implement gmp_rsa_private_key.decrypt()

diff --git a/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c b/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c
index 8809307..b395a80 100644 (file)
--- a/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c
+++ b/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c
@@ -313,11 +313,40 @@ static bool sign(private_gmp_rsa_private_key_t *this, signature_scheme_t scheme,
 /**
  * Implementation of gmp_rsa_private_key.decrypt.
  */
-static bool decrypt(private_gmp_rsa_private_key_t *this,
-                                       chunk_t crypto, chunk_t *plain)
+static bool decrypt(private_gmp_rsa_private_key_t *this, chunk_t crypto,
+                                       chunk_t *plain)
 {
-       DBG1("RSA private key decryption not implemented");
-       return FALSE;
+       chunk_t em, stripped;
+       bool success = FALSE;
+       
+       /* rsa decryption using PKCS#1 RSADP */
+       stripped = em = rsadp(this, crypto);
+
+       /* PKCS#1 v1.5 8.1 encryption-block formatting (EB = 00 || 02 || PS || 00 || D) */
+
+       /* check for hex pattern 00 02 in decrypted message */
+       if ((*stripped.ptr++ != 0x00) || (*(stripped.ptr++) != 0x02))
+       {
+               DBG1("incorrect padding - probably wrong rsa key");
+               goto end;
+       }
+       stripped.len -= 2;
+
+       /* the plaintext data starts after first 0x00 byte */
+       while (stripped.len-- > 0 && *stripped.ptr++ != 0x00)
+
+       if (stripped.len == 0)
+       {
+               DBG1("no plaintext data");
+               goto end;
+       }
+
+       *plain = chunk_clone(stripped);
+       success = TRUE;
+
+end:
+       chunk_clear(&em);
+       return success;
 }
 
 /**

diff --git a/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c b/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c
index 534a865..725e1f9 100644 (file)
--- a/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c
+++ b/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c
@@ -377,6 +377,7 @@ static bool encrypt_(private_gmp_rsa_public_key_t *this, chunk_t plain,
        memcpy(pos, plain.ptr, plain.len);
        DBG3("padded data before rsa encryption: %B", &em);
        
+       /* rsa encryption using PKCS#1 RSAEP */
        *crypto = rsaep(this, em);
        DBG3("rsa encrypted data: %B", crypto);
        chunk_clear(&em);