/*
* Sanity checks public PGP key, to make sure it's valid for encrypting MIME entities.
*/
static void SanityCheckCryptographyKey(PgpPublicKey key)
{
if (!key.IsEncryptionKey)
{
throw new ArgumentException($"Key with fingerprint of '{PgpHelpers.GetFingerprint(key)}' is not an encryption key");
}
if (key.IsRevoked())
{
throw new ArgumentException($"Key with fingerprint of '{PgpHelpers.GetFingerprint(key)}' is revoked");
}
}
/*
* Cryptographically signs an entity.
*/
static MultipartSigned Sign(
MimeEntity entity,
string armoredPrivateKey,
string keyPassword)
{
var algo = DigestAlgorithm.Sha256;
using (var ctx = new CreatePgpMimeContext {
Password = keyPassword
})
{
return(MultipartSigned.Create(
ctx,
PgpHelpers.GetSecretKeyFromAsciiArmored(armoredPrivateKey),
algo,
entity));
}
}
/*
* Cryptographically signs and encrypts an entity.
*/
static MultipartEncrypted SignAndEncrypt(
MimeEntity entity,
Node encryptionNode,
string armoredPrivateKey,
string keyPassword)
{
var algo = DigestAlgorithm.Sha256;
using (var ctx = new CreatePgpMimeContext {
Password = keyPassword
})
{
return(MultipartEncrypted.SignAndEncrypt(
ctx,
PgpHelpers.GetSecretKeyFromAsciiArmored(armoredPrivateKey),
algo,
GetEncryptionKeys(encryptionNode),
entity));
}
}
/*
* Returns all public keys referenced in lambda object, somehow.
* Values can exist either as value of node, and/or valuesof children of node given.
*/
static IEnumerable <PgpPublicKey> GetEncryptionKeys(Node encryptionKey)
{
// Returning any public encryption key found in value of node first.
if (encryptionKey.Value != null)
{
var result = PgpHelpers.GetPublicKeyFromAsciiArmored(encryptionKey.GetEx <string>());
// Sanity checking key, before returning to caller.
SanityCheckCryptographyKey(result);
yield return(result);
}
// Looping through children, in case caller provided a collection of encryption keys, that should all be used.
foreach (var idx in encryptionKey.Children)
{
var result = PgpHelpers.GetPublicKeyFromAsciiArmored(idx.GetEx <string>());
// Sanity checking key, before returning to caller.
SanityCheckCryptographyKey(result);
yield return(result);
}
}
