start on verify command

.gitignore

@@ -0,0 +1 @@
+gss

command_verify.go

@@ -1,5 +1,115 @@
 package main
 
+import (
+	"bytes"
+	"encoding/pem"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/mastahyeti/cms"
+)
+
 func commandVerify() int {
+	if len(fileArgs) < 2 {
+		return verifyAttached()
+	}
+
+	return verifyDetached()
+}
+
+func verifyAttached() int {
+	var (
+		f   *os.File
+		err error
+	)
+
+	// Read in signature
+	if len(fileArgs) == 1 {
+		if f, err = os.Open(fileArgs[0]); err != nil {
+			panic(err)
+		}
+		defer f.Close()
+	} else {
+		f = os.Stdin
+	}
+
+	buf := new(bytes.Buffer)
+	if _, err = io.Copy(buf, f); err != nil {
+		panic(err)
+	}
+
+	// Try decoding as PEM
+	var der []byte
+	if blk, _ := pem.Decode(buf.Bytes()); blk != nil {
+		der = blk.Bytes
+	} else {
+		der = buf.Bytes()
+	}
+
+	// Parse signature
+	sd, err := cms.ParseSignedData(der)
+	if err != nil {
+		panic(err)
+	}
+
+	// Verify signature
+	if err = sd.Verify(); err != nil {
+		fmt.Printf("Sinature verification failed: %s\n", err.Error())
+		return 1
+	}
+
+	fmt.Println("Signature verified")
+	return 0
+}
+
+func verifyDetached() int {
+	// Read in signature
+	f, err := os.Open(fileArgs[0])
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+
+	buf := new(bytes.Buffer)
+	if _, err = io.Copy(buf, f); err != nil {
+		panic(err)
+	}
+
+	// Try decoding as PEM
+	var der []byte
+	if blk, _ := pem.Decode(buf.Bytes()); blk != nil {
+		der = blk.Bytes
+	} else {
+		der = buf.Bytes()
+	}
+
+	// Parse signature
+	sd, err := cms.ParseSignedData(der)
+	if err != nil {
+		panic(err)
+	}
+
+	// Read in signed data
+	if fileArgs[1] == "-" {
+		f = os.Stdin
+	} else {
+		if f, err = os.Open(fileArgs[1]); err != nil {
+			panic(err)
+		}
+		defer f.Close()
+	}
+
+	// Verify signature
+	buf.Reset()
+	if _, err = io.Copy(buf, f); err != nil {
+		panic(err)
+	}
+	if err = sd.VerifyDetached(buf.Bytes()); err != nil {
+		fmt.Printf("Sinature verification failed: %s\n", err.Error())
+		return 1
+	}
+
+	fmt.Println("Signature verified")
 	return 0
 }

main.go

@@ -19,12 +19,14 @@ var (
 	armorFlag      = getopt.BoolLong("armor", 'a', "create ascii armored output")
 	statusFdOpt    = getopt.IntLong("status-fd", 0, -1, "Write special status strings to the file descriptor n.", "n")
 	keyFormatOpt   = getopt.EnumLong("keyid-format", 0, []string{"short", "0xshort", "long", "0xlong"}, "short", "Select  how  to  display key IDs.", "{short|0xshort|long|0xlong}")
+	fileArgs       []string
 )
 
 func main() {
 	getopt.HelpColumn = 30
 	getopt.SetParameters("[files]")
 	getopt.Parse()
+	fileArgs = getopt.Args()
 
 	status := 1
 	if *helpFlag {