Mares Smart Apnea

[Jef Driesen]

On 2015-09-09 14:04, Giorgio Marzano wrote:
> I have compiled this sniplet:
> 
> main (int argc, char *argv[])
> {
> int i;
> const mares_iconhd_model_t models[] = {
> {"Matrix",      MATRIX},
> // {"Smart Apnea", SMARTAPNEA},
> {"Smart",       SMART},
> {"Icon HD",     ICONHD},
> {"Icon AIR",    ICONHDNET},
> {"Puck Pro",    PUCKPRO},
> {"Nemo Wide 2", NEMOWIDE2},
> {"Puck 2",      PUCK2},
> };
> 
> // Check the product name in the version packet against the list
> // with valid names, and return the corresponding model number.
> unsigned int model = 0;
> for ( i = 0; i < 7; ++i) {
> printf ("i: %d, sizeof: %d, strlen:  
> %d\n",i,sizeof(models[i].name),strlen
> (models[i].name));
> 
> }
> }
> 
> and the corresponding ouput is:
> 
> 
> giorgio at giorgio-laptop:~$ ./prova i: 0, sizeof: 17, strlen: 6 i: 1, 
> sizeof:
> 17, strlen: 5 i: 2, sizeof: 17, strlen: 7 i: 3, sizeof: 17, strlen: 8 
> i: 4,
> sizeof: 17, strlen: 8 i: 5, sizeof: 17, strlen: 11 i: 6, sizeof: 17,
> strlen: 6
> 
> 
> So it seems to me that either we use strlen or we use strcmp

No, the memcmp is correct. In the mares header, the name is a 16 byte 
array. If the name is shorter than 16 bytes, the remaining bytes are 
padded with zero's. But if there would be a name that's exactly 16 bytes 
long, then there won't be a terminating zero byte. In that case, strlen 
and strcmp will result in a buffer overflow! That's why we use memcmp. 
The other reason is that I want to do an exact match. The "Smart" entry 
should not match "Smart Apnea". Future models needs to be added 
explicitly, and not detected by accident.

Jef