From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Wed, 20 May 2020 08:16:29 +0000 (+0300)
Subject: lib: Add buffer_create_dynamic_max()
X-Git-Tag: 2.3.14.rc1~103
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=024d6f96b8f56539d8e7b81120fc703864ebc359;p=thirdparty%2Fdovecot%2Fcore.git

lib: Add buffer_create_dynamic_max()
---

diff --git a/src/lib/buffer.c b/src/lib/buffer.c
index f9a5f2659a..66f1b1b265 100644
--- a/src/lib/buffer.c
+++ b/src/lib/buffer.c
@@ -12,7 +12,7 @@ struct real_buffer {
 
 	/* private: */
 	unsigned char *w_buffer;
-	size_t dirty, alloc;
+	size_t dirty, alloc, max_size;
 
 	pool_t pool;
 
@@ -46,7 +46,7 @@ buffer_check_limits(struct real_buffer *buf, size_t pos, size_t data_size)
 	unsigned int extra;
 	size_t new_size;
 
-	if (unlikely(SIZE_MAX - pos < data_size))
+	if (unlikely(buf->max_size - pos < data_size))
 		i_panic("Buffer write out of range (%zu + %zu)", pos, data_size);
 
 	new_size = pos + data_size;
@@ -106,7 +106,7 @@ void buffer_create_from_data(buffer_t *buffer, void *data, size_t size)
 
 	buf = (struct real_buffer *)buffer;
 	i_zero(buf);
-	buf->alloc = size;
+	buf->alloc = buf->max_size = size;
 	buf->r_buffer = buf->w_buffer = data;
 	/* clear the whole memory area. unnecessary usually, but if the
 	   buffer is used by e.g. str_c() it tries to access uninitialized
@@ -125,12 +125,18 @@ void buffer_create_from_const_data(buffer_t *buffer,
 	buf = (struct real_buffer *)buffer;
 	i_zero(buf);
 
-	buf->used = buf->alloc = size;
+	buf->used = buf->alloc = buf->max_size = size;
 	buf->r_buffer = data;
 	i_assert(buf->w_buffer == NULL);
 }
 
 buffer_t *buffer_create_dynamic(pool_t pool, size_t init_size)
+{
+	return buffer_create_dynamic_max(pool, init_size, SIZE_MAX);
+}
+
+buffer_t *buffer_create_dynamic_max(pool_t pool, size_t init_size,
+				    size_t max_size)
 {
 	struct real_buffer *buf;
 
@@ -146,6 +152,7 @@ buffer_t *buffer_create_dynamic(pool_t pool, size_t init_size)
 	buf = p_new(pool, struct real_buffer, 1);
 	buf->pool = pool;
 	buf->dynamic = TRUE;
+	buf->max_size = max_size;
 	/* buffer_alloc() reserves +1 for str_c() NIL, so add +1 here to
 	   init_size so we can actually write that much to the buffer without
 	   realloc */
diff --git a/src/lib/buffer.h b/src/lib/buffer.h
index 0901bc8a6b..f28969d276 100644
--- a/src/lib/buffer.h
+++ b/src/lib/buffer.h
@@ -4,7 +4,7 @@
 struct buffer {
 	const void *data;
 	const size_t used;
-	void *priv[5];
+	void *priv[6];
 };
 
 /* WARNING: Be careful with functions that return pointers to data.
@@ -30,6 +30,10 @@ void buffer_create_from_const_data(buffer_t *buffer,
 /* Creates a dynamically growing buffer. Whenever write would exceed the
    current size it's grown. */
 buffer_t *buffer_create_dynamic(pool_t pool, size_t init_size);
+/* Create a dynamically growing buffer with a maximum size. Writes past the
+   maximum size will i_panic(). */
+buffer_t *buffer_create_dynamic_max(pool_t pool, size_t init_size,
+				    size_t max_size);
 
 #define t_buffer_create(init_size) \
 	buffer_create_dynamic(pool_datastack_create(), (init_size))
diff --git a/src/lib/test-buffer.c b/src/lib/test-buffer.c
index 0b4417b1d1..9d9f02e5dd 100644
--- a/src/lib/test-buffer.c
+++ b/src/lib/test-buffer.c
@@ -335,3 +335,26 @@ void test_buffer(void)
 	test_buffer_truncate_bits();
 	test_buffer_replace();
 }
+
+enum fatal_test_state fatal_buffer(unsigned int stage)
+{
+	buffer_t *buf;
+
+	switch (stage) {
+	case 0:
+		test_begin("fatal buffer_create_dynamic_max()");
+		buf = buffer_create_dynamic_max(default_pool, 1, 5);
+		buffer_append(buf, "12345", 5);
+		test_expect_fatal_string("Buffer write out of range");
+		buffer_append_c(buf, 'x');
+		return FATAL_TEST_FAILURE;
+	case 1:
+		buf = buffer_create_dynamic_max(default_pool, 1, 5);
+		test_expect_fatal_string("Buffer write out of range");
+		buffer_append(buf, "123456", 6);
+		return FATAL_TEST_FAILURE;
+	default:
+		test_end();
+		return FATAL_TEST_FINISHED;
+	}
+}
diff --git a/src/lib/test-lib.inc b/src/lib/test-lib.inc
index ec03b22c79..b9bbac617e 100644
--- a/src/lib/test-lib.inc
+++ b/src/lib/test-lib.inc
@@ -12,6 +12,7 @@ TEST(test_bits)
 TEST(test_bsearch_insert_pos)
 TEST(test_buffer)
 TEST(test_buffer_append_full)
+FATAL(fatal_buffer)
 TEST(test_byteorder)
 TEST(test_connection)
 TEST(test_crc32)