source: openpam/trunk/modules/pam_oath/oath_key.c @ 643

/*-
 * Copyright (c) 2013 Universitetet i Oslo
 * All rights reserved.
 *
 * 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.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 * $Id: oath_key.c 643 2013-03-05 15:24:00Z des $
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <sys/types.h>

#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <security/pam_appl.h>
#include <security/openpam.h>

#include "openpam_asprintf.h"
#include "openpam_strlcmp.h"

#include "oath.h"

/*
 * Allocate a struct oath_key with sufficient additional space for the
 * label and key.
 */
struct oath_key *
oath_key_alloc(size_t extra)
{
        struct oath_key *key;

        if ((key = calloc(1, sizeof *key + extra)) == NULL) {
                openpam_log(PAM_LOG_ERROR, "malloc(): %s", strerror(errno));
                return (NULL);
        }
        key->datalen = extra;
        /* XXX should try to wire */
        return (key);
}

/*
 * Wipe and free a struct oath_key
 */
void
oath_key_free(struct oath_key *key)
{

        if (key != NULL) {
                memset(key, 0, sizeof *key + key->datalen);
                free(key);
        }
}

/*
 * Allocate a struct oath_key and populate it from a Google Authenticator
 * otpauth URI
 */
struct oath_key *
oath_key_from_uri(const char *uri)
{
        struct oath_key *key;
        const char *p, *q, *r;
        uintmax_t n;
        char *e;

        /*
         * The URI string contains the label, the base32-encoded key and
         * some fluff, so the combined length of the label and key can
         * never exceed the length of the URI string.
         */
        if ((key = oath_key_alloc(strlen(uri))) == NULL)
                return (NULL);

        /* check method */
        p = uri;
        if (strlcmp("otpauth://", p, 10) != 0)
                goto invalid;
        p += 10;

        /* check mode (hotp = event, totp = time-sync) */
        if ((q = strchr(p, '/')) == NULL)
                goto invalid;
        if (strlcmp("hotp", p, q - p) == 0) {
                key->mode = om_hotp;
        } else if (strlcmp("totp", p, q - p) == 0) {
                key->mode = om_totp;
        } else {
                goto invalid;
        }
        p = q + 1;

        /* extract label */
        if ((q = strchr(p, '?')) == NULL)
                goto invalid;
        key->label = (char *)key->data;
        key->labellen = (q - p) + 1;
        memcpy(key->label, p, q - p);
        key->label[q - p] = '\0';
        p = q + 1;

        /* extract parameters */
        key->counter = UINT64_MAX;
        while (*p != '\0') {
                if ((q = strchr(p, '=')) == NULL)
                        goto invalid;
                q = q + 1;
                if ((r = strchr(p, '&')) == NULL)
                        r = strchr(p, '\0');
                if (r < q)
                        /* & before = */
                        goto invalid;
                /* p points to key, q points to value, r points to & or NUL */
                if (strlcmp("secret=", p, q - p) == 0) {
                        if (key->keylen != 0)
                                /* dupe */
                                goto invalid;
                        /* base32-encoded key - multiple of 40 bits */
                        if ((r - q) % 8 != 0 ||
                            base32_declen(r - q) > OATH_MAX_KEYLEN)
                                goto invalid;
                        key->key = key->data + key->labellen;
                        key->keylen = key->datalen - key->labellen;
                        if (base32_dec(q, r - q, key->key, &key->keylen) != 0)
                                goto invalid;
                        if (base32_enclen(key->keylen) != (size_t)(r - q))
                                goto invalid;
                } else if (strlcmp("algorithm=", p, q - p) == 0) {
                        if (key->hash != oh_undef)
                                /* dupe */
                                goto invalid;
                        if (strlcmp("SHA1", q, r - q) == 0)
                                key->hash = oh_sha1;
                        else if (strlcmp("SHA256", q, r - q) == 0)
                                key->hash = oh_sha256;
                        else if (strlcmp("SHA512", q, r - q) == 0)
                                key->hash = oh_sha512;
                        else if (strlcmp("MD5", q, r - q) == 0)
                                key->hash = oh_md5;
                        else
                                goto invalid;
                } else if (strlcmp("digits=", p, q - p) == 0) {
                        if (key->digits != 0)
                                /* dupe */
                                goto invalid;
                        /* only 6 or 8 */
                        if (r - q != 1 || (*q != '6' && *q != '8'))
                                goto invalid;
                        key->digits = *q - '0';
                } else if (strlcmp("counter=", p, q - p) == 0) {
                        if (key->counter != UINT64_MAX)
                                /* dupe */
                                goto invalid;
                        n = strtoumax(q, &e, 10);
                        if (e != r || n >= UINT64_MAX)
                                goto invalid;
                        key->counter = (uint64_t)n;
                } else if (strlcmp("period=", p, q - p) == 0) {
                        if (key->timestep != 0)
                                /* dupe */
                                goto invalid;
                        n = strtoumax(q, &e, 10);
                        if (e != r || n > OATH_MAX_TIMESTEP)
                                goto invalid;
                        key->timestep = n;
                } else {
                        goto invalid;
                }
                /* final parameter? */
                if (*r == '\0')
                        break;
                /* skip & and continue */
                p = r + 1;
        }

        /* sanity checks and default values */
        if (key->mode == om_hotp) {
                if (key->timestep != 0)
                        goto invalid;
                if (key->counter == UINTMAX_MAX)
                        key->counter = 0;
        } else if (key->mode == om_totp) {
                if (key->counter != UINTMAX_MAX)
                        goto invalid;
                if (key->timestep == 0)
                        key->timestep = OATH_DEF_TIMESTEP;
        } else {
                /* unreachable */
                oath_key_free(key);
                return (NULL);
        }
        if (key->hash == oh_undef)
                key->hash = oh_sha1;
        if (key->digits == 0)
                key->digits = 6;
        if (key->keylen == 0)
                goto invalid;
        return (key);

invalid:
        openpam_log(PAM_LOG_NOTICE, "invalid OATH URI: %s", uri);
        oath_key_free(key);
        return (NULL);
}

struct oath_key *
oath_key_from_file(const char *filename)
{
        struct oath_key *key;
        FILE *f;
        char *line;
        size_t len;

        if ((f = fopen(filename, "r")) == NULL)
                return (NULL);
        /* get first non-empty non-comment line */
        line = openpam_readline(f, NULL, &len);
        if (strlcmp("otpauth://", line, len) == 0) {
                key = oath_key_from_uri(line);
        } else {
                openpam_log(PAM_LOG_ERROR,
                    "unrecognized key file format: %s", filename);
                key = NULL;
        }
        fclose(f);
        return (key);
}

char *
oath_key_to_uri(const struct oath_key *key)
{
        const char *hash;
        char *tmp, *uri;
        size_t kslen, urilen;

        switch (key->hash) {
        case oh_sha1:
                hash = "SHA1";
                break;
        case oh_sha256:
                hash = "SHA256";
                break;
        case oh_sha512:
                hash = "SHA512";
                break;
        case oh_md5:
                hash = "MD5";
                break;
        default:
                return (NULL);
        }

        if (key->mode == om_hotp) {
                urilen = asprintf(&uri, "otpauth://"
                    "%s/%s?algorithm=%s&digits=%d&counter=%ju&secret=",
                    "hotp", key->label, hash, key->digits,
                    (uintmax_t)key->counter);
        } else if (key->mode == om_totp) {
                urilen = asprintf(&uri, "otpauth://"
                    "%s/%s?algorithm=%s&digits=%d&period=%u&secret=",
                    "totp", key->label, hash, key->digits, key->timestep);
        } else {
                /* unreachable */
                return (NULL);
        }

        /* compute length of base32-encoded key and append it */
        kslen = base32_enclen(key->keylen) + 1;
        if ((tmp = realloc(uri, urilen + kslen)) == NULL) {
                free(uri);
                return (NULL);
        }
        uri = tmp;
        if (base32_enc(key->key, key->keylen, uri + urilen, &kslen) != 0) {
                free(uri);
                return (NULL);
        }

        return (uri);
}

struct oath_key *
oath_dummy_key(enum oath_mode mode, enum oath_hash hash, unsigned int digits)
{
        struct oath_key *key;

        if ((key = oath_key_alloc(DUMMY_LABELLEN + DUMMY_KEYLEN)) == NULL)
                return (NULL);
        key->mode = mode;
        key->digits = digits;
        key->counter = 0;
        key->timestep = 30;
        key->hash = hash;
        key->label = (char *)key->data;
        memcpy(key->label, DUMMY_LABEL, DUMMY_LABELLEN);
        key->key = key->data + DUMMY_LABELLEN;
        key->keylen = DUMMY_KEYLEN;
        return (key);
}