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Add ca-key flag to enable generating multiple certs from the same CA #2

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Add ca-key flag to enable generating multiple certs from the same CA #2

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2 changes: 2 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,8 @@ certs/leaf.pem: | $(GENERATE_TLS_CERT)
generate_cert: certs/leaf.pem | $(GENERATE_TLS_CERT)
```

There is an optional `--ca-key` flag to use an existing CA key instead of generating one.

## Client Side

Here's how to make requests that validate, using your new TLS certificates.
Expand Down
35 changes: 30 additions & 5 deletions generate.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ import (
"encoding/pem"
"flag"
"fmt"
"io/ioutil"
"log"
"math/big"
"net"
Expand All @@ -24,9 +25,10 @@ var (
validFrom = flag.String("start-date", "", "Creation date formatted as Jan 1 15:04:05 2011 (default now)")
validFor = flag.Duration("duration", 365*24*time.Hour, "Duration that certificate is valid for")
version = flag.Bool("version", false, "Print the version string")
caKeyPath = flag.String("ca-key", "", "A root ca key that will be used to sign certificates. If omitted, a new root key will be generated.")
)

const Version = "0.1"
const Version = "0.1.1"

func main() {
flag.Parse()
Expand Down Expand Up @@ -56,11 +58,18 @@ func main() {
if err != nil {
log.Fatalf("failed to generate serial number: %s", err)
}
rootKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
panic(err)

var rootKey *ecdsa.PrivateKey
if len(*caKeyPath) == 0 {
rootKey, err = ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
panic(err)
}
keyToFile("root.key", rootKey)
} else {
log.Printf("Using %s as the root key\n", *caKeyPath)
rootKey = keyFromFile(*caKeyPath)
}
keyToFile("root.key", rootKey)

rootTemplate := x509.Certificate{
SerialNumber: serialNumber,
Expand Down Expand Up @@ -201,6 +210,22 @@ func keyToFile(filename string, key *ecdsa.PrivateKey) {
}
}

// keyFromFile reads in a PEM serialiazed key from |filename| and parses it as a ec private key
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Extra 'a' in "serialized"

func keyFromFile(filename string) *ecdsa.PrivateKey {
pemBts, err := ioutil.ReadFile(*caKeyPath)
if err != nil {
panic(err)
}

block, _ := pem.Decode(pemBts)
key, err := x509.ParseECPrivateKey(block.Bytes)
if err != nil {
panic(err)
}

return key
}

func certToFile(filename string, derBytes []byte) {
certOut, err := os.Create(filename)
if err != nil {
Expand Down