[apparmor] [PATCH 1/2] parser: Adjust writeu16() to output escaped byte sequences

[Seth Arnold]

On Wed, Aug 27, 2014 at 05:01:45PM -0500, Tyler Hicks wrote:
> The writeu16() function was outputting unescaped byte sequences to the
> rule buffer. That resulted the generation of in an incomplete rule if
> one of those unescaped byte sequences contained 0x00.
> 
> This patch uses u8 pointers, instead of char pointers, when writing out
> the big endian u16 value. More importantly, it casts the u8 values to
> unsigned ints, which is what's needed to get the properly escaped byte
> sequences.
> 
> Signed-off-by: Tyler Hicks <tyhicks at canonical.com>

Acked-by: Seth Arnold <seth.arnold at canonical.com>

Thanks

> ---
> 
> Before:
> 
>   $ echo "/t { unix (connect,read,write) type=stream, }" | apparmor_parser -qQD dfa-states
>   {1} <== (allow/deny/audit/quiet)
>   {2} (0x 4/0/0/0)
>   {3} (0x 4/0/0/0)
>   {5} (0x 46/0/0/0)
>   
>   {1} -> {2}: 0x2
>   {1} -> {3}: 0x4
>   {1} -> {2}: 0x7
>   {1} -> {2}: 0x9
>   {1} -> {2}: 0xa
>   {1} -> {2}: 0x20 \ 
>   {1} -> {4}: 0x34 4
>   {3}  (0x 4/0/0/0) -> {5}: 0x0
>   {4} -> {6}: 0x0
>   {6} -> {2}: 0x31 1
>   
> 
> After (the next patch fixes the pointer values that are being written out):
> 
>   $ echo "/t { unix (connect,read,write) type=stream, }" | apparmor_parser -qQD dfa-states
>   {1} <== (allow/deny/audit/quiet)
>   {2} (0x 4/0/0/0)
>   {3} (0x 4/0/0/0)
>   {43} (0x 46/0/0/0)
>   {44} (0x 46/0/0/0)
>   
>   {1} -> {2}: 0x2
>   {1} -> {3}: 0x4
>   {1} -> {2}: 0x7
>   {1} -> {2}: 0x9
>   {1} -> {2}: 0xa
>   {1} -> {2}: 0x20 \ 
>   {1} -> {4}: 0x34 4
>   {3}  (0x 4/0/0/0) -> {5}: 0x0
>   {4} -> {6}: 0x0
>   {5} -> {7}: 0x1
>   {6} -> {2}: 0x31 1
>   {7} -> {8}: 0x30 0
>   {8} -> {9}: 0x78 x
>   {9} -> {10}: 0x37 7
>   {10} -> {11}: 0x66 f
>   {11} -> {12}: 0x66 f
>   {12} -> {13}: 0x66 f
>   {13} -> {14}: 0x31 1
>   {14} -> {15}: 0x30 0
>   {15} -> {16}: 0x34 4
>   {16} -> {17}: 0x66 f
>   {17} -> {18}: 0x33 3
>   {18} -> {19}: 0x35 5
>   {19} -> {20}: 0x31 1
>   {20} -> {21}: 0x38 8
>   {21} -> {22}: 0x0
>   {22} -> {23}: 0x1
>   {23} -> {24}: 0x30 0
>   {24} -> {25}: 0x78 x
>   {25} -> {26}: 0x37 7
>   {26} -> {27}: 0x66 f
>   {27} -> {28}: 0x66 f
>   {28} -> {29}: 0x66 f
>   {29} -> {30}: 0x31 1
>   {30} -> {31}: 0x30 0
>   {31} -> {32}: 0x34 4
>   {32} -> {33}: 0x66 f
>   {33} -> {34}: 0x33 3
>   {34} -> {35}: 0x35 5
>   {35} -> {36}: 0x31 1
>   {36} -> {37}: 0x38 8
>   {37} -> {38}: []
>   {38} -> {39}: []
>   {39} -> {40}: 0x0
>   {39} -> {39}: []
>   {40} -> {40}: 0x0
>   {40} -> {41}: 0x1
>   {40} -> {39}: []
>   {41} -> {42}: 0x0
>   {41} -> {39}: []
>   {42} -> {40}: 0x0
>   {42} -> {44}: 0x1
>   {42} -> {43}: []
>   {43}  (0x 46/0/0/0) -> {40}: 0x0
>   {43}  (0x 46/0/0/0) -> {43}: []
>   {44}  (0x 46/0/0/0) -> {42}: 0x0
>   {44}  (0x 46/0/0/0) -> {43}: []
> 
>  parser/af_unix.cc | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/parser/af_unix.cc b/parser/af_unix.cc
> index 34b93a4..7f6c0d0 100644
> --- a/parser/af_unix.cc
> +++ b/parser/af_unix.cc
> @@ -192,9 +192,11 @@ static void warn_once(const char *name)
>  std::ostringstream &writeu16(std::ostringstream &o, int v)
>  {
>  	u16 tmp = htobe16((u16) v);
> -	char *c = (char *) &tmp;
> -	o << "\\x" << std::setfill('0') << std::setw(2) << std::hex << *c++;
> -	o << "\\x" << std::setfill('0') << std::setw(2) << std::hex << *c;
> +	u8 *byte1 = (u8 *)&tmp;
> +	u8 *byte2 = byte1 + 1;
> +
> +	o << "\\x" << std::setfill('0') << std::setw(2) << std::hex << static_cast<unsigned int>(*byte1);
> +	o << "\\x" << std::setfill('0') << std::setw(2) << std::hex << static_cast<unsigned int>(*byte2);
>  	return o;
>  }
>  
> -- 
> 2.1.0
> 
> 
> -- 
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