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b2da4a4d75
Both lexer and parser reject invalid escape sequences in strings. The
parser's check is useless.
The lexer ends the token right after the first non-well-formed byte.
This tends to lead to suboptimal error reporting. For instance, input
{"abc\@ijk": 1}
produces the tokens
JSON_LCURLY {
JSON_ERROR "abc\@
JSON_KEYWORD ijk
JSON_ERROR ": 1}\n
The parser then reports three errors
Invalid JSON syntax
JSON parse error, invalid keyword 'ijk'
Invalid JSON syntax
before it recovers at the newline.
Drop the lexer's escape sequence checking, and make it accept the same
characters after backslash it accepts elsewhere in strings. It now
produces
JSON_LCURLY {
JSON_STRING "abc\@ijk"
JSON_COLON :
JSON_INTEGER 1
JSON_RCURLY
and the parser reports just
JSON parse error, invalid escape sequence in string
While there, fix parse_string()'s inaccurate function comment.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180823164025.12553-27-armbru@redhat.com>
387 lines
10 KiB
C
387 lines
10 KiB
C
/*
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* JSON lexer
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*
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* Copyright IBM, Corp. 2009
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "qemu-common.h"
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#include "qapi/qmp/json-lexer.h"
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#define MAX_TOKEN_SIZE (64ULL << 20)
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/*
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* From RFC 8259 "The JavaScript Object Notation (JSON) Data
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* Interchange Format", with [comments in brackets]:
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*
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* The set of tokens includes six structural characters, strings,
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* numbers, and three literal names.
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*
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* These are the six structural characters:
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*
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* begin-array = ws %x5B ws ; [ left square bracket
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* begin-object = ws %x7B ws ; { left curly bracket
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* end-array = ws %x5D ws ; ] right square bracket
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* end-object = ws %x7D ws ; } right curly bracket
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* name-separator = ws %x3A ws ; : colon
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* value-separator = ws %x2C ws ; , comma
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*
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* Insignificant whitespace is allowed before or after any of the six
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* structural characters.
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* [This lexer accepts it before or after any token, which is actually
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* the same, as the grammar always has structural characters between
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* other tokens.]
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*
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* ws = *(
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* %x20 / ; Space
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* %x09 / ; Horizontal tab
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* %x0A / ; Line feed or New line
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* %x0D ) ; Carriage return
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*
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* [...] three literal names:
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* false null true
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* [This lexer accepts [a-z]+, and leaves rejecting unknown literal
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* names to the parser.]
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*
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* [Numbers:]
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*
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* number = [ minus ] int [ frac ] [ exp ]
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* decimal-point = %x2E ; .
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* digit1-9 = %x31-39 ; 1-9
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* e = %x65 / %x45 ; e E
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* exp = e [ minus / plus ] 1*DIGIT
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* frac = decimal-point 1*DIGIT
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* int = zero / ( digit1-9 *DIGIT )
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* minus = %x2D ; -
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* plus = %x2B ; +
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* zero = %x30 ; 0
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*
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* [Strings:]
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* string = quotation-mark *char quotation-mark
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*
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* char = unescaped /
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* escape (
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* %x22 / ; " quotation mark U+0022
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* %x5C / ; \ reverse solidus U+005C
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* %x2F / ; / solidus U+002F
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* %x62 / ; b backspace U+0008
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* %x66 / ; f form feed U+000C
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* %x6E / ; n line feed U+000A
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* %x72 / ; r carriage return U+000D
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* %x74 / ; t tab U+0009
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* %x75 4HEXDIG ) ; uXXXX U+XXXX
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* escape = %x5C ; \
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* quotation-mark = %x22 ; "
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* unescaped = %x20-21 / %x23-5B / %x5D-10FFFF
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* [This lexer accepts any non-control character after escape, and
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* leaves rejecting invalid ones to the parser.]
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*
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*
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* Extensions over RFC 8259:
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* - Extra escape sequence in strings:
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* 0x27 (apostrophe) is recognized after escape, too
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* - Single-quoted strings:
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* Like double-quoted strings, except they're delimited by %x27
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* (apostrophe) instead of %x22 (quotation mark), and can't contain
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* unescaped apostrophe, but can contain unescaped quotation mark.
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* - Interpolation:
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* interpolation = %((l|ll|I64)[du]|[ipsf])
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*
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* Note:
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* - Input must be encoded in modified UTF-8.
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* - Decoding and validating is left to the parser.
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*/
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enum json_lexer_state {
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IN_ERROR = 0, /* must really be 0, see json_lexer[] */
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IN_DQ_STRING_ESCAPE,
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IN_DQ_STRING,
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IN_SQ_STRING_ESCAPE,
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IN_SQ_STRING,
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IN_ZERO,
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IN_DIGITS,
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IN_DIGIT,
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IN_EXP_E,
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IN_MANTISSA,
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IN_MANTISSA_DIGITS,
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IN_NONZERO_NUMBER,
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IN_NEG_NONZERO_NUMBER,
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IN_KEYWORD,
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IN_ESCAPE,
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IN_ESCAPE_L,
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IN_ESCAPE_LL,
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IN_ESCAPE_I,
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IN_ESCAPE_I6,
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IN_ESCAPE_I64,
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IN_WHITESPACE,
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IN_START,
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};
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QEMU_BUILD_BUG_ON((int)JSON_MIN <= (int)IN_START);
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#define TERMINAL(state) [0 ... 0x7F] = (state)
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/* Return whether TERMINAL is a terminal state and the transition to it
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from OLD_STATE required lookahead. This happens whenever the table
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below uses the TERMINAL macro. */
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#define TERMINAL_NEEDED_LOOKAHEAD(old_state, terminal) \
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(terminal != IN_ERROR && json_lexer[(old_state)][0] == (terminal))
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static const uint8_t json_lexer[][256] = {
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/* Relies on default initialization to IN_ERROR! */
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/* double quote string */
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[IN_DQ_STRING_ESCAPE] = {
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[0x20 ... 0xFD] = IN_DQ_STRING,
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},
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[IN_DQ_STRING] = {
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[0x20 ... 0xFD] = IN_DQ_STRING,
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['\\'] = IN_DQ_STRING_ESCAPE,
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['"'] = JSON_STRING,
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},
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/* single quote string */
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[IN_SQ_STRING_ESCAPE] = {
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[0x20 ... 0xFD] = IN_SQ_STRING,
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},
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[IN_SQ_STRING] = {
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[0x20 ... 0xFD] = IN_SQ_STRING,
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['\\'] = IN_SQ_STRING_ESCAPE,
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['\''] = JSON_STRING,
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},
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/* Zero */
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[IN_ZERO] = {
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TERMINAL(JSON_INTEGER),
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['0' ... '9'] = IN_ERROR,
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['.'] = IN_MANTISSA,
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},
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/* Float */
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[IN_DIGITS] = {
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TERMINAL(JSON_FLOAT),
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['0' ... '9'] = IN_DIGITS,
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},
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[IN_DIGIT] = {
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['0' ... '9'] = IN_DIGITS,
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},
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[IN_EXP_E] = {
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['-'] = IN_DIGIT,
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['+'] = IN_DIGIT,
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['0' ... '9'] = IN_DIGITS,
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},
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[IN_MANTISSA_DIGITS] = {
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TERMINAL(JSON_FLOAT),
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['0' ... '9'] = IN_MANTISSA_DIGITS,
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['e'] = IN_EXP_E,
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['E'] = IN_EXP_E,
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},
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[IN_MANTISSA] = {
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['0' ... '9'] = IN_MANTISSA_DIGITS,
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},
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/* Number */
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[IN_NONZERO_NUMBER] = {
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TERMINAL(JSON_INTEGER),
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['0' ... '9'] = IN_NONZERO_NUMBER,
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['e'] = IN_EXP_E,
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['E'] = IN_EXP_E,
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['.'] = IN_MANTISSA,
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},
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[IN_NEG_NONZERO_NUMBER] = {
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['0'] = IN_ZERO,
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['1' ... '9'] = IN_NONZERO_NUMBER,
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},
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/* keywords */
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[IN_KEYWORD] = {
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TERMINAL(JSON_KEYWORD),
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['a' ... 'z'] = IN_KEYWORD,
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},
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/* whitespace */
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[IN_WHITESPACE] = {
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TERMINAL(JSON_SKIP),
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[' '] = IN_WHITESPACE,
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['\t'] = IN_WHITESPACE,
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['\r'] = IN_WHITESPACE,
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['\n'] = IN_WHITESPACE,
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},
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/* escape */
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[IN_ESCAPE_LL] = {
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['d'] = JSON_ESCAPE,
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['u'] = JSON_ESCAPE,
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},
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[IN_ESCAPE_L] = {
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['d'] = JSON_ESCAPE,
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['l'] = IN_ESCAPE_LL,
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['u'] = JSON_ESCAPE,
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},
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[IN_ESCAPE_I64] = {
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['d'] = JSON_ESCAPE,
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['u'] = JSON_ESCAPE,
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},
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[IN_ESCAPE_I6] = {
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['4'] = IN_ESCAPE_I64,
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},
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[IN_ESCAPE_I] = {
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['6'] = IN_ESCAPE_I6,
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},
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[IN_ESCAPE] = {
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['d'] = JSON_ESCAPE,
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['i'] = JSON_ESCAPE,
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['p'] = JSON_ESCAPE,
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['s'] = JSON_ESCAPE,
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['u'] = JSON_ESCAPE,
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['f'] = JSON_ESCAPE,
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['l'] = IN_ESCAPE_L,
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['I'] = IN_ESCAPE_I,
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},
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/* top level rule */
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[IN_START] = {
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['"'] = IN_DQ_STRING,
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['\''] = IN_SQ_STRING,
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['0'] = IN_ZERO,
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['1' ... '9'] = IN_NONZERO_NUMBER,
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['-'] = IN_NEG_NONZERO_NUMBER,
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['{'] = JSON_LCURLY,
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['}'] = JSON_RCURLY,
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['['] = JSON_LSQUARE,
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[']'] = JSON_RSQUARE,
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[','] = JSON_COMMA,
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[':'] = JSON_COLON,
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['a' ... 'z'] = IN_KEYWORD,
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['%'] = IN_ESCAPE,
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[' '] = IN_WHITESPACE,
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['\t'] = IN_WHITESPACE,
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['\r'] = IN_WHITESPACE,
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['\n'] = IN_WHITESPACE,
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},
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};
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void json_lexer_init(JSONLexer *lexer, JSONLexerEmitter func)
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{
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lexer->emit = func;
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lexer->state = IN_START;
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lexer->token = g_string_sized_new(3);
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lexer->x = lexer->y = 0;
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}
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static int json_lexer_feed_char(JSONLexer *lexer, char ch, bool flush)
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{
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int char_consumed, new_state;
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lexer->x++;
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if (ch == '\n') {
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lexer->x = 0;
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lexer->y++;
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}
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do {
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assert(lexer->state <= ARRAY_SIZE(json_lexer));
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new_state = json_lexer[lexer->state][(uint8_t)ch];
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char_consumed = !TERMINAL_NEEDED_LOOKAHEAD(lexer->state, new_state);
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if (char_consumed && !flush) {
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g_string_append_c(lexer->token, ch);
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}
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switch (new_state) {
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case JSON_LCURLY:
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case JSON_RCURLY:
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case JSON_LSQUARE:
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case JSON_RSQUARE:
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case JSON_COLON:
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case JSON_COMMA:
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case JSON_ESCAPE:
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case JSON_INTEGER:
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case JSON_FLOAT:
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case JSON_KEYWORD:
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case JSON_STRING:
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lexer->emit(lexer, lexer->token, new_state, lexer->x, lexer->y);
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/* fall through */
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case JSON_SKIP:
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g_string_truncate(lexer->token, 0);
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new_state = IN_START;
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break;
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case IN_ERROR:
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/* XXX: To avoid having previous bad input leaving the parser in an
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* unresponsive state where we consume unpredictable amounts of
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* subsequent "good" input, percolate this error state up to the
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* tokenizer/parser by forcing a NULL object to be emitted, then
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* reset state.
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*
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* Also note that this handling is required for reliable channel
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* negotiation between QMP and the guest agent, since chr(0xFF)
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* is placed at the beginning of certain events to ensure proper
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* delivery when the channel is in an unknown state. chr(0xFF) is
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* never a valid ASCII/UTF-8 sequence, so this should reliably
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* induce an error/flush state.
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*/
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lexer->emit(lexer, lexer->token, JSON_ERROR, lexer->x, lexer->y);
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g_string_truncate(lexer->token, 0);
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new_state = IN_START;
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lexer->state = new_state;
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return 0;
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default:
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break;
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}
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lexer->state = new_state;
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} while (!char_consumed && !flush);
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/* Do not let a single token grow to an arbitrarily large size,
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* this is a security consideration.
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*/
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if (lexer->token->len > MAX_TOKEN_SIZE) {
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lexer->emit(lexer, lexer->token, lexer->state, lexer->x, lexer->y);
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g_string_truncate(lexer->token, 0);
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lexer->state = IN_START;
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}
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return 0;
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}
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int json_lexer_feed(JSONLexer *lexer, const char *buffer, size_t size)
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{
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size_t i;
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for (i = 0; i < size; i++) {
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int err;
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err = json_lexer_feed_char(lexer, buffer[i], false);
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if (err < 0) {
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return err;
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}
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}
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return 0;
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}
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int json_lexer_flush(JSONLexer *lexer)
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{
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return lexer->state == IN_START ? 0 : json_lexer_feed_char(lexer, 0, true);
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}
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void json_lexer_destroy(JSONLexer *lexer)
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{
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g_string_free(lexer->token, true);
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}
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