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-rw-r--r--sm/encrypt.c317
1 files changed, 305 insertions, 12 deletions
diff --git a/sm/encrypt.c b/sm/encrypt.c
index 6213a6604..865b103c1 100644
--- a/sm/encrypt.c
+++ b/sm/encrypt.c
@@ -1,6 +1,8 @@
/* encrypt.c - Encrypt a message
* Copyright (C) 2001, 2003, 2004, 2007, 2008,
* 2010 Free Software Foundation, Inc.
+ * Copyright (C) 2001-2019 Werner Koch
+ * Copyright (C) 2015-2020 g10 Code GmbH
*
* This file is part of GnuPG.
*
@@ -16,6 +18,7 @@
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
+ * SPDX-License-Identifier: GPL-3.0-or-later
*/
#include <config.h>
@@ -144,7 +147,7 @@ init_dek (DEK dek)
return 0;
}
-
+/* Encode an RSA session key. */
static int
encode_session_key (DEK dek, gcry_sexp_t * r_data)
{
@@ -165,10 +168,282 @@ encode_session_key (DEK dek, gcry_sexp_t * r_data)
}
+/* Encrypt DEK using ECDH. S_PKEY is the public key. On success the
+ * result is stored at R_ENCVAL. Example of a public key:
+ *
+ * (public-key (ecc (curve "1.3.132.0.34") (q #04B0[...]B8#)))
+ *
+ */
+static gpg_error_t
+ecdh_encrypt (DEK dek, gcry_sexp_t s_pkey, gcry_sexp_t *r_encval)
+{
+ gpg_error_t err;
+ gcry_sexp_t l1;
+ char *curvebuf = NULL;
+ const char *curve;
+ unsigned int curvebits;
+ const char *encr_algo_str;
+ const char *wrap_algo_str;
+ int hash_algo, cipher_algo;
+ unsigned int keylen, hashlen;
+ unsigned char key[32];
+ gcry_sexp_t s_data = NULL;
+ gcry_sexp_t s_encr = NULL;
+ gcry_buffer_t ioarray[2] = { {0}, {0} };
+ unsigned char *secret; /* Alias for ioarray[0]. */
+ unsigned int secretlen;
+ unsigned char *pubkey; /* Alias for ioarray[1]. */
+ unsigned int pubkeylen;
+ gcry_cipher_hd_t cipher_hd = NULL;
+ unsigned char *result = NULL;
+ unsigned int resultlen;
+
+ *r_encval = NULL;
+
+ /* Figure out the encryption and wrap algo OIDs. */
+ /* Get the curve name if any, */
+ l1 = gcry_sexp_find_token (s_pkey, "curve", 0);
+ if (l1)
+ {
+ curvebuf = gcry_sexp_nth_string (l1, 1);
+ gcry_sexp_release (l1);
+ }
+ if (!curvebuf)
+ {
+ err = gpg_error (GPG_ERR_INV_CURVE);
+ log_error ("%s: invalid public key: no curve\n", __func__);
+ goto leave;
+ }
+
+ /* We need to use our OpenPGP mapping to turn a curve name into its
+ * canonical numerical OID. We also use this to get the size of the
+ * curve which we need to figure out a suitable hash algo. We
+ * should have a Libgcrypt function to do this; see bug report #4926. */
+ curve = openpgp_curve_to_oid (curvebuf, &curvebits, NULL);
+ if (!curve)
+ {
+ err = gpg_error (GPG_ERR_UNKNOWN_CURVE);
+ log_error ("%s: invalid public key: %s\n", __func__, gpg_strerror (err));
+ goto leave;
+ }
+ xfree (curvebuf);
+ curvebuf = NULL;
+
+ /* Our mapping matches the recommended algorithms from RFC-5753 but
+ * not supporing the short curves which would require 3DES. */
+ if (curvebits < 255)
+ {
+ err = gpg_error (GPG_ERR_UNKNOWN_CURVE);
+ log_error ("%s: curve '%s' is not supported\n", __func__, curve);
+ goto leave;
+ }
+ else if (curvebits <= 256)
+ {
+ /* dhSinglePass-stdDH-sha256kdf-scheme */
+ encr_algo_str = "1.3.132.1.11.1";
+ wrap_algo_str = "2.16.840.1.101.3.4.1.5";
+ hash_algo = GCRY_MD_SHA256;
+ hashlen = 32;
+ cipher_algo = GCRY_CIPHER_AES128;
+ keylen = 16;
+ }
+ else if (curvebits <= 384)
+ {
+ /* dhSinglePass-stdDH-sha384kdf-scheme */
+ encr_algo_str = "1.3.132.1.11.2";
+ wrap_algo_str = "2.16.840.1.101.3.4.1.25";
+ hash_algo = GCRY_MD_SHA384;
+ hashlen = 48;
+ cipher_algo = GCRY_CIPHER_AES256;
+ keylen = 24;
+ }
+ else
+ {
+ /* dhSinglePass-stdDH-sha512kdf-scheme*/
+ encr_algo_str = "1.3.132.1.11.3";
+ wrap_algo_str = "2.16.840.1.101.3.4.1.45";
+ hash_algo = GCRY_MD_SHA512;
+ hashlen = 64;
+ cipher_algo = GCRY_CIPHER_AES256;
+ keylen = 32;
+ }
+
+
+ /* Create a secret and an ephemeral key. */
+ {
+ char *k;
+ k = gcry_random_bytes_secure ((curvebits+7)/8, GCRY_STRONG_RANDOM);
+ if (DBG_CRYPTO)
+ log_printhex (k, (curvebits+7)/8, "ephm. k .:");
+ err = gcry_sexp_build (&s_data, NULL, "%b", (int)(curvebits+7)/8, k);
+ xfree (k);
+ }
+ if (err)
+ {
+ log_error ("%s: error building ephemeral secret: %s\n",
+ __func__, gpg_strerror (err));
+ goto leave;
+ }
+
+ err = gcry_pk_encrypt (&s_encr, s_data, s_pkey);
+ if (err)
+ {
+ log_error ("%s: error encrypting ephemeral secret: %s\n",
+ __func__, gpg_strerror (err));
+ goto leave;
+ }
+ err = gcry_sexp_extract_param (s_encr, NULL, "&se",
+ &ioarray+0, ioarray+1, NULL);
+ if (err)
+ {
+ log_error ("%s: error extracting ephemeral key and secret: %s\n",
+ __func__, gpg_strerror (err));
+ goto leave;
+ }
+ secret = ioarray[0].data;
+ secretlen = ioarray[0].len;
+ pubkey = ioarray[1].data;
+ pubkeylen = ioarray[1].len;
+
+ if (DBG_CRYPTO)
+ {
+ log_printhex (pubkey, pubkeylen, "pubkey ..:");
+ log_printhex (secret, secretlen, "secret ..:");
+ }
+
+ /* Extract X coordinate from SECRET. */
+ if (secretlen < 5) /* 5 because N could be reduced to (n-1)/2. */
+ err = gpg_error (GPG_ERR_BAD_DATA);
+ else if (*secret == 0x04)
+ {
+ secretlen--;
+ memmove (secret, secret+1, secretlen);
+ if ((secretlen & 1))
+ {
+ err = gpg_error (GPG_ERR_BAD_DATA);
+ goto leave;
+ }
+ secretlen /= 2;
+ }
+ else if (*secret == 0x40 || *secret == 0x41)
+ {
+ secretlen--;
+ memmove (secret, secret+1, secretlen);
+ }
+ else
+ err = gpg_error (GPG_ERR_BAD_DATA);
+ if (err)
+ goto leave;
+
+ if (DBG_CRYPTO)
+ log_printhex (secret, secretlen, "ECDH X ..:");
+
+ /* Derive a KEK (key wrapping key) using MESSAGE and SECRET_X.
+ * According to SEC1 3.6.1 we should check that
+ * SECRETLEN + UKMLEN + 4 < maxhashlen
+ * However, we have no practical limit on the hash length and thus
+ * there is no point in checking this. The second check that
+ * KEYLEN < hashlen*(2^32-1)
+ * is obviously also not needed. Because with our allowed
+ * parameters KEYLEN is always less or equal to HASHLEN so that we
+ * do not need to iterate at all.
+ */
+ log_assert (gcry_md_get_algo_dlen (hash_algo) == hashlen);
+ {
+ gcry_md_hd_t hash_hd;
+ err = gcry_md_open (&hash_hd, hash_algo, 0);
+ if (err)
+ goto leave;
+ gcry_md_write(hash_hd, secret, secretlen);
+ gcry_md_write(hash_hd, "\x00\x00\x00\x01", 4); /* counter */
+ err = hash_ecc_cms_shared_info (hash_hd, wrap_algo_str, keylen, NULL, 0);
+ gcry_md_final (hash_hd);
+ log_assert (keylen <= sizeof key && keylen <= hashlen);
+ memcpy (key, gcry_md_read (hash_hd, 0), keylen);
+ gcry_md_close (hash_hd);
+ if (err)
+ goto leave;
+ }
+
+ if (DBG_CRYPTO)
+ log_printhex (key, keylen, "KEK .....:");
+
+ /* Wrap the key. */
+ if ((dek->keylen % 8) || dek->keylen < 16)
+ {
+ log_error ("%s: can't use a session key of %u bytes\n",
+ __func__, dek->keylen);
+ err = gpg_error (GPG_ERR_BAD_DATA);
+ goto leave;
+ }
+
+ resultlen = dek->keylen + 8;
+ result = xtrymalloc_secure (resultlen);
+ if (!result)
+ {
+ err = gpg_error_from_syserror ();
+ goto leave;
+ }
+
+ err = gcry_cipher_open (&cipher_hd, cipher_algo, GCRY_CIPHER_MODE_AESWRAP, 0);
+ if (err)
+ {
+ log_error ("%s: failed to initialize AESWRAP: %s\n",
+ __func__, gpg_strerror (err));
+ goto leave;
+ }
+
+ err = gcry_cipher_setkey (cipher_hd, key, keylen);
+ wipememory (key, sizeof key);
+ if (err)
+ {
+ log_error ("%s: failed in gcry_cipher_setkey: %s\n",
+ __func__, gpg_strerror (err));
+ goto leave;
+ }
+
+ err = gcry_cipher_encrypt (cipher_hd, result, resultlen,
+ dek->key, dek->keylen);
+ if (err)
+ {
+ log_error ("%s: failed in gcry_cipher_encrypt: %s\n",
+ __func__, gpg_strerror (err));
+ goto leave;
+ }
+
+ if (DBG_CRYPTO)
+ log_printhex (result, resultlen, "w(CEK) ..:");
+
+ err = gcry_sexp_build (r_encval, NULL,
+ "(enc-val(ecdh(e%b)(s%b)(encr-algo%s)(wrap-algo%s)))",
+ (int)pubkeylen, pubkey,
+ (int)resultlen, result,
+ encr_algo_str,
+ wrap_algo_str,
+ NULL);
+ if (err)
+ log_error ("%s: failed building final S-exp: %s\n",
+ __func__, gpg_strerror (err));
+
+ leave:
+ gcry_cipher_close (cipher_hd);
+ wipememory (key, sizeof key);
+ xfree (result);
+ xfree (ioarray[0].data);
+ xfree (ioarray[1].data);
+ gcry_sexp_release (s_data);
+ gcry_sexp_release (s_encr);
+ xfree (curvebuf);
+ return err;
+}
+
+
/* Encrypt the DEK under the key contained in CERT and return it as a
- canonical S-Exp in encval. */
+ * canonical S-expressions at ENCVAL. PK_ALGO is the public key
+ * algorithm which the caller has already retrieved from CERT. */
static int
-encrypt_dek (const DEK dek, ksba_cert_t cert, unsigned char **encval)
+encrypt_dek (const DEK dek, ksba_cert_t cert, int pk_algo,
+ unsigned char **encval)
{
gcry_sexp_t s_ciph, s_data, s_pkey;
int rc;
@@ -198,20 +473,38 @@ encrypt_dek (const DEK dek, ksba_cert_t cert, unsigned char **encval)
return rc;
}
+ if (DBG_CRYPTO)
+ {
+ log_printsexp (" pubkey:", s_pkey);
+ log_printhex (dek->key, dek->keylen, "CEK .....:");
+ }
+
/* Put the encoded cleartext into a simple list. */
s_data = NULL; /* (avoid compiler warning) */
- rc = encode_session_key (dek, &s_data);
- if (rc)
+ if (pk_algo == GCRY_PK_ECC)
{
- log_error ("encode_session_key failed: %s\n", gpg_strerror (rc));
- return rc;
+ rc = ecdh_encrypt (dek, s_pkey, &s_ciph);
}
+ else
+ {
+ rc = encode_session_key (dek, &s_data);
+ if (rc)
+ {
+ log_error ("encode_session_key failed: %s\n", gpg_strerror (rc));
+ return rc;
+ }
+ if (DBG_CRYPTO)
+ log_printsexp (" data:", s_data);
- /* pass it to libgcrypt */
- rc = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
+ /* pass it to libgcrypt */
+ rc = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
+ }
gcry_sexp_release (s_data);
gcry_sexp_release (s_pkey);
+ if (DBG_CRYPTO)
+ log_printsexp ("enc-val:", s_ciph);
+
/* Reformat it. */
if (!rc)
{
@@ -386,7 +679,7 @@ gpgsm_encrypt (ctrl_t ctrl, certlist_t recplist, int data_fd, estream_t out_fp)
err = ksba_cms_set_reader_writer (cms, reader, writer);
if (err)
{
- log_debug ("ksba_cms_set_reader_writer failed: %s\n",
+ log_error ("ksba_cms_set_reader_writer failed: %s\n",
gpg_strerror (err));
rc = err;
goto leave;
@@ -401,7 +694,7 @@ gpgsm_encrypt (ctrl_t ctrl, certlist_t recplist, int data_fd, estream_t out_fp)
err = ksba_cms_set_content_type (cms, 1, KSBA_CT_DATA);
if (err)
{
- log_debug ("ksba_cms_set_content_type failed: %s\n",
+ log_error ("ksba_cms_set_content_type failed: %s\n",
gpg_strerror (err));
rc = err;
goto leave;
@@ -498,7 +791,7 @@ gpgsm_encrypt (ctrl_t ctrl, certlist_t recplist, int data_fd, estream_t out_fp)
&& !gnupg_pk_is_compliant (CO_DE_VS, pk_algo, NULL, nbits, NULL))
compliant = 0;
- rc = encrypt_dek (dek, cl->cert, &encval);
+ rc = encrypt_dek (dek, cl->cert, pk_algo, &encval);
if (rc)
{
audit_log_cert (ctrl->audit, AUDIT_ENCRYPTED_TO, cl->cert, rc);
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-13 00:34:42 +0100