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json: replace JSON_FORMAT_REFUSE_SENSITIVE with JSON_FORMAT_CENSOR_SENSITIVE

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Previously, the flag would completely refuse formatting a JSON object if
any field of it was marked sensitive. With this change we'll simply
replace the subobject with the string "<sensitive data>", and show
everything else.

This is tremendously useful when debugging, since it means that we can
again trace varlink calls through the stack: we can show all the message
metadata and just suppress the actually sensitive parameters.

The ability to debug this matters, and we should not hide more
information that we can get away with, to keep things debuggable and
maintainable.
This commit is contained in:
Lennart Poettering 2024-01-16 11:55:54 +01:00
parent c609338b1d
commit 9912897170
4 changed files with 53 additions and 40 deletions

13
src/shared/json.c

@ -1612,6 +1612,15 @@ static int json_format(FILE *f, JsonVariant *v, JsonFormatFlags flags, const cha
assert(f);
assert(v);
if (FLAGS_SET(flags, JSON_FORMAT_CENSOR_SENSITIVE) && json_variant_is_sensitive(v)) {
if (flags & JSON_FORMAT_COLOR)
fputs(ansi_red(), f);
fputs("\"<sensitive data>\"", f);
if (flags & JSON_FORMAT_COLOR)
fputs(ANSI_NORMAL, f);
return 0;
}
switch (json_variant_type(v)) {
case JSON_VARIANT_REAL: {
@ -1818,10 +1827,6 @@ int json_variant_format(JsonVariant *v, JsonFormatFlags flags, char **ret) {
if (flags & JSON_FORMAT_OFF)
return -ENOEXEC;
if ((flags & JSON_FORMAT_REFUSE_SENSITIVE))
if (json_variant_is_sensitive_recursive(v))
return -EPERM;
f = memstream_init(&m);
if (!f)
return -ENOMEM;

2
src/shared/json.h

@ -197,7 +197,7 @@ typedef enum JsonFormatFlags {
JSON_FORMAT_FLUSH = 1 << 8, /* call fflush() after dumping JSON */
JSON_FORMAT_EMPTY_ARRAY = 1 << 9, /* output "[]" for empty input */
JSON_FORMAT_OFF = 1 << 10, /* make json_variant_format() fail with -ENOEXEC */
JSON_FORMAT_REFUSE_SENSITIVE = 1 << 11, /* return EPERM if any node in the tree is marked as senstitive */
JSON_FORMAT_CENSOR_SENSITIVE = 1 << 11, /* Replace all sensitive elements with the string "<sensitive data>" */
} JsonFormatFlags;
int json_variant_format(JsonVariant *v, JsonFormatFlags flags, char **ret);

42
src/shared/varlink.c

@ -1860,56 +1860,60 @@ Varlink* varlink_flush_close_unref(Varlink *v) {
static int varlink_format_json(Varlink *v, JsonVariant *m) {
_cleanup_(erase_and_freep) char *text = NULL;
bool sensitive = false;
int r;
int sz, r;
assert(v);
assert(m);
r = json_variant_format(m, JSON_FORMAT_REFUSE_SENSITIVE, &text);
if (r == -EPERM) {
sensitive = true;
r = json_variant_format(m, /* flags= */ 0, &text);
}
if (r < 0)
return r;
assert(text[r] == '\0');
sz = json_variant_format(m, /* flags= */ 0, &text);
if (sz < 0)
return sz;
assert(text[sz] == '\0');
if (v->output_buffer_size + r + 1 > VARLINK_BUFFER_MAX)
if (v->output_buffer_size + sz + 1 > VARLINK_BUFFER_MAX)
return -ENOBUFS;
varlink_log(v, "Sending message: %s", sensitive ? "<sensitive data>" : text);
if (DEBUG_LOGGING) {
_cleanup_(erase_and_freep) char *censored_text = NULL;
/* Suppress sensitive fields in the debug output */
r = json_variant_format(m, /* flags= */ JSON_FORMAT_CENSOR_SENSITIVE, &censored_text);
if (r < 0)
return r;
varlink_log(v, "Sending message: %s", censored_text);
}
if (v->output_buffer_size == 0) {
free_and_replace(v->output_buffer, text);
v->output_buffer_size = r + 1;
v->output_buffer_size = sz + 1;
v->output_buffer_index = 0;
} else if (v->output_buffer_index == 0) {
if (!GREEDY_REALLOC(v->output_buffer, v->output_buffer_size + r + 1))
if (!GREEDY_REALLOC(v->output_buffer, v->output_buffer_size + sz + 1))
return -ENOMEM;
memcpy(v->output_buffer + v->output_buffer_size, text, r + 1);
v->output_buffer_size += r + 1;
memcpy(v->output_buffer + v->output_buffer_size, text, sz + 1);
v->output_buffer_size += sz + 1;
} else {
char *n;
const size_t new_size = v->output_buffer_size + r + 1;
const size_t new_size = v->output_buffer_size + sz + 1;
n = new(char, new_size);
if (!n)
return -ENOMEM;
memcpy(mempcpy(n, v->output_buffer + v->output_buffer_index, v->output_buffer_size), text, r + 1);
memcpy(mempcpy(n, v->output_buffer + v->output_buffer_index, v->output_buffer_size), text, sz + 1);
free_and_replace(v->output_buffer, n);
v->output_buffer_size = new_size;
v->output_buffer_index = 0;
}
if (sensitive)
if (json_variant_is_sensitive_recursive(m))
v->output_buffer_sensitive = true; /* Propagate sensitive flag */
else
text = mfree(text); /* No point in the erase_and_free() destructor declared above */

36
src/test/test-json.c

@ -107,9 +107,9 @@ static void test_variant_one(const char *data, Test test) {
assert_se(json_variant_equal(v, w));
s = mfree(s);
r = json_variant_format(w, JSON_FORMAT_REFUSE_SENSITIVE, &s);
assert_se(r == -EPERM);
assert_se(!s);
r = json_variant_format(w, JSON_FORMAT_CENSOR_SENSITIVE, &s);
assert_se(s);
assert_se(streq_ptr(s, "\"<sensitive data>\""));
s = mfree(s);
r = json_variant_format(w, JSON_FORMAT_PRETTY, &s);
@ -886,10 +886,11 @@ TEST(json_sensitive) {
json_variant_sensitive(a);
assert_se(json_variant_format(a, JSON_FORMAT_REFUSE_SENSITIVE, &s) == -EPERM);
assert_se(!s);
assert_se(json_variant_format(a, JSON_FORMAT_CENSOR_SENSITIVE, &s) >= 0);
assert_se(streq_ptr(s, "\"<sensitive data>\""));
s = mfree(s);
r = json_variant_format(b, JSON_FORMAT_REFUSE_SENSITIVE, &s);
r = json_variant_format(b, JSON_FORMAT_CENSOR_SENSITIVE, &s);
assert_se(r >= 0);
assert_se(s);
assert_se((size_t) r == strlen(s));
@ -901,7 +902,7 @@ TEST(json_sensitive) {
JSON_BUILD_PAIR("e", JSON_BUILD_EMPTY_OBJECT))) >= 0);
json_variant_dump(v, JSON_FORMAT_COLOR|JSON_FORMAT_PRETTY, NULL, NULL);
r = json_variant_format(v, JSON_FORMAT_REFUSE_SENSITIVE, &s);
r = json_variant_format(v, JSON_FORMAT_CENSOR_SENSITIVE, &s);
assert_se(r >= 0);
assert_se(s);
assert_se((size_t) r == strlen(s));
@ -915,7 +916,7 @@ TEST(json_sensitive) {
JSON_BUILD_PAIR("e", JSON_BUILD_EMPTY_OBJECT))) >= 0);
json_variant_dump(v, JSON_FORMAT_COLOR|JSON_FORMAT_PRETTY, NULL, NULL);
r = json_variant_format(v, JSON_FORMAT_REFUSE_SENSITIVE, &s);
r = json_variant_format(v, JSON_FORMAT_CENSOR_SENSITIVE, &s);
assert_se(r >= 0);
assert_se(s);
assert_se((size_t) r == strlen(s));
@ -930,8 +931,9 @@ TEST(json_sensitive) {
JSON_BUILD_PAIR("e", JSON_BUILD_EMPTY_OBJECT))) >= 0);
json_variant_dump(v, JSON_FORMAT_COLOR|JSON_FORMAT_PRETTY, NULL, NULL);
assert_se(json_variant_format(v, JSON_FORMAT_REFUSE_SENSITIVE, &s) == -EPERM);
assert_se(!s);
assert_se(json_variant_format(v, JSON_FORMAT_CENSOR_SENSITIVE, &s) >= 0);
assert_se(streq_ptr(s, "{\"b\":[\"foo\",\"bar\",\"baz\",\"qux\"],\"a\":\"<sensitive data>\",\"c\":-9223372036854775808,\"d\":\"-9223372036854775808\",\"e\":{}}"));
s = mfree(s);
v = json_variant_unref(v);
assert_se(json_build(&v, JSON_BUILD_OBJECT(
@ -942,8 +944,9 @@ TEST(json_sensitive) {
JSON_BUILD_PAIR("e", JSON_BUILD_EMPTY_OBJECT))) >= 0);
json_variant_dump(v, JSON_FORMAT_COLOR|JSON_FORMAT_PRETTY, NULL, NULL);
assert_se(json_variant_format(v, JSON_FORMAT_REFUSE_SENSITIVE, &s) == -EPERM);
assert_se(!s);
assert_se(json_variant_format(v, JSON_FORMAT_CENSOR_SENSITIVE, &s) >= 0);
assert_se(streq_ptr(s, "{\"b\":[\"foo\",\"bar\",\"baz\",\"qux\"],\"c\":-9223372036854775808,\"a\":\"<sensitive data>\",\"d\":\"-9223372036854775808\",\"e\":{}}"));
s = mfree(s);
v = json_variant_unref(v);
assert_se(json_build(&v, JSON_BUILD_OBJECT(
@ -954,8 +957,9 @@ TEST(json_sensitive) {
JSON_BUILD_PAIR("e", JSON_BUILD_EMPTY_OBJECT))) >= 0);
json_variant_dump(v, JSON_FORMAT_COLOR|JSON_FORMAT_PRETTY, NULL, NULL);
assert_se(json_variant_format(v, JSON_FORMAT_REFUSE_SENSITIVE, &s) == -EPERM);
assert_se(!s);
assert_se(json_variant_format(v, JSON_FORMAT_CENSOR_SENSITIVE, &s) >= 0);
assert_se(streq_ptr(s, "{\"b\":[\"foo\",\"bar\",\"baz\",\"qux\"],\"c\":-9223372036854775808,\"d\":\"-9223372036854775808\",\"a\":\"<sensitive data>\",\"e\":{}}"));
s = mfree(s);
v = json_variant_unref(v);
assert_se(json_build(&v, JSON_BUILD_OBJECT(
@ -966,8 +970,8 @@ TEST(json_sensitive) {
JSON_BUILD_PAIR_VARIANT("a", a))) >= 0);
json_variant_dump(v, JSON_FORMAT_COLOR|JSON_FORMAT_PRETTY, NULL, NULL);
assert_se(json_variant_format(v, JSON_FORMAT_REFUSE_SENSITIVE, &s) == -EPERM);
assert_se(!s);
assert_se(json_variant_format(v, JSON_FORMAT_CENSOR_SENSITIVE, &s) >= 0);
assert_se(streq_ptr(s, "{\"b\":[\"foo\",\"bar\",\"baz\",\"qux\"],\"c\":-9223372036854775808,\"d\":\"-9223372036854775808\",\"e\":{},\"a\":\"<sensitive data>\"}"));
}
TEST(json_iovec) {