static gpg_error_t get_it (PKT_pubkey_enc *enc, DEK *dek, PKT_public_key *sk, u32 *keyid) { gpg_error_t err; byte *frame = NULL; unsigned int n; size_t nframe; u16 csum, csum2; int card = 0; gcry_sexp_t s_data; char *desc; char *keygrip; byte fp[MAX_FINGERPRINT_LEN]; size_t fpn; const int pkalgo = map_pk_openpgp_to_gcry (sk->pubkey_algo); /* Get the keygrip. */ err = hexkeygrip_from_pk (sk, &keygrip); if (err) goto leave; /* Convert the data to an S-expression. */ if (pkalgo == GCRY_PK_ELG || pkalgo == GCRY_PK_ELG_E) { if (!enc->data[0] || !enc->data[1]) err = gpg_error (GPG_ERR_BAD_MPI); else err = gcry_sexp_build (&s_data, NULL, "(enc-val(elg(a%m)(b%m)))", enc->data[0], enc->data[1]); } else if (pkalgo == GCRY_PK_RSA || pkalgo == GCRY_PK_RSA_E) { if (!enc->data[0]) err = gpg_error (GPG_ERR_BAD_MPI); else err = gcry_sexp_build (&s_data, NULL, "(enc-val(rsa(a%m)))", enc->data[0]); } else if (pkalgo == GCRY_PK_ECDH) { if (!enc->data[0] || !enc->data[1]) err = gpg_error (GPG_ERR_BAD_MPI); else err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))", enc->data[0], enc->data[1]); } else err = gpg_error (GPG_ERR_BUG); if (err) goto leave; if (sk->pubkey_algo == PUBKEY_ALGO_ECDH) { fingerprint_from_pk (sk, fp, &fpn); assert (fpn == 20); } /* Decrypt. */ desc = gpg_format_keydesc (sk, 0, 1); err = agent_pkdecrypt (NULL, keygrip, desc, s_data, &frame, &nframe); xfree (desc); gcry_sexp_release (s_data); if (err) goto leave; /* Now get the DEK (data encryption key) from the frame * * Old versions encode the DEK in in this format (msb is left): * * 0 1 DEK(16 bytes) CSUM(2 bytes) 0 RND(n bytes) 2 * * Later versions encode the DEK like this: * * 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes) * * (mpi_get_buffer already removed the leading zero). * * RND are non-zero randow bytes. * A is the cipher algorithm * DEK is the encryption key (session key) with length k * CSUM */ if (DBG_CIPHER) log_printhex ("DEK frame:", frame, nframe); n = 0; if (sk->pubkey_algo == PUBKEY_ALGO_ECDH) { gcry_mpi_t shared_mpi; gcry_mpi_t decoded; /* At the beginning the frame are the bytes of shared point MPI. */ err = gcry_mpi_scan (&shared_mpi, GCRYMPI_FMT_USG, frame, nframe, NULL); if (err) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } err = pk_ecdh_decrypt (&decoded, fp, enc->data[1]/*encr data as an MPI*/, shared_mpi, sk->pkey); mpi_release (shared_mpi); if(err) goto leave; /* Reuse NFRAME, which size is sufficient to include the session key. */ err = gcry_mpi_print (GCRYMPI_FMT_USG, frame, nframe, &nframe, decoded); mpi_release (decoded); if (err) goto leave; /* Now the frame are the bytes decrypted but padded session key. */ /* Allow double padding for the benefit of DEK size concealment. Higher than this is wasteful. */ if (!nframe || frame[nframe-1] > 8*2 || nframe <= 8 || frame[nframe-1] > nframe) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } nframe -= frame[nframe-1]; /* Remove padding. */ assert (!n); /* (used just below) */ } else { if (!card) { if (n + 7 > nframe) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } if (frame[n] == 1 && frame[nframe - 1] == 2) { log_info (_("old encoding of the DEK is not supported\n")); err = gpg_error (GPG_ERR_CIPHER_ALGO); goto leave; } if (frame[n] != 2) /* Something went wrong. */ { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes. */ ; n++; /* Skip the zero byte. */ } } if (n + 4 > nframe) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } dek->keylen = nframe - (n + 1) - 2; dek->algo = frame[n++]; if (dek->algo == CIPHER_ALGO_IDEA) write_status (STATUS_RSA_OR_IDEA); err = openpgp_cipher_test_algo (dek->algo); if (err) { if (!opt.quiet && gpg_err_code (err) == GPG_ERR_CIPHER_ALGO) { log_info (_("cipher algorithm %d%s is unknown or disabled\n"), dek->algo, dek->algo == CIPHER_ALGO_IDEA ? " (IDEA)" : ""); if (dek->algo == CIPHER_ALGO_IDEA) idea_cipher_warn (0); } dek->algo = 0; goto leave; } if (dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo)) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } /* Copy the key to DEK and compare the checksum. */ csum = frame[nframe - 2] << 8; csum |= frame[nframe - 1]; memcpy (dek->key, frame + n, dek->keylen); for (csum2 = 0, n = 0; n < dek->keylen; n++) csum2 += dek->key[n]; if (csum != csum2) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } if (DBG_CIPHER) log_printhex ("DEK is:", dek->key, dek->keylen); /* Check that the algo is in the preferences and whether it has expired. */ { PKT_public_key *pk = NULL; KBNODE pkb = get_pubkeyblock (keyid); if (!pkb) { err = -1; log_error ("oops: public key not found for preference check\n"); } else if (pkb->pkt->pkt.public_key->selfsigversion > 3 && dek->algo != CIPHER_ALGO_3DES && !opt.quiet && !is_algo_in_prefs (pkb, PREFTYPE_SYM, dek->algo)) log_info (_("WARNING: cipher algorithm %s not found in recipient" " preferences\n"), openpgp_cipher_algo_name (dek->algo)); if (!err) { KBNODE k; for (k = pkb; k; k = k->next) { if (k->pkt->pkttype == PKT_PUBLIC_KEY || k->pkt->pkttype == PKT_PUBLIC_SUBKEY) { u32 aki[2]; keyid_from_pk (k->pkt->pkt.public_key, aki); if (aki[0] == keyid[0] && aki[1] == keyid[1]) { pk = k->pkt->pkt.public_key; break; } } } if (!pk) BUG (); if (pk->expiredate && pk->expiredate <= make_timestamp ()) { log_info (_("NOTE: secret key %s expired at %s\n"), keystr (keyid), asctimestamp (pk->expiredate)); } } if (pk && pk->flags.revoked) { log_info (_("NOTE: key has been revoked")); log_printf ("\n"); show_revocation_reason (pk, 1); } release_kbnode (pkb); err = 0; } leave: xfree (frame); xfree (keygrip); return err; }
static gpg_error_t get_it (ctrl_t ctrl, PKT_pubkey_enc *enc, DEK *dek, PKT_public_key *sk, u32 *keyid) { gpg_error_t err; byte *frame = NULL; unsigned int n; size_t nframe; u16 csum, csum2; int padding; gcry_sexp_t s_data; char *desc; char *keygrip; byte fp[MAX_FINGERPRINT_LEN]; size_t fpn; if (DBG_CLOCK) log_clock ("decryption start"); /* Get the keygrip. */ err = hexkeygrip_from_pk (sk, &keygrip); if (err) goto leave; /* Convert the data to an S-expression. */ if (sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL || sk->pubkey_algo == PUBKEY_ALGO_ELGAMAL_E) { if (!enc->data[0] || !enc->data[1]) err = gpg_error (GPG_ERR_BAD_MPI); else err = gcry_sexp_build (&s_data, NULL, "(enc-val(elg(a%m)(b%m)))", enc->data[0], enc->data[1]); } else if (sk->pubkey_algo == PUBKEY_ALGO_RSA || sk->pubkey_algo == PUBKEY_ALGO_RSA_E) { if (!enc->data[0]) err = gpg_error (GPG_ERR_BAD_MPI); else err = gcry_sexp_build (&s_data, NULL, "(enc-val(rsa(a%m)))", enc->data[0]); } else if (sk->pubkey_algo == PUBKEY_ALGO_ECDH) { if (!enc->data[0] || !enc->data[1]) err = gpg_error (GPG_ERR_BAD_MPI); else err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))", enc->data[1], enc->data[0]); } else err = gpg_error (GPG_ERR_BUG); if (err) goto leave; if (sk->pubkey_algo == PUBKEY_ALGO_ECDH) { fingerprint_from_pk (sk, fp, &fpn); log_assert (fpn == 20); } /* Decrypt. */ desc = gpg_format_keydesc (ctrl, sk, FORMAT_KEYDESC_NORMAL, 1); err = agent_pkdecrypt (NULL, keygrip, desc, sk->keyid, sk->main_keyid, sk->pubkey_algo, s_data, &frame, &nframe, &padding); xfree (desc); gcry_sexp_release (s_data); if (err) goto leave; /* Now get the DEK (data encryption key) from the frame * * Old versions encode the DEK in this format (msb is left): * * 0 1 DEK(16 bytes) CSUM(2 bytes) 0 RND(n bytes) 2 * * Later versions encode the DEK like this: * * 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes) * * (mpi_get_buffer already removed the leading zero). * * RND are non-zero randow bytes. * A is the cipher algorithm * DEK is the encryption key (session key) with length k * CSUM */ if (DBG_CRYPTO) log_printhex (frame, nframe, "DEK frame:"); n = 0; if (sk->pubkey_algo == PUBKEY_ALGO_ECDH) { gcry_mpi_t shared_mpi; gcry_mpi_t decoded; /* At the beginning the frame are the bytes of shared point MPI. */ err = gcry_mpi_scan (&shared_mpi, GCRYMPI_FMT_USG, frame, nframe, NULL); if (err) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } err = pk_ecdh_decrypt (&decoded, fp, enc->data[1]/*encr data as an MPI*/, shared_mpi, sk->pkey); mpi_release (shared_mpi); if(err) goto leave; xfree (frame); err = gcry_mpi_aprint (GCRYMPI_FMT_USG, &frame, &nframe, decoded); mpi_release (decoded); if (err) goto leave; /* Now the frame are the bytes decrypted but padded session key. */ /* Allow double padding for the benefit of DEK size concealment. Higher than this is wasteful. */ if (!nframe || frame[nframe-1] > 8*2 || nframe <= 8 || frame[nframe-1] > nframe) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } nframe -= frame[nframe-1]; /* Remove padding. */ log_assert (!n); /* (used just below) */ } else { if (padding) { if (n + 7 > nframe) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } if (frame[n] == 1 && frame[nframe - 1] == 2) { log_info (_("old encoding of the DEK is not supported\n")); err = gpg_error (GPG_ERR_CIPHER_ALGO); goto leave; } if (frame[n] != 2) /* Something went wrong. */ { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } for (n++; n < nframe && frame[n]; n++) /* Skip the random bytes. */ ; n++; /* Skip the zero byte. */ } } if (n + 4 > nframe) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } dek->keylen = nframe - (n + 1) - 2; dek->algo = frame[n++]; err = openpgp_cipher_test_algo (dek->algo); if (err) { if (!opt.quiet && gpg_err_code (err) == GPG_ERR_CIPHER_ALGO) { log_info (_("cipher algorithm %d%s is unknown or disabled\n"), dek->algo, dek->algo == CIPHER_ALGO_IDEA ? " (IDEA)" : ""); } dek->algo = 0; goto leave; } if (dek->keylen != openpgp_cipher_get_algo_keylen (dek->algo)) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } /* Copy the key to DEK and compare the checksum. */ csum = buf16_to_u16 (frame+nframe-2); memcpy (dek->key, frame + n, dek->keylen); for (csum2 = 0, n = 0; n < dek->keylen; n++) csum2 += dek->key[n]; if (csum != csum2) { err = gpg_error (GPG_ERR_WRONG_SECKEY); goto leave; } if (DBG_CLOCK) log_clock ("decryption ready"); if (DBG_CRYPTO) log_printhex (dek->key, dek->keylen, "DEK is:"); /* Check that the algo is in the preferences and whether it has * expired. Also print a status line with the key's fingerprint. */ { PKT_public_key *pk = NULL; PKT_public_key *mainpk = NULL; KBNODE pkb = get_pubkeyblock (ctrl, keyid); if (!pkb) { err = -1; log_error ("oops: public key not found for preference check\n"); } else if (pkb->pkt->pkt.public_key->selfsigversion > 3 && dek->algo != CIPHER_ALGO_3DES && !opt.quiet && !is_algo_in_prefs (pkb, PREFTYPE_SYM, dek->algo)) log_info (_("WARNING: cipher algorithm %s not found in recipient" " preferences\n"), openpgp_cipher_algo_name (dek->algo)); if (!err) { kbnode_t k; int first = 1; for (k = pkb; k; k = k->next) { if (k->pkt->pkttype == PKT_PUBLIC_KEY || k->pkt->pkttype == PKT_PUBLIC_SUBKEY) { u32 aki[2]; if (first) { first = 0; mainpk = k->pkt->pkt.public_key; } keyid_from_pk (k->pkt->pkt.public_key, aki); if (aki[0] == keyid[0] && aki[1] == keyid[1]) { pk = k->pkt->pkt.public_key; break; } } } if (!pk) BUG (); if (pk->expiredate && pk->expiredate <= make_timestamp ()) { log_info (_("Note: secret key %s expired at %s\n"), keystr (keyid), asctimestamp (pk->expiredate)); } } if (pk && pk->flags.revoked) { log_info (_("Note: key has been revoked")); log_printf ("\n"); show_revocation_reason (ctrl, pk, 1); } if (is_status_enabled () && pk && mainpk) { char pkhex[MAX_FINGERPRINT_LEN*2+1]; char mainpkhex[MAX_FINGERPRINT_LEN*2+1]; hexfingerprint (pk, pkhex, sizeof pkhex); hexfingerprint (mainpk, mainpkhex, sizeof mainpkhex); /* Note that we do not want to create a trustdb just for * getting the ownertrust: If there is no trustdb there can't * be ulitmately trusted key anyway and thus the ownertrust * value is irrelevant. */ write_status_printf (STATUS_DECRYPTION_KEY, "%s %s %c", pkhex, mainpkhex, get_ownertrust_info (ctrl, mainpk, 1)); } release_kbnode (pkb); err = 0; } leave: xfree (frame); xfree (keygrip); return err; }