Initial commit

11 files changed, 472 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
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index 0000000..fc08677
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/meseircd
diff --git a/LICENSE.CC0 b/LICENSE.CC0
new file mode 100644
index 0000000..7c5febc
--- /dev/null
+++ b/LICENSE.CC0
@@ -0,0 +1,124 @@
+This license applies to code written for the MeseIRCd project.
+
+Creative Commons Legal Code
+
+CC0 1.0 Universal
+
+    CREATIVE COMMONS CORPORATION IS NOT A LAW FIRM AND DOES NOT PROVIDE
+    LEGAL SERVICES. DISTRIBUTION OF THIS DOCUMENT DOES NOT CREATE AN
+    ATTORNEY-CLIENT RELATIONSHIP. CREATIVE COMMONS PROVIDES THIS
+    INFORMATION ON AN "AS-IS" BASIS. CREATIVE COMMONS MAKES NO WARRANTIES
+    REGARDING THE USE OF THIS DOCUMENT OR THE INFORMATION OR WORKS
+    PROVIDED HEREUNDER, AND DISCLAIMS LIABILITY FOR DAMAGES RESULTING FROM
+    THE USE OF THIS DOCUMENT OR THE INFORMATION OR WORKS PROVIDED
+    HEREUNDER.
+
+Statement of Purpose
+
+The laws of most jurisdictions throughout the world automatically confer
+exclusive Copyright and Related Rights (defined below) upon the creator
+and subsequent owner(s) (each and all, an "owner") of an original work of
+authorship and/or a database (each, a "Work").
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+Certain owners wish to permanently relinquish those rights to a Work for
+the purpose of contributing to a commons of creative, cultural and
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+works, reuse and redistribute as freely as possible in any form whatsoever
+and for any purposes, including without limitation commercial purposes.
+These owners may contribute to the Commons to promote the ideal of a free
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+works, or to gain reputation or greater distribution for their Work in
+part through the use and efforts of others.
+
+For these and/or other purposes and motivations, and without any
+expectation of additional consideration or compensation, the person
+associating CC0 with a Work (the "Affirmer"), to the extent that he or she
+is an owner of Copyright and Related Rights in the Work, voluntarily
+elects to apply CC0 to the Work and publicly distribute the Work under its
+terms, with knowledge of his or her Copyright and Related Rights in the
+Work and the meaning and intended legal effect of CC0 on those rights.
+
+1. Copyright and Related Rights. A Work made available under CC0 may be
+protected by copyright and related or neighboring rights ("Copyright and
+Related Rights"). Copyright and Related Rights include, but are not
+limited to, the following:
+
+  i. the right to reproduce, adapt, distribute, perform, display,
+     communicate, and translate a Work;
+ ii. moral rights retained by the original author(s) and/or performer(s);
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+  v. rights protecting the extraction, dissemination, use and reuse of data
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+ vi. database rights (such as those arising under Directive 96/9/EC of the
+     European Parliament and of the Council of 11 March 1996 on the legal
+     protection of databases, and under any national implementation
+     thereof, including any amended or successor version of such
+     directive); and
+vii. other similar, equivalent or corresponding rights throughout the
+     world based on applicable law or treaty, and any national
+     implementations thereof.
+
+2. Waiver. To the greatest extent permitted by, but not in contravention
+of, applicable law, Affirmer hereby overtly, fully, permanently,
+irrevocably and unconditionally waives, abandons, and surrenders all of
+Affirmer's Copyright and Related Rights and associated claims and causes
+of action, whether now known or unknown (including existing as well as
+future claims and causes of action), in the Work (i) in all territories
+worldwide, (ii) for the maximum duration provided by applicable law or
+treaty (including future time extensions), (iii) in any current or future
+medium and for any number of copies, and (iv) for any purpose whatsoever,
+including without limitation commercial, advertising or promotional
+purposes (the "Waiver"). Affirmer makes the Waiver for the benefit of each
+member of the public at large and to the detriment of Affirmer's heirs and
+successors, fully intending that such Waiver shall not be subject to
+revocation, rescission, cancellation, termination, or any other legal or
+equitable action to disrupt the quiet enjoyment of the Work by the public
+as contemplated by Affirmer's express Statement of Purpose.
+
+3. Public License Fallback. Should any part of the Waiver for any reason
+be judged legally invalid or ineffective under applicable law, then the
+Waiver shall be preserved to the maximum extent permitted taking into
+account Affirmer's express Statement of Purpose. In addition, to the
+extent the Waiver is so judged Affirmer hereby grants to each affected
+person a royalty-free, non transferable, non sublicensable, non exclusive,
+irrevocable and unconditional license to exercise Affirmer's Copyright and
+Related Rights in the Work (i) in all territories worldwide, (ii) for the
+maximum duration provided by applicable law or treaty (including future
+time extensions), (iii) in any current or future medium and for any number
+of copies, and (iv) for any purpose whatsoever, including without
+limitation commercial, advertising or promotional purposes (the
+"License"). The License shall be deemed effective as of the date CC0 was
+applied by Affirmer to the Work. Should any part of the License for any
+reason be judged legally invalid or ineffective under applicable law, such
+partial invalidity or ineffectiveness shall not invalidate the remainder
+of the License, and in such case Affirmer hereby affirms that he or she
+will not (i) exercise any of his or her remaining Copyright and Related
+Rights in the Work or (ii) assert any associated claims and causes of
+action with respect to the Work, in either case contrary to Affirmer's
+express Statement of Purpose.
+
+4. Limitations and Disclaimers.
+
+ a. No trademark or patent rights held by Affirmer are waived, abandoned,
+    surrendered, licensed or otherwise affected by this document.
+ b. Affirmer offers the Work as-is and makes no representations or
+    warranties of any kind concerning the Work, express, implied,
+    statutory or otherwise, including without limitation warranties of
+    title, merchantability, fitness for a particular purpose, non
+    infringement, or the absence of latent or other defects, accuracy, or
+    the present or absence of errors, whether or not discoverable, all to
+    the greatest extent permissible under applicable law.
+ c. Affirmer disclaims responsibility for clearing rights of other persons
+    that may apply to the Work or any use thereof, including without
+    limitation any person's Copyright and Related Rights in the Work.
+    Further, Affirmer disclaims responsibility for obtaining any necessary
+    consents, permissions or other rights required for any use of the
+    Work.
+ d. Affirmer understands and acknowledges that Creative Commons is not a
+    party to this document and has no duty or obligation with respect to
+    this CC0 or use of the Work.
+
diff --git a/LICENSE.MIT b/LICENSE.MIT
new file mode 100644
index 0000000..6c8954c
--- /dev/null
+++ b/LICENSE.MIT
@@ -0,0 +1,16 @@
+This license applies to code copied from Ergo IRCd.
+
+Copyright (c) 2016-2021 Daniel Oaks
+Copyright (c) 2018-2021 Shivaram Lingamneni
+
+Permission to use, copy, modify, and/or distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+PERFORMANCE OF THIS SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..551a422
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# MeseIRCd
+
+A primitive internet relay chat daemon.
diff --git a/const.go b/const.go
new file mode 100644
index 0000000..962db26
--- /dev/null
+++ b/const.go
@@ -0,0 +1,7 @@
+package main
+
+const (
+	MaxlenTags    = 8191
+	MaxlenTagData = MaxlenTags - 2
+	MaxlenBody    = 510
+)
diff --git a/errors.go b/errors.go
new file mode 100644
index 0000000..2d4ed02
--- /dev/null
+++ b/errors.go
@@ -0,0 +1,13 @@
+package main
+
+import (
+	"errors"
+)
+
+var (
+	ErrEmptyMessage      = errors.New("empty message")
+	ErrIllegalByte       = errors.New("illegal byte")
+	ErrTagsTooLong       = errors.New("tags too long")
+	ErrInvalidTagContent = errors.New("invalid tag content")
+	ErrBodyTooLong       = errors.New("body too long")
+)
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..5447113
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.sr.ht/~runxiyu/meseircd
+
+go 1.23.3
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..0898bd5
--- /dev/null
+++ b/main.go
@@ -0,0 +1,53 @@
+package main
+
+import (
+	"bufio"
+	"log"
+	"log/slog"
+	"net"
+)
+
+type Client struct {
+	conn net.Conn
+}
+
+func main() {
+	listener, err := net.Listen("tcp", ":6667")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer listener.Close()
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		client := &Client{
+			conn: conn,
+		}
+		go func() {
+			defer func() {
+				raised := recover()
+				if raised != nil {
+					slog.Error("connection routine panicked", "raised", raised)
+				}
+			}()
+			client.handleConnection()
+		}()
+	}
+}
+
+func (client *Client) handleConnection() {
+	reader := bufio.NewReader(client.conn)
+	for {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			slog.Error("error while reading from connection", "error", err)
+			client.conn.Close()
+			return
+		}
+		_, _ = parseIRCMsg(line)
+	}
+}
diff --git a/msg.go b/msg.go
new file mode 100644
index 0000000..ff4b3a4
--- /dev/null
+++ b/msg.go
@@ -0,0 +1,125 @@
+package main
+
+import (
+	"strings"
+)
+
+type Msg struct {
+	RawMessage string
+	RawSource  string
+	Command    string
+	Tags       map[string]string
+	Params     []string
+}
+
+// Partially adapted from https://github.com/ergochat/irc-go.git
+func parseIRCMsg(line string) (msg Msg, err error) {
+	msg = Msg{
+		RawMessage: line,
+	}
+
+	line = strings.TrimSuffix(line, "\n")
+	line = strings.TrimSuffix(line, "\r")
+
+	if len(line) == 0 {
+		err = ErrEmptyMessage
+		return
+	}
+
+	for _, v := range line {
+		if v == '\x00' || v == '\r' || v == '\n' {
+			err = ErrIllegalByte
+			return
+		}
+	}
+
+	// IRCv3 tags
+	if line[0] == '@' {
+		tagEnd := strings.IndexByte(line, ' ')
+		if tagEnd == -1 {
+			err = ErrEmptyMessage
+			return
+		}
+		tagsString := line[1:tagEnd]
+		if 0 < MaxlenTagData && MaxlenTagData < len(tagsString) {
+			err = ErrTagsTooLong
+			return
+		}
+		msg.Tags, err = parseTags(tagsString)
+		if err != nil {
+			return
+		}
+		// Skip over the tags and the separating space
+		line = line[tagEnd+1:]
+	}
+
+	if len(line) > MaxlenBody {
+		err = ErrBodyTooLong
+		line = line[:MaxlenBody]
+	}
+
+	line = trimInitialSpaces(line)
+
+	// Source
+	if 0 < len(line) && line[0] == ':' {
+		sourceEnd := strings.IndexByte(line, ' ')
+		if sourceEnd == -1 {
+			err = ErrEmptyMessage
+			return
+		}
+		msg.RawSource = line[1:sourceEnd]
+		// Skip over the source and the separating space
+		line = line[sourceEnd+1:]
+	}
+
+	// Command
+	commandEnd := strings.IndexByte(line, ' ')
+	paramStart := commandEnd + 1
+	if commandEnd == -1 {
+		commandEnd = len(line)
+		paramStart = len(line)
+	}
+	baseCommand := line[:commandEnd]
+	if len(baseCommand) == 0 {
+		err = ErrEmptyMessage
+		return
+	}
+	// TODO: Actually must be either letters or a 3-digit numeric
+	if !isASCII(baseCommand) {
+		err = ErrIllegalByte
+		return
+	}
+	msg.Command = strings.ToUpper(baseCommand)
+	line = line[paramStart:]
+
+	// Other arguments
+	for {
+		line = trimInitialSpaces(line)
+		if len(line) == 0 {
+			break
+		}
+		// Trailing
+		if line[0] == ':' {
+			msg.Params = append(msg.Params, line[1:])
+			break
+		}
+		paramEnd := strings.IndexByte(line, ' ')
+		if paramEnd == -1 {
+			msg.Params = append(msg.Params, line)
+			break
+		}
+		msg.Params = append(msg.Params, line[:paramEnd])
+		line = line[paramEnd+1:]
+	}
+
+	return
+}
+
+func isASCII(str string) bool {
+	for i := 0; i < len(str); i++ {
+		if str[i] > 127 {
+			return false
+		}
+	}
+	return true
+}
diff --git a/tags.go b/tags.go
new file mode 100644
index 0000000..43a2833
--- /dev/null
+++ b/tags.go
@@ -0,0 +1,119 @@
+// Almost everything in this file is adapted from Ergo IRCd
+// This is probably considered a derived work for copyright purposes
+//
+// SPDX-License-Identifier: MIT
+
+package main
+
+import (
+	"strings"
+	"unicode/utf8"
+)
+
+func parseTags(tagsString string) (tags map[string]string, err error) {
+	tags = make(map[string]string)
+	for 0 < len(tagsString) {
+		tagEnd := strings.IndexByte(tagsString, ';')
+		endPos := tagEnd
+		nextPos := tagEnd + 1
+		if tagEnd == -1 {
+			endPos = len(tagsString)
+			nextPos = len(tagsString)
+		}
+		tagPair := tagsString[:endPos]
+		equalsIndex := strings.IndexByte(tagPair, '=')
+		var tagName, tagValue string
+		if equalsIndex == -1 {
+			// Tag with no value
+			tagName = tagPair
+		} else {
+			tagName, tagValue = tagPair[:equalsIndex], tagPair[equalsIndex+1:]
+		}
+		// "Implementations [...] MUST NOT perform any validation that would
+		//  reject the message if an invalid tag key name is used."
+		if validateTagName(tagName) {
+			if !validateTagValue(tagValue) {
+				err = ErrInvalidTagContent
+				return
+			}
+			tags[tagName] = UnescapeTagValue(tagValue)
+		}
+		tagsString = tagsString[nextPos:]
+	}
+	return
+}
+
+func UnescapeTagValue(inString string) string {
+	// buf.Len() == 0 is the fastpath where we have not needed to unescape any chars
+	var buf strings.Builder
+	remainder := inString
+	for {
+		backslashPos := strings.IndexByte(remainder, '\\')
+
+		if backslashPos == -1 {
+			if buf.Len() == 0 {
+				return inString
+			} else {
+				buf.WriteString(remainder)
+				break
+			}
+		} else if backslashPos == len(remainder)-1 {
+			// trailing backslash, which we strip
+			if buf.Len() == 0 {
+				return inString[:len(inString)-1]
+			} else {
+				buf.WriteString(remainder[:len(remainder)-1])
+				break
+			}
+		}
+
+		// Non-trailing backslash detected; we're now on the slowpath
+		// where we modify the string
+		if buf.Len() < len(inString) {
+			buf.Grow(len(inString))
+		}
+		buf.WriteString(remainder[:backslashPos])
+		buf.WriteByte(escapedCharLookupTable[remainder[backslashPos+1]])
+		remainder = remainder[backslashPos+2:]
+	}
+
+	return buf.String()
+}
+
+var escapedCharLookupTable [256]byte
+
+func init() {
+	for i := 0; i < 256; i += 1 {
+		escapedCharLookupTable[i] = byte(i)
+	}
+	escapedCharLookupTable[':'] = ';'
+	escapedCharLookupTable['s'] = ' '
+	escapedCharLookupTable['r'] = '\r'
+	escapedCharLookupTable['n'] = '\n'
+}
+
+// https://ircv3.net/specs/extensions/message-tags.html#rules-for-naming-message-tags
+func validateTagName(name string) bool {
+	if len(name) == 0 {
+		return false
+	}
+	if name[0] == '+' {
+		name = name[1:]
+	}
+	if len(name) == 0 {
+		return false
+	}
+	// Let's err on the side of leniency here; allow -./ (45-47) in any position
+	for i := 0; i < len(name); i++ {
+		c := name[i]
+		if !(('-' <= c && c <= '/') || ('0' <= c && c <= '9') || ('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z')) {
+			return false
+		}
+	}
+	return true
+}
+
+// "Tag values MUST be encoded as UTF8."
+func validateTagValue(value string) bool {
+	return utf8.ValidString(value)
+}
diff --git a/util.go b/util.go
new file mode 100644
index 0000000..0037330
--- /dev/null
+++ b/util.go
@@ -0,0 +1,8 @@
+package main
+
+func trimInitialSpaces(line string) string {
+	var i int
+	for i = 0; i < len(line) && line[i] == ' '; i++ {
+	}
+	return line[i:]
+}