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/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2020, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file qstring.c
* \brief Implement QuotedString parsing.
*
* Note that this is only used for controller authentication; do not
* create new users for this. Instead, prefer the cstring.c functions.
**/
#include "orconfig.h"
#include "lib/encoding/qstring.h"
#include "lib/malloc/malloc.h"
#include "lib/log/util_bug.h"
/** If the first <b>in_len_max</b> characters in <b>start</b> contain a
* QuotedString, return the length of that
* string (as encoded, including quotes). Otherwise return -1. */
static inline int
get_qstring_length(const char *start, size_t in_len_max,
int *chars_out)
{
const char *cp, *end;
int chars = 0;
if (*start != '\"')
return -1;
cp = start+1;
end = start+in_len_max;
/* Calculate length. */
while (1) {
if (cp >= end) {
return -1; /* Too long. */
} else if (*cp == '\\') {
if (++cp == end)
return -1; /* Can't escape EOS. */
++cp;
++chars;
} else if (*cp == '\"') {
break;
} else {
++cp;
++chars;
}
}
if (chars_out)
*chars_out = chars;
return (int)(cp - start+1);
}
/** Given a pointer to a string starting at <b>start</b> containing
* <b>in_len_max</b> characters, decode a string beginning with one double
* quote, containing any number of non-quote characters or characters escaped
* with a backslash, and ending with a final double quote. Place the resulting
* string (unquoted, unescaped) into a newly allocated string in *<b>out</b>;
* store its length in <b>out_len</b>. On success, return a pointer to the
* character immediately following the escaped string. On failure, return
* NULL. */
const char *
decode_qstring(const char *start, size_t in_len_max,
char **out, size_t *out_len)
{
const char *cp, *end;
char *outp;
int len, n_chars = 0;
len = get_qstring_length(start, in_len_max, &n_chars);
if (len<0)
return NULL;
end = start+len-1; /* Index of last quote. */
tor_assert(*end == '\"');
outp = *out = tor_malloc(len+1);
*out_len = n_chars;
cp = start+1;
while (cp < end) {
if (*cp == '\\')
++cp;
*outp++ = *cp++;
}
*outp = '\0';
tor_assert((outp - *out) == (int)*out_len);
return end+1;
}
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