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lib/libsecureboot/openpgp/opgp_key.c

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/*-
* Copyright (c) 2018, Juniper Networks, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "../libsecureboot-priv.h"
#include "decode.h"
#include "packet.h"
/**
* @brief decode user-id packet
*
* This is trivial
*
* @sa rfc4880:5.11
*/
ssize_t
decode_user(int tag, unsigned char **pptr, size_t len, OpenPGP_user *user)
{
char *cp;
if (tag == 13) {
user->id = malloc(len + 1);
strncpy(user->id, (char *)*pptr, len);
user->id[len] = '\0';
user->name = user->id;
cp = strchr(user->id, '<');
if (cp > user->id) {
user->id = strdup(user->id);
cp[-1] = '\0';
}
}
*pptr += len;
return ((ssize_t)len);
}
/**
* @brief decode a key packet
*
* We only really support v4 and RSA
*
* @sa rfc4880:5.5.1.1
*/
ssize_t
decode_key(int tag, unsigned char **pptr, size_t len, OpenPGP_key *key)
{
unsigned char *ptr;
int version;
#ifdef USE_BEARSSL
br_sha1_context mctx;
unsigned char mdata[br_sha512_SIZE];
size_t mlen;
#else
RSA *rsa = NULL;
const EVP_MD *md = NULL;
EVP_MD_CTX mctx;
unsigned char mdata[EVP_MAX_MD_SIZE];
unsigned int mlen;
#endif
if (tag != 6)
return (-1);
key->key = NULL;
ptr = *pptr;
version = *ptr;
if (version == 4) { /* all we support really */
/* comput key fingerprint and id @sa rfc4880:12.2 */
mdata[0] = 0x99; /* rfc4880: 12.2.a.1 */
mdata[1] = (len >> 8) & 0xff;
mdata[2] = len & 0xff;
#ifdef USE_BEARSSL
br_sha1_init(&mctx);
br_sha1_update(&mctx, mdata, 3);
br_sha1_update(&mctx, ptr, len);
br_sha1_out(&mctx, mdata);
mlen = br_sha1_SIZE;
#else
md = EVP_get_digestbyname("sha1");
EVP_DigestInit(&mctx, md);
EVP_DigestUpdate(&mctx, mdata, 3);
EVP_DigestUpdate(&mctx, ptr, len);
mlen = (unsigned int)sizeof(mdata);
EVP_DigestFinal(&mctx, mdata, &mlen);
#endif
key->id = octets2hex(&mdata[mlen - 8], 8);
}
ptr += 1; /* done with version */
ptr += 4; /* skip ctime */
if (version == 3)
ptr += 2; /* valid days */
key->sig_alg = *ptr++;
if (key->sig_alg == 1) { /* RSA */
#ifdef USE_BEARSSL
key->key = NEW(br_rsa_public_key);
if (!key->key)
goto oops;
key->key->n = mpi2bn(&ptr, &key->key->nlen);
key->key->e = mpi2bn(&ptr, &key->key->elen);
#else
rsa = RSA_new();
if (!rsa)
goto oops;
rsa->n = mpi2bn(&ptr);
rsa->e = mpi2bn(&ptr);
key->key = EVP_PKEY_new();
if (!key->key || !rsa->n || !rsa->e) {
goto oops;
}
if (!EVP_PKEY_set1_RSA(key->key, rsa))
goto oops;
#endif
}
/* we are done */
return ((ssize_t)len);
oops:
#ifdef USE_BEARSSL
free(key->key);
key->key = NULL;
#else
if (rsa)
RSA_free(rsa);
if (key->key) {
EVP_PKEY_free(key->key);
key->key = NULL;
}
#endif
return (-1);
}
static OpenPGP_key *
load_key_buf(unsigned char *buf, size_t nbytes)
{
unsigned char *data = NULL;
unsigned char *ptr;
ssize_t rc;
int tag;
OpenPGP_key *key;
if (!buf)
return (NULL);
initialize();
if (!(buf[0] & OPENPGP_TAG_ISTAG)) {
data = dearmor((char *)buf, nbytes, &nbytes);
ptr = data;
} else
ptr = buf;
key = NEW(OpenPGP_key);
if (key) {
rc = decode_packet(0, &ptr, nbytes, (decoder_t)decode_key,
key);
if (rc < 0) {
free(key);
key = NULL;
} else if (rc > 8) {
int isnew, ltype;
tag = decode_tag(ptr, &isnew, &ltype);
if (tag == 13) {
key->user = NEW(OpenPGP_user);
rc = decode_packet(0, &ptr, (size_t)rc,
(decoder_t)decode_user, key->user);
}
}
}
free(data);
return (key);
}
static LIST_HEAD(, OpenPGP_key_) trust_list;
/**
* @brief add a key to our list
*/
void
openpgp_trust_add(OpenPGP_key *key)
{
static int once = 0;
if (!once) {
once = 1;
LIST_INIT(&trust_list);
}
if (key)
LIST_INSERT_HEAD(&trust_list, key, entries);
}
/**
* @brief if keyID is in our list return the key
*
* @return key or NULL
*/
OpenPGP_key *
openpgp_trust_get(const char *keyID)
{
OpenPGP_key *key;
openpgp_trust_add(NULL); /* initialize if needed */
LIST_FOREACH(key, &trust_list, entries) {
if (strcmp(key->id, keyID) == 0)
return (key);
}
return (NULL);
}
/**
* @brief load a key from file
*/
OpenPGP_key *
load_key_file(const char *kfile)
{
unsigned char *data = NULL;
size_t n;
OpenPGP_key *key;
data = read_file(kfile, &n);
key = load_key_buf(data, n);
free(data);
openpgp_trust_add(key);
return (key);
}
#include <ta_asc.h>
#ifndef _STANDALONE
/* we can lookup keyID in filesystem */
static const char *trust_store[] = {
"/var/db/trust",
"/etc/db/trust",
NULL,
};
/**
* @brief lookup key id in trust store
*
*/
static OpenPGP_key *
load_trusted_key_id(const char *keyID)
{
char kfile[MAXPATHLEN];
const char **tp;
size_t n;
for (tp = trust_store; *tp; tp++) {
n = (size_t)snprintf(kfile, sizeof(kfile), "%s/%s", *tp, keyID);
if (n >= sizeof(kfile))
return (NULL);
if (access(kfile, R_OK) == 0) {
return (load_key_file(kfile));
}
}
return (NULL);
}
#endif
/**
* @brief return key if trusted
*/
OpenPGP_key *
load_key_id(const char *keyID)
{
static int once = 0;
OpenPGP_key *key;
if (!once) {
#ifdef HAVE_TA_ASC
const char **tp;
char *cp;
size_t n;
for (tp = ta_ASC; *tp; tp++) {
if ((cp = strdup(*tp))) {
n = strlen(cp);
key = load_key_buf((unsigned char *)cp, n);
free(cp);
openpgp_trust_add(key);
}
}
#endif
once = 1;
}
key = openpgp_trust_get(keyID);
#ifndef _STANDALONE
if (!key)
key = load_trusted_key_id(keyID);
#endif
return (key);
}
/**
* @brief test that we can verify a signature
*
* Unlike X.509 certificates, we only support RSA keys
* so we stop after first successful signature verification
* (which should also be the first attempt ;-)
*/
int
openpgp_self_tests(void)
{
static int rc = -1; /* remember result */
#ifdef HAVE_VC_ASC
const char **vp, **tp;
char *fdata, *sdata = NULL;
size_t fbytes, sbytes;
for (tp = ta_ASC, vp = vc_ASC; *tp && *vp && rc; tp++, vp++) {
if ((fdata = strdup(*tp)) &&
(sdata = strdup(*vp))) {
fbytes = strlen(fdata);
sbytes = strlen(sdata);
rc = openpgp_verify("ta_ASC",
(unsigned char *)fdata, fbytes,
(unsigned char *)sdata, sbytes, 0);
printf("Testing verify OpenPGP signature:\t\t%s\n",
rc ? "Failed" : "Passed");
}
free(fdata);
free(sdata);
}
#endif
return (rc);
}