Mirror of :pserver:cvs@cvs.fefe.de:/cvs libowfat https://www.fefe.de/libowfat/
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 

116 lines
3.1 KiB

#include <string.h>
#include "fmt.h"
#include "textcode.h"
#include "str.h"
#include "scan.h"
#include "case.h"
#include "haveinline.h"
/* src is UTF-8 encoded */
size_t fmt_jsonescape(char* dest,const char* src,size_t len) {
register const unsigned char* s=(const unsigned char*) src;
size_t written=0,i;
char c;
for (i=0; i<len; ++i) {
switch (s[i]) {
case '<':
/* If you are outputting the json inside a <script> tag in HTML,
* and the string is attacker controlled and contains "</script>",
* that would allow cross site scripting. So we escape that here. */
if (len-i>=9 && case_equalb(s+i+1,8,"/script>"))
goto unicodeescape;
goto noneed;
case '\\':
case '"':
c=s[i];
escape:
if (dest) {
dest[written]='\\';
dest[written+1]=c;
}
written+=2;
break;
case '\n': c='n'; goto escape;
case '\r': c='r'; goto escape;
case '\b': c='b'; goto escape;
case '\t': c='t'; goto escape;
case '\f': c='f'; goto escape;
default:
if (s[i]<' ') {
unicodeescape:
if (dest) {
dest[written]='\\';
dest[written+1]='u';
dest[written+2]='0';
dest[written+3]='0';
dest[written+4]=fmt_tohex(s[i]>>4);
dest[written+5]=fmt_tohex(s[i]&0xf);
}
written+=6;
} else if (s[i]>0x7f) {
/* UTF-8! Convert to surrogate pair if needed. */
uint32_t u;
size_t j=scan_utf8_sem((const char*)s+i,len-i,&u);
if (j==0) { /* Invalid UTF-8! Try to limp on! */
written+=fmt_utf8(dest?dest+written:0,s[i]);
break;
}
/* It turns out we are not required to escape these.
* So we won't. */
#if 0
if (u>0xffff) {
if (dest) {
dest[written ]='\\';
dest[written+1]='u';
fmt_xlong(dest+written+2,0xd800 + ((u>>10) & 0x3bf));
dest[written+6]='\\';
dest[written+7]='u';
fmt_xlong(dest+written+8,0xdc00 + (u & 0x3ff));
}
written+=12;
} else
#endif
{
if (dest) memcpy(dest+written,s+i,j);
written+=j;
}
i+=j-1; /* -1 because the for loop will also add 1 */
break;
} else {
noneed:
if (dest) dest[written]=s[i];
++written;
}
break;
}
/* in case someone gives us malicious input */
if (written>((size_t)-1)/2) return (size_t)-1;
}
return written;
}
#ifdef UNITTEST
#include <assert.h>
#include <string.h>
#undef UNITTEST
#include "fmt/fmt_tohex.c"
#include "case/case_diffb.c"
#include "fmt/fmt_utf8.c"
#include "scan/scan_utf8_sem.c"
#include "scan/scan_utf8.c"
int main() {
char buf[100];
/* test utf-8 pass-through and correct encoding of \t */
assert(fmt_jsonescape(buf,"\tfnörd",7)==8 && !memcmp(buf,"\\tfnörd",8));
/* test escaping of unprintable characters */
assert(fmt_jsonescape(buf,"\001x",2)==7 && !memcmp(buf,"\\u0001x",7));
/* test conversion of large UTF-8 chars to UTF-16 surrogate pairs (poop emoji) */
/* EDIT: this escaping is not actually needed, so we aren't doing it
* anymore. This test will fail now:
assert(fmt_jsonescape(buf,"\xf0\x9f\x92\xa9x",5)==13 && !memcmp(buf,"\\ud83d\\udca9x",13)); */
assert(fmt_jsonescape(buf,"a\x81x",3)==4 && !memcmp(buf,"a\xc2\x81x",4));
assert(fmt_jsonescape(buf,"</Script>",9)==14 && !memcmp(buf,"\\u003c/Script>",14));
}
#endif