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[PATCH 2/4] trace2: redact passwords from https:// URLs by default

From
Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>
Date
Nov 22, 2023, 19:18 UTC
Message-ID
<a1686ab52f1bec4bddeaab973c9b77e55e8b539b.1700680717.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.1616.git.1700680717.gitgitgadget@gmail.com>
From: Johannes Schindelin <johannes.schindelin@gmx.de>
It is an unsafe practice to call something like
	git clone https://user:password@example.com/

This not only risks leaking the password "over the shoulder" or into the readline history of the current Unix shell, it also gets logged via Trace2 if enabled.

Let's at least avoid logging such secrets via Trace2, much like we avoid logging secrets in `http.c`. Much like the code in `http.c` is guarded via `GIT_TRACE_REDACT` (defaulting to `true`), we guard the new code via `GIT_TRACE2_REDACT` (also defaulting to `true`).

The new tests added in this commit uncover leaks in `builtin/clone.c` and `remote.c`. Therefore we need to turn off `TEST_PASSES_SANITIZE_LEAK`. The reasons:

- We observed that `the_repository->remote_status` is not released
  properly.
- We are using `url...insteadOf` and that runs into a code path where an
  allocated URL is replaced with another URL, and the original URL is
  never released.
- `remote_states` contains plenty of `struct remote`s whose refspecs
  seem to be usually allocated by never released.

More investigation is needed here to identify the exact cause and proper fixes for these leaks/bugs.

Co-authored-by: Jeff Hostetler <jeffhostetler@github.com>
Signed-off-by: Jeff Hostetler <jeffhostetler@github.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 t/t0210-trace2-normal.sh |  20 ++++++-
 trace2.c                 | 120 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 136 insertions(+), 4 deletions(-)
diff --git a/t/t0210-trace2-normal.sh b/t/t0210-trace2-normal.sh
index 80e76a4695e..c312657a12c 100755
--- a/t/t0210-trace2-normal.sh
+++ b/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
diff --git a/trace2.c b/trace2.c
index 6dc74dff4c7..87d9a3a0361 100644
--- a/trace2.c
+++ b/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();
 
@@ -247,12 +250,93 @@ 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;
@@ -260,10 +344,14 @@ void trace2_cmd_start_fl(const char *file, int line, const char **argv)
 	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)

-- 
gitgitgadget
Previous: Junio C HamanoNext: Elijah Newren
Message 4 of 9 in “Redact unsafe URLs in the Trace2 output”
  1. 0/4 Redact unsafe URLs in the Trace2 outputJohannes Schindelin via GitGitGadget, Nov 22, 2023
  2. 1/4 trace2: fix signature of trace2_def_param() macroJeff Hostetler via GitGitGadget, Nov 22, 2023
  3. Junio C HamanoNov 23, 2023
  4. 2/4 trace2: redact passwords from https:// URLs by defaultJohannes Schindelin via GitGitGadget, Nov 22, 2023
  5. Elijah NewrenNov 23, 2023
  6. Jeff KingNov 27, 2023
  7. 3/4 t0211: test URL redacting in PERF formatJeff Hostetler via GitGitGadget, Nov 22, 2023
  8. 4/4 t0212: test URL redacting in EVENT formatJeff Hostetler via GitGitGadget, Nov 22, 2023
  9. Elijah NewrenNov 23, 2023

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