/* $OpenBSD: auth2-pubkeyfile.c,v 1.4 2023/03/05 05:34:09 dtucker Exp $ */
/*
 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
 * Copyright (c) 2010 Damien Miller.  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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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 "includes.h"

#include <sys/types.h>
#include <sys/stat.h>

#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "ssh.h"
#include "log.h"
#include "misc.h"
#include "sshkey.h"
#include "digest.h"
#include "hostfile.h"
#include "auth.h"
#include "auth-options.h"
#include "authfile.h"
#include "match.h"
#include "ssherr.h"

int
auth_authorise_keyopts(struct passwd *pw, struct sshauthopt *opts,
    int allow_cert_authority, const char *remote_ip, const char *remote_host,
    const char *loc)
{
        time_t now = time(NULL);
        char buf[64];

        /*
         * Check keys/principals file expiry time.
         * NB. validity interval in certificate is handled elsewhere.
         */
        if (opts->valid_before && now > 0 &&
            opts->valid_before < (uint64_t)now) {
                format_absolute_time(opts->valid_before, buf, sizeof(buf));
                debug("%s: entry expired at %s", loc, buf);
                auth_debug_add("%s: entry expired at %s", loc, buf);
                return -1;
        }
        /* Consistency checks */
        if (opts->cert_principals != NULL && !opts->cert_authority) {
                debug("%s: principals on non-CA key", loc);
                auth_debug_add("%s: principals on non-CA key", loc);
                /* deny access */
                return -1;
        }
        /* cert-authority flag isn't valid in authorized_principals files */
        if (!allow_cert_authority && opts->cert_authority) {
                debug("%s: cert-authority flag invalid here", loc);
                auth_debug_add("%s: cert-authority flag invalid here", loc);
                /* deny access */
                return -1;
        }

        /* Perform from= checks */
        if (opts->required_from_host_keys != NULL) {
                switch (match_host_and_ip(remote_host, remote_ip,
                    opts->required_from_host_keys )) {
                case 1:
                        /* Host name matches. */
                        break;
                case -1:
                default:
                        debug("%s: invalid from criteria", loc);
                        auth_debug_add("%s: invalid from criteria", loc);
                        /* FALLTHROUGH */
                case 0:
                        logit("%s: Authentication tried for %.100s with "
                            "correct key but not from a permitted "
                            "host (host=%.200s, ip=%.200s, required=%.200s).",
                            loc, pw->pw_name, remote_host, remote_ip,
                            opts->required_from_host_keys);
                        auth_debug_add("%s: Your host '%.200s' is not "
                            "permitted to use this key for login.",
                            loc, remote_host);
                        /* deny access */
                        return -1;
                }
        }
        /* Check source-address restriction from certificate */
        if (opts->required_from_host_cert != NULL) {
                switch (addr_match_cidr_list(remote_ip,
                    opts->required_from_host_cert)) {
                case 1:
                        /* accepted */
                        break;
                case -1:
                default:
                        /* invalid */
                        error("%s: Certificate source-address invalid", loc);
                        /* FALLTHROUGH */
                case 0:
                        logit("%s: Authentication tried for %.100s with valid "
                            "certificate but not from a permitted source "
                            "address (%.200s).", loc, pw->pw_name, remote_ip);
                        auth_debug_add("%s: Your address '%.200s' is not "
                            "permitted to use this certificate for login.",
                            loc, remote_ip);
                        return -1;
                }
        }
        /*
         *
         * XXX this is spammy. We should report remotely only for keys
         *     that are successful in actual auth attempts, and not PK_OK
         *     tests.
         */
        auth_log_authopts(loc, opts, 1);

        return 0;
}

static int
match_principals_option(const char *principal_list, struct sshkey_cert *cert)
{
        char *result;
        u_int i;

        /* XXX percent_expand() sequences for authorized_principals? */

        for (i = 0; i < cert->nprincipals; i++) {
                if ((result = match_list(cert->principals[i],
                    principal_list, NULL)) != NULL) {
                        debug3("matched principal from key options \"%.100s\"",
                            result);
                        free(result);
                        return 1;
                }
        }
        return 0;
}

/*
 * Process a single authorized_principals format line. Returns 0 and sets
 * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
 * log preamble for file/line information.
 */
int
auth_check_principals_line(char *cp, const struct sshkey_cert *cert,
    const char *loc, struct sshauthopt **authoptsp)
{
        u_int i, found = 0;
        char *ep, *line_opts;
        const char *reason = NULL;
        struct sshauthopt *opts = NULL;

        if (authoptsp != NULL)
                *authoptsp = NULL;

        /* Trim trailing whitespace. */
        ep = cp + strlen(cp) - 1;
        while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
                *ep-- = '\0';

        /*
         * If the line has internal whitespace then assume it has
         * key options.
         */
        line_opts = NULL;
        if ((ep = strrchr(cp, ' ')) != NULL ||
            (ep = strrchr(cp, '\t')) != NULL) {
                for (; *ep == ' ' || *ep == '\t'; ep++)
                        ;
                line_opts = cp;
                cp = ep;
        }
        if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
                debug("%s: bad principals options: %s", loc, reason);
                auth_debug_add("%s: bad principals options: %s", loc, reason);
                return -1;
        }
        /* Check principals in cert against those on line */
        for (i = 0; i < cert->nprincipals; i++) {
                if (strcmp(cp, cert->principals[i]) != 0)
                        continue;
                debug3("%s: matched principal \"%.100s\"",
                    loc, cert->principals[i]);
                found = 1;
        }
        if (found && authoptsp != NULL) {
                *authoptsp = opts;
                opts = NULL;
        }
        sshauthopt_free(opts);
        return found ? 0 : -1;
}

int
auth_process_principals(FILE *f, const char *file,
    const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
{
        char loc[256], *line = NULL, *cp, *ep;
        size_t linesize = 0;
        u_long linenum = 0, nonblank = 0;
        u_int found_principal = 0;

        if (authoptsp != NULL)
                *authoptsp = NULL;

        while (getline(&line, &linesize, f) != -1) {
                linenum++;
                /* Always consume entire input */
                if (found_principal)
                        continue;

                /* Skip leading whitespace. */
                for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
                        ;
                /* Skip blank and comment lines. */
                if ((ep = strchr(cp, '#')) != NULL)
                        *ep = '\0';
                if (!*cp || *cp == '\n')
                        continue;

                nonblank++;
                snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
                if (auth_check_principals_line(cp, cert, loc, authoptsp) == 0)
                        found_principal = 1;
        }
        debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum);
        free(line);
        return found_principal;
}

/*
 * Check a single line of an authorized_keys-format file. Returns 0 if key
 * matches, -1 otherwise. Will return key/cert options via *authoptsp
 * on success. "loc" is used as file/line location in log messages.
 */
int
auth_check_authkey_line(struct passwd *pw, struct sshkey *key,
    char *cp, const char *remote_ip, const char *remote_host, const char *loc,
    struct sshauthopt **authoptsp)
{
        int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
        struct sshkey *found = NULL;
        struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
        char *key_options = NULL, *fp = NULL;
        const char *reason = NULL;
        int ret = -1;

        if (authoptsp != NULL)
                *authoptsp = NULL;

        if ((found = sshkey_new(want_keytype)) == NULL) {
                debug3_f("keytype %d failed", want_keytype);
                goto out;
        }

        /* XXX djm: peek at key type in line and skip if unwanted */

        if (sshkey_read(found, &cp) != 0) {
                /* no key?  check for options */
                debug2("%s: check options: '%s'", loc, cp);
                key_options = cp;
                if (sshkey_advance_past_options(&cp) != 0) {
                        reason = "invalid key option string";
                        goto fail_reason;
                }
                skip_space(&cp);
                if (sshkey_read(found, &cp) != 0) {
                        /* still no key?  advance to next line*/
                        debug2("%s: advance: '%s'", loc, cp);
                        goto out;
                }
        }
        /* Parse key options now; we need to know if this is a CA key */
        if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
                debug("%s: bad key options: %s", loc, reason);
                auth_debug_add("%s: bad key options: %s", loc, reason);
                goto out;
        }
        /* Ignore keys that don't match or incorrectly marked as CAs */
        if (sshkey_is_cert(key)) {
                /* Certificate; check signature key against CA */
                if (!sshkey_equal(found, key->cert->signature_key) ||
                    !keyopts->cert_authority)
                        goto out;
        } else {
                /* Plain key: check it against key found in file */
                if (!sshkey_equal(found, key) || keyopts->cert_authority)
                        goto out;
        }

        /* We have a candidate key, perform authorisation checks */
        if ((fp = sshkey_fingerprint(found,
            SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL)
                fatal_f("fingerprint failed");

        debug("%s: matching %s found: %s %s", loc,
            sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);

        if (auth_authorise_keyopts(pw, keyopts,
            sshkey_is_cert(key), remote_ip, remote_host, loc) != 0) {
                reason = "Refused by key options";
                goto fail_reason;
        }
        /* That's all we need for plain keys. */
        if (!sshkey_is_cert(key)) {
                verbose("Accepted key %s %s found at %s",
                    sshkey_type(found), fp, loc);
                finalopts = keyopts;
                keyopts = NULL;
                goto success;
        }

        /*
         * Additional authorisation for certificates.
         */

        /* Parse and check options present in certificate */
        if ((certopts = sshauthopt_from_cert(key)) == NULL) {
                reason = "Invalid certificate options";
                goto fail_reason;
        }
        if (auth_authorise_keyopts(pw, certopts, 0,
            remote_ip, remote_host, loc) != 0) {
                reason = "Refused by certificate options";
                goto fail_reason;
        }
        if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
                goto fail_reason;

        /*
         * If the user has specified a list of principals as
         * a key option, then prefer that list to matching
         * their username in the certificate principals list.
         */
        if (keyopts->cert_principals != NULL &&
            !match_principals_option(keyopts->cert_principals, key->cert)) {
                reason = "Certificate does not contain an authorized principal";
                goto fail_reason;
        }
        if (sshkey_cert_check_authority_now(key, 0, 0, 0,
            keyopts->cert_principals == NULL ? pw->pw_name : NULL,
            &reason) != 0)
                goto fail_reason;

        verbose("Accepted certificate ID \"%s\" (serial %llu) "
            "signed by CA %s %s found at %s",
            key->cert->key_id,
            (unsigned long long)key->cert->serial,
            sshkey_type(found), fp, loc);

 success:
        if (finalopts == NULL)
                fatal_f("internal error: missing options");
        if (authoptsp != NULL) {
                *authoptsp = finalopts;
                finalopts = NULL;
        }
        /* success */
        ret = 0;
        goto out;

 fail_reason:
        error("%s", reason);
        auth_debug_add("%s", reason);
 out:
        free(fp);
        sshauthopt_free(keyopts);
        sshauthopt_free(certopts);
        sshauthopt_free(finalopts);
        sshkey_free(found);
        return ret;
}

/*
 * Checks whether key is allowed in authorized_keys-format file,
 * returns 1 if the key is allowed or 0 otherwise.
 */
int
auth_check_authkeys_file(struct passwd *pw, FILE *f, char *file,
    struct sshkey *key, const char *remote_ip,
    const char *remote_host, struct sshauthopt **authoptsp)
{
        char *cp, *line = NULL, loc[256];
        size_t linesize = 0;
        int found_key = 0;
        u_long linenum = 0, nonblank = 0;

        if (authoptsp != NULL)
                *authoptsp = NULL;

        while (getline(&line, &linesize, f) != -1) {
                linenum++;
                /* Always consume entire file */
                if (found_key)
                        continue;

                /* Skip leading whitespace, empty and comment lines. */
                cp = line;
                skip_space(&cp);
                if (!*cp || *cp == '\n' || *cp == '#')
                        continue;

                nonblank++;
                snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
                if (auth_check_authkey_line(pw, key, cp,
                    remote_ip, remote_host, loc, authoptsp) == 0)
                        found_key = 1;
        }
        free(line);
        debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum);
        return found_key;
}

static FILE *
auth_openfile(const char *file, struct passwd *pw, int strict_modes,
    int log_missing, char *file_type)
{
        char line[1024];
        struct stat st;
        int fd;
        FILE *f;

        if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
                if (errno != ENOENT) {
                        logit("Could not open user '%s' %s '%s': %s",
                            pw->pw_name, file_type, file, strerror(errno));
                } else if (log_missing) {
                        debug("Could not open user '%s' %s '%s': %s",
                            pw->pw_name, file_type, file, strerror(errno));
                }
                return NULL;
        }

        if (fstat(fd, &st) == -1) {
                close(fd);
                return NULL;
        }
        if (!S_ISREG(st.st_mode)) {
                logit("User '%s' %s '%s' is not a regular file",
                    pw->pw_name, file_type, file);
                close(fd);
                return NULL;
        }
        unset_nonblock(fd);
        if ((f = fdopen(fd, "r")) == NULL) {
                close(fd);
                return NULL;
        }
        if (strict_modes &&
            safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
                fclose(f);
                logit("Authentication refused: %s", line);
                auth_debug_add("Ignored %s: %s", file_type, line);
                return NULL;
        }

        return f;
}


FILE *
auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
{
        return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
}

FILE *
auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
{
        return auth_openfile(file, pw, strict_modes, 0,
            "authorized principals");
}