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From 26de3af817b0c5746cb61b798ae8e138e01ea17c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Mon, 9 Jul 2018 07:03:01 +0200
Subject: [PATCH] Introduce free_and_strndup and use it in bus-message.c
v2: fix error in free_and_strndup()
When the orignal and copied message were the same, but shorter than specified
length l, memory read past the end of the buffer would be performed. A test
case is included: a string that had an embedded NUL ("q\0") is used to replace
"q".
v3: Fix one more bug in free_and_strndup and add tests.
v4: Some style fixed based on review, one more use of free_and_replace, and
make the tests more comprehensive.
(cherry picked from commit 7f546026abbdc56c453a577e52d57159458c3e9c)
Resolves: #1635428
---
src/basic/string-util.c | 28 +++++++-
src/basic/string-util.h | 1 +
src/libsystemd/sd-bus/bus-message.c | 34 ++++------
src/test/test-string-util.c | 62 ++++++++++++++++++
...h-b88ad9ecf4aacf4a0caca5b5543953265367f084 | Bin 0 -> 32 bytes
5 files changed, 103 insertions(+), 22 deletions(-)
create mode 100644 test/fuzz/fuzz-bus-message/crash-b88ad9ecf4aacf4a0caca5b5543953265367f084
diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 0a40683493..dfa739996f 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -1004,7 +1004,7 @@ int free_and_strdup(char **p, const char *s) {
assert(p);
- /* Replaces a string pointer with an strdup()ed new string,
+ /* Replaces a string pointer with a strdup()ed new string,
* possibly freeing the old one. */
if (streq_ptr(*p, s))
@@ -1023,6 +1023,32 @@ int free_and_strdup(char **p, const char *s) {
return 1;
}
+int free_and_strndup(char **p, const char *s, size_t l) {
+ char *t;
+
+ assert(p);
+ assert(s || l == 0);
+
+ /* Replaces a string pointer with a strndup()ed new string,
+ * freeing the old one. */
+
+ if (!*p && !s)
+ return 0;
+
+ if (*p && s && strneq(*p, s, l) && (l > strlen(*p) || (*p)[l] == '\0'))
+ return 0;
+
+ if (s) {
+ t = strndup(s, l);
+ if (!t)
+ return -ENOMEM;
+ } else
+ t = NULL;
+
+ free_and_replace(*p, t);
+ return 1;
+}
+
#if !HAVE_EXPLICIT_BZERO
/*
* Pointer to memset is volatile so that compiler must de-reference
diff --git a/src/basic/string-util.h b/src/basic/string-util.h
index c0cc4e78d7..96a9260f93 100644
--- a/src/basic/string-util.h
+++ b/src/basic/string-util.h
@@ -176,6 +176,7 @@ char *strrep(const char *s, unsigned n);
int split_pair(const char *s, const char *sep, char **l, char **r);
int free_and_strdup(char **p, const char *s);
+int free_and_strndup(char **p, const char *s, size_t l);
/* Normal memmem() requires haystack to be nonnull, which is annoying for zero-length buffers */
static inline void *memmem_safe(const void *haystack, size_t haystacklen, const void *needle, size_t needlelen) {
diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index 381034f5f8..7c8bad2bdd 100644
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -4175,20 +4175,19 @@ _public_ int sd_bus_message_peek_type(sd_bus_message *m, char *type, const char
if (contents) {
size_t l;
- char *sig;
r = signature_element_length(c->signature+c->index+1, &l);
if (r < 0)
return r;
- assert(l >= 1);
+ /* signature_element_length does verification internally */
- sig = strndup(c->signature + c->index + 1, l);
- if (!sig)
+ assert(l >= 1);
+ if (free_and_strndup(&c->peeked_signature,
+ c->signature + c->index + 1, l) < 0)
return -ENOMEM;
- free(c->peeked_signature);
- *contents = c->peeked_signature = sig;
+ *contents = c->peeked_signature;
}
if (type)
@@ -4201,19 +4200,17 @@ _public_ int sd_bus_message_peek_type(sd_bus_message *m, char *type, const char
if (contents) {
size_t l;
- char *sig;
r = signature_element_length(c->signature+c->index, &l);
if (r < 0)
return r;
assert(l >= 2);
- sig = strndup(c->signature + c->index + 1, l - 2);
- if (!sig)
+ if (free_and_strndup(&c->peeked_signature,
+ c->signature + c->index + 1, l - 2) < 0)
return -ENOMEM;
- free(c->peeked_signature);
- *contents = c->peeked_signature = sig;
+ *contents = c->peeked_signature;
}
if (type)
@@ -4253,9 +4250,8 @@ _public_ int sd_bus_message_peek_type(sd_bus_message *m, char *type, const char
if (k > c->item_size)
return -EBADMSG;
- free(c->peeked_signature);
- c->peeked_signature = strndup((char*) q + 1, k - 1);
- if (!c->peeked_signature)
+ if (free_and_strndup(&c->peeked_signature,
+ (char*) q + 1, k - 1) < 0)
return -ENOMEM;
if (!signature_is_valid(c->peeked_signature, true))
@@ -5085,25 +5081,21 @@ int bus_message_parse_fields(sd_bus_message *m) {
if (*p == 0) {
size_t l;
- char *c;
/* We found the beginning of the signature
* string, yay! We require the body to be a
* structure, so verify it and then strip the
* opening/closing brackets. */
- l = ((char*) m->footer + m->footer_accessible) - p - (1 + sz);
+ l = (char*) m->footer + m->footer_accessible - p - (1 + sz);
if (l < 2 ||
p[1] != SD_BUS_TYPE_STRUCT_BEGIN ||
p[1 + l - 1] != SD_BUS_TYPE_STRUCT_END)
return -EBADMSG;
- c = strndup(p + 1 + 1, l - 2);
- if (!c)
+ if (free_and_strndup(&m->root_container.signature,
+ p + 1 + 1, l - 2) < 0)
return -ENOMEM;
-
- free(m->root_container.signature);
- m->root_container.signature = c;
break;
}
diff --git a/src/test/test-string-util.c b/src/test/test-string-util.c
index 3e72ce2c0a..43a6b14c34 100644
--- a/src/test/test-string-util.c
+++ b/src/test/test-string-util.c
@@ -5,6 +5,7 @@
#include "macro.h"
#include "string-util.h"
#include "strv.h"
+#include "tests.h"
#include "utf8.h"
static void test_string_erase(void) {
@@ -30,6 +31,64 @@ static void test_string_erase(void) {
assert_se(x[9] == '\0');
}
+static void test_free_and_strndup_one(char **t, const char *src, size_t l, const char *expected, bool change) {
+ int r;
+
+ log_debug("%s: \"%s\", \"%s\", %zd (expect \"%s\", %s)",
+ __func__, strnull(*t), strnull(src), l, strnull(expected), yes_no(change));
+
+ r = free_and_strndup(t, src, l);
+ assert_se(streq_ptr(*t, expected));
+ assert_se(r == change); /* check that change occurs only when necessary */
+}
+
+static void test_free_and_strndup(void) {
+ static const struct test_case {
+ const char *src;
+ size_t len;
+ const char *expected;
+ } cases[] = {
+ {"abc", 0, ""},
+ {"abc", 0, ""},
+ {"abc", 1, "a"},
+ {"abc", 2, "ab"},
+ {"abc", 3, "abc"},
+ {"abc", 4, "abc"},
+ {"abc", 5, "abc"},
+ {"abc", 5, "abc"},
+ {"abc", 4, "abc"},
+ {"abc", 3, "abc"},
+ {"abc", 2, "ab"},
+ {"abc", 1, "a"},
+ {"abc", 0, ""},
+
+ {"", 0, ""},
+ {"", 1, ""},
+ {"", 2, ""},
+ {"", 0, ""},
+ {"", 1, ""},
+ {"", 2, ""},
+ {"", 2, ""},
+ {"", 1, ""},
+ {"", 0, ""},
+
+ {NULL, 0, NULL},
+
+ {"foo", 3, "foo"},
+ {"foobar", 6, "foobar"},
+ };
+
+ _cleanup_free_ char *t = NULL;
+ const char *prev_expected = t;
+
+ for (unsigned i = 0; i < ELEMENTSOF(cases); i++) {
+ test_free_and_strndup_one(&t,
+ cases[i].src, cases[i].len, cases[i].expected,
+ !streq_ptr(cases[i].expected, prev_expected));
+ prev_expected = t;
+ }
+}
+
static void test_ascii_strcasecmp_n(void) {
assert_se(ascii_strcasecmp_n("", "", 0) == 0);
@@ -497,7 +556,10 @@ static void test_memory_startswith(void) {
}
int main(int argc, char *argv[]) {
+ test_setup_logging(LOG_DEBUG);
+
test_string_erase();
+ test_free_and_strndup();
test_ascii_strcasecmp_n();
test_ascii_strcasecmp_nn();
test_cellescape();
diff --git a/test/fuzz/fuzz-bus-message/crash-b88ad9ecf4aacf4a0caca5b5543953265367f084 b/test/fuzz/fuzz-bus-message/crash-b88ad9ecf4aacf4a0caca5b5543953265367f084
new file mode 100644
index 0000000000000000000000000000000000000000..52469650b5498a45d5d95bd9d933c989cfb47ca7
GIT binary patch
literal 32
ccmd1#|DTBg0(2Mzp)7_%AVVXuuuM|`09r!?!~g&Q
literal 0
HcmV?d00001
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