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glib/glib/gvariant-serialiser.c
Philip Withnall 409ff69bd1 gvariant: Re-use g_variant_serialised_check() to check alignment 
Rather than duplicating the alignment checks when constructing a new
GVariant, re-use the alignment checks from GVariantSerialised. This
ensures that the same checks are done everywhere in the GVariant code.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://gitlab.gnome.org/GNOME/glib/issues/1342
2018-11-06 12:49:25 +00:00

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/*
* Copyright © 2007, 2008 Ryan Lortie
* Copyright © 2010 Codethink Limited
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
* Author: Ryan Lortie <desrt@desrt.ca>
*/
/* Prologue {{{1 */
#include "config.h"
#include "gvariant-serialiser.h"
#include <glib/gvariant-internal.h>
#include <glib/gtestutils.h>
#include <glib/gstrfuncs.h>
#include <glib/gtypes.h>
#include <string.h>
/* GVariantSerialiser
*
* After this prologue section, this file has roughly 2 parts.
*
* The first part is split up into sections according to various
* container types. Maybe, Array, Tuple, Variant. The Maybe and Array
* sections are subdivided for element types being fixed or
* variable-sized types.
*
* Each section documents the format of that particular type of
* container and implements 5 functions for dealing with it:
*
* n_children:
* - determines (according to serialised data) how many child values
* are inside a particular container value.
*
* get_child:
* - gets the type of and the serialised data corresponding to a
* given child value within the container value.
*
* needed_size:
* - determines how much space would be required to serialise a
* container of this type, containing the given children so that
* buffers can be preallocated before serialising.
*
* serialise:
* - write the serialised data for a container of this type,
* containing the given children, to a buffer.
*
* is_normal:
* - check the given data to ensure that it is in normal form. For a
* given set of child values, there is exactly one normal form for
* the serialised data of a container. Other forms are possible
* while maintaining the same children (for example, by inserting
* something other than zero bytes as padding) but only one form is
* the normal form.
*
* The second part contains the main entry point for each of the above 5
* functions and logic to dispatch it to the handler for the appropriate
* container type code.
*
* The second part also contains a routine to byteswap serialised
* values. This code makes use of the n_children() and get_child()
* functions above to do its work so no extra support is needed on a
* per-container-type basis.
*
* There is also additional code for checking for normal form. All
* numeric types are always in normal form since the full range of
* values is permitted (eg: 0 to 255 is a valid byte). Special checks
* need to be performed for booleans (only 0 or 1 allowed), strings
* (properly nul-terminated) and object paths and signature strings
* (meeting the D-Bus specification requirements). Depth checks need to be
* performed for nested types (arrays, tuples, and variants), to avoid massive
* recursion which could exhaust our stack when handling untrusted input.
*/
/* < private >
* GVariantSerialised:
* @type_info: the #GVariantTypeInfo of this value
* @data: (nullable): the serialised data of this value, or %NULL
* @size: the size of this value
*
* A structure representing a GVariant in serialised form. This
* structure is used with #GVariantSerialisedFiller functions and as the
* primary interface to the serialiser. See #GVariantSerialisedFiller
* for a description of its use there.
*
* When used with the serialiser API functions, the following invariants
* apply to all #GVariantTypeSerialised structures passed to and
* returned from the serialiser.
*
* @type_info must be non-%NULL.
*
* @data must be properly aligned for the type described by @type_info.
*
* If @type_info describes a fixed-sized type then @size must always be
* equal to the fixed size of that type.
*
* For fixed-sized types (and only fixed-sized types), @data may be
* %NULL even if @size is non-zero. This happens when a framing error
* occurs while attempting to extract a fixed-sized value out of a
* variable-sized container. There is no data to return for the
* fixed-sized type, yet @size must be non-zero. The effect of this
* combination should be as if @data were a pointer to an
* appropriately-sized zero-filled region.
*
* @depth has no restrictions; the depth of a top-level serialised #GVariant is
* zero, and it increases for each level of nested child.
*/
/* < private >
* g_variant_serialised_check:
* @serialised: a #GVariantSerialised struct
*
* Checks @serialised for validity according to the invariants described
* above.
*
* Returns: %TRUE if @serialised is valid; %FALSE otherwise
*/
gboolean
g_variant_serialised_check (GVariantSerialised serialised)
{
gsize fixed_size;
guint alignment;
if (serialised.type_info == NULL)
return FALSE;
g_variant_type_info_query (serialised.type_info, &alignment, &fixed_size);
if (fixed_size != 0 && serialised.size != fixed_size)
return FALSE;
else if (fixed_size == 0 &&
!(serialised.size == 0 || serialised.data != NULL))
return FALSE;
/* Depending on the native alignment requirements of the machine, the
* compiler will insert either 3 or 7 padding bytes after the char.
* This will result in the sizeof() the struct being 12 or 16.
* Subtract 9 to get 3 or 7 which is a nice bitmask to apply to get
* the alignment bits that we "care about" being zero: in the
* 4-aligned case, we care about 2 bits, and in the 8-aligned case, we
* care about 3 bits.
*/
alignment &= sizeof (struct {
char a;
union {
guint64 x;
void *y;
gdouble z;
} b;
}
) - 9;
/* Some OSes (FreeBSD is a known example) have a malloc() that returns
* unaligned memory if you request small sizes. 'malloc (1);', for
* example, has been seen to return pointers aligned to 6 mod 16.
*
* Check if this is a small allocation and return without enforcing
* the alignment assertion if this is the case.
*/
return (serialised.size <= alignment ||
(alignment & (gsize) serialised.data) == 0);
}
/* < private >
* GVariantSerialisedFiller:
* @serialised: a #GVariantSerialised instance to fill
* @data: data from the children array
*
* This function is called back from g_variant_serialiser_needed_size()
* and g_variant_serialiser_serialise(). It fills in missing details
* from a partially-complete #GVariantSerialised.
*
* The @data parameter passed back to the function is one of the items
* that was passed to the serialiser in the @children array. It
* represents a single child item of the container that is being
* serialised. The information filled in to @serialised is the
* information for this child.
*
* If the @type_info field of @serialised is %NULL then the callback
* function must set it to the type information corresponding to the
* type of the child. No reference should be added. If it is non-%NULL
* then the callback should assert that it is equal to the actual type
* of the child.
*
* If the @size field is zero then the callback must fill it in with the
* required amount of space to store the serialised form of the child.
* If it is non-zero then the callback should assert that it is equal to
* the needed size of the child.
*
* If @data is non-%NULL then it points to a space that is properly
* aligned for and large enough to store the serialised data of the
* child. The callback must store the serialised form of the child at
* @data.
*
* If the child value is another container then the callback will likely
* recurse back into the serialiser by calling
* g_variant_serialiser_needed_size() to determine @size and
* g_variant_serialiser_serialise() to write to @data.
*/
/* PART 1: Container types {{{1
*
* This section contains the serialiser implementation functions for
* each container type.
*/
/* Maybe {{{2
*
* Maybe types are handled depending on if the element type of the maybe
* type is a fixed-sized or variable-sized type. Although all maybe
* types themselves are variable-sized types, herein, a maybe value with
* a fixed-sized element type is called a "fixed-sized maybe" for
* convenience and a maybe value with a variable-sized element type is
* called a "variable-sized maybe".
*/
/* Fixed-sized Maybe {{{3
*
* The size of a maybe value with a fixed-sized element type is either 0
* or equal to the fixed size of its element type. The case where the
* size of the maybe value is zero corresponds to the "Nothing" case and
* the case where the size of the maybe value is equal to the fixed size
* of the element type corresponds to the "Just" case; in that case, the
* serialised data of the child value forms the entire serialised data
* of the maybe value.
*
* In the event that a fixed-sized maybe value is presented with a size
* that is not equal to the fixed size of the element type then the
* value must be taken to be "Nothing".
*/
static gsize
gvs_fixed_sized_maybe_n_children (GVariantSerialised value)
{
gsize element_fixed_size;
g_variant_type_info_query_element (value.type_info, NULL,
&element_fixed_size);
return (element_fixed_size == value.size) ? 1 : 0;
}
static GVariantSerialised
gvs_fixed_sized_maybe_get_child (GVariantSerialised value,
gsize index_)
{
/* the child has the same bounds as the
* container, so just update the type.
*/
value.type_info = g_variant_type_info_element (value.type_info);
g_variant_type_info_ref (value.type_info);
value.depth++;
return value;
}
static gsize
gvs_fixed_sized_maybe_needed_size (GVariantTypeInfo *type_info,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
if (n_children)
{
gsize element_fixed_size;
g_variant_type_info_query_element (type_info, NULL,
&element_fixed_size);
return element_fixed_size;
}
else
return 0;
}
static void
gvs_fixed_sized_maybe_serialise (GVariantSerialised value,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
if (n_children)
{
GVariantSerialised child = { NULL, value.data, value.size, value.depth + 1 };
gvs_filler (&child, children[0]);
}
}
static gboolean
gvs_fixed_sized_maybe_is_normal (GVariantSerialised value)
{
if (value.size > 0)
{
gsize element_fixed_size;
g_variant_type_info_query_element (value.type_info,
NULL, &element_fixed_size);
if (value.size != element_fixed_size)
return FALSE;
/* proper element size: "Just". recurse to the child. */
value.type_info = g_variant_type_info_element (value.type_info);
value.depth++;
return g_variant_serialised_is_normal (value);
}
/* size of 0: "Nothing" */
return TRUE;
}
/* Variable-sized Maybe
*
* The size of a maybe value with a variable-sized element type is
* either 0 or strictly greater than 0. The case where the size of the
* maybe value is zero corresponds to the "Nothing" case and the case
* where the size of the maybe value is greater than zero corresponds to
* the "Just" case; in that case, the serialised data of the child value
* forms the first part of the serialised data of the maybe value and is
* followed by a single zero byte. This zero byte is always appended,
* regardless of any zero bytes that may already be at the end of the
* serialised ata of the child value.
*/
static gsize
gvs_variable_sized_maybe_n_children (GVariantSerialised value)
{
return (value.size > 0) ? 1 : 0;
}
static GVariantSerialised
gvs_variable_sized_maybe_get_child (GVariantSerialised value,
gsize index_)
{
/* remove the padding byte and update the type. */
value.type_info = g_variant_type_info_element (value.type_info);
g_variant_type_info_ref (value.type_info);
value.size--;
/* if it's zero-sized then it may as well be NULL */
if (value.size == 0)
value.data = NULL;
value.depth++;
return value;
}
static gsize
gvs_variable_sized_maybe_needed_size (GVariantTypeInfo *type_info,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
if (n_children)
{
GVariantSerialised child = { 0, };
gvs_filler (&child, children[0]);
return child.size + 1;
}
else
return 0;
}
static void
gvs_variable_sized_maybe_serialise (GVariantSerialised value,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
if (n_children)
{
GVariantSerialised child = { NULL, value.data, value.size - 1, value.depth + 1 };
/* write the data for the child. */
gvs_filler (&child, children[0]);
value.data[child.size] = '\0';
}
}
static gboolean
gvs_variable_sized_maybe_is_normal (GVariantSerialised value)
{
if (value.size == 0)
return TRUE;
if (value.data[value.size - 1] != '\0')
return FALSE;
value.type_info = g_variant_type_info_element (value.type_info);
value.size--;
value.depth++;
return g_variant_serialised_is_normal (value);
}
/* Arrays {{{2
*
* Just as with maybe types, array types are handled depending on if the
* element type of the array type is a fixed-sized or variable-sized
* type. Similar to maybe types, for convenience, an array value with a
* fixed-sized element type is called a "fixed-sized array" and an array
* value with a variable-sized element type is called a "variable sized
* array".
*/
/* Fixed-sized Array {{{3
*
* For fixed sized arrays, the serialised data is simply a concatenation
* of the serialised data of each element, in order. Since fixed-sized
* values always have a fixed size that is a multiple of their alignment
* requirement no extra padding is required.
*
* In the event that a fixed-sized array is presented with a size that
* is not an integer multiple of the element size then the value of the
* array must be taken as being empty.
*/
static gsize
gvs_fixed_sized_array_n_children (GVariantSerialised value)
{
gsize element_fixed_size;
g_variant_type_info_query_element (value.type_info, NULL,
&element_fixed_size);
if (value.size % element_fixed_size == 0)
return value.size / element_fixed_size;
return 0;
}
static GVariantSerialised
gvs_fixed_sized_array_get_child (GVariantSerialised value,
gsize index_)
{
GVariantSerialised child = { 0, };
child.type_info = g_variant_type_info_element (value.type_info);
g_variant_type_info_query (child.type_info, NULL, &child.size);
child.data = value.data + (child.size * index_);
g_variant_type_info_ref (child.type_info);
child.depth = value.depth + 1;
return child;
}
static gsize
gvs_fixed_sized_array_needed_size (GVariantTypeInfo *type_info,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
gsize element_fixed_size;
g_variant_type_info_query_element (type_info, NULL, &element_fixed_size);
return element_fixed_size * n_children;
}
static void
gvs_fixed_sized_array_serialise (GVariantSerialised value,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
GVariantSerialised child = { 0, };
gsize i;
child.type_info = g_variant_type_info_element (value.type_info);
g_variant_type_info_query (child.type_info, NULL, &child.size);
child.data = value.data;
child.depth = value.depth + 1;
for (i = 0; i < n_children; i++)
{
gvs_filler (&child, children[i]);
child.data += child.size;
}
}
static gboolean
gvs_fixed_sized_array_is_normal (GVariantSerialised value)
{
GVariantSerialised child = { 0, };
child.type_info = g_variant_type_info_element (value.type_info);
g_variant_type_info_query (child.type_info, NULL, &child.size);
child.depth = value.depth + 1;
if (value.size % child.size != 0)
return FALSE;
for (child.data = value.data;
child.data < value.data + value.size;
child.data += child.size)
{
if (!g_variant_serialised_is_normal (child))
return FALSE;
}
return TRUE;
}
/* Variable-sized Array {{{3
*
* Variable sized arrays, containing variable-sized elements, must be
* able to determine the boundaries between the elements. The items
* cannot simply be concatenated. Additionally, we are faced with the
* fact that non-fixed-sized values do not necessarily have a size that
* is a multiple of their alignment requirement, so we may need to
* insert zero-filled padding.
*
* While it is possible to find the start of an item by starting from
* the end of the item before it and padding for alignment, it is not
* generally possible to do the reverse operation. For this reason, we
* record the end point of each element in the array.
*
* GVariant works in terms of "offsets". An offset is a pointer to a
* boundary between two bytes. In 4 bytes of serialised data, there
* would be 5 possible offsets: one at the start ('0'), one between each
* pair of adjacent bytes ('1', '2', '3') and one at the end ('4').
*
* The numeric value of an offset is an unsigned integer given relative
* to the start of the serialised data of the array. Offsets are always
* stored in little endian byte order and are always only as big as they
* need to be. For example, in 255 bytes of serialised data, there are
* 256 offsets. All possibilities can be stored in an 8 bit unsigned
* integer. In 256 bytes of serialised data, however, there are 257
* possible offsets so 16 bit integers must be used. The size of an
* offset is always a power of 2.
*
* The offsets are stored at the end of the serialised data of the
* array. They are simply concatenated on without any particular
* alignment. The size of the offsets is included in the size of the
* serialised data for purposes of determining the size of the offsets.
* This presents a possibly ambiguity; in certain cases, a particular
* value of array could have two different serialised forms.
*
* Imagine an array containing a single string of 253 bytes in length
* (so, 254 bytes including the nul terminator). Now the offset must be
* written. If an 8 bit offset is written, it will bring the size of
* the array's serialised data to 255 -- which means that the use of an
* 8 bit offset was valid. If a 16 bit offset is used then the total
* size of the array will be 256 -- which means that the use of a 16 bit
* offset was valid. Although both of these will be accepted by the
* deserialiser, only the smaller of the two is considered to be in
* normal form and that is the one that the serialiser must produce.
*/
/* bytes may be NULL if (size == 0). */
static inline gsize
gvs_read_unaligned_le (guchar *bytes,
guint size)
{
union
{
guchar bytes[GLIB_SIZEOF_SIZE_T];
gsize integer;
} tmpvalue;
tmpvalue.integer = 0;
if (bytes != NULL)
memcpy (&tmpvalue.bytes, bytes, size);
return GSIZE_FROM_LE (tmpvalue.integer);
}
static inline void
gvs_write_unaligned_le (guchar *bytes,
gsize value,
guint size)
{
union
{
guchar bytes[GLIB_SIZEOF_SIZE_T];
gsize integer;
} tmpvalue;
tmpvalue.integer = GSIZE_TO_LE (value);
memcpy (bytes, &tmpvalue.bytes, size);
}
static guint
gvs_get_offset_size (gsize size)
{
if (size > G_MAXUINT32)
return 8;
else if (size > G_MAXUINT16)
return 4;
else if (size > G_MAXUINT8)
return 2;
else if (size > 0)
return 1;
return 0;
}
static gsize
gvs_calculate_total_size (gsize body_size,
gsize offsets)
{
if (body_size + 1 * offsets <= G_MAXUINT8)
return body_size + 1 * offsets;
if (body_size + 2 * offsets <= G_MAXUINT16)
return body_size + 2 * offsets;
if (body_size + 4 * offsets <= G_MAXUINT32)
return body_size + 4 * offsets;
return body_size + 8 * offsets;
}
static gsize
gvs_variable_sized_array_n_children (GVariantSerialised value)
{
gsize offsets_array_size;
gsize offset_size;
gsize last_end;
if (value.size == 0)
return 0;
offset_size = gvs_get_offset_size (value.size);
last_end = gvs_read_unaligned_le (value.data + value.size -
offset_size, offset_size);
if (last_end > value.size)
return 0;
offsets_array_size = value.size - last_end;
if (offsets_array_size % offset_size)
return 0;
return offsets_array_size / offset_size;
}
static GVariantSerialised
gvs_variable_sized_array_get_child (GVariantSerialised value,
gsize index_)
{
GVariantSerialised child = { 0, };
gsize offset_size;
gsize last_end;
gsize start;
gsize end;
child.type_info = g_variant_type_info_element (value.type_info);
g_variant_type_info_ref (child.type_info);
child.depth = value.depth + 1;
offset_size = gvs_get_offset_size (value.size);
last_end = gvs_read_unaligned_le (value.data + value.size -
offset_size, offset_size);
if (index_ > 0)
{
guint alignment;
start = gvs_read_unaligned_le (value.data + last_end +
(offset_size * (index_ - 1)),
offset_size);
g_variant_type_info_query (child.type_info, &alignment, NULL);
start += (-start) & alignment;
}
else
start = 0;
end = gvs_read_unaligned_le (value.data + last_end +
(offset_size * index_),
offset_size);
if (start < end && end <= value.size && end <= last_end)
{
child.data = value.data + start;
child.size = end - start;
}
return child;
}
static gsize
gvs_variable_sized_array_needed_size (GVariantTypeInfo *type_info,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
guint alignment;
gsize offset;
gsize i;
g_variant_type_info_query (type_info, &alignment, NULL);
offset = 0;
for (i = 0; i < n_children; i++)
{
GVariantSerialised child = { 0, };
offset += (-offset) & alignment;
gvs_filler (&child, children[i]);
offset += child.size;
}
return gvs_calculate_total_size (offset, n_children);
}
static void
gvs_variable_sized_array_serialise (GVariantSerialised value,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
guchar *offset_ptr;
gsize offset_size;
guint alignment;
gsize offset;
gsize i;
g_variant_type_info_query (value.type_info, &alignment, NULL);
offset_size = gvs_get_offset_size (value.size);
offset = 0;
offset_ptr = value.data + value.size - offset_size * n_children;
for (i = 0; i < n_children; i++)
{
GVariantSerialised child = { 0, };
while (offset & alignment)
value.data[offset++] = '\0';
child.data = value.data + offset;
gvs_filler (&child, children[i]);
offset += child.size;
gvs_write_unaligned_le (offset_ptr, offset, offset_size);
offset_ptr += offset_size;
}
}
static gboolean
gvs_variable_sized_array_is_normal (GVariantSerialised value)
{
GVariantSerialised child = { 0, };
gsize offsets_array_size;
guchar *offsets_array;
guint offset_size;
guint alignment;
gsize last_end;
gsize length;
gsize offset;
gsize i;
if (value.size == 0)
return TRUE;
offset_size = gvs_get_offset_size (value.size);
last_end = gvs_read_unaligned_le (value.data + value.size -
offset_size, offset_size);
if (last_end > value.size)
return FALSE;
offsets_array_size = value.size - last_end;
if (offsets_array_size % offset_size)
return FALSE;
offsets_array = value.data + value.size - offsets_array_size;
length = offsets_array_size / offset_size;
if (length == 0)
return FALSE;
child.type_info = g_variant_type_info_element (value.type_info);
g_variant_type_info_query (child.type_info, &alignment, NULL);
child.depth = value.depth + 1;
offset = 0;
for (i = 0; i < length; i++)
{
gsize this_end;
this_end = gvs_read_unaligned_le (offsets_array + offset_size * i,
offset_size);
if (this_end < offset || this_end > last_end)
return FALSE;
while (offset & alignment)
{
if (!(offset < this_end && value.data[offset] == '\0'))
return FALSE;
offset++;
}
child.data = value.data + offset;
child.size = this_end - offset;
if (child.size == 0)
child.data = NULL;
if (!g_variant_serialised_is_normal (child))
return FALSE;
offset = this_end;
}
g_assert (offset == last_end);
return TRUE;
}
/* Tuples {{{2
*
* Since tuples can contain a mix of variable- and fixed-sized items,
* they are, in terms of serialisation, a hybrid of variable-sized and
* fixed-sized arrays.
*
* Offsets are only stored for variable-sized items. Also, since the
* number of items in a tuple is known from its type, we are able to
* know exactly how many offsets to expect in the serialised data (and
* therefore how much space is taken up by the offset array). This
* means that we know where the end of the serialised data for the last
* item is -- we can just subtract the size of the offset array from the
* total size of the tuple. For this reason, the last item in the tuple
* doesn't need an offset stored.
*
* Tuple offsets are stored in reverse. This design choice allows
* iterator-based deserialisers to be more efficient.
*
* Most of the "heavy lifting" here is handled by the GVariantTypeInfo
* for the tuple. See the notes in gvarianttypeinfo.h.
*/
static gsize
gvs_tuple_n_children (GVariantSerialised value)
{
return g_variant_type_info_n_members (value.type_info);
}
static GVariantSerialised
gvs_tuple_get_child (GVariantSerialised value,
gsize index_)
{
const GVariantMemberInfo *member_info;
GVariantSerialised child = { 0, };
gsize offset_size;
gsize start, end, last_end;
member_info = g_variant_type_info_member_info (value.type_info, index_);
child.type_info = g_variant_type_info_ref (member_info->type_info);
child.depth = value.depth + 1;
offset_size = gvs_get_offset_size (value.size);
/* tuples are the only (potentially) fixed-sized containers, so the
* only ones that have to deal with the possibility of having %NULL
* data with a non-zero %size if errors occurred elsewhere.
*/
if G_UNLIKELY (value.data == NULL && value.size != 0)
{
g_variant_type_info_query (child.type_info, NULL, &child.size);
/* this can only happen in fixed-sized tuples,
* so the child must also be fixed sized.
*/
g_assert (child.size != 0);
child.data = NULL;
return child;
}
if (member_info->ending_type == G_VARIANT_MEMBER_ENDING_OFFSET)
{
if (offset_size * (member_info->i + 2) > value.size)
return child;
}
else
{
if (offset_size * (member_info->i + 1) > value.size)
{
/* if the child is fixed size, return its size.
* if child is not fixed-sized, return size = 0.
*/
g_variant_type_info_query (child.type_info, NULL, &child.size);
return child;
}
}
if (member_info->i + 1)
start = gvs_read_unaligned_le (value.data + value.size -
offset_size * (member_info->i + 1),
offset_size);
else
start = 0;
start += member_info->a;
start &= member_info->b;
start |= member_info->c;
if (member_info->ending_type == G_VARIANT_MEMBER_ENDING_LAST)
end = value.size - offset_size * (member_info->i + 1);
else if (member_info->ending_type == G_VARIANT_MEMBER_ENDING_FIXED)
{
gsize fixed_size;
g_variant_type_info_query (child.type_info, NULL, &fixed_size);
end = start + fixed_size;
child.size = fixed_size;
}
else /* G_VARIANT_MEMBER_ENDING_OFFSET */
end = gvs_read_unaligned_le (value.data + value.size -
offset_size * (member_info->i + 2),
offset_size);
/* The child should not extend into the offset table. */
if (index_ != g_variant_type_info_n_members (value.type_info) - 1)
{
GVariantSerialised last_child;
last_child = gvs_tuple_get_child (value,
g_variant_type_info_n_members (value.type_info) - 1);
last_end = last_child.data + last_child.size - value.data;
g_variant_type_info_unref (last_child.type_info);
}
else
last_end = end;
if (start < end && end <= value.size && end <= last_end)
{
child.data = value.data + start;
child.size = end - start;
}
return child;
}
static gsize
gvs_tuple_needed_size (GVariantTypeInfo *type_info,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
const GVariantMemberInfo *member_info = NULL;
gsize fixed_size;
gsize offset;
gsize i;
g_variant_type_info_query (type_info, NULL, &fixed_size);
if (fixed_size)
return fixed_size;
offset = 0;
for (i = 0; i < n_children; i++)
{
guint alignment;
member_info = g_variant_type_info_member_info (type_info, i);
g_variant_type_info_query (member_info->type_info,
&alignment, &fixed_size);
offset += (-offset) & alignment;
if (fixed_size)
offset += fixed_size;
else
{
GVariantSerialised child = { 0, };
gvs_filler (&child, children[i]);
offset += child.size;
}
}
return gvs_calculate_total_size (offset, member_info->i + 1);
}
static void
gvs_tuple_serialise (GVariantSerialised value,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
gsize offset_size;
gsize offset;
gsize i;
offset_size = gvs_get_offset_size (value.size);
offset = 0;
for (i = 0; i < n_children; i++)
{
const GVariantMemberInfo *member_info;
GVariantSerialised child = { 0, };
guint alignment;
member_info = g_variant_type_info_member_info (value.type_info, i);
g_variant_type_info_query (member_info->type_info, &alignment, NULL);
while (offset & alignment)
value.data[offset++] = '\0';
child.data = value.data + offset;
gvs_filler (&child, children[i]);
offset += child.size;
if (member_info->ending_type == G_VARIANT_MEMBER_ENDING_OFFSET)
{
value.size -= offset_size;
gvs_write_unaligned_le (value.data + value.size,
offset, offset_size);
}
}
while (offset < value.size)
value.data[offset++] = '\0';
}
static gboolean
gvs_tuple_is_normal (GVariantSerialised value)
{
guint offset_size;
gsize offset_ptr;
gsize length;
gsize offset;
gsize i;
/* as per the comment in gvs_tuple_get_child() */
if G_UNLIKELY (value.data == NULL && value.size != 0)
return FALSE;
offset_size = gvs_get_offset_size (value.size);
length = g_variant_type_info_n_members (value.type_info);
offset_ptr = value.size;
offset = 0;
for (i = 0; i < length; i++)
{
const GVariantMemberInfo *member_info;
GVariantSerialised child;
gsize fixed_size;
guint alignment;
gsize end;
member_info = g_variant_type_info_member_info (value.type_info, i);
child.type_info = member_info->type_info;
child.depth = value.depth + 1;
g_variant_type_info_query (child.type_info, &alignment, &fixed_size);
while (offset & alignment)
{
if (offset > value.size || value.data[offset] != '\0')
return FALSE;
offset++;
}
child.data = value.data + offset;
switch (member_info->ending_type)
{
case G_VARIANT_MEMBER_ENDING_FIXED:
end = offset + fixed_size;
break;
case G_VARIANT_MEMBER_ENDING_LAST:
end = offset_ptr;
break;
case G_VARIANT_MEMBER_ENDING_OFFSET:
if (offset_ptr < offset_size)
return FALSE;
offset_ptr -= offset_size;
if (offset_ptr < offset)
return FALSE;
end = gvs_read_unaligned_le (value.data + offset_ptr, offset_size);
break;
default:
g_assert_not_reached ();
}
if (end < offset || end > offset_ptr)
return FALSE;
child.size = end - offset;
if (child.size == 0)
child.data = NULL;
if (!g_variant_serialised_is_normal (child))
return FALSE;
offset = end;
}
{
gsize fixed_size;
guint alignment;
g_variant_type_info_query (value.type_info, &alignment, &fixed_size);
if (fixed_size)
{
g_assert (fixed_size == value.size);
g_assert (offset_ptr == value.size);
if (i == 0)
{
if (value.data[offset++] != '\0')
return FALSE;
}
else
{
while (offset & alignment)
if (value.data[offset++] != '\0')
return FALSE;
}
g_assert (offset == value.size);
}
}
return offset_ptr == offset;
}
/* Variants {{{2
*
* Variants are stored by storing the serialised data of the child,
* followed by a '\0' character, followed by the type string of the
* child.
*
* In the case that a value is presented that contains no '\0'
* character, or doesn't have a single well-formed definite type string
* following that character, the variant must be taken as containing the
* unit tuple: ().
*/
static inline gsize
gvs_variant_n_children (GVariantSerialised value)
{
return 1;
}
static inline GVariantSerialised
gvs_variant_get_child (GVariantSerialised value,
gsize index_)
{
GVariantSerialised child = { 0, };
/* NOTE: not O(1) and impossible for it to be... */
if (value.size)
{
/* find '\0' character */
for (child.size = value.size - 1; child.size; child.size--)
if (value.data[child.size] == '\0')
break;
/* ensure we didn't just hit the start of the string */
if (value.data[child.size] == '\0')
{
const gchar *type_string = (gchar *) &value.data[child.size + 1];
const gchar *limit = (gchar *) &value.data[value.size];
const gchar *end;
if (g_variant_type_string_scan (type_string, limit, &end) &&
end == limit)
{
const GVariantType *type = (GVariantType *) type_string;
if (g_variant_type_is_definite (type))
{
gsize fixed_size;
gsize child_type_depth;
child.type_info = g_variant_type_info_get (type);
child.depth = value.depth + 1;
if (child.size != 0)
/* only set to non-%NULL if size > 0 */
child.data = value.data;
g_variant_type_info_query (child.type_info,
NULL, &fixed_size);
child_type_depth = g_variant_type_info_query_depth (child.type_info);
if ((!fixed_size || fixed_size == child.size) &&
value.depth < G_VARIANT_MAX_RECURSION_DEPTH - child_type_depth)
return child;
g_variant_type_info_unref (child.type_info);
}
}
}
}
child.type_info = g_variant_type_info_get (G_VARIANT_TYPE_UNIT);
child.data = NULL;
child.size = 1;
child.depth = value.depth + 1;
return child;
}
static inline gsize
gvs_variant_needed_size (GVariantTypeInfo *type_info,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
GVariantSerialised child = { 0, };
const gchar *type_string;
gvs_filler (&child, children[0]);
type_string = g_variant_type_info_get_type_string (child.type_info);
return child.size + 1 + strlen (type_string);
}
static inline void
gvs_variant_serialise (GVariantSerialised value,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
GVariantSerialised child = { 0, };
const gchar *type_string;
child.data = value.data;
gvs_filler (&child, children[0]);
type_string = g_variant_type_info_get_type_string (child.type_info);
value.data[child.size] = '\0';
memcpy (value.data + child.size + 1, type_string, strlen (type_string));
}
static inline gboolean
gvs_variant_is_normal (GVariantSerialised value)
{
GVariantSerialised child;
gboolean normal;
gsize child_type_depth;
child = gvs_variant_get_child (value, 0);
child_type_depth = g_variant_type_info_query_depth (child.type_info);
normal = (value.depth < G_VARIANT_MAX_RECURSION_DEPTH - child_type_depth) &&
(child.data != NULL || child.size == 0) &&
g_variant_serialised_is_normal (child);
g_variant_type_info_unref (child.type_info);
return normal;
}
/* PART 2: Serialiser API {{{1
*
* This is the implementation of the API of the serialiser as advertised
* in gvariant-serialiser.h.
*/
/* Dispatch Utilities {{{2
*
* These macros allow a given function (for example,
* g_variant_serialiser_serialise) to be dispatched to the appropriate
* type-specific function above (fixed/variable-sized maybe,
* fixed/variable-sized array, tuple or variant).
*/
#define DISPATCH_FIXED(type_info, before, after) \
{ \
gsize fixed_size; \
\
g_variant_type_info_query_element (type_info, NULL, \
&fixed_size); \
\
if (fixed_size) \
{ \
before ## fixed_sized ## after \
} \
else \
{ \
before ## variable_sized ## after \
} \
}
#define DISPATCH_CASES(type_info, before, after) \
switch (g_variant_type_info_get_type_char (type_info)) \
{ \
case G_VARIANT_TYPE_INFO_CHAR_MAYBE: \
DISPATCH_FIXED (type_info, before, _maybe ## after) \
\
case G_VARIANT_TYPE_INFO_CHAR_ARRAY: \
DISPATCH_FIXED (type_info, before, _array ## after) \
\
case G_VARIANT_TYPE_INFO_CHAR_DICT_ENTRY: \
case G_VARIANT_TYPE_INFO_CHAR_TUPLE: \
{ \
before ## tuple ## after \
} \
\
case G_VARIANT_TYPE_INFO_CHAR_VARIANT: \
{ \
before ## variant ## after \
} \
}
/* Serialiser entry points {{{2
*
* These are the functions that are called in order for the serialiser
* to do its thing.
*/
/* < private >
* g_variant_serialised_n_children:
* @serialised: a #GVariantSerialised
*
* For serialised data that represents a container value (maybes,
* tuples, arrays, variants), determine how many child items are inside
* that container.
*
* Returns: the number of children
*/
gsize
g_variant_serialised_n_children (GVariantSerialised serialised)
{
g_assert (g_variant_serialised_check (serialised));
DISPATCH_CASES (serialised.type_info,
return gvs_/**/,/**/_n_children (serialised);
)
g_assert_not_reached ();
}
/* < private >
* g_variant_serialised_get_child:
* @serialised: a #GVariantSerialised
* @index_: the index of the child to fetch
*
* Extracts a child from a serialised data representing a container
* value.
*
* It is an error to call this function with an index out of bounds.
*
* If the result .data == %NULL and .size > 0 then there has been an
* error extracting the requested fixed-sized value. This number of
* zero bytes needs to be allocated instead.
*
* In the case that .data == %NULL and .size == 0 then a zero-sized
* item of a variable-sized type is being returned.
*
* .data is never non-%NULL if size is 0.
*
* Returns: a #GVariantSerialised for the child
*/
GVariantSerialised
g_variant_serialised_get_child (GVariantSerialised serialised,
gsize index_)
{
GVariantSerialised child;
g_assert (g_variant_serialised_check (serialised));
if G_LIKELY (index_ < g_variant_serialised_n_children (serialised))
{
DISPATCH_CASES (serialised.type_info,
child = gvs_/**/,/**/_get_child (serialised, index_);
g_assert (child.size || child.data == NULL);
g_assert (g_variant_serialised_check (child));
return child;
)
g_assert_not_reached ();
}
g_error ("Attempt to access item %"G_GSIZE_FORMAT
" in a container with only %"G_GSIZE_FORMAT" items",
index_, g_variant_serialised_n_children (serialised));
}
/* < private >
* g_variant_serialiser_serialise:
* @serialised: a #GVariantSerialised, properly set up
* @gvs_filler: the filler function
* @children: an array of child items
* @n_children: the size of @children
*
* Writes data in serialised form.
*
* The type_info field of @serialised must be filled in to type info for
* the type that we are serialising.
*
* The size field of @serialised must be filled in with the value
* returned by a previous call to g_variant_serialiser_needed_size().
*
* The data field of @serialised must be a pointer to a properly-aligned
* memory region large enough to serialise into (ie: at least as big as
* the size field).
*
* This function is only resonsible for serialising the top-level
* container. @gvs_filler is called on each child of the container in
* order for all of the data of that child to be filled in.
*/
void
g_variant_serialiser_serialise (GVariantSerialised serialised,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
g_assert (g_variant_serialised_check (serialised));
DISPATCH_CASES (serialised.type_info,
gvs_/**/,/**/_serialise (serialised, gvs_filler,
children, n_children);
return;
)
g_assert_not_reached ();
}
/* < private >
* g_variant_serialiser_needed_size:
* @type_info: the type to serialise for
* @gvs_filler: the filler function
* @children: an array of child items
* @n_children: the size of @children
*
* Determines how much memory would be needed to serialise this value.
*
* This function is only resonsible for performing calculations for the
* top-level container. @gvs_filler is called on each child of the
* container in order to determine its size.
*/
gsize
g_variant_serialiser_needed_size (GVariantTypeInfo *type_info,
GVariantSerialisedFiller gvs_filler,
const gpointer *children,
gsize n_children)
{
DISPATCH_CASES (type_info,
return gvs_/**/,/**/_needed_size (type_info, gvs_filler,
children, n_children);
)
g_assert_not_reached ();
}
/* Byteswapping {{{2 */
/* < private >
* g_variant_serialised_byteswap:
* @value: a #GVariantSerialised
*
* Byte-swap serialised data. The result of this function is only
* well-defined if the data is in normal form.
*/
void
g_variant_serialised_byteswap (GVariantSerialised serialised)
{
gsize fixed_size;
guint alignment;
g_assert (g_variant_serialised_check (serialised));
if (!serialised.data)
return;
/* the types we potentially need to byteswap are
* exactly those with alignment requirements.
*/
g_variant_type_info_query (serialised.type_info, &alignment, &fixed_size);
if (!alignment)
return;
/* if fixed size and alignment are equal then we are down
* to the base integer type and we should swap it. the
* only exception to this is if we have a tuple with a
* single item, and then swapping it will be OK anyway.
*/
if (alignment + 1 == fixed_size)
{
switch (fixed_size)
{
case 2:
{
guint16 *ptr = (guint16 *) serialised.data;
g_assert_cmpint (serialised.size, ==, 2);
*ptr = GUINT16_SWAP_LE_BE (*ptr);
}
return;
case 4:
{
guint32 *ptr = (guint32 *) serialised.data;
g_assert_cmpint (serialised.size, ==, 4);
*ptr = GUINT32_SWAP_LE_BE (*ptr);
}
return;
case 8:
{
guint64 *ptr = (guint64 *) serialised.data;
g_assert_cmpint (serialised.size, ==, 8);
*ptr = GUINT64_SWAP_LE_BE (*ptr);
}
return;
default:
g_assert_not_reached ();
}
}
/* else, we have a container that potentially contains
* some children that need to be byteswapped.
*/
else
{
gsize children, i;
children = g_variant_serialised_n_children (serialised);
for (i = 0; i < children; i++)
{
GVariantSerialised child;
child = g_variant_serialised_get_child (serialised, i);
g_variant_serialised_byteswap (child);
g_variant_type_info_unref (child.type_info);
}
}
}
/* Normal form checking {{{2 */
/* < private >
* g_variant_serialised_is_normal:
* @serialised: a #GVariantSerialised
*
* Determines, recursively if @serialised is in normal form. There is
* precisely one normal form of serialised data for each possible value.
*
* It is possible that multiple byte sequences form the serialised data
* for a given value if, for example, the padding bytes are filled in
* with something other than zeros, but only one form is the normal
* form.
*/
gboolean
g_variant_serialised_is_normal (GVariantSerialised serialised)
{
DISPATCH_CASES (serialised.type_info,
return gvs_/**/,/**/_is_normal (serialised);
)
if (serialised.data == NULL)
return FALSE;
if (serialised.depth >= G_VARIANT_MAX_RECURSION_DEPTH)
return FALSE;
/* some hard-coded terminal cases */
switch (g_variant_type_info_get_type_char (serialised.type_info))
{
case 'b': /* boolean */
return serialised.data[0] < 2;
case 's': /* string */
return g_variant_serialiser_is_string (serialised.data,
serialised.size);
case 'o':
return g_variant_serialiser_is_object_path (serialised.data,
serialised.size);
case 'g':
return g_variant_serialiser_is_signature (serialised.data,
serialised.size);
default:
/* all of the other types are fixed-sized numerical types for
* which all possible values are valid (including various NaN
* representations for floating point values).
*/
return TRUE;
}
}
/* Validity-checking functions {{{2
*
* Checks if strings, object paths and signature strings are valid.
*/
/* < private >
* g_variant_serialiser_is_string:
* @data: a possible string
* @size: the size of @data
*
* Ensures that @data is a valid string with a nul terminator at the end
* and no nul bytes embedded.
*/
gboolean
g_variant_serialiser_is_string (gconstpointer data,
gsize size)
{
const gchar *expected_end;
const gchar *end;
/* Strings must end with a nul terminator. */
if (size == 0)
return FALSE;
expected_end = ((gchar *) data) + size - 1;
if (*expected_end != '\0')
return FALSE;
g_utf8_validate_len (data, size, &end);
return end == expected_end;
}
/* < private >
* g_variant_serialiser_is_object_path:
* @data: a possible D-Bus object path
* @size: the size of @data
*
* Performs the checks for being a valid string.
*
* Also, ensures that @data is a valid DBus object path, as per the D-Bus
* specification.
*/
gboolean
g_variant_serialiser_is_object_path (gconstpointer data,
gsize size)
{
const gchar *string = data;
gsize i;
if (!g_variant_serialiser_is_string (data, size))
return FALSE;
/* The path must begin with an ASCII '/' (integer 47) character */
if (string[0] != '/')
return FALSE;
for (i = 1; string[i]; i++)
/* Each element must only contain the ASCII characters
* "[A-Z][a-z][0-9]_"
*/
if (g_ascii_isalnum (string[i]) || string[i] == '_')
;
/* must consist of elements separated by slash characters. */
else if (string[i] == '/')
{
/* No element may be the empty string. */
/* Multiple '/' characters cannot occur in sequence. */
if (string[i - 1] == '/')
return FALSE;
}
else
return FALSE;
/* A trailing '/' character is not allowed unless the path is the
* root path (a single '/' character).
*/
if (i > 1 && string[i - 1] == '/')
return FALSE;
return TRUE;
}
/* < private >
* g_variant_serialiser_is_signature:
* @data: a possible D-Bus signature
* @size: the size of @data
*
* Performs the checks for being a valid string.
*
* Also, ensures that @data is a valid D-Bus type signature, as per the
* D-Bus specification. Note that this means the empty string is valid, as the
* D-Bus specification defines a signature as “zero or more single complete
* types”.
*/
gboolean
g_variant_serialiser_is_signature (gconstpointer data,
gsize size)
{
const gchar *string = data;
gsize first_invalid;
if (!g_variant_serialiser_is_string (data, size))
return FALSE;
/* make sure no non-definite characters appear */
first_invalid = strspn (string, "ybnqiuxthdvasog(){}");
if (string[first_invalid])
return FALSE;
/* make sure each type string is well-formed */
while (*string)
if (!g_variant_type_string_scan (string, NULL, &string))
return FALSE;
return TRUE;
}
/* Epilogue {{{1 */
/* vim:set foldmethod=marker: */
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