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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 09:59:15 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-27 09:59:15 +0000
commit8de1ee1b2b676b0d07586f0752750dd6b0fb7511 (patch)
treedd46fd7dc3863045696cd0e48032d8a36fa0daf5 /g10/ecdh.c
parentInitial commit. (diff)
downloadgnupg2-8de1ee1b2b676b0d07586f0752750dd6b0fb7511.tar.xz
gnupg2-8de1ee1b2b676b0d07586f0752750dd6b0fb7511.zip
Adding upstream version 2.2.27.upstream/2.2.27upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'g10/ecdh.c')
-rw-r--r--g10/ecdh.c495
1 files changed, 495 insertions, 0 deletions
diff --git a/g10/ecdh.c b/g10/ecdh.c
new file mode 100644
index 0000000..5bbea96
--- /dev/null
+++ b/g10/ecdh.c
@@ -0,0 +1,495 @@
+/* ecdh.c - ECDH public key operations used in public key glue code
+ * Copyright (C) 2010, 2011 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include "gpg.h"
+#include "../common/util.h"
+#include "pkglue.h"
+#include "main.h"
+#include "options.h"
+
+/* A table with the default KEK parameters used by GnuPG. */
+static const struct
+{
+ unsigned int qbits;
+ int openpgp_hash_id; /* KEK digest algorithm. */
+ int openpgp_cipher_id; /* KEK cipher algorithm. */
+} kek_params_table[] =
+ /* Note: Must be sorted by ascending values for QBITS. */
+ {
+ { 256, DIGEST_ALGO_SHA256, CIPHER_ALGO_AES },
+ { 384, DIGEST_ALGO_SHA384, CIPHER_ALGO_AES192 },
+
+ /* Note: 528 is 521 rounded to the 8 bit boundary */
+ { 528, DIGEST_ALGO_SHA512, CIPHER_ALGO_AES256 }
+ };
+
+
+
+/* Return KEK parameters as an opaque MPI The caller must free the
+ returned value. Returns NULL and sets ERRNO on error. */
+gcry_mpi_t
+pk_ecdh_default_params (unsigned int qbits)
+{
+ byte *kek_params;
+ int i;
+
+ kek_params = xtrymalloc (4);
+ if (!kek_params)
+ return NULL;
+ kek_params[0] = 3; /* Number of bytes to follow. */
+ kek_params[1] = 1; /* Version for KDF+AESWRAP. */
+
+ /* Search for matching KEK parameter. Defaults to the strongest
+ possible choices. Performance is not an issue here, only
+ interoperability. */
+ for (i=0; i < DIM (kek_params_table); i++)
+ {
+ if (kek_params_table[i].qbits >= qbits
+ || i+1 == DIM (kek_params_table))
+ {
+ kek_params[2] = kek_params_table[i].openpgp_hash_id;
+ kek_params[3] = kek_params_table[i].openpgp_cipher_id;
+ break;
+ }
+ }
+ log_assert (i < DIM (kek_params_table));
+ if (DBG_CRYPTO)
+ log_printhex (kek_params, sizeof(kek_params), "ECDH KEK params are");
+
+ return gcry_mpi_set_opaque (NULL, kek_params, 4 * 8);
+}
+
+
+/* Encrypts/decrypts DATA using a key derived from the ECC shared
+ point SHARED_MPI using the FIPS SP 800-56A compliant method
+ key_derivation+key_wrapping. If IS_ENCRYPT is true the function
+ encrypts; if false, it decrypts. PKEY is the public key and PK_FP
+ the fingerprint of this public key. On success the result is
+ stored at R_RESULT; on failure NULL is stored at R_RESULT and an
+ error code returned. */
+gpg_error_t
+pk_ecdh_encrypt_with_shared_point (int is_encrypt, gcry_mpi_t shared_mpi,
+ const byte pk_fp[MAX_FINGERPRINT_LEN],
+ gcry_mpi_t data, gcry_mpi_t *pkey,
+ gcry_mpi_t *r_result)
+{
+ gpg_error_t err;
+ byte *secret_x;
+ int secret_x_size;
+ unsigned int nbits;
+ const unsigned char *kek_params;
+ size_t kek_params_size;
+ int kdf_hash_algo;
+ int kdf_encr_algo;
+ unsigned char message[256];
+ size_t message_size;
+
+ *r_result = NULL;
+
+ nbits = pubkey_nbits (PUBKEY_ALGO_ECDH, pkey);
+ if (!nbits)
+ return gpg_error (GPG_ERR_TOO_SHORT);
+
+ {
+ size_t nbytes;
+
+ /* Extract x component of the shared point: this is the actual
+ shared secret. */
+ nbytes = (mpi_get_nbits (pkey[1] /* public point */)+7)/8;
+ secret_x = xtrymalloc_secure (nbytes);
+ if (!secret_x)
+ return gpg_error_from_syserror ();
+
+ err = gcry_mpi_print (GCRYMPI_FMT_USG, secret_x, nbytes,
+ &nbytes, shared_mpi);
+ if (err)
+ {
+ xfree (secret_x);
+ log_error ("ECDH ephemeral export of shared point failed: %s\n",
+ gpg_strerror (err));
+ return err;
+ }
+
+ /* Expected size of the x component */
+ secret_x_size = (nbits+7)/8;
+
+ /* Extract X from the result. It must be in the format of:
+ 04 || X || Y
+ 40 || X
+ 41 || X
+
+ Since it always comes with the prefix, it's larger than X. In
+ old experimental version of libgcrypt, there is a case where it
+ returns X with no prefix of 40, so, nbytes == secret_x_size
+ is allowed. */
+ if (nbytes < secret_x_size)
+ {
+ xfree (secret_x);
+ return gpg_error (GPG_ERR_BAD_DATA);
+ }
+
+ /* Remove the prefix. */
+ if ((nbytes & 1))
+ memmove (secret_x, secret_x+1, secret_x_size);
+
+ /* Clear the rest of data. */
+ if (nbytes - secret_x_size)
+ memset (secret_x+secret_x_size, 0, nbytes-secret_x_size);
+
+ if (DBG_CRYPTO)
+ log_printhex (secret_x, secret_x_size, "ECDH shared secret X is:");
+ }
+
+ /*** We have now the shared secret bytes in secret_x. ***/
+
+ /* At this point we are done with PK encryption and the rest of the
+ * function uses symmetric key encryption techniques to protect the
+ * input DATA. The following two sections will simply replace
+ * current secret_x with a value derived from it. This will become
+ * a KEK.
+ */
+ if (!gcry_mpi_get_flag (pkey[2], GCRYMPI_FLAG_OPAQUE))
+ {
+ xfree (secret_x);
+ return gpg_error (GPG_ERR_BUG);
+ }
+ kek_params = gcry_mpi_get_opaque (pkey[2], &nbits);
+ kek_params_size = (nbits+7)/8;
+
+ if (DBG_CRYPTO)
+ log_printhex (kek_params, kek_params_size, "ecdh KDF params:");
+
+ /* Expect 4 bytes 03 01 hash_alg symm_alg. */
+ if (kek_params_size != 4 || kek_params[0] != 3 || kek_params[1] != 1)
+ {
+ xfree (secret_x);
+ return gpg_error (GPG_ERR_BAD_PUBKEY);
+ }
+
+ kdf_hash_algo = kek_params[2];
+ kdf_encr_algo = kek_params[3];
+
+ if (DBG_CRYPTO)
+ log_debug ("ecdh KDF algorithms %s+%s with aeswrap\n",
+ openpgp_md_algo_name (kdf_hash_algo),
+ openpgp_cipher_algo_name (kdf_encr_algo));
+
+ if (kdf_hash_algo != GCRY_MD_SHA256
+ && kdf_hash_algo != GCRY_MD_SHA384
+ && kdf_hash_algo != GCRY_MD_SHA512)
+ {
+ xfree (secret_x);
+ return gpg_error (GPG_ERR_BAD_PUBKEY);
+ }
+ if (kdf_encr_algo != CIPHER_ALGO_AES
+ && kdf_encr_algo != CIPHER_ALGO_AES192
+ && kdf_encr_algo != CIPHER_ALGO_AES256)
+ {
+ xfree (secret_x);
+ return gpg_error (GPG_ERR_BAD_PUBKEY);
+ }
+
+ /* Build kdf_params. */
+ {
+ IOBUF obuf;
+
+ obuf = iobuf_temp();
+ /* variable-length field 1, curve name OID */
+ err = gpg_mpi_write_nohdr (obuf, pkey[0]);
+ /* fixed-length field 2 */
+ iobuf_put (obuf, PUBKEY_ALGO_ECDH);
+ /* variable-length field 3, KDF params */
+ err = (err ? err : gpg_mpi_write_nohdr (obuf, pkey[2]));
+ /* fixed-length field 4 */
+ iobuf_write (obuf, "Anonymous Sender ", 20);
+ /* fixed-length field 5, recipient fp */
+ iobuf_write (obuf, pk_fp, 20);
+
+ message_size = iobuf_temp_to_buffer (obuf, message, sizeof message);
+ iobuf_close (obuf);
+ if (err)
+ {
+ xfree (secret_x);
+ return err;
+ }
+
+ if(DBG_CRYPTO)
+ log_printhex (message, message_size, "ecdh KDF message params are:");
+ }
+
+ /* Derive a KEK (key wrapping key) using MESSAGE and SECRET_X. */
+ {
+ gcry_md_hd_t h;
+ int old_size;
+
+ err = gcry_md_open (&h, kdf_hash_algo, 0);
+ if (err)
+ {
+ log_error ("gcry_md_open failed for kdf_hash_algo %d: %s",
+ kdf_hash_algo, gpg_strerror (err));
+ xfree (secret_x);
+ return err;
+ }
+ gcry_md_write(h, "\x00\x00\x00\x01", 4); /* counter = 1 */
+ gcry_md_write(h, secret_x, secret_x_size); /* x of the point X */
+ gcry_md_write(h, message, message_size); /* KDF parameters */
+
+ gcry_md_final (h);
+
+ log_assert( gcry_md_get_algo_dlen (kdf_hash_algo) >= 32 );
+
+ memcpy (secret_x, gcry_md_read (h, kdf_hash_algo),
+ gcry_md_get_algo_dlen (kdf_hash_algo));
+ gcry_md_close (h);
+
+ old_size = secret_x_size;
+ log_assert( old_size >= gcry_cipher_get_algo_keylen( kdf_encr_algo ) );
+ secret_x_size = gcry_cipher_get_algo_keylen( kdf_encr_algo );
+ log_assert( secret_x_size <= gcry_md_get_algo_dlen (kdf_hash_algo) );
+
+ /* We could have allocated more, so clean the tail before returning. */
+ memset (secret_x+secret_x_size, 0, old_size - secret_x_size);
+ if (DBG_CRYPTO)
+ log_printhex (secret_x, secret_x_size, "ecdh KEK is:");
+ }
+
+ /* And, finally, aeswrap with key secret_x. */
+ {
+ gcry_cipher_hd_t hd;
+ size_t nbytes;
+
+ byte *data_buf;
+ int data_buf_size;
+
+ gcry_mpi_t result;
+
+ err = gcry_cipher_open (&hd, kdf_encr_algo, GCRY_CIPHER_MODE_AESWRAP, 0);
+ if (err)
+ {
+ log_error ("ecdh failed to initialize AESWRAP: %s\n",
+ gpg_strerror (err));
+ xfree (secret_x);
+ return err;
+ }
+
+ err = gcry_cipher_setkey (hd, secret_x, secret_x_size);
+ xfree (secret_x);
+ secret_x = NULL;
+ if (err)
+ {
+ gcry_cipher_close (hd);
+ log_error ("ecdh failed in gcry_cipher_setkey: %s\n",
+ gpg_strerror (err));
+ return err;
+ }
+
+ data_buf_size = (gcry_mpi_get_nbits(data)+7)/8;
+ if ((data_buf_size & 7) != (is_encrypt ? 0 : 1))
+ {
+ log_error ("can't use a shared secret of %d bytes for ecdh\n",
+ data_buf_size);
+ return gpg_error (GPG_ERR_BAD_DATA);
+ }
+
+ data_buf = xtrymalloc_secure( 1 + 2*data_buf_size + 8);
+ if (!data_buf)
+ {
+ err = gpg_error_from_syserror ();
+ gcry_cipher_close (hd);
+ return err;
+ }
+
+ if (is_encrypt)
+ {
+ byte *in = data_buf+1+data_buf_size+8;
+
+ /* Write data MPI into the end of data_buf. data_buf is size
+ aeswrap data. */
+ err = gcry_mpi_print (GCRYMPI_FMT_USG, in,
+ data_buf_size, &nbytes, data/*in*/);
+ if (err)
+ {
+ log_error ("ecdh failed to export DEK: %s\n", gpg_strerror (err));
+ gcry_cipher_close (hd);
+ xfree (data_buf);
+ return err;
+ }
+
+ if (DBG_CRYPTO)
+ log_printhex (in, data_buf_size, "ecdh encrypting :");
+
+ err = gcry_cipher_encrypt (hd, data_buf+1, data_buf_size+8,
+ in, data_buf_size);
+ memset (in, 0, data_buf_size);
+ gcry_cipher_close (hd);
+ if (err)
+ {
+ log_error ("ecdh failed in gcry_cipher_encrypt: %s\n",
+ gpg_strerror (err));
+ xfree (data_buf);
+ return err;
+ }
+ data_buf[0] = data_buf_size+8;
+
+ if (DBG_CRYPTO)
+ log_printhex (data_buf+1, data_buf[0], "ecdh encrypted to:");
+
+ result = gcry_mpi_set_opaque (NULL, data_buf, 8 * (1+data_buf[0]));
+ if (!result)
+ {
+ err = gpg_error_from_syserror ();
+ xfree (data_buf);
+ log_error ("ecdh failed to create an MPI: %s\n",
+ gpg_strerror (err));
+ return err;
+ }
+
+ *r_result = result;
+ }
+ else
+ {
+ byte *in;
+ const void *p;
+
+ p = gcry_mpi_get_opaque (data, &nbits);
+ nbytes = (nbits+7)/8;
+ if (!p || nbytes > data_buf_size || !nbytes)
+ {
+ xfree (data_buf);
+ return gpg_error (GPG_ERR_BAD_MPI);
+ }
+ memcpy (data_buf, p, nbytes);
+ if (data_buf[0] != nbytes-1)
+ {
+ log_error ("ecdh inconsistent size\n");
+ xfree (data_buf);
+ return gpg_error (GPG_ERR_BAD_MPI);
+ }
+ in = data_buf+data_buf_size;
+ data_buf_size = data_buf[0];
+
+ if (DBG_CRYPTO)
+ log_printhex (data_buf+1, data_buf_size, "ecdh decrypting :");
+
+ err = gcry_cipher_decrypt (hd, in, data_buf_size, data_buf+1,
+ data_buf_size);
+ gcry_cipher_close (hd);
+ if (err)
+ {
+ log_error ("ecdh failed in gcry_cipher_decrypt: %s\n",
+ gpg_strerror (err));
+ xfree (data_buf);
+ return err;
+ }
+
+ data_buf_size -= 8;
+
+ if (DBG_CRYPTO)
+ log_printhex (in, data_buf_size, "ecdh decrypted to :");
+
+ /* Padding is removed later. */
+ /* if (in[data_buf_size-1] > 8 ) */
+ /* { */
+ /* log_error ("ecdh failed at decryption: invalid padding." */
+ /* " 0x%02x > 8\n", in[data_buf_size-1] ); */
+ /* return gpg_error (GPG_ERR_BAD_KEY); */
+ /* } */
+
+ err = gcry_mpi_scan (&result, GCRYMPI_FMT_USG, in, data_buf_size, NULL);
+ xfree (data_buf);
+ if (err)
+ {
+ log_error ("ecdh failed to create a plain text MPI: %s\n",
+ gpg_strerror (err));
+ return err;
+ }
+
+ *r_result = result;
+ }
+ }
+
+ return err;
+}
+
+
+static gcry_mpi_t
+gen_k (unsigned nbits)
+{
+ gcry_mpi_t k;
+
+ k = gcry_mpi_snew (nbits);
+ if (DBG_CRYPTO)
+ log_debug ("choosing a random k of %u bits\n", nbits);
+
+ gcry_mpi_randomize (k, nbits-1, GCRY_STRONG_RANDOM);
+
+ if (DBG_CRYPTO)
+ {
+ unsigned char *buffer;
+ if (gcry_mpi_aprint (GCRYMPI_FMT_HEX, &buffer, NULL, k))
+ BUG ();
+ log_debug ("ephemeral scalar MPI #0: %s\n", buffer);
+ gcry_free (buffer);
+ }
+
+ return k;
+}
+
+
+/* Generate an ephemeral key for the public ECDH key in PKEY. On
+ success the generated key is stored at R_K; on failure NULL is
+ stored at R_K and an error code returned. */
+gpg_error_t
+pk_ecdh_generate_ephemeral_key (gcry_mpi_t *pkey, gcry_mpi_t *r_k)
+{
+ unsigned int nbits;
+ gcry_mpi_t k;
+
+ *r_k = NULL;
+
+ nbits = pubkey_nbits (PUBKEY_ALGO_ECDH, pkey);
+ if (!nbits)
+ return gpg_error (GPG_ERR_TOO_SHORT);
+ k = gen_k (nbits);
+ if (!k)
+ BUG ();
+
+ *r_k = k;
+ return 0;
+}
+
+
+
+/* Perform ECDH decryption. */
+int
+pk_ecdh_decrypt (gcry_mpi_t * result, const byte sk_fp[MAX_FINGERPRINT_LEN],
+ gcry_mpi_t data, gcry_mpi_t shared, gcry_mpi_t * skey)
+{
+ if (!data)
+ return gpg_error (GPG_ERR_BAD_MPI);
+ return pk_ecdh_encrypt_with_shared_point (0 /*=decryption*/, shared,
+ sk_fp, data/*encr data as an MPI*/,
+ skey, result);
+}