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egismoc: Use strictly sized types to hold check bytes contents

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So we are sure about the size we're sending at compile time too.
This commit is contained in:
Marco Trevisan (Treviño)
2024-02-19 21:12:14 +01:00
parent ed1815c3d9
commit 6768bd0ff4
1 changed files with 12 additions and 13 deletions
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23
libfprint/drivers/egismoc/egismoc.c
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@@ -273,12 +273,15 @@ egismoc_cmd_ssm_done (FpiSsm *ssm,
data->callback (device, NULL, 0, g_steal_pointer (&local_error));
}
typedef union egismoc_check_bytes
typedef union
{
unsigned short check_short;
guint16 check_value;
guchar check_bytes[EGISMOC_CHECK_BYTES_LENGTH];
} EgisMocCheckBytes;
G_STATIC_ASSERT (G_SIZEOF_MEMBER (EgisMocCheckBytes, check_value) ==
sizeof (guint8) * EGISMOC_CHECK_BYTES_LENGTH);
/*
* Derive the 2 "check bytes" for write payloads
* 32-bit big-endian sum of all 16-bit words (including check bytes) MOD 0xFFFF
@@ -290,26 +293,22 @@ egismoc_get_check_bytes (const guchar *value,
{
fp_dbg ("Get check bytes");
EgisMocCheckBytes check_bytes;
unsigned short value_bigendian_shorts[(int) ((value_length + 1) / 2)];
guint16 big_endian_values[(int) ((value_length + 1) / 2)];
size_t sum_values = 0;
int s = 0;
for (int i = 0; i < value_length; i = i + 2, s++)
{
if (i + 1 < value_length)
value_bigendian_shorts[s] = (((short) value[i + 1]) << 8) | (0x00ff & value[i]);
big_endian_values[s] = (((guint16) value[i + 1]) << 8) | (0x00ff & value[i]);
else
value_bigendian_shorts[s] = (((short) 0x00) << 8) | (0x00ff & value[i]);
big_endian_values[s] = (((guint16) 0x00) << 8) | (0x00ff & value[i]);
}
unsigned long sum_shorts = 0;
for (int i = 0; i < s; i++)
sum_shorts += value_bigendian_shorts[i];
sum_values += big_endian_values[i];
/*
derive the "first possible occurrence" of check bytes as:
`0xFFFF - (sum_of_32bit_words % 0xFFFF)
*/
check_bytes.check_short = 0xffff - (sum_shorts % 0xffff);
check_bytes.check_value = 0xffff - (sum_values % 0xffff);
return check_bytes;
}