credentials;
+    if (want_user_credentials())
+    {
+        fetch_opts.callbacks.credentials = user_credentials;
+    }
     fetch_opts.callbacks.sideband_progress = sideband_progress;
     fetch_opts.callbacks.transfer_progress = fetch_progress;
     fetch_opts.callbacks.payload = &pd;

src/subcommand/push_subcommand.cpp

@@ -172,7 +172,10 @@ void push_subcommand::run()
     auto remote = repo.find_remote(remote_name);
 
     git_push_options push_opts = GIT_PUSH_OPTIONS_INIT;
-    push_opts.callbacks.credentials = user_credentials;
+    if (want_user_credentials())
+    {
+        push_opts.callbacks.credentials = user_credentials;
+    }
     push_opts.callbacks.push_transfer_progress = push_transfer_progress;
     push_opts.callbacks.push_update_reference = push_update_reference;
 

src/utils/credentials.cpp

@@ -47,3 +47,9 @@ int user_credentials(
     giterr_set_str(GIT_ERROR_HTTP, "Unexpected credentials request");
     return GIT_ERROR;
 }
+
+bool want_user_credentials()
+{
+    const char* env_var = std::getenv("GIT_CREDENTIAL_CALLBACK");
+    return env_var == nullptr || std::string_view(env_var) != "0";
+}

src/utils/credentials.hpp

@@ -11,3 +11,5 @@ int user_credentials(
     unsigned int allowed_types,
     void* payload
 );
+
+bool want_user_credentials();

src/wasm/stream.cpp

@@ -8,6 +8,7 @@
 #    include <emscripten.h>
 
 #    include "../utils/common.hpp"
+#    include "../utils/credentials.hpp"
 #    include "constants.hpp"
 #    include "read_buffer.hpp"
 #    include "response.hpp"
@@ -464,28 +465,38 @@ static int create_credential(wasm_http_stream* stream)
     }
     subtransport->m_authorization_header = "";
 
-    // Check that response headers show support for 'www-authenticate: Basic'.
-    if (!stream->m_response.has_header_starts_with("www-authenticate", "Basic"))
+    if (!want_user_credentials())
     {
-        git_error_set(
-            GIT_ERROR_HTTP,
-            "remote host for request %s does not support Basic authentication",
-            stream->m_unconverted_url.c_str()
-        );
-        return -1;
+        // Check that response headers show support for 'www-authenticate: Basic'.
+        if (!stream->m_response.has_header_starts_with("www-authenticate", "Basic"))
+        {
+            git_error_set(
+                GIT_ERROR_HTTP,
+                "remote host for request %s does not support Basic authentication",
+                stream->m_unconverted_url.c_str()
+            );
+            return -1;
+        }
     }
 
     // Get credentials from user via libgit2 registered callback.
-    if (git_transport_smart_credentials(
-            &subtransport->m_credential,
-            subtransport->m_owner,
-            nullptr,
-            GIT_CREDENTIAL_USERPASS_PLAINTEXT
-        )
+    int err;
+    if ((err = git_transport_smart_credentials(
+             &subtransport->m_credential,
+             subtransport->m_owner,
+             nullptr,
+             GIT_CREDENTIAL_USERPASS_PLAINTEXT
+         ))
         < 0)
     {
+        if (err == GIT_PASSTHROUGH)
+        {
+            // Use same error message as libgit2
+            git_error_set(GIT_ERROR_HTTP, "remote authentication required but no callback set");
+        }
+
         // credentials_callback will have set git error.
-        return -1;
+        return err;
     }
 
     if (subtransport->m_credential->credtype != GIT_CREDENTIAL_USERPASS_PLAINTEXT)

test/conftest.py

@@ -51,6 +51,14 @@ def commit_env_config(monkeypatch):
             monkeypatch.setenv(key, value)
 
 
+@pytest.fixture
+def disable_credential_callback(monkeypatch):
+    if GIT2CPP_TEST_WASM:
+        subprocess.run(["export", "GIT_CREDENTIAL_CALLBACK=0"], check=True)
+    else:
+        monkeypatch.setenv("GIT_CREDENTIAL_CALLBACK", "0")
+
+
 @pytest.fixture
 def repo_init_with_commit(commit_env_config, git2cpp_path, tmp_path):
     cmd_init = [git2cpp_path, "init", ".", "-b", "main"]

test/test_clone.py

@@ -128,6 +128,17 @@ def test_clone_private_repo_fails_on_no_password(
     assert p_clone.stdout.count("Password:") == 1
 
 
+def test_clone_private_repo_fails_with_no_credential_callback(
+    git2cpp_path, tmp_path, run_in_tmp_path, disable_credential_callback
+):
+    clone_cmd = [git2cpp_path, "clone", "https://github.com/QuantStack/git2cpp-test-private"]
+    p_clone = subprocess.run(clone_cmd, capture_output=True, text=True)
+
+    assert p_clone.returncode != 0
+    assert "Cloning into 'git2cpp-test-private'..." in p_clone.stdout
+    assert "error: remote authentication required but no callback set" in p_clone.stderr
+
+
 @pytest.mark.parametrize("protocol", ["http", "https"])
 def test_clone_gitlab(git2cpp_path, tmp_path, run_in_tmp_path, protocol):
     repo_url = f"{protocol}://gitlab.quantstack.net/ianthomas23_group/cockle-playground"