Redact unsafe URLs in the Trace2 output (git-for-windows#616)

The Trace2 output can contain secrets when a user issues a Git command
with sensitive information in the command-line. A typical (if highly
discouraged) example is: `git clone https://user:password@host.com/`.

With this PR, the Trace2 output redacts passwords in such URLs by
default.

This series also includes a commit to temporarily disable leak checking on t0210,t0211 because the tests uncover other unrelated bugs in Git.

t/helper/test-trace2.c

@@ -412,6 +412,56 @@ static int ut_201counter(int argc, const char **argv)
 	return 0;
 }
 
+static int ut_300redact_start(int argc, const char **argv)
+{
+	if (!argc)
+		die("expect <argv...>");
+
+	trace2_cmd_start(argv);
+
+	return 0;
+}
+
+static int ut_301redact_child_start(int argc, const char **argv)
+{
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	int k;
+
+	if (!argc)
+		die("expect <argv...>");
+
+	for (k = 0; argv[k]; k++)
+		strvec_push(&cmd.args, argv[k]);
+
+	trace2_child_start(&cmd);
+
+	strvec_clear(&cmd.args);
+
+	return 0;
+}
+
+static int ut_302redact_exec(int argc, const char **argv)
+{
+	if (!argc)
+		die("expect <exe> <argv...>");
+
+	trace2_exec(argv[0], &argv[1]);
+
+	return 0;
+}
+
+static int ut_303redact_def_param(int argc, const char **argv)
+{
+	struct key_value_info kvi = KVI_INIT;
+
+	if (argc < 2)
+		die("expect <key> <value>");
+
+	trace2_def_param(argv[0], argv[1], &kvi);
+
+	return 0;
+}
+
 /*
  * Usage:
  *     test-tool trace2 <ut_name_1> <ut_usage_1>
@@ -438,6 +488,11 @@ static struct unit_test ut_table[] = {
 
 	{ ut_200counter,  "200counter", "<v1> [<v2> [<v3> [...]]]" },
 	{ ut_201counter,  "201counter", "<v1> <v2> <threads>" },
+
+	{ ut_300redact_start,       "300redact_start",       "<argv...>" },
+	{ ut_301redact_child_start, "301redact_child_start", "<argv...>" },
+	{ ut_302redact_exec,        "302redact_exec",        "<exe> <argv...>" },
+	{ ut_303redact_def_param,   "303redact_def_param",   "<key> <value>" },
 };
 /* clang-format on */
 

t/t0210-trace2-normal.sh

@@ -2,7 +2,7 @@
 
 test_description='test trace2 facility (normal target)'
 
-TEST_PASSES_SANITIZE_LEAK=true
+TEST_PASSES_SANITIZE_LEAK=false
 . ./test-lib.sh
 
 # Turn off any inherited trace2 settings for this test.
@@ -283,4 +283,22 @@ test_expect_success 'using global config with include' '
 	test_cmp expect actual
 '
 
+test_expect_success 'unsafe URLs are redacted by default' '
+	test_when_finished \
+		"rm -r trace.normal unredacted.normal clone clone2" &&
+
+	test_config_global \
+		"url.$(pwd).insteadOf" https://user:pwd@example.com/ &&
+	test_config_global trace2.configParams "core.*,remote.*.url" &&
+
+	GIT_TRACE2="$(pwd)/trace.normal" \
+		git clone https://user:pwd@example.com/ clone &&
+	! grep user:pwd trace.normal &&
+
+	GIT_TRACE2_REDACT=0 GIT_TRACE2="$(pwd)/unredacted.normal" \
+		git clone https://user:pwd@example.com/ clone2 &&
+	grep "start .* clone https://user:pwd@example.com" unredacted.normal &&
+	grep "remote.origin.url=https://user:pwd@example.com" unredacted.normal
+'
+
 test_done

t/t0211-trace2-perf.sh

@@ -2,7 +2,7 @@
 
 test_description='test trace2 facility (perf target)'
 
-TEST_PASSES_SANITIZE_LEAK=true
+TEST_PASSES_SANITIZE_LEAK=false
 . ./test-lib.sh
 
 # Turn off any inherited trace2 settings for this test.
@@ -268,4 +268,23 @@ test_expect_success PTHREADS 'global counter test/test2' '
 	have_counter_event "main" "counter" "test" "test2" 60 actual
 '
 
+test_expect_success 'unsafe URLs are redacted by default' '
+	test_when_finished \
+		"rm -r actual trace.perf unredacted.perf clone clone2" &&
+
+	test_config_global \
+		"url.$(pwd).insteadOf" https://user:pwd@example.com/ &&
+	test_config_global trace2.configParams "core.*,remote.*.url" &&
+
+	GIT_TRACE2_PERF="$(pwd)/trace.perf" \
+		git clone https://user:pwd@example.com/ clone &&
+	! grep user:pwd trace.perf &&
+
+	GIT_TRACE2_REDACT=0 GIT_TRACE2_PERF="$(pwd)/unredacted.perf" \
+		git clone https://user:pwd@example.com/ clone2 &&
+	perl "$TEST_DIRECTORY/t0211/scrub_perf.perl" <unredacted.perf >actual &&
+	grep "d0|main|start|.* clone https://user:pwd@example.com" actual &&
+	grep "d0|main|def_param|.*|remote.origin.url:https://user:pwd@example.com" actual
+'
+
 test_done

t/t0212-trace2-event.sh

@@ -323,4 +323,44 @@ test_expect_success 'discard traces when there are too many files' '
 	head -n2 trace_target_dir/git-trace2-discard | tail -n1 | grep \"event\":\"too_many_files\"
 '
 
+# In the following "...redact..." tests, skip testing the GIT_TRACE2_REDACT=0
+# case because we would need to exactly model the full JSON event stream like
+# we did in the basic tests above and I do not think it is worth it.
+
+test_expect_success 'unsafe URLs are redacted by default in cmd_start events' '
+	test_when_finished \
+		"rm -r trace.event" &&
+
+	GIT_TRACE2_EVENT="$(pwd)/trace.event" \
+		test-tool trace2 300redact_start git clone https://user:pwd@example.com/ clone2 &&
+	! grep user:pwd trace.event
+'
+
+test_expect_success 'unsafe URLs are redacted by default in child_start events' '
+	test_when_finished \
+		"rm -r trace.event" &&
+
+	GIT_TRACE2_EVENT="$(pwd)/trace.event" \
+		test-tool trace2 301redact_child_start git clone https://user:pwd@example.com/ clone2 &&
+	! grep user:pwd trace.event
+'
+
+test_expect_success 'unsafe URLs are redacted by default in exec events' '
+	test_when_finished \
+		"rm -r trace.event" &&
+
+	GIT_TRACE2_EVENT="$(pwd)/trace.event" \
+		test-tool trace2 302redact_exec git clone https://user:pwd@example.com/ clone2 &&
+	! grep user:pwd trace.event
+'
+
+test_expect_success 'unsafe URLs are redacted by default in def_param events' '
+	test_when_finished \
+		"rm -r trace.event" &&
+
+	GIT_TRACE2_EVENT="$(pwd)/trace.event" \
+		test-tool trace2 303redact_def_param url https://user:pwd@example.com/ &&
+	! grep user:pwd trace.event
+'
+
 test_done

trace2.c

@@ -20,6 +20,7 @@
 #include "trace2/tr2_tmr.h"
 
 static int trace2_enabled;
+static int trace2_redact = 1;
 
 static int tr2_next_child_id; /* modify under lock */
 static int tr2_next_exec_id; /* modify under lock */
@@ -227,6 +228,8 @@ void trace2_initialize_fl(const char *file, int line)
 	if (!tr2_tgt_want_builtins())
 		return;
 	trace2_enabled = 1;
+	if (!git_env_bool("GIT_TRACE2_REDACT", 1))
+		trace2_redact = 0;
 
 	tr2_sid_get();
 
@@ -247,23 +250,108 @@ int trace2_is_enabled(void)
 	return trace2_enabled;
 }
 
+/*
+ * Redacts an argument, i.e. ensures that no password in
+ * https://user:password@host/-style URLs is logged.
+ *
+ * Returns the original if nothing needed to be redacted.
+ * Returns a pointer that needs to be `free()`d otherwise.
+ */
+static const char *redact_arg(const char *arg)
+{
+	const char *p, *colon;
+	size_t at;
+
+	if (!trace2_redact ||
+	    (!skip_prefix(arg, "https://", &p) &&
+	     !skip_prefix(arg, "http://", &p)))
+		return arg;
+
+	at = strcspn(p, "@/");
+	if (p[at] != '@')
+		return arg;
+
+	colon = memchr(p, ':', at);
+	if (!colon)
+		return arg;
+
+	return xstrfmt("%.*s:<REDACTED>%s", (int)(colon - arg), arg, p + at);
+}
+
+/*
+ * Redacts arguments in an argument list.
+ *
+ * Returns the original if nothing needed to be redacted.
+ * Otherwise, returns a new array that needs to be released
+ * via `free_redacted_argv()`.
+ */
+static const char **redact_argv(const char **argv)
+{
+	int i, j;
+	const char *redacted = NULL;
+	const char **ret;
+
+	if (!trace2_redact)
+		return argv;
+
+	for (i = 0; argv[i]; i++)
+		if ((redacted = redact_arg(argv[i])) != argv[i])
+			break;
+
+	if (!argv[i])
+		return argv;
+
+	for (j = 0; argv[j]; j++)
+		; /* keep counting */
+
+	ALLOC_ARRAY(ret, j + 1);
+	ret[j] = NULL;
+
+	for (j = 0; j < i; j++)
+		ret[j] = argv[j];
+	ret[i] = redacted;
+	for (++i; argv[i]; i++) {
+		redacted = redact_arg(argv[i]);
+		ret[i] = redacted ? redacted : argv[i];
+	}
+
+	return ret;
+}
+
+static void free_redacted_argv(const char **redacted, const char **argv)
+{
+	int i;
+
+	if (redacted != argv) {
+		for (i = 0; argv[i]; i++)
+			if (redacted[i] != argv[i])
+				free((void *)redacted[i]);
+		free((void *)redacted);
+	}
+}
+
 void trace2_cmd_start_fl(const char *file, int line, const char **argv)
 {
 	struct tr2_tgt *tgt_j;
 	int j;
 	uint64_t us_now;
 	uint64_t us_elapsed_absolute;
+	const char **redacted;
 
 	if (!trace2_enabled)
 		return;
 
 	us_now = getnanotime() / 1000;
 	us_elapsed_absolute = tr2tls_absolute_elapsed(us_now);
 
+	redacted = redact_argv(argv);
+
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_start_fl)
 			tgt_j->pfn_start_fl(file, line, us_elapsed_absolute,
-					    argv);
+					    redacted);
+
+	free_redacted_argv(redacted, argv);
 }
 
 void trace2_cmd_exit_fl(const char *file, int line, int code)
@@ -409,6 +497,7 @@ void trace2_child_start_fl(const char *file, int line,
 	int j;
 	uint64_t us_now;
 	uint64_t us_elapsed_absolute;
+	const char **orig_argv = cmd->args.v;
 
 	if (!trace2_enabled)
 		return;
@@ -419,10 +508,24 @@ void trace2_child_start_fl(const char *file, int line,
 	cmd->trace2_child_id = tr2tls_locked_increment(&tr2_next_child_id);
 	cmd->trace2_child_us_start = us_now;
 
+	/*
+	 * The `pfn_child_start_fl` API takes a `struct child_process`
+	 * rather than a simple `argv` for the child because some
+	 * targets make use of the additional context bits/values. So
+	 * temporarily replace the original argv (inside the `strvec`)
+	 * with a possibly redacted version.
+	 */
+	cmd->args.v = redact_argv(orig_argv);
+
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_child_start_fl)
 			tgt_j->pfn_child_start_fl(file, line,
 						  us_elapsed_absolute, cmd);
+
+	if (cmd->args.v != orig_argv) {
+		free_redacted_argv(cmd->args.v, orig_argv);
+		cmd->args.v = orig_argv;
+	}
 }
 
 void trace2_child_exit_fl(const char *file, int line, struct child_process *cmd,
@@ -493,6 +596,7 @@ int trace2_exec_fl(const char *file, int line, const char *exe,
 	int exec_id;
 	uint64_t us_now;
 	uint64_t us_elapsed_absolute;
+	const char **redacted;
 
 	if (!trace2_enabled)
 		return -1;
@@ -502,10 +606,14 @@ int trace2_exec_fl(const char *file, int line, const char *exe,
 
 	exec_id = tr2tls_locked_increment(&tr2_next_exec_id);
 
+	redacted = redact_argv(argv);
+
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_exec_fl)
 			tgt_j->pfn_exec_fl(file, line, us_elapsed_absolute,
-					   exec_id, exe, argv);
+					   exec_id, exe, redacted);
+
+	free_redacted_argv(redacted, argv);
 
 	return exec_id;
 }
@@ -637,13 +745,19 @@ void trace2_def_param_fl(const char *file, int line, const char *param,
 {
 	struct tr2_tgt *tgt_j;
 	int j;
+	const char *redacted;
 
 	if (!trace2_enabled)
 		return;
 
+	redacted = redact_arg(value);
+
 	for_each_wanted_builtin (j, tgt_j)
 		if (tgt_j->pfn_param_fl)
-			tgt_j->pfn_param_fl(file, line, param, value, kvi);
+			tgt_j->pfn_param_fl(file, line, param, redacted, kvi);
+
+	if (redacted != value)
+		free((void *)redacted);
 }
 
 void trace2_def_repo_fl(const char *file, int line, struct repository *repo)

trace2.h

@@ -337,8 +337,8 @@ struct key_value_info;
 void trace2_def_param_fl(const char *file, int line, const char *param,
 			 const char *value, const struct key_value_info *kvi);
 
-#define trace2_def_param(param, value) \
-	trace2_def_param_fl(__FILE__, __LINE__, (param), (value))
+#define trace2_def_param(param, value, kvi) \
+	trace2_def_param_fl(__FILE__, __LINE__, (param), (value), (kvi))
 
 /*
  * Tell trace2 about a newly instantiated repo object and assign