[7.17](backport #30658) Fix dissect trim panics from DELETE (\u007f) character

CHANGELOG.next.asciidoc

@@ -36,7 +36,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix the ability for subcommands to be ran properly from the beats containers. {pull}30452[30452]
 - Log errors when parsing and applying config blocks and if the input is disabled. {pull}30534[30534]
 - Fixes Beats crashing when glibc >= 2.35 is used {issue}30576[30576]
-
+- Fix dissect trim panics from DELETE (127)(\u007f) character {issue}30657[30657] {pull}30658[30658]
 
 *Auditbeat*
 

libbeat/processors/dissect/trim.go

@@ -37,7 +37,7 @@ func newTrimmer(trimChars string, trimLeft, trimRight bool) (t trimmer, err erro
 }
 
 type asciiTrimmer struct {
-	chars       [127]byte
+	chars       [asciiLimit]byte
 	left, right bool
 }
 

libbeat/processors/dissect/trim_test.go

@@ -215,6 +215,46 @@ func TestTrimmer(t *testing.T) {
 			input:    "\t\t༄𑅀߹꧁߹𑁍 ÿ",
 			expected: "༄𑅀߹꧁߹𑁍",
 		},
+		{ // demonstrates that unicode \u is converted to char in golang strings
+			name:     "trim ASCII TILDE",
+			cutset:   " ",
+			left:     true,
+			right:    true,
+			input:    "  hello world! \u007e ",
+			expected: "hello world! ~",
+		},
+		{
+			name:     "trim ASCII DELETE",
+			cutset:   " ",
+			left:     true,
+			right:    true,
+			input:    "  hello world! \u007f ",
+			expected: "hello world! \u007f",
+		},
+		{
+			name:     "trim UTF-8 CONTROL",
+			cutset:   " ",
+			left:     true,
+			right:    true,
+			input:    "  hello world! \u0080 ",
+			expected: "hello world! \u0080",
+		},
+		{
+			name:     "trim ASCII DELETE cutset in UTF-8 input",
+			cutset:   " \u007f",
+			left:     true,
+			right:    true,
+			input:    "  hello world! \u0080 \u007f",
+			expected: "hello world! \u0080",
+		},
+		{
+			name:     "trim UTF-8 CONTROL cutset in UTF-8 input",
+			cutset:   " \u0080",
+			left:     true,
+			right:    true,
+			input:    "  hello world! \u007f \u0080",
+			expected: "hello world! \u007f",
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			trimmer, err := newTrimmer(test.cutset, test.left, test.right)