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    Subject[PATCH 06/16] KEYS: Add a DSA crypto key subtype [ver #2]
    Date
    Add a key subtype for handling DSA crypto keys.  For the moment it only
    provides a signature verification facility.

    Signed-off-by: David Howells <dhowells@redhat.com>
    ---

    security/Kconfig | 10 +
    security/keys/Makefile | 2
    security/keys/crypto_dsa.h | 36 ++++
    security/keys/crypto_dsa_subtype.c | 338 ++++++++++++++++++++++++++++++++++++
    4 files changed, 386 insertions(+), 0 deletions(-)
    create mode 100644 security/keys/crypto_dsa.h
    create mode 100644 security/keys/crypto_dsa_subtype.c


    diff --git a/security/Kconfig b/security/Kconfig
    index ef39878..48926af 100644
    --- a/security/Kconfig
    +++ b/security/Kconfig
    @@ -62,6 +62,16 @@ config CRYPTO_KEY_TYPE
    required for cryptographic operations such as encryption, decryption,
    signature generation and signature verification.

    +config CRYPTO_KEY_DSA
    + tristate "DSA key type"
    + depends on CRYPTO_KEY_TYPE
    + select CRYPTO
    + select MPILIB
    + select MPILIB_EXTRA
    + help
    + This option makes DSA cryptographic keys available. They can be used
    + for signature verification.
    +
    config KEYS_DEBUG_PROC_KEYS
    bool "Enable the /proc/keys file by which keys may be viewed"
    depends on KEYS
    diff --git a/security/keys/Makefile b/security/keys/Makefile
    index ca85b01..8c499b1 100644
    --- a/security/keys/Makefile
    +++ b/security/keys/Makefile
    @@ -16,8 +16,10 @@ obj-y := \
    obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
    obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted-keys/
    obj-$(CONFIG_CRYPTO_KEY_TYPE) += crypto_keys.o
    +obj-$(CONFIG_CRYPTO_KEY_DSA) += crypto_dsa.o
    obj-$(CONFIG_KEYS_COMPAT) += compat.o
    obj-$(CONFIG_PROC_FS) += proc.o
    obj-$(CONFIG_SYSCTL) += sysctl.o

    crypto_keys-y := crypto_type.o pgp_parse.o
    +crypto_dsa-y := crypto_dsa_subtype.o
    diff --git a/security/keys/crypto_dsa.h b/security/keys/crypto_dsa.h
    new file mode 100644
    index 0000000..0455634
    --- /dev/null
    +++ b/security/keys/crypto_dsa.h
    @@ -0,0 +1,36 @@
    +/* DSA internal definitions
    + *
    + * Copyright (C) 2011 Red Hat, Inc. All Rights Reserved.
    + * Written by David Howells (dhowells@redhat.com)
    + *
    + * This program is free software; you can redistribute it and/or
    + * modify it under the terms of the GNU General Public Licence
    + * as published by the Free Software Foundation; either version
    + * 2 of the Licence, or (at your option) any later version.
    + */
    +
    +#define DSA_NPKEY 4 /* number of MPI's in DSA public key */
    +
    +extern struct crypto_key_subtype DSA_crypto_key_subtype;
    +
    +/*
    + * public key record
    + */
    +struct DSA_public_key {
    + struct pgp_parse_pubkey pgp;
    + union {
    + MPI pkey[DSA_NPKEY];
    + struct {
    + MPI p; /* DSA prime */
    + MPI q; /* DSA group order */
    + MPI g; /* DSA group generator */
    + MPI y; /* DSA public-key value = g^x mod p */
    + };
    + };
    +};
    +
    +struct DSA_payload {
    + u8 key_id[8]; /* ID of this key pair */
    + u8 key_id_size; /* Number of bytes in key_id */
    + struct DSA_public_key *public_key;
    +};
    diff --git a/security/keys/crypto_dsa_subtype.c b/security/keys/crypto_dsa_subtype.c
    new file mode 100644
    index 0000000..ae6133b
    --- /dev/null
    +++ b/security/keys/crypto_dsa_subtype.c
    @@ -0,0 +1,338 @@
    +/* DSA crypto key subtype
    + *
    + * Copyright (C) 2011 Red Hat, Inc. All Rights Reserved.
    + * Written by David Howells (dhowells@redhat.com)
    + *
    + * This file is derived from GnuPG.
    + * Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
    + *
    + * 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 2 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, write to the Free Software
    + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
    + */
    +
    +#define DEBUG
    +#define pr_fmt(fmt) "DSA: "fmt
    +#include <keys/crypto-subtype.h>
    +#include <linux/module.h>
    +#include <linux/kernel.h>
    +#include <linux/slab.h>
    +#include <linux/mpi.h>
    +#include <linux/pgp.h>
    +#include <crypto/hash.h>
    +#define __KDEBUG
    +#include "internal.h"
    +#include "crypto_dsa.h"
    +
    +MODULE_LICENSE("GPL");
    +
    +static inline void digest_putc(struct shash_desc *digest, uint8_t ch)
    +{
    + crypto_shash_update(digest, &ch, 1);
    +}
    +
    +/*
    + * Destroy the contents of a DSA payload
    + */
    +static void DSA_destroy_payload(struct DSA_payload *dsa)
    +{
    + int i;
    +
    + if (dsa->public_key) {
    + for (i = 0; i < DSA_NPKEY; i++)
    + mpi_free(dsa->public_key->pkey[i]);
    + kfree(dsa->public_key);
    + }
    + kfree(dsa);
    +}
    +
    +/*
    + * Calculate the public key ID (RFC4880 12.2)
    + */
    +static void DSA_calc_pk_keyid(struct shash_desc *digest,
    + struct DSA_public_key *pk)
    +{
    + unsigned n;
    + unsigned nb[DSA_NPKEY];
    + unsigned nn[DSA_NPKEY];
    + u8 *pp[DSA_NPKEY];
    + u32 a32;
    + int i;
    + int npkey = DSA_NPKEY;
    +
    + kenter("");
    +
    + n = (pk->pgp.version < PGP_KEY_VERSION_4) ? 8 : 6;
    + for (i = 0; i < npkey; i++) {
    + nb[i] = mpi_get_nbits(pk->pkey[i]);
    + pp[i] = mpi_get_buffer(pk->pkey[i], nn + i, NULL);
    + n += 2 + nn[i];
    + }
    +
    + digest_putc(digest, 0x99); /* ctb */
    + digest_putc(digest, n >> 8); /* 16-bit header length */
    + digest_putc(digest, n);
    + digest_putc(digest, pk->pgp.version);
    +
    + a32 = pk->pgp.creation_time;
    + digest_putc(digest, a32 >> 24);
    + digest_putc(digest, a32 >> 16);
    + digest_putc(digest, a32 >> 8);
    + digest_putc(digest, a32 >> 0);
    +
    + if (pk->pgp.version < PGP_KEY_VERSION_4) {
    + u16 a16;
    +
    + if( pk->pgp.expires_at)
    + a16 = (pk->pgp.expires_at - pk->pgp.creation_time) / 86400UL;
    + else
    + a16 = 0;
    + digest_putc(digest, a16 >> 8);
    + digest_putc(digest, a16 >> 0);
    + }
    +
    + digest_putc(digest, PGP_PUBKEY_DSA);
    +
    + for (i = 0; i < npkey; i++) {
    + digest_putc(digest, nb[i] >> 8);
    + digest_putc(digest, nb[i]);
    + crypto_shash_update(digest, pp[i], nn[i]);
    + kfree(pp[i]);
    + }
    +
    + kleave("");
    +}
    +
    +/*
    + * Calculate and check the public key ID fingerprint against the key ID
    + */
    +static int DSA_get_fingerprint(struct DSA_payload *dsa,
    + struct DSA_public_key *pk,
    + char **_fingerprint)
    +{
    + struct crypto_shash *tfm;
    + struct shash_desc *digest;
    + int digest_size, offset;
    + char *fingerprint;
    + u8 *raw_fingerprint;
    + int ret, i;
    +
    + ret = -ENOMEM;
    + tfm = crypto_alloc_shash(pk->pgp.version < PGP_KEY_VERSION_4 ?
    + "md5" : "sha1", 0, 0);
    + if (!tfm)
    + goto cleanup;
    +
    + digest = kmalloc(sizeof(*digest) + crypto_shash_descsize(tfm),
    + GFP_KERNEL);
    + if (!digest)
    + goto cleanup_tfm;
    +
    + digest->tfm = tfm;
    + digest->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
    + ret = crypto_shash_init(digest);
    + if (ret < 0)
    + goto cleanup_hash;
    +
    + DSA_calc_pk_keyid(digest, pk);
    +
    + digest_size = crypto_shash_digestsize(tfm);
    +
    + raw_fingerprint = kmalloc(digest_size, GFP_KERNEL);
    + if (!raw_fingerprint)
    + goto cleanup_hash;
    +
    + ret = crypto_shash_final(digest, raw_fingerprint);
    + if (ret < 0)
    + goto cleanup_raw_fingerprint;
    +
    + fingerprint = kmalloc(digest_size * 2 + 1, GFP_KERNEL);
    + if (!fingerprint)
    + goto cleanup_raw_fingerprint;
    +
    + offset = digest_size - 8;
    + kdebug("offset %u/%u", offset, digest_size);
    +
    + for (i = 0; i < digest_size; i++)
    + sprintf(fingerprint + i * 2, "%02x", raw_fingerprint[i]);
    + kdebug("fingerprint %s", fingerprint);
    +
    + memcpy(&dsa->key_id, raw_fingerprint + offset, 8);
    + dsa->key_id_size = 8;
    +
    + *_fingerprint = fingerprint;
    + fingerprint = NULL;
    + ret = 0;
    +cleanup_raw_fingerprint:
    + kfree(raw_fingerprint);
    +cleanup_hash:
    + kfree(digest);
    +cleanup_tfm:
    + crypto_free_shash(tfm);
    +cleanup:
    + kleave(" = %d", ret);
    + return ret;
    +}
    +
    +struct DSA_pk_parse_context {
    + struct pgp_parse_context pgp;
    + struct DSA_payload *dsa;
    + struct DSA_public_key *pk;
    + char *fingerprint;
    +};
    +
    +/*
    + * Extract a public key or subkey from the PGP stream.
    + */
    +static int DSA_parse_public_key(struct pgp_parse_context *context,
    + enum pgp_packet_tag type,
    + u8 headerlen,
    + const u8 *data,
    + size_t datalen)
    +{
    + struct DSA_pk_parse_context *ctx =
    + container_of(context, struct DSA_pk_parse_context, pgp);
    + struct DSA_payload *dsa = ctx->dsa;
    + struct DSA_public_key *pk;
    + int i, ret;
    +
    + kenter(",%u,%u,,%zu", type, headerlen, datalen);
    +
    + if (dsa->public_key) {
    + kleave(" = -ENOKEY [already]");
    + return -ENOKEY;
    + }
    +
    + pk = kzalloc(sizeof(struct DSA_public_key), GFP_KERNEL);
    + if (!pk)
    + return -ENOMEM;
    +
    + ret = pgp_parse_public_key(&data, &datalen, &pk->pgp);
    + if (pk->pgp.pubkey_algo != PGP_PUBKEY_DSA) {
    + pr_debug("Ignoring non-DSA public key [%u]\n",
    + pk->pgp.pubkey_algo);
    + ret = -ENOKEY;
    + goto cleanup;
    + }
    +
    + ret = -ENOMEM;
    + for (i = 0; i < DSA_NPKEY; i++) {
    + unsigned int remaining = datalen;
    + pk->pkey[i] = mpi_read_from_buffer(data, &remaining);
    + if (!pk->pkey[i])
    + goto cleanup;
    + data += remaining;
    + datalen -= remaining;
    + }
    +
    + ret = DSA_get_fingerprint(dsa, pk, &ctx->fingerprint);
    + if (ret < 0)
    + goto cleanup;
    +
    + dsa->public_key = pk;
    + kleave(" = 0 [use]");
    + return 0;
    +
    +cleanup:
    + kdebug("cleanup");
    + if (pk) {
    + for (i = 0; i < DSA_NPKEY; i++)
    + mpi_free(pk->pkey[i]);
    + kfree(pk);
    + }
    + kleave(" = %d", ret);
    + return ret;
    +}
    +
    +/*
    + * Instantiate a DSA key
    + */
    +static int DSA_instantiate(struct key *key,
    + const void *data, size_t datalen)
    +{
    + struct DSA_pk_parse_context ctx;
    + struct DSA_payload *dsa;
    + int ret;
    +
    + kenter("");
    +
    + ret = key_payload_reserve(key, datalen);
    + if (ret < 0)
    + return ret;
    +
    + dsa = kzalloc(sizeof(struct DSA_payload), GFP_KERNEL);
    + if (!dsa)
    + return -ENOMEM;
    +
    + ctx.pgp.types_of_interest =
    + (1 << PGP_PKT_PUBLIC_KEY) | (1 << PGP_PKT_PUBLIC_SUBKEY);
    + ctx.pgp.process_packet = DSA_parse_public_key;
    + ctx.dsa = dsa;
    + ctx.pk = NULL;
    + ctx.fingerprint = NULL;
    +
    + ret = pgp_parse_packets(data, datalen, &ctx.pgp);
    + if (ret < 0) {
    + DSA_destroy_payload(dsa);
    + kfree(ctx.fingerprint);
    + key_payload_reserve(key, 0);
    + return ret;
    + }
    +
    + key->type_data.p[0] = &DSA_crypto_key_subtype;
    + key->type_data.p[1] = ctx.fingerprint;
    + key->payload.data = dsa;
    + return 0;
    +}
    +
    +/*
    + * Destroy a DSA key
    + */
    +static void DSA_destroy(struct key *key)
    +{
    + if (key->payload.data)
    + DSA_destroy_payload(key->payload.data);
    +}
    +
    +/*
    + * DSA crypto key subtype
    + */
    +struct crypto_key_subtype DSA_crypto_key_subtype = {
    + .owner = THIS_MODULE,
    + .name = "dsa",
    + .pubkey_algo = PGP_PUBKEY_DSA,
    + .info = CRYPTO_KEY_IS_PUBKEY_ALGO,
    + .instantiate = DSA_instantiate,
    + .destroy = DSA_destroy,
    +
    + .verify_sig_begin = DSA_verify_sig_begin,
    + .verify_sig_add_data = DSA_verify_sig_add_data,
    + .verify_sig_end = DSA_verify_sig_end,
    + .verify_sig_cancel = DSA_verify_sig_cancel,
    +};
    +
    +/*
    + * Module stuff
    + */
    +static int __init DSA_init(void)
    +{
    + return register_crypto_key_subtype(&DSA_crypto_key_subtype);
    +}
    +
    +static void __exit DSA_cleanup(void)
    +{
    + unregister_crypto_key_subtype(&DSA_crypto_key_subtype);
    +}
    +
    +module_init(DSA_init);
    +module_exit(DSA_cleanup);


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