add api for public keys

This enables pkictl to generate public keys from private keys in the rsa
and ecdsa format.

1 files changed, 46 insertions, 0 deletions

diff --git a/public_key.go b/public_key.go
new file mode 100644
index 0000000..fc1ea23
--- /dev/null
+++ b/public_key.go
@@ -0,0 +1,46 @@
+package main
+
+import (
+  "crypto/x509"
+  "encoding/pem"
+  "flag"
+  "fmt"
+  "io"
+  "os"
+)
+
+type (
+  PublicKeyFlags struct {
+    PrivateKeyPath string
+    Output         string
+
+    output_stream io.WriteCloser // the actual stream to the output
+  }
+)
+
+func create_public_key() {
+  var err error
+  flags := parse_public_key_flags()
+  flags.output_stream, err = open_output_stream(flags.Output)
+  if err != nil {
+    crash_with_help(2, fmt.Sprintf("Error when creating file %s: %s", flags.Output, err))
+  }
+  priv_key := load_private_key(flags.PrivateKeyPath)
+  marshal, err := x509.MarshalPKIXPublicKey(priv_key.Public())
+  if err != nil {
+    crash_with_help(2, fmt.Sprintf("Problems marshalling the public key: %s", err))
+  }
+
+  block := &pem.Block{Type: TypeLabelPubKey, Bytes: marshal}
+  pem.Encode(flags.output_stream, block)
+}
+
+func parse_public_key_flags() PublicKeyFlags {
+  flags := PublicKeyFlags{}
+  fs := flag.NewFlagSet("create-public", flag.ExitOnError)
+  fs.StringVar(&flags.PrivateKeyPath, "private-key", "", "path to the private key file")
+  fs.StringVar(&flags.Output, "output", "STDOUT", "path where the generated csr should be stored")
+  fs.Parse(os.Args[2:])
+
+  return flags
+}