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Add the WPACKET_reserve_bytes() function

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WPACKET_allocate_bytes() requires you to know the size of the data you
are allocating for, before you create it. Sometimes this isn't the case,
for example we know the maximum size that a signature will be before we
create it, but not the actual size. WPACKET_reserve_bytes() enables us to
reserve bytes in the WPACKET, but not count them as written yet. We then
subsequently need to acall WPACKET_allocate_bytes to actually count them as
written.

Reviewed-by: Rich Salz <rsalz@openssl.org>
This commit is contained in:
Matt Caswell 2016-09-29 11:43:37 +01:00
parent ac8cc3efb2
commit 1ff8434040
2 changed files with 55 additions and 8 deletions
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33
ssl/packet.c
View file

@ -13,6 +13,27 @@
#define DEFAULT_BUF_SIZE 256
int WPACKET_allocate_bytes(WPACKET *pkt, size_t len, unsigned char **allocbytes)
{
if (!WPACKET_reserve_bytes(pkt, len, allocbytes))
return 0;
pkt->written += len;
pkt->curr += len;
return 1;
}
int WPACKET_sub_allocate_bytes__(WPACKET *pkt, size_t len,
unsigned char **allocbytes, size_t lenbytes)
{
if (!WPACKET_start_sub_packet_len__(pkt, lenbytes)
|| !WPACKET_allocate_bytes(pkt, len, allocbytes)
|| !WPACKET_close(pkt))
return 0;
return 1;
}
int WPACKET_reserve_bytes(WPACKET *pkt, size_t len, unsigned char **allocbytes)
{
/* Internal API, so should not fail */
assert(pkt->subs != NULL && len != 0);
@ -39,20 +60,18 @@ int WPACKET_allocate_bytes(WPACKET *pkt, size_t len, unsigned char **allocbytes)
return 0;
}
*allocbytes = (unsigned char *)pkt->buf->data + pkt->curr;
pkt->written += len;
pkt->curr += len;
return 1;
}
int WPACKET_sub_allocate_bytes__(WPACKET *pkt, size_t len,
unsigned char **allocbytes, size_t lenbytes)
int WPACKET_sub_reserve_bytes__(WPACKET *pkt, size_t len,
unsigned char **allocbytes, size_t lenbytes)
{
if (!WPACKET_start_sub_packet_len__(pkt, lenbytes)
|| !WPACKET_allocate_bytes(pkt, len, allocbytes)
|| !WPACKET_close(pkt))
if (!WPACKET_reserve_bytes(pkt, lenbytes + len, allocbytes))
return 0;
*allocbytes += lenbytes;
return 1;
}

30
ssl/packet_locl.h
View file

@ -675,7 +675,7 @@ int WPACKET_start_sub_packet(WPACKET *pkt);
* WPACKET_* calls. If not then the underlying buffer may be realloc'd and
* change its location.
*/
int WPACKET_allocate_bytes(WPACKET *pkt, size_t bytes,
int WPACKET_allocate_bytes(WPACKET *pkt, size_t len,
unsigned char **allocbytes);
/*
@ -700,6 +700,34 @@ int WPACKET_sub_allocate_bytes__(WPACKET *pkt, size_t len,
#define WPACKET_sub_allocate_bytes_u32(pkt, len, bytes) \
WPACKET_sub_allocate_bytes__((pkt), (len), (bytes), 4)
/*
* The same as WPACKET_allocate_bytes() except the reserved bytes are not
* actually counted as written. Typically this will be for when we don't know
* how big arbitrary data is going to be up front, but we do know what the
* maximum size will be. If this function is used, then it should be immediately
* followed by a WPACKET_allocate_bytes() call before any other WPACKET
* functions are called (unless the write to the allocated bytes is abandoned).
*/
int WPACKET_reserve_bytes(WPACKET *pkt, size_t len, unsigned char **allocbytes);
/*
* The "reserve_bytes" equivalent of WPACKET_sub_allocate_bytes__()
*/
int WPACKET_sub_reserve_bytes__(WPACKET *pkt, size_t len,
unsigned char **allocbytes, size_t lenbytes);
/*
* Convenience macros for WPACKET_sub_reserve_bytes with different lengths
*/
#define WPACKET_sub_reserve_bytes_u8(pkt, len, bytes) \
WPACKET_reserve_bytes__((pkt), (len), (bytes), 1)
#define WPACKET_sub_reserve_bytes_u16(pkt, len, bytes) \
WPACKET_sub_reserve_bytes__((pkt), (len), (bytes), 2)
#define WPACKET_sub_reserve_bytes_u24(pkt, len, bytes) \
WPACKET_sub_reserve_bytes__((pkt), (len), (bytes), 3)
#define WPACKET_sub_reserve_bytes_u32(pkt, len, bytes) \
WPACKET_sub_reserve_bytes__((pkt), (len), (bytes), 4)
/*
* Write the value stored in |val| into the WPACKET. The value will consume
* |bytes| amount of storage. An error will occur if |val| cannot be