Wildcard support for x509_cert files (#6952)

* Accept standard unix glob matching rules

* comply with indentation

* update readme

* move globing expand and url parsing into Init()

* chore: rebase branch on upstream master

* rename refreshFilePaths to expandFilePaths
* expandFilePaths handles '/path/to/*.pem' and 'files:///path/to/*.pem'
* update sample config

* fix: recompile files globing pattern at every gather tic

 * add var globFilePathsToUrls to stack files path
 * add var globpaths to stack compiled globpath
 * rework sourcesToURLs to compile files path and stack them
 * rename expandFilePaths to expandFilePathsToUrls
 * rework expandFilePathsToUrls to only match compiled globpath
 * rework the `Gather` ticker to match globpath at each call

* fix: comply with requested changes

 * add specifics regarding relative paths in sample config
 * add logger and use it in expandFilePathsToUrls()
 * precompile glob for `files://`, `/` and `://`

* fix: update README to match last changes

* fix: comply with last requested changes

 * rename expandFilePathsToUrls() to collectCertURLs()
 * collectCertURLs() now returns []*url.URL to avoid extra field
globFilePathsToUrls in structure
 * update the Gather() ticker accordingly

* fix(windows): do not try to compile glopath for windows path as it's not supposed to be supported by the OS

* fix(ci): apply go fmt

* fix(ci): empty-lines/import-shadowing

Co-authored-by: Anthony LE BERRE <aleberre@vente-privee.com>

plugins/inputs/x509_cert/README.md

@@ -9,8 +9,10 @@ file or network connection.
 ```toml
 # Reads metrics from a SSL certificate
 [[inputs.x509_cert]]
-  ## List certificate sources
-  sources = ["/etc/ssl/certs/ssl-cert-snakeoil.pem", "https://example.org:443"]
+  ## List certificate sources, support wildcard expands for files
+  ## Prefix your entry with 'file://' if you intend to use relative paths
+  sources = ["/etc/ssl/certs/ssl-cert-snakeoil.pem", "tcp://example.org:443",
+            "/etc/mycerts/*.mydomain.org.pem", "file:///path/to/*.pem"]
 
   ## Timeout for SSL connection
   # timeout = "5s"

plugins/inputs/x509_cert/x509_cert.go

@@ -16,13 +16,16 @@ import (
 
 	"github.com/influxdata/telegraf"
 	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/internal/globpath"
 	_tls "github.com/influxdata/telegraf/plugins/common/tls"
 	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
 const sampleConfig = `
   ## List certificate sources
-  sources = ["/etc/ssl/certs/ssl-cert-snakeoil.pem", "tcp://example.org:443"]
+  ## Prefix your entry with 'file://' if you intend to use relative paths
+  sources = ["/etc/ssl/certs/ssl-cert-snakeoil.pem", "tcp://example.org:443",
+            "/etc/mycerts/*.mydomain.org.pem", "file:///path/to/*.pem"]
 
   ## Timeout for SSL connection
   # timeout = "5s"
@@ -45,6 +48,9 @@ type X509Cert struct {
 	ServerName string            `toml:"server_name"`
 	tlsCfg     *tls.Config
 	_tls.ClientConfig
+	locations []*url.URL
+	globpaths []*globpath.GlobPath
+	Log       telegraf.Logger
 }
 
 // Description returns description of the plugin.
@@ -57,20 +63,31 @@ func (c *X509Cert) SampleConfig() string {
 	return sampleConfig
 }
 
-func (c *X509Cert) locationToURL(location string) (*url.URL, error) {
-	if strings.HasPrefix(location, "/") {
-		location = "file://" + location
-	}
-	if strings.Index(location, ":\\") == 1 {
-		location = "file://" + filepath.ToSlash(location)
+func (c *X509Cert) sourcesToURLs() error {
+	for _, source := range c.Sources {
+		if strings.HasPrefix(source, "file://") ||
+			strings.HasPrefix(source, "/") ||
+			strings.Index(source, ":\\") != 1 {
+			source = filepath.ToSlash(strings.TrimPrefix(source, "file://"))
+			g, err := globpath.Compile(source)
+			if err != nil {
+				return fmt.Errorf("could not compile glob %v: %v", source, err)
+			}
+			c.globpaths = append(c.globpaths, g)
+		} else {
+			if strings.Index(source, ":\\") == 1 {
+				source = "file://" + filepath.ToSlash(source)
+			}
+			u, err := url.Parse(source)
+			if err != nil {
+				return fmt.Errorf("failed to parse cert location - %s", err.Error())
+			}
+
+			c.locations = append(c.locations, u)
+		}
 	}
 
-	u, err := url.Parse(location)
-	if err != nil {
-		return nil, fmt.Errorf("failed to parse cert location - %s", err.Error())
-	}
-
-	return u, nil
+	return nil
 }
 
 func (c *X509Cert) serverName(u *url.URL) (string, error) {
@@ -204,25 +221,45 @@ func getTags(cert *x509.Certificate, location string) map[string]string {
 	return tags
 }
 
+func (c *X509Cert) collectCertURLs() ([]*url.URL, error) {
+	var urls []*url.URL
+
+	for _, path := range c.globpaths {
+		files := path.Match()
+		if len(files) <= 0 {
+			c.Log.Errorf("could not find file: %v", path)
+			continue
+		}
+		for _, file := range files {
+			file = "file://" + file
+			u, err := url.Parse(file)
+			if err != nil {
+				return urls, fmt.Errorf("failed to parse cert location - %s", err.Error())
+			}
+			urls = append(urls, u)
+		}
+	}
+
+	return urls, nil
+}
+
 // Gather adds metrics into the accumulator.
 func (c *X509Cert) Gather(acc telegraf.Accumulator) error {
 	now := time.Now()
+	collectedUrls, err := c.collectCertURLs()
+	if err != nil {
+		acc.AddError(fmt.Errorf("cannot get file: %s", err.Error()))
+	}
 
-	for _, location := range c.Sources {
-		u, err := c.locationToURL(location)
-		if err != nil {
-			acc.AddError(err)
-			return nil
-		}
-
-		certs, err := c.getCert(u, c.Timeout.Duration)
+	for _, location := range append(c.locations, collectedUrls...) {
+		certs, err := c.getCert(location, c.Timeout.Duration*time.Second)
 		if err != nil {
 			acc.AddError(fmt.Errorf("cannot get SSL cert '%s': %s", location, err.Error()))
 		}
 
 		for i, cert := range certs {
 			fields := getFields(cert, now)
-			tags := getTags(cert, location)
+			tags := getTags(cert, location.String())
 
 			// The first certificate is the leaf/end-entity certificate which needs DNS
 			// name validation against the URL hostname.
@@ -231,7 +268,7 @@ func (c *X509Cert) Gather(acc telegraf.Accumulator) error {
 				KeyUsages:     []x509.ExtKeyUsage{x509.ExtKeyUsageAny},
 			}
 			if i == 0 {
-				opts.DNSName, err = c.serverName(u)
+				opts.DNSName, err = c.serverName(location)
 				if err != nil {
 					return err
 				}
@@ -263,6 +300,11 @@ func (c *X509Cert) Gather(acc telegraf.Accumulator) error {
 }
 
 func (c *X509Cert) Init() error {
+	err := c.sourcesToURLs()
+	if err != nil {
+		return err
+	}
+
 	tlsCfg, err := c.ClientConfig.TLSConfig()
 	if err != nil {
 		return err