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dkim: Implement internal dkim signing and verification
This patch implements internal DKIM signing and verification.
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,260 @@ | ||
package main | ||
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||
import ( | ||
"bytes" | ||
"context" | ||
"crypto" | ||
"crypto/ed25519" | ||
"crypto/rand" | ||
"crypto/rsa" | ||
"crypto/x509" | ||
"encoding/base64" | ||
"encoding/pem" | ||
"fmt" | ||
"io" | ||
"net/mail" | ||
"os" | ||
"path" | ||
"path/filepath" | ||
"strings" | ||
"time" | ||
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"blitiri.com.ar/go/chasquid/internal/dkim" | ||
"blitiri.com.ar/go/chasquid/internal/envelope" | ||
"blitiri.com.ar/go/chasquid/internal/normalize" | ||
) | ||
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func dkimSign() { | ||
domain := args["$2"] | ||
selector := args["$3"] | ||
keyPath := args["$4"] | ||
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msg, err := io.ReadAll(os.Stdin) | ||
if err != nil { | ||
Fatalf("%v", err) | ||
} | ||
msg = normalize.ToCRLF(msg) | ||
|
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if domain == "" { | ||
domain = getDomainFromMsg(msg) | ||
} | ||
if selector == "" { | ||
selector = findSelectorForDomain(domain) | ||
} | ||
if keyPath == "" { | ||
keyPath = keyPathFor(domain, selector) | ||
} | ||
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signer := &dkim.Signer{ | ||
Domain: domain, | ||
Selector: selector, | ||
Signer: loadPrivateKey(keyPath), | ||
} | ||
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ctx := context.Background() | ||
if _, verbose := args["-v"]; verbose { | ||
ctx = dkim.WithTraceFunc(ctx, | ||
func(format string, args ...interface{}) { | ||
fmt.Fprintf(os.Stderr, format+"\n", args...) | ||
}) | ||
} | ||
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header, err := signer.Sign(ctx, string(msg)) | ||
if err != nil { | ||
Fatalf("Error signing message: %v", err) | ||
} | ||
fmt.Printf("DKIM-Signature: %s\r\n", | ||
strings.ReplaceAll(header, "\r\n", "\r\n\t")) | ||
} | ||
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func dkimVerify() { | ||
msg, err := io.ReadAll(os.Stdin) | ||
if err != nil { | ||
Fatalf("%v", err) | ||
} | ||
msg = normalize.ToCRLF(msg) | ||
|
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ctx := context.Background() | ||
if _, verbose := args["-v"]; verbose { | ||
ctx = dkim.WithTraceFunc(ctx, | ||
func(format string, args ...interface{}) { | ||
fmt.Fprintf(os.Stderr, format+"\n", args...) | ||
}) | ||
} | ||
|
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results, err := dkim.VerifyMessage(ctx, string(msg)) | ||
if err != nil { | ||
Fatalf("Error verifying message: %v", err) | ||
} | ||
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hostname, _ := os.Hostname() | ||
ar := "Authentication-Results: " + hostname + "\r\n\t" | ||
ar += strings.ReplaceAll( | ||
results.AuthenticationResults(), "\r\n", "\r\n\t") | ||
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fmt.Println(ar) | ||
} | ||
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func dkimDNS() { | ||
domain := args["$2"] | ||
selector := args["$3"] | ||
keyPath := args["$4"] | ||
|
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if domain == "" { | ||
Fatalf("Error: missing domain parameter") | ||
} | ||
if selector == "" { | ||
selector = findSelectorForDomain(domain) | ||
} | ||
if keyPath == "" { | ||
keyPath = keyPathFor(domain, selector) | ||
} | ||
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fmt.Println(dnsRecordFor(domain, selector, loadPrivateKey(keyPath))) | ||
} | ||
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func dnsRecordFor(domain, selector string, private crypto.Signer) string { | ||
public := private.Public() | ||
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var err error | ||
algoStr := "" | ||
pubBytes := []byte{} | ||
switch private.(type) { | ||
case *rsa.PrivateKey: | ||
algoStr = "rsa" | ||
pubBytes, err = x509.MarshalPKIXPublicKey(public) | ||
case ed25519.PrivateKey: | ||
algoStr = "ed25519" | ||
pubBytes = public.(ed25519.PublicKey) | ||
} | ||
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if err != nil { | ||
Fatalf("Error marshaling public key: %v", err) | ||
} | ||
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return fmt.Sprintf( | ||
"%s._domainkey.%s\tTXT\t\"v=DKIM1; k=%s; p=%s\"", | ||
selector, domain, | ||
algoStr, base64.StdEncoding.EncodeToString(pubBytes)) | ||
} | ||
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func dkimKeygen() { | ||
domain := args["$2"] | ||
selector := args["$3"] | ||
keyPath := args["$4"] | ||
algo := args["--algo"] | ||
|
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if domain == "" { | ||
Fatalf("Error: missing domain parameter") | ||
} | ||
if selector == "" { | ||
selector = time.Now().UTC().Format("20060102") | ||
} | ||
if keyPath == "" { | ||
keyPath = keyPathFor(domain, selector) | ||
} | ||
|
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if _, err := os.Stat(keyPath); !os.IsNotExist(err) { | ||
Fatalf("Error: key already exists at %q", keyPath) | ||
} | ||
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var private crypto.Signer | ||
var err error | ||
switch algo { | ||
case "", "rsa3072": | ||
private, err = rsa.GenerateKey(rand.Reader, 3072) | ||
case "rsa4096": | ||
private, err = rsa.GenerateKey(rand.Reader, 4096) | ||
case "ed25519": | ||
_, private, err = ed25519.GenerateKey(rand.Reader) | ||
default: | ||
Fatalf("Error: unsupported algorithm %q", algo) | ||
} | ||
|
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if err != nil { | ||
Fatalf("Error generating key: %v", err) | ||
} | ||
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privB, err := x509.MarshalPKCS8PrivateKey(private) | ||
if err != nil { | ||
Fatalf("Error marshaling private key: %v", err) | ||
} | ||
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f, err := os.OpenFile(keyPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0660) | ||
if err != nil { | ||
Fatalf("Error creating key file %q: %v", keyPath, err) | ||
} | ||
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block := &pem.Block{ | ||
Type: "PRIVATE KEY", | ||
Bytes: privB, | ||
} | ||
if err := pem.Encode(f, block); err != nil { | ||
Fatalf("Error PEM-encoding key: %v", err) | ||
} | ||
f.Close() | ||
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fmt.Printf("Key written to %q\n\n", keyPath) | ||
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fmt.Println(dnsRecordFor(domain, selector, private)) | ||
} | ||
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func keyPathFor(domain, selector string) string { | ||
return path.Clean(fmt.Sprintf("%s/domains/%s/dkim:%s.pem", | ||
configDir, domain, selector)) | ||
} | ||
|
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func getDomainFromMsg(msg []byte) string { | ||
m, err := mail.ReadMessage(bytes.NewReader(msg)) | ||
if err != nil { | ||
Fatalf("Error parsing message: %v", err) | ||
} | ||
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addr, err := mail.ParseAddress(m.Header.Get("From")) | ||
if err != nil { | ||
Fatalf("Error parsing From: header: %v", err) | ||
} | ||
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return envelope.DomainOf(addr.Address) | ||
} | ||
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func findSelectorForDomain(domain string) string { | ||
glob := path.Clean(configDir + "/domains/" + domain + "/dkim:*.pem") | ||
ms, err := filepath.Glob(glob) | ||
if err != nil { | ||
Fatalf("Error finding DKIM keys: %v", err) | ||
} | ||
for _, m := range ms { | ||
base := filepath.Base(m) | ||
selector := strings.TrimPrefix(base, "dkim:") | ||
selector = strings.TrimSuffix(selector, ".pem") | ||
return selector | ||
} | ||
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Fatalf("No DKIM keys found in %q", glob) | ||
return "" | ||
} | ||
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func loadPrivateKey(path string) crypto.Signer { | ||
key, err := os.ReadFile(path) | ||
if err != nil { | ||
Fatalf("Error reading private key from %q: %v", path, err) | ||
} | ||
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block, _ := pem.Decode(key) | ||
if block == nil { | ||
Fatalf("Error decoding PEM block") | ||
} | ||
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switch strings.ToUpper(block.Type) { | ||
case "PRIVATE KEY": | ||
k, err := x509.ParsePKCS8PrivateKey(block.Bytes) | ||
if err != nil { | ||
Fatalf("Error parsing private key: %v", err) | ||
} | ||
return k.(crypto.Signer) | ||
default: | ||
Fatalf("Unsupported key type: %s", block.Type) | ||
return nil | ||
} | ||
} |
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