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FairEmail
mirror of https://github.com/M66B/FairEmail.git
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Native DKIM improvements

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pull/212/head
M66B 3 years ago
parent 4aa93c46f6
commit 0f393841a8
1 changed files with 49 additions and 14 deletions
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61
app/src/main/java/eu/faircode/email/MessageHelper.java
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@ -1988,7 +1988,7 @@ public class MessageHelper {
return true;
}
boolean verifyDKIM(Context context) throws MessagingException {
Boolean verifyDKIM(Context context) throws MessagingException {
// Proof of concept, doesn't work 100% reliable
if (true)
return true;
@ -1996,14 +1996,25 @@ public class MessageHelper {
// https://datatracker.ietf.org/doc/html/rfc6376/
String[] headers = imessage.getHeader("DKIM-Signature");
if (headers == null || headers.length < 1)
return false;
return null;
boolean valid = false;
for (String header : headers) {
Map<String, String> kv = getKeyValues(MimeUtility.unfold(header));
String a = kv.get("a");
if (!"rsa-sha256".equals(a))
String halgo;
String salgo;
if ("rsa-sha1".equals(a)) {
halgo = "SHA-1";
salgo = "SHA1withRSA";
} else if ("rsa-sha256".equals(a)) {
halgo = "SHA-256";
salgo = "SHA256withRSA";
} else {
Log.i("DKIM a=" + a);
return false;
}
try {
String dns = kv.get("s") + "._domainkey." + kv.get("d");
@ -2017,20 +2028,35 @@ public class MessageHelper {
String[] c = kv.get("c").split("/");
StringBuilder head = new StringBuilder();
// TODO: check presence from
Log.i("DKIM headers=" + kv.get("h"));
List<String> _h = new ArrayList<>();
_h.addAll(Arrays.asList(kv.get("h").split(":")));
_h.add("DKIM-Signature");
List<String> processed = new ArrayList<>();
for (String n : _h) {
n = n.trim();
if (processed.contains(n)) {
Log.i("DKIM duplicate header='" + n + "'");
continue;
}
processed.add(n);
String[] h = ("DKIM-Signature".equals(n) ? new String[]{header} : imessage.getHeader(n));
// TODO: missing header = \r\n?
if (h == null) {
Log.i("DKIM missing header='" + n + "'");
continue;
}
for (int i = h.length - 1; i >= 0; i--) {
String v = h[i];
if ("DKIM-Signature".equals(n)) {
int b = v.lastIndexOf(" b=");
v = v.substring(0, b + 2);
int s = v.indexOf(";", b + 3);
v = v.substring(0, b + 3) + (s < 0 ? "" : v.substring(s));
Log.i("DKIM v=" + v);
}
} else
Log.i("DKIM " + n + "=" + v.replaceAll("\\r?\\n", "|"));
if ("simple".equals(c[0]))
head.append(n).append(": ")
@ -2051,7 +2077,7 @@ public class MessageHelper {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
Helper.copy(imessage.getRawInputStream(), bos);
String body = bos.toString(); // TODO: charset
if ("simple".equals(c[1])) {
if ("simple".equals(c[c.length > 1 ? 1 : 0])) {
if (TextUtils.isEmpty(body))
body = "\r\n";
else if (!body.endsWith("\r\n"))
@ -2060,7 +2086,7 @@ public class MessageHelper {
while (body.endsWith("\r\n\r\n"))
body = body.substring(0, body.length() - 2);
}
} else if ("relaxed".equals(c[1])) {
} else if ("relaxed".equals(c[c.length > 1 ? 1 : 0])) {
if (TextUtils.isEmpty(body))
body = "";
else {
@ -2076,7 +2102,7 @@ public class MessageHelper {
Log.i("DKIM body=" + body.replace("\r\n", "|"));
byte[] bh = MessageDigest.getInstance("SHA-256").digest(body.getBytes()); // TODO: charset
byte[] bh = MessageDigest.getInstance(halgo).digest(body.getBytes()); // TODO: charset
Log.i("DKIM bh=" + Base64.encodeToString(bh, Base64.NO_WRAP) + "/" + kv.get("bh"));
String p = dk.get("p").replaceAll("\\s+", "");
@ -2085,25 +2111,34 @@ public class MessageHelper {
X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(Base64.decode(p, Base64.DEFAULT));
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);
Signature sig = Signature.getInstance("SHA256withRSA"); // a=
Signature sig = Signature.getInstance(salgo); // a=
String s = kv.get("b").replaceAll("\\s+", "");
Log.i("DKIM signature=" + s);
byte[] signature = Base64.decode(s, Base64.DEFAULT);
// TODO: check signature length
sig.initVerify(pubKey);
sig.update(head.toString().getBytes());
Log.i("DKIM valid=" + sig.verify(signature) +
boolean verified = sig.verify(signature);
Log.i("DKIM valid=" + verified +
" dns=" + dns +
" results=" + getAuthentication("dkim", getAuthentication()) +
" from=" + formatAddresses(getFrom()));
if (verified)
valid = true;
}
} catch (Throwable ex) {
Log.i("DKIM " + ex);
Log.i("DKIM error=" + ex);
Log.e(ex);
}
}
return true;
Log.i("DKIM passed=" + valid);
return valid;
}
Address[] getMailFrom(String[] headers) {

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