5 Security Considerations ....................................... 47
6 References .................................................... 48
7 Author's Address .............................................. 50
-8 Full Copyright Statement ...................................... 50
+Appendix A ...................................................... XXXX
+Appendix B ...................................................... XXXX
+Full Copyright Statement ........................................ XXXX
.ti 0
List of Figures
from the ID lists. Note that the nickname MUST be in
lowercase format before computing the hash value. Since
nicknames are UTF-8 encoded, some characters cannot be
- converted to lower case. All characters that has a
- lowercase alternative in the Unicode standard MUST be
- converted to lowercase.
+ converted to lower case. All upper case characters that
+ has a lowercase alternative in the Unicode standard MUST
+ be converted to lowercase. Note that the conversion MUST
+ be done without regard to the current system character
+ subset to ensure interoperability.
.in 3
Collisions could occur when more than 2^8 clients using same nickname
and hostnames are UTF-8 encoded. This definition does not affect
messages sent in SILC, as the Message Payload provides its own mechanism
to indicate whether a message is UTF-8 text message, data message, which
-might use its own character encoding, or pure binary message [SILC2].
+may use its own character encoding, or pure binary message [SILC2].
Certain limitations are imposed on the UTF-8 encoded strings in SILC.
The UTF-8 encoded strings MUST NOT include any characters that are
-marked in the Unicode standard as control codes, Unicode noncharacters,
+marked in the Unicode standard as control codes, noncharacters,
reserved or private range characters, or any other illegal Unicode
characters. Also the BOM (Byte-Order Mark) MUST NOT be used as byte
order signature in UTF-8 encoded strings. A string containing these
-characters MUST be treated as malformed UTF-8 encoding.
+characters MUST be treated as malformed UTF-8 encoding. See the
+Appendix A for list of prohibited characters.
Because of these limitations on the UTF-8 encoded strings the
implementation may need to have access to full Unicode implementation
Server also need to have the capability to convert character case from
upper case to lower case characters, when applicable.
-The ISO 10646 defines that malformed sequences shall be signalled
+The Unicode standard defines that malformed sequences shall be signalled
by replacing the sequence with a replacement character. Even though,
in case of SILC these strings may not be malformed UTF-8 encodings
they MUST be treated as malformed strings. Implementation MAY use
-a replacement character, however, the ISO 10646 defined character is
-prohibited with nicknames and channel names in SILC. Implementation
-MAY use some other replacement character or the ISO 10646 defined
-character when it is applicable. It is, however, RECOMMENDED that an
-error is returned instead of using replacement character if it is
-possible. For example, when setting a nickname with SILC_COMMAND_NICK
-command, implementation is able to send error indication back to the
-command sender. It must be noted that on server implementation if
-a character sequence is merely outside of current character subset,
-but is otherwise valid character, it MUST NOT be replaced by a
-replacement character. Server SHOULD inspect the UTF-8 strings without
-regard to current system character subset.
+a replacement character, however, the character Unicode standard defines
+MUST NOT be used, but another character must be chosen. It is, however,
+RECOMMENDED that an error is returned instead of using replacement
+character if it is possible. For example, when setting a nickname
+with SILC_COMMAND_NICK command, implementation is able to send error
+indication back to the command sender. It must be noted that on server
+implementation if a character sequence is merely outside of current
+character subset, but is otherwise valid character, it MUST NOT be
+replaced by a replacement character. Server SHOULD inspect the UTF-8
+strings without regard to current system character subset.
On user interface where UTF-8 strings are displayed the implementation
is RECOMMENDED to escape any character that it is unable to render
The nicknames and channel names are also UTF-8 encoded in SILC protocol.
As these strings may be used as message destination indicator on the
-user interface certain additional limitations has been imposed to it.
+user interface certain additional limitations has been imposed to them.
In addition of general UTF-8 string limitations described in previous
section, the UTF-8 encoded nickname and channel name strings MUST NOT
include any characters that has been marked in the Unicode standard as
-space (white space) characters, line and paragraph separators,
-mathematical symbol characters (with exception of US-ASCII mathematical
-symbol characters), currency symbol characters, or any other symbol
-characters, special characters or tags. In addition nicknames and
-channel names MUST NOT include commas (','), '@', '!' or any wildcard
-characters.
+space characters, line and paragraph separators, mathematical symbol
+characters (with exception of US-ASCII mathematical symbol characters),
+currency symbol characters, or any other symbol characters (with
+execption of CJK and other similar symbols), special characters or tags.
+In addition nicknames and channel names MUST NOT include commas (','),
+'@', '!' or any wildcard characters. See the Appendix A and Appendix B
+for list of prohibited characters.
This definition means that these strings generally may only include
letters, numbers, most punctuation characters and some other characters.
-For practical reasons all symbol characters and many other special
+For practical reasons most symbol characters and many other special
characters are prohibited. Conforming implementation MUST treat
strings with prohibited characters as malformed strings.
.ti 0
-8 Full Copyright Statement
+Appendix A
+
+This appendix lists the generally prohibited characters in UTF-8 encoded
+strings in SILC. The characters listed in this appendix MUST NOT appear
+in any UTF-8 encoded string. When a new version of Unicode standard
+defines new characters that are marked into the same category as the
+characters listed in this appendix they are also prohibited. Implementor
+SHOULD NOT trust the following list but should verify the actual list of
+characters from the Unicode standard.
+
+Control codes
+0000-001F 007F-009F
+
+Noncharacters
+FDD0-FDEF
+0FFFE-0FFFF 1FFFE-1FFFF 2FFFE-2FFFF 3FFFE-3FFFF 4FFFE-4FFFF
+5FFFE-5FFFF 6FFFE-6FFFF 7FFFE-7FFFF 8FFFE-8FFFF 9FFFE-9FFFF
+AFFFE-AFFFF BFFFE-BFFFF CFFFE-CFFFF DFFFE-DFFFF EFFFE-EFFFF
+FFFFE-FFFFF 10FFFE-10FFFF
+
+Surrogate codes
+D800-DFFF
+
+Private characters
+E000-F8FF F0000-FFFFD 100000-10FFFD
+
+BOM as signature
+FEFF
+
+Replacement character
+FFFD
+
+
+.ti 0
+Appendix B
+
+This appendix lists additional prohibited characters in UTF-8 encoded
+nickname and channel name strings. The characters listed in this
+appendix MUST NOT appear in UTF-8 encoded nickname and channel name
+strings. When a new version of Unicode standard defines new characters
+that are marked into the same category as the characters listed in this
+appendix they are also prohibited. Implementor SHOULD NOT trust the
+following list but should verify the actual list of characters from
+the Unicode standard.
+
+Reserved US-ASCII characters
+0021 002A 002C 003F 0040
+
+Space characters
+0020 00A0 1680 180E 2000-200B 202F 205F 3000
+
+Line and paragraph separators
+2028 2029
+
+Symbol characters and other symbol like characters (with execption of
+CJK and other similar symbols)
+00A2-00A9 00AC 00AE 00AF 00B0 00B1 00B4 00B6 00B8 00D7 00F7
+02C2-02C5 02D2-02FF 0374 0375 0384 0385 03F6 0482 060E 060F
+06E9 06FD 06FE 09F2 09F3 09FA 0AF1 0B70 0BF3-0BFA 0E3F
+0F01-0F03 0F13-0F17 0F1A-0F1F 0F34 0F36 0F38 0FBE 0FBF
+0FC0-0FC5 0FC7-0FCF 17DB 1940 19E0-19FF 1FBD 1FBF-1FC1
+1FCD-1FCF 1FDD-1FDF 1FED-1FEF 1FFD 1FFE 2044 2052 207A-207C
+208A-208C 20A0-20B1 2100-214F 2150-218F 2190-21FF 2200-22FF
+2300-23FF 2400-243F 2440-245F 2460-24FF 2500-257F 2580-259F
+25A0-25FF 2600-26FF 2700-27BF 27C0-27EF 27F0-27FF 2800-28FF
+2900-297F 2980-29FF 2A00-2AFF 2B00-2BFF 2E9A 2EF4-2EFF
+2FF0-2FFF 303B-303D 3040 3095-3098 309F-30A0 30FF-3104
+312D-3130 318F 31B8-31FF 321D-321F 3244-325F 327C-327E
+32B1-32BF 32CC-32CF 32FF 3377-337A 33DE-33DF 33FF 4DB6-4DFF
+9FA6-9FFF A48D-A48F A4A2-A4A3 A4B4 A4C1 A4C5 A4C7-ABFF
+D7A4-D7FF FA2E-FAFF FFE0-FFEE FFFC 10000-1007F 100080-100FF
+10100-1013F 1D000-1D0FF 1D100-1D1FF 1D300-1D35F 1D400-1D7FF
+
+Specials and tags
+FFF0-FFFF
+E0000-E007F
+
+Other characters
+E0100-E01EF
+
+
+.ti 0
+Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
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