t5563: verify that NTLM authentication works

Although NTLM authentication is considered weak (extending even to
NTLMv2, which purportedly allows brute-forcing reasonably complex
8-character passwords in a matter of days, given ample compute
resources), it _is_ one of the authentication methods supported by
libcurl.

Note: The added test case *cannot* reuse the existing `custom_auth`
facility. The reason is that that facility is backed by an NPH script
("No Parse Headers"), which does not allow handling the 3-phase NTLM
authentication correctly (in my hands, the NPH script would not even be
called upon the Type 3 message, a "200 OK" would be returned, but no
headers, let alone the `git http-backend` output as payload). Having a
separate NTLM authentication script makes the exact workings clearer and
more readable, anyway.

Co-authored-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

t/lib-httpd.sh

@@ -168,6 +168,7 @@ prepare_httpd() {
 	install_script apply-one-time-script.sh
 	install_script nph-custom-auth.sh
 	install_script http-429.sh
+	install_script ntlm-handshake.sh
 
 	ln -s "$LIB_HTTPD_MODULE_PATH" "$HTTPD_ROOT_PATH/modules"
 

t/lib-httpd/apache.conf

@@ -155,6 +155,13 @@ SetEnv PERL_PATH ${PERL_PATH}
 	CGIPassAuth on
 	</IfDefine>
 </LocationMatch>
+<LocationMatch /ntlm_auth/>
+	SetEnv GIT_EXEC_PATH ${GIT_EXEC_PATH}
+	SetEnv GIT_HTTP_EXPORT_ALL
+	<IfDefine USE_CGIPASSAUTH>
+	CGIPassAuth on
+	</IfDefine>
+</LocationMatch>
 ScriptAlias /smart/incomplete_length/git-upload-pack incomplete-length-upload-pack-v2-http.sh/
 ScriptAlias /smart/incomplete_body/git-upload-pack incomplete-body-upload-pack-v2-http.sh/
 ScriptAlias /smart/no_report/git-receive-pack error-no-report.sh/
@@ -166,6 +173,7 @@ ScriptAlias /error/ error.sh/
 ScriptAliasMatch /one_time_script/(.*) apply-one-time-script.sh/$1
 ScriptAliasMatch /http_429/(.*) http-429.sh/$1
 ScriptAliasMatch /custom_auth/(.*) nph-custom-auth.sh/$1
+ScriptAliasMatch /ntlm_auth/(.*) ntlm-handshake.sh/$1
 <Directory ${GIT_EXEC_PATH}>
 	Options FollowSymlinks
 </Directory>

t/lib-httpd/ntlm-handshake.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+
+case "$HTTP_AUTHORIZATION" in
+'')
+	# No Authorization header -> send NTLM challenge
+	echo "Status: 401 Unauthorized"
+	echo "WWW-Authenticate: NTLM"
+	echo
+	;;
+"NTLM TlRMTVNTUAAB"*)
+	# Type 1 -> respond with Type 2 challenge (hardcoded)
+	echo "Status: 401 Unauthorized"
+	# Base64-encoded version of the Type 2 challenge:
+	# signature: 'NTLMSSP\0'
+	# message_type: 2
+	# target_name: 'NTLM-GIT-SERVER'
+	# flags: 0xa2898205 =
+	#   NEGOTIATE_UNICODE, REQUEST_TARGET, NEGOTIATE_NT_ONLY,
+	#   TARGET_TYPE_SERVER, TARGET_TYPE_SHARE, REQUEST_NON_NT_SESSION_KEY,
+	#   NEGOTIATE_VERSION, NEGOTIATE_128, NEGOTIATE_56
+	# challenge: 0xfa3dec518896295b
+	# context: '0000000000000000'
+	# target_info_present: true
+	# target_info_len: 128
+	# version: '10.0 (build 19041)'
+	echo "WWW-Authenticate: NTLM TlRMTVNTUAACAAAAHgAeADgAAAAFgomi+j3sUYiWKVsAAAAAAAAAAIAAgABWAAAACgBhSgAAAA9OAFQATABNAC0ARwBJAFQALQBTAEUAUgBWAEUAUgACABIAVwBPAFIASwBHAFIATwBVAFAAAQAeAE4AVABMAE0ALQBHAEkAVAAtAFMARQBSAFYARQBSAAQAEgBXAE8AUgBLAEcAUgBPAFUAUAADAB4ATgBUAEwATQAtAEcASQBUAC0AUwBFAFIAVgBFAFIABwAIAACfOcZKYNwBAAAAAA=="
+	echo
+	;;
+"NTLM TlRMTVNTUAAD"*)
+	# Type 3 -> accept without validation
+	exec "$GIT_EXEC_PATH"/git-http-backend
+	;;
+*)
+	echo "Status: 500 Unrecognized"
+	echo
+	echo "Unhandled auth: '$HTTP_AUTHORIZATION'"
+	;;
+esac

t/t5563-simple-http-auth.sh

@@ -719,4 +719,19 @@ test_expect_success 'access using three-legged auth' '
 	EOF
 '
 
+test_lazy_prereq NTLM 'curl --version | grep -q NTLM'
+
+test_expect_success NTLM 'access using NTLM auth' '
+	test_when_finished "per_test_cleanup" &&
+
+	set_credential_reply get <<-EOF &&
+	username=user
+	password=pwd
+	EOF
+
+	test_config_global credential.helper test-helper &&
+	GIT_TRACE_CURL=1 \
+	git ls-remote "$HTTPD_URL/ntlm_auth/repo.git"
+'
+
 test_done