feat(syslogreceiver): validate protocol name (open-telemetry#27581)

**Description:**

Add validation of protocol name and be case insensitive

**Link to tracking Issue:**

**Testing:**

Unit Tests

**Documentation:**

N/A

---------

Signed-off-by: Dominik Rosiek <drosiek@sumologic.com>

.chloggen/drosiek-syslog-improvement.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: syslogreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: validate protocol name
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [27581]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

pkg/stanza/operator/parser/syslog/syslog.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	sl "github.com/influxdata/go-syslog/v3"
@@ -77,17 +78,21 @@ func (c Config) Build(logger *zap.SugaredLogger) (operator.Operator, error) {
 		return nil, err
 	}
 
+	proto := strings.ToLower(c.Protocol)
+
 	switch {
-	case c.Protocol == "":
+	case proto == "":
 		return nil, fmt.Errorf("missing field 'protocol'")
-	case c.Protocol != RFC5424 && (c.NonTransparentFramingTrailer != nil || c.EnableOctetCounting):
+	case proto != RFC5424 && (c.NonTransparentFramingTrailer != nil || c.EnableOctetCounting):
 		return nil, errors.New("octet_counting and non_transparent_framing are only compatible with protocol rfc5424")
-	case c.Protocol == RFC5424 && (c.NonTransparentFramingTrailer != nil && c.EnableOctetCounting):
+	case proto == RFC5424 && (c.NonTransparentFramingTrailer != nil && c.EnableOctetCounting):
 		return nil, errors.New("only one of octet_counting or non_transparent_framing can be enabled")
-	case c.Protocol == RFC5424 && c.NonTransparentFramingTrailer != nil:
+	case proto == RFC5424 && c.NonTransparentFramingTrailer != nil:
 		if *c.NonTransparentFramingTrailer != NULTrailer && *c.NonTransparentFramingTrailer != LFTrailer {
 			return nil, fmt.Errorf("invalid non_transparent_framing_trailer '%s'. Must be either 'LF' or 'NUL'", *c.NonTransparentFramingTrailer)
 		}
+	case proto != RFC5424 && proto != RFC3164:
+		return nil, fmt.Errorf("unsupported protocol version: %s", proto)
 	}
 
 	if c.Location == "" {
@@ -101,7 +106,7 @@ func (c Config) Build(logger *zap.SugaredLogger) (operator.Operator, error) {
 
 	return &Parser{
 		ParserOperator:               parserOperator,
-		protocol:                     c.Protocol,
+		protocol:                     proto,
 		location:                     location,
 		enableOctetCounting:          c.EnableOctetCounting,
 		nonTransparentFramingTrailer: c.NonTransparentFramingTrailer,

pkg/stanza/operator/parser/syslog/syslog_test.go

@@ -77,3 +77,19 @@ func TestSyslogParseRFC5424_SDNameTooLong(t *testing.T) {
 		require.FailNow(t, "Timed out waiting for entry to be processed")
 	}
 }
+
+func TestSyslogProtocolConfig(t *testing.T) {
+	for _, proto := range []string{"RFC5424", "rfc5424", "RFC3164", "rfc3164"} {
+		cfg := basicConfig()
+		cfg.Protocol = proto
+		_, err := cfg.Build(testutil.Logger(t))
+		require.NoError(t, err)
+	}
+
+	for _, proto := range []string{"RFC5424a", "rfc5424b", "RFC3164c", "rfc3164d"} {
+		cfg := basicConfig()
+		cfg.Protocol = proto
+		_, err := cfg.Build(testutil.Logger(t))
+		require.Error(t, err)
+	}
+}