feat(pcr0tool): Add verb pcrread

cmd/pcr0tool/commands/pcrread/command.go

@@ -0,0 +1,79 @@
+package pcrread
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/google/go-tpm/tpm2"
+
+	"github.com/9elements/converged-security-suite/v2/pkg/bootflow/subsystems/trustchains/tpm/pcr"
+	"github.com/9elements/converged-security-suite/v2/pkg/tpm"
+)
+
+func assertNoError(err error) {
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func usageAndExit() {
+	flag.Usage()
+	os.Exit(2)
+}
+
+// Command is the implementation of `commands.Command`.
+type Command struct {
+	hashAlgo *string
+}
+
+// Usage prints the syntax of arguments for this command
+func (cmd Command) Usage() string {
+	return "<PCR index>"
+}
+
+// Description explains what this verb commands to do
+func (cmd Command) Description() string {
+	return "read the PCR value"
+}
+
+// SetupFlagSet is called to allow the command implementation
+// to setup which option flags it has.
+func (cmd *Command) SetupFlagSet(flag *flag.FlagSet) {
+	cmd.hashAlgo = flag.String("hash-algo", tpm2.AlgSHA1.String(), "")
+}
+
+// Execute is the main function here. It is responsible to
+// start the execution of the command.
+//
+// `args` are the arguments left unused by verb itself and options.
+func (cmd Command) Execute(ctx context.Context, args []string) {
+	if len(args) < 1 {
+		_, _ = fmt.Fprintf(flag.CommandLine.Output(), "error: no PCR index is specified\n")
+		usageAndExit()
+	}
+	if len(args) > 1 {
+		_, _ = fmt.Fprintf(flag.CommandLine.Output(), "error: too many parameters\n")
+		usageAndExit()
+	}
+	pcrIndexString := args[0]
+	pcrIndex, err := strconv.ParseUint(pcrIndexString, 10, 64)
+	assertNoError(err)
+
+	hashAlgo := tpm2.AlgUnknown
+	for _, alg := range []tpm2.Algorithm{tpm2.AlgSHA1, tpm2.AlgSHA256} {
+		if strings.EqualFold(*cmd.hashAlgo, alg.String()) {
+			hashAlgo = alg
+		}
+	}
+	if hashAlgo == tpm2.AlgUnknown {
+		panic(fmt.Errorf("algo '%s' is unknown", *cmd.hashAlgo))
+	}
+	pcr, err := tpm.ReadPCRFromTPM(pcr.ID(pcrIndex), hashAlgo)
+	assertNoError(err)
+	fmt.Printf("%X\n", pcr)
+}

cmd/pcr0tool/main.go

@@ -14,6 +14,7 @@ import (
 	"github.com/9elements/converged-security-suite/v2/cmd/pcr0tool/commands/displayfwinfo"
 	"github.com/9elements/converged-security-suite/v2/cmd/pcr0tool/commands/dumpfit"
 	"github.com/9elements/converged-security-suite/v2/cmd/pcr0tool/commands/dumpregisters"
+	"github.com/9elements/converged-security-suite/v2/cmd/pcr0tool/commands/pcrread"
 	"github.com/9elements/converged-security-suite/v2/cmd/pcr0tool/commands/printnodes"
 	"github.com/9elements/converged-security-suite/v2/cmd/pcr0tool/commands/sum"
 	validatesecurity "github.com/9elements/converged-security-suite/v2/cmd/pcr0tool/commands/validate_security"
@@ -33,6 +34,7 @@ var knownCommands = map[string]commands.Command{
 	"dump_registers":               &dumpregisters.Command{},
 	"printnodes":                   &printnodes.Command{},
 	"validate_security":            &validatesecurity.Command{},
+	"pcrread":                      &pcrread.Command{},
 	"sum":                          &sum.Command{},
 }