httpserver/url.c at master · AdrS/httpserver · GitHub

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#include"url.h"
#include<assert.h>
#include<ctype.h>

//takes character 0-9 | a-f | A-F and returns corresponding hex value
staticintdecode_hex_char(charc) {
if('0' <= c&&c <= '9') returnc-'0';
if('A' <= c&&c <= 'F') returnc-'A'+10;
if('A' <= c&&c <= 'f') returnc-'a'+10;
return-1;
}

//percent decodes string in place, returns -1 on invalid encoding
intpercent_decode(char*str, int*len) {
assert(str);
assert(len);
char*spos=str, *dpos=str;
inthas_null=0;
while(*spos) {
//found beginning of percent encoded character
if(*spos=='%') {
//check that encoding is valid
if(!(isxdigit(spos[1]) &&isxdigit(spos[2]))) {
return-1;
 }

*dpos= (char)((decode_hex_char(spos[1]) << 4) +decode_hex_char(spos[2]));

//check for percent encoded null bytes
if(!*dpos) {
has_null=1;
 }
++dpos;
spos+=3;
 } else {
*dpos++=*spos++;
 }
	}
*dpos='\0';
*len= (int)(dpos-str);
returnhas_null;
}

intsafe_path(constchar*path) {
assert(path);
constchar*pos=path;
if(*path=='/') {
return0;
	}

while(*pos) {
if(pos[0] =='.'&&pos[1] =='.') {
//check for patterns:
//"<start of string>..\0" => path = ".."
//"<start of string>../" => path starts with "../"
//"/..\0"	=> path ends with "/.."
//"/../"	=> path contains
if((pos==path||*(pos-1) =='/') &&
 (pos[2] =='/'||pos[2] =='\0')) {
return0;
 }
 } elseif(pos[0] =='/'&&pos[1] =='/') {
return0;
 }
++pos;
	}
return1;
}