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[nginx] Core: escaping of chars not allowed in URIs per RFC 3986.

Maxim Dounin
June 28, 2021 02:38PM
details: https://hg.nginx.org/nginx/rev/dfd8dfb436e5
branches:
changeset: 7880:dfd8dfb436e5
user: Maxim Dounin <mdounin@mdounin.ru>
date: Mon Jun 28 18:01:11 2021 +0300
description:
Core: escaping of chars not allowed in URIs per RFC 3986.

Per RFC 3986 only the following characters are allowed in URIs unescaped:

unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "@"
sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
/ "*" / "+" / "," / ";" / "="

And "%" can appear as a part of escaping itself. The following
characters are not allowed and need to be escaped: %00-%1F, %7F-%FF,
" ", """, "<", ">", "\", "^", "`", "{", "|", "}".

Not escaping ">" is known to cause problems at least with MS Exchange (see
http://nginx.org/pipermail/nginx-ru/2010-January/031261.html) and in
Tomcat (ticket #2191).

The patch adds escaping of the following chars in all URI parts: """, "<",
">", "\", "^", "`", "{", "|", "}". Note that comments are mostly preserved
to outline important characters being escaped.

diffstat:

src/core/ngx_string.c | 45 +++++++++++++++++++++++++++++----------------
1 files changed, 29 insertions(+), 16 deletions(-)

diffs (112 lines):

diff -r b7407334c60d -r dfd8dfb436e5 src/core/ngx_string.c
--- a/src/core/ngx_string.c Mon Jun 28 18:01:09 2021 +0300
+++ b/src/core/ngx_string.c Mon Jun 28 18:01:11 2021 +0300
@@ -1493,19 +1493,32 @@ ngx_escape_uri(u_char *dst, u_char *src,
uint32_t *escape;
static u_char hex[] = "0123456789ABCDEF";

- /* " ", "#", "%", "?", %00-%1F, %7F-%FF */
+ /*
+ * Per RFC 3986 only the following chars are allowed in URIs unescaped:
+ *
+ * unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
+ * gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "@"
+ * sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
+ * / "*" / "+" / "," / ";" / "="
+ *
+ * And "%" can appear as a part of escaping itself. The following
+ * characters are not allowed and need to be escaped: %00-%1F, %7F-%FF,
+ * " ", """, "<", ">", "\", "^", "`", "{", "|", "}".
+ */
+
+ /* " ", "#", "%", "?", not allowed */

static uint32_t uri[] = {
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */

/* ?>=< ;:98 7654 3210 /.-, +*)( '&%$ #"! */
- 0x80000029, /* 1000 0000 0000 0000 0000 0000 0010 1001 */
+ 0xd000002d, /* 1101 0000 0000 0000 0000 0000 0010 1101 */

/* _^]\ [ZYX WVUT SRQP ONML KJIH GFED CBA@ */
- 0x00000000, /* 0000 0000 0000 0000 0000 0000 0000 0000 */
+ 0x50000000, /* 0101 0000 0000 0000 0000 0000 0000 0000 */

/* ~}| {zyx wvut srqp onml kjih gfed cba` */
- 0x80000000, /* 1000 0000 0000 0000 0000 0000 0000 0000 */
+ 0xb8000001, /* 1011 1000 0000 0000 0000 0000 0000 0001 */

0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
@@ -1513,19 +1526,19 @@ ngx_escape_uri(u_char *dst, u_char *src,
0xffffffff /* 1111 1111 1111 1111 1111 1111 1111 1111 */
};

- /* " ", "#", "%", "&", "+", ";", "?", %00-%1F, %7F-%FF */
+ /* " ", "#", "%", "&", "+", ";", "?", not allowed */

static uint32_t args[] = {
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */

/* ?>=< ;:98 7654 3210 /.-, +*)( '&%$ #"! */
- 0x88000869, /* 1000 1000 0000 0000 0000 1000 0110 1001 */
+ 0xd800086d, /* 1101 1000 0000 0000 0000 1000 0110 1101 */

/* _^]\ [ZYX WVUT SRQP ONML KJIH GFED CBA@ */
- 0x00000000, /* 0000 0000 0000 0000 0000 0000 0000 0000 */
+ 0x50000000, /* 0101 0000 0000 0000 0000 0000 0000 0000 */

/* ~}| {zyx wvut srqp onml kjih gfed cba` */
- 0x80000000, /* 1000 0000 0000 0000 0000 0000 0000 0000 */
+ 0xb8000001, /* 1011 1000 0000 0000 0000 0000 0000 0001 */

0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
@@ -1553,19 +1566,19 @@ ngx_escape_uri(u_char *dst, u_char *src,
0xffffffff /* 1111 1111 1111 1111 1111 1111 1111 1111 */
};

- /* " ", "#", """, "%", "'", %00-%1F, %7F-%FF */
+ /* " ", "#", """, "%", "'", not allowed */

static uint32_t html[] = {
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */

/* ?>=< ;:98 7654 3210 /.-, +*)( '&%$ #"! */
- 0x000000ad, /* 0000 0000 0000 0000 0000 0000 1010 1101 */
+ 0x500000ad, /* 0101 0000 0000 0000 0000 0000 1010 1101 */

/* _^]\ [ZYX WVUT SRQP ONML KJIH GFED CBA@ */
- 0x00000000, /* 0000 0000 0000 0000 0000 0000 0000 0000 */
+ 0x50000000, /* 0101 0000 0000 0000 0000 0000 0000 0000 */

/* ~}| {zyx wvut srqp onml kjih gfed cba` */
- 0x80000000, /* 1000 0000 0000 0000 0000 0000 0000 0000 */
+ 0xb8000001, /* 1011 1000 0000 0000 0000 0000 0000 0001 */

0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
@@ -1573,19 +1586,19 @@ ngx_escape_uri(u_char *dst, u_char *src,
0xffffffff /* 1111 1111 1111 1111 1111 1111 1111 1111 */
};

- /* " ", """, "'", %00-%1F, %7F-%FF */
+ /* " ", """, "'", not allowed */

static uint32_t refresh[] = {
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */

/* ?>=< ;:98 7654 3210 /.-, +*)( '&%$ #"! */
- 0x00000085, /* 0000 0000 0000 0000 0000 0000 1000 0101 */
+ 0x50000085, /* 0101 0000 0000 0000 0000 0000 1000 0101 */

/* _^]\ [ZYX WVUT SRQP ONML KJIH GFED CBA@ */
- 0x00000000, /* 0000 0000 0000 0000 0000 0000 0000 0000 */
+ 0x50000000, /* 0101 0000 0000 0000 0000 0000 0000 0000 */

/* ~}| {zyx wvut srqp onml kjih gfed cba` */
- 0x80000000, /* 1000 0000 0000 0000 0000 0000 0000 0000 */
+ 0xd8000001, /* 1011 1000 0000 0000 0000 0000 0000 0001 */

0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
0xffffffff, /* 1111 1111 1111 1111 1111 1111 1111 1111 */
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[nginx] Core: escaping of chars not allowed in URIs per RFC 3986.

Maxim Dounin 98 June 28, 2021 02:38PM



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