Lua: Add support for more advanced syntax (#2908)

* Add lua/rocksepc support for variables substitution
* Lua: Skip expressions in rockspec packages
* Lua: Add support for concatenation of string and variables
* Lua: Skip expressions in local
* Lua: Skip build sections in Rockspec files
* Lua: skip function blocks in Rockspec
* Lua: Add support for multi variable per line
---------
Signed-off-by: Laurent Goderre <laurent.goderre@docker.com>

syft/pkg/cataloger/lua/parse_rockspec_test.go

@@ -76,6 +76,27 @@ func TestParseRockspec(t *testing.T) {
 				},
 			},
 		},
+		{
+			Fixture: "test-fixtures/rockspec/luasyslog-2.0.1-1.rockspec",
+			ExpectedPkg: pkg.Package{
+				Name:     "luasyslog",
+				Version:  "2.0.1-1",
+				PURL:     "pkg:luarocks/luasyslog@2.0.1-1",
+				Type:     pkg.LuaRocksPkg,
+				Language: pkg.Lua,
+				Licenses: pkg.NewLicenseSet(
+					pkg.NewLicenseFromLocations("MIT/X11", file.NewLocation("test-fixtures/rockspec/luasyslog-2.0.1-1.rockspec")),
+				),
+				Metadata: pkg.LuaRocksPackage{
+					Name:        "luasyslog",
+					Version:     "2.0.1-1",
+					License:     "MIT/X11",
+					Homepage:    "https://github.com/lunarmodules/luasyslog",
+					Description: "Syslog logging for Lua",
+					URL:         "git://github.com/lunarmodules/luasyslog.git",
+				},
+			},
+		},
 	}
 
 	for _, test := range tests {

syft/pkg/cataloger/lua/rockspec_parser.go

@@ -45,7 +45,8 @@ func parseRockspecData(reader io.Reader) (rockspec, error) {
 	}
 
 	i := 0
-	blocks, err := parseRockspecBlock(data, &i)
+	locals := make(map[string]string)
+	blocks, err := parseRockspecBlock(data, &i, locals)
 
 	if err != nil {
 		return noReturn, err
@@ -56,9 +57,9 @@ func parseRockspecData(reader io.Reader) (rockspec, error) {
 	}, nil
 }
 
-func parseRockspecBlock(data []byte, i *int) ([]rockspecNode, error) {
+func parseRockspecBlock(data []byte, i *int, locals map[string]string) ([]rockspecNode, error) {
 	var out []rockspecNode
-	var iterator func(data []byte, i *int) (*rockspecNode, error)
+	var iterator func(data []byte, i *int, locals map[string]string) (*rockspecNode, error)
 
 	parsing.SkipWhitespace(data, i)
 
@@ -67,6 +68,14 @@ func parseRockspecBlock(data []byte, i *int) ([]rockspecNode, error) {
 	}
 
 	c := data[*i]
+
+	// Block starting with a comment
+	if c == '-' {
+		parseComment(data, i)
+		parsing.SkipWhitespace(data, i)
+		c = data[*i]
+	}
+
 	switch {
 	case c == '"' || c == '\'':
 		iterator = parseRockspecListItem
@@ -77,7 +86,7 @@ func parseRockspecBlock(data []byte, i *int) ([]rockspecNode, error) {
 	}
 
 	for *i < len(data) {
-		item, err := iterator(data, i)
+		item, err := iterator(data, i, locals)
 		if err != nil {
 			return nil, fmt.Errorf("%w\n%s", err, parsing.PrintError(data, *i))
 		}
@@ -99,7 +108,7 @@ func parseRockspecBlock(data []byte, i *int) ([]rockspecNode, error) {
 }
 
 //nolint:funlen, gocognit
-func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
+func parseRockspecNode(data []byte, i *int, locals map[string]string) (*rockspecNode, error) {
 	parsing.SkipWhitespace(data, i)
 
 	if *i >= len(data) {
@@ -136,7 +145,7 @@ func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
 		return nil, fmt.Errorf("invalid literal character: %s", string(c))
 	}
 
-	key, err := parseRockspecLiteral(data, i)
+	key, err := parseRockspecLiteral(data, i, locals)
 	if err != nil {
 		return nil, err
 	}
@@ -147,6 +156,16 @@ func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
 		return nil, fmt.Errorf("unexpected end of node at %d", *i)
 	}
 
+	if key == "local" {
+		err := parseLocal(data, i, locals)
+		if err != nil {
+			return nil, err
+		}
+		return &rockspecNode{
+			key: ",",
+		}, nil
+	}
+
 	c = data[*i]
 	if c != '=' {
 		return nil, fmt.Errorf("unexpected character: %s", string(c))
@@ -159,6 +178,14 @@ func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
 		return nil, fmt.Errorf("unexpected end of node at %d", *i)
 	}
 
+	if key == "build" {
+		skipBuildNode(data, i)
+
+		return &rockspecNode{
+			key: ",",
+		}, nil
+	}
+
 	c = data[*i]
 
 	switch c {
@@ -180,7 +207,7 @@ func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
 
 		parsing.SkipWhitespace(data, i)
 
-		obj, err := parseRockspecBlock(data, i)
+		obj, err := parseRockspecBlock(data, i, locals)
 
 		if err != nil {
 			return nil, err
@@ -190,16 +217,10 @@ func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
 		return &rockspecNode{
 			key, value,
 		}, nil
-	case '"', '\'':
-		str, err := parseRockspecString(data, i)
-
-		if err != nil {
-			return nil, err
-		}
-		value := str.value
-
+	case '(':
+		skipExpression(data, i)
 		return &rockspecNode{
-			key, value,
+			key: ",",
 		}, nil
 	case '[':
 		offset := *i + 1
@@ -214,7 +235,7 @@ func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
 
 		*i++
 
-		str, err := parseRockspecString(data, i)
+		str, err := parseRockspecString(data, i, locals)
 
 		if err != nil {
 			return nil, err
@@ -234,10 +255,18 @@ func parseRockspecNode(data []byte, i *int) (*rockspecNode, error) {
 		}, nil
 	}
 
-	return nil, nil
+	value, err := parseRockspecValue(data, i, locals, "")
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &rockspecNode{
+		key, value,
+	}, nil
 }
 
-func parseRockspecListItem(data []byte, i *int) (*rockspecNode, error) {
+func parseRockspecListItem(data []byte, i *int, locals map[string]string) (*rockspecNode, error) {
 	parsing.SkipWhitespace(data, i)
 
 	if *i >= len(data) {
@@ -269,14 +298,70 @@ func parseRockspecListItem(data []byte, i *int) (*rockspecNode, error) {
 		}, nil
 	}
 
-	str, err := parseRockspecString(data, i)
+	str, err := parseRockspecString(data, i, locals)
 	if err != nil {
 		return nil, err
 	}
 	return str, nil
 }
 
-func parseRockspecLiteral(data []byte, i *int) (string, error) {
+func parseRockspecValue(data []byte, i *int, locals map[string]string, initialValue string) (string, error) {
+	c := data[*i]
+
+	var value string
+
+	switch c {
+	case '"', '\'':
+		str, err := parseRockspecString(data, i, locals)
+
+		if err != nil {
+			return "", err
+		}
+		value = str.value.(string)
+	default:
+		local, err := parseRockspecLiteral(data, i, locals)
+
+		if err != nil {
+			return "", err
+		}
+
+		l, ok := locals[local]
+
+		if !ok {
+			return "", fmt.Errorf("unknown local: %s", local)
+		}
+
+		value = l
+	}
+
+	value = fmt.Sprintf("%s%s", initialValue, value)
+
+	skipWhitespaceNoNewLine(data, i)
+
+	if len(data) > *i+2 {
+		if data[*i] == '.' && data[*i+1] == '.' {
+			*i += 2
+
+			skipWhitespaceNoNewLine(data, i)
+
+			if *i >= len(data) {
+				return "", fmt.Errorf("unexpected end of expression at %d", *i)
+			}
+
+			v, err := parseRockspecValue(data, i, locals, value)
+
+			if err != nil {
+				return "", err
+			}
+
+			value = v
+		}
+	}
+
+	return value, nil
+}
+
+func parseRockspecLiteral(data []byte, i *int, locals map[string]string) (string, error) {
 	var buf bytes.Buffer
 out:
 	for *i < len(data) {
@@ -284,7 +369,7 @@ out:
 		switch {
 		case c == '[':
 			*i++
-			nested, err := parseRockspecString(data, i)
+			nested, err := parseRockspecString(data, i, locals)
 			if err != nil {
 				return "", err
 			}
@@ -303,7 +388,7 @@ out:
 	return buf.String(), nil
 }
 
-func parseRockspecString(data []byte, i *int) (*rockspecNode, error) {
+func parseRockspecString(data []byte, i *int, _ map[string]string) (*rockspecNode, error) {
 	delim := data[*i]
 	var endDelim byte
 	switch delim {
@@ -344,9 +429,171 @@ func parseComment(data []byte, i *int) {
 	}
 }
 
+//nolint:funlen
+func parseLocal(data []byte, i *int, locals map[string]string) error {
+	keys := []string{}
+	values := []string{}
+
+keys:
+	for {
+		parsing.SkipWhitespace(data, i)
+
+		key, err := parseRockspecLiteral(data, i, locals)
+		if err != nil {
+			return err
+		}
+
+		if key == "function" {
+			err := skipFunction(data, i)
+			if err != nil {
+				return err
+			}
+			return nil
+		}
+
+		keys = append(keys, key)
+
+		parsing.SkipWhitespace(data, i)
+
+		c := data[*i]
+
+		switch c {
+		case ',':
+			*i++
+			continue
+		case '=':
+			*i++
+			break keys
+		default:
+			return fmt.Errorf("unexpected character: %s", string(c))
+		}
+	}
+
+values:
+	for {
+		skipWhitespaceNoNewLine(data, i)
+
+		c := data[*i]
+
+		switch c {
+		case '"', '\'':
+			value, err := parseRockspecString(data, i, locals)
+
+			if err != nil {
+				return err
+			}
+			values = append(values, value.value.(string))
+		default:
+			ref, err := parseRockspecLiteral(data, i, locals)
+			if err != nil {
+				return err
+			}
+
+			// Skip if it's an expression
+			skipWhitespaceNoNewLine(data, i)
+			c := data[*i]
+
+			var value string
+
+			if c != '\n' && c != '\r' {
+				skipExpression(data, i)
+				value = ""
+			} else {
+				value = locals[ref]
+			}
+
+			values = append(values, value)
+		}
+
+		skipWhitespaceNoNewLine(data, i)
+
+		c = data[*i]
+
+		switch c {
+		case ',':
+			*i++
+			continue
+		case '\n', '\r':
+			parsing.SkipWhitespace(data, i)
+			break values
+		}
+	}
+
+	if len(keys) != len(values) {
+		return fmt.Errorf("expected %d values got %d", len(keys), len(values))
+	}
+
+	for i := 0; i < len(keys); i++ {
+		locals[keys[i]] = values[i]
+	}
+
+	return nil
+}
+
+func skipBuildNode(data []byte, i *int) {
+	bracesCount := 0
+
+	for *i < len(data) {
+		c := data[*i]
+
+		switch c {
+		case '{':
+			bracesCount++
+		case '}':
+			bracesCount--
+		}
+
+		if bracesCount == 0 {
+			return
+		}
+
+		*i++
+	}
+}
+
+func skipFunction(data []byte, i *int) error {
+	blocks := 1
+
+	for *i < len(data)-5 {
+		if parsing.IsWhitespace(data[*i]) {
+			switch {
+			case string(data[*i+1:*i+3]) == "if" && parsing.IsWhitespace(data[*i+3]):
+				blocks++
+				*i += 3
+			case string(data[*i+1:*i+4]) == "end" && parsing.IsWhitespace(data[*i+4]):
+				blocks--
+				*i += 4
+
+				if blocks == 0 {
+					return nil
+				}
+			default:
+				*i++
+			}
+		} else {
+			*i++
+		}
+	}
+
+	return fmt.Errorf("unterminated function at %d", *i)
+}
+
+func skipExpression(data []byte, i *int) {
+	parseComment(data, i)
+}
+
+func skipWhitespaceNoNewLine(data []byte, i *int) {
+	for *i < len(data) && (data[*i] == ' ' || data[*i] == '\t') {
+		*i++
+	}
+}
+
 func isLiteral(c byte) bool {
 	if c == '[' || c == ']' {
 		return true
 	}
+	if c == '.' {
+		return false
+	}
 	return parsing.IsLiteral(c)
 }

syft/pkg/cataloger/lua/rockspec_parser_test.go

@@ -60,6 +60,49 @@ multiline = [[
 	a multiline
 	string
 ]]
+`,
+		},
+		{
+			name: "variables",
+			content: `
+local foo = "bar"
+local baz = foo
+
+hello = baz
+`,
+		},
+		{
+			name: "multiple variables in one line",
+			content: `
+local foo, bar = "hello", "world"
+baz = foo
+test = bar
+`,
+		},
+		{
+			name: "skip expressions",
+			content: `
+test = (hello == "world") and "foo" or "bar"
+baz = "123"
+`,
+		},
+		{
+			name: "skip expressions in locals",
+			content: `
+local var1 = "foo"
+local var2 = var1 == "foo" and "true" or ("false")
+
+foo = "bar"
+`,
+		},
+		{
+			name: "concatenation",
+			content: `
+local foo = "bar"
+local baz = "123"
+hello = "world"..baz
+baz = foo.." "..baz
+test = foo .. baz
 `,
 		},
 		{
@@ -80,6 +123,17 @@ object = {
 	hello = "world"
 	-- this is another comment
 }
+`,
+		},
+		{
+			name: "content start with comment",
+			content: `
+foo = "bar"
+-- this is a comment
+object = {
+	-- this is another comment
+	hello = "world"
+}
 `,
 		},
 		{
@@ -91,6 +145,33 @@ list = {
 	-- "baz"
 	"hello"
 }
+`,
+		},
+		{
+			name: "skip build section",
+			content: `
+foo = "bar"
+build = {
+	a = {
+		{
+			content
+		}
+	}
+}
+bar = "baz"
+`,
+		},
+		{
+			name: "skip functions",
+			content: `
+local function test
+	if foo == bar then
+		if hello = world then
+			blah
+		end
+	end
+end
+test = "blah"
 `,
 		},
 		{
@@ -153,6 +234,20 @@ list = {
 	"bar",
 	-`,
 		},
+		{
+			name:    "undefined local",
+			wantErr: require.Error,
+			content: `
+test = hello
+		`,
+		},
+		{
+			name:    "unterminated concatenation",
+			wantErr: require.Error,
+			content: `
+local foo = "123"
+hello = foo..  `,
+		},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {

syft/pkg/cataloger/lua/test-fixtures/rockspec/luasyslog-2.0.1-1.rockspec

@@ -0,0 +1,36 @@
+local package_name = "luasyslog"
+local package_version = "2.0.1"
+local rockspec_revision = "1"
+local github_account_name = "lunarmodules"
+local github_repo_name = package_name
+
+
+package = package_name
+version = package_version.."-"..rockspec_revision
+source = {
+   url = "git://github.com/"..github_account_name.."/"..github_repo_name..".git",
+   branch = (package_version == "dev") and "main" or nil,
+   tag = (package_version ~= "dev") and package_version or nil,
+}
+description = {
+   summary = "Syslog logging for Lua",
+   detailed = [[
+     Addon for LuaLogging to log to the system log on unix systems.
+     Can also be used without LuaLogging to directly write to syslog.
+   ]],
+   license = "MIT/X11",
+   homepage = "https://github.com/"..github_account_name.."/"..github_repo_name,
+}
+dependencies = {
+   "lua >= 5.1",
+   "lualogging >= 1.4.0, < 2.0.0",
+}
+build = {
+   type = "builtin",
+   modules = {
+      lsyslog = {
+         sources = "lsyslog.c",
+      },
+      ["logging.syslog"] = "syslog.lua",
+   }
+}