drm: Add atomic_cmpxchg()

[dragonfly.git] / crypto / openssh / auth2-pubkey.c

/* $OpenBSD: auth2-pubkey.c,v 1.41 2014/07/15 15:54:14 millert Exp $ */
/*
 * Copyright (c) 2000 Markus Friedl.  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 <sys/wait.h>

#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_PATHS_H
# include <paths.h>
#endif
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "compat.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "pathnames.h"
#include "uidswap.h"
#include "auth-options.h"
#include "canohost.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "authfile.h"
#include "match.h"

/* import */
extern ServerOptions options;
extern u_char *session_id2;
extern u_int session_id2_len;

static int
userauth_pubkey(Authctxt *authctxt)
{
        Buffer b;
        Key *key = NULL;
        char *pkalg, *userstyle;
        u_char *pkblob, *sig;
        u_int alen, blen, slen;
        int have_sig, pktype;
        int authenticated = 0;

        if (!authctxt->valid) {
                debug2("userauth_pubkey: disabled because of invalid user");
                return 0;
        }
        have_sig = packet_get_char();
        if (datafellows & SSH_BUG_PKAUTH) {
                debug2("userauth_pubkey: SSH_BUG_PKAUTH");
                /* no explicit pkalg given */
                pkblob = packet_get_string(&blen);
                buffer_init(&b);
                buffer_append(&b, pkblob, blen);
                /* so we have to extract the pkalg from the pkblob */
                pkalg = buffer_get_string(&b, &alen);
                buffer_free(&b);
        } else {
                pkalg = packet_get_string(&alen);
                pkblob = packet_get_string(&blen);
        }
        pktype = key_type_from_name(pkalg);
        if (pktype == KEY_UNSPEC) {
                /* this is perfectly legal */
                logit("userauth_pubkey: unsupported public key algorithm: %s",
                    pkalg);
                goto done;
        }
        key = key_from_blob(pkblob, blen);
        if (key == NULL) {
                error("userauth_pubkey: cannot decode key: %s", pkalg);
                goto done;
        }
        if (key->type != pktype) {
                error("userauth_pubkey: type mismatch for decoded key "
                    "(received %d, expected %d)", key->type, pktype);
                goto done;
        }
        if (key_type_plain(key->type) == KEY_RSA &&
            (datafellows & SSH_BUG_RSASIGMD5) != 0) {
                logit("Refusing RSA key because client uses unsafe "
                    "signature scheme");
                goto done;
        }
        if (have_sig) {
                sig = packet_get_string(&slen);
                packet_check_eom();
                buffer_init(&b);
                if (datafellows & SSH_OLD_SESSIONID) {
                        buffer_append(&b, session_id2, session_id2_len);
                } else {
                        buffer_put_string(&b, session_id2, session_id2_len);
                }
                /* reconstruct packet */
                buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
                xasprintf(&userstyle, "%s%s%s", authctxt->user,
                    authctxt->style ? ":" : "",
                    authctxt->style ? authctxt->style : "");
                buffer_put_cstring(&b, userstyle);
                free(userstyle);
                buffer_put_cstring(&b,
                    datafellows & SSH_BUG_PKSERVICE ?
                    "ssh-userauth" :
                    authctxt->service);
                if (datafellows & SSH_BUG_PKAUTH) {
                        buffer_put_char(&b, have_sig);
                } else {
                        buffer_put_cstring(&b, "publickey");
                        buffer_put_char(&b, have_sig);
                        buffer_put_cstring(&b, pkalg);
                }
                buffer_put_string(&b, pkblob, blen);
#ifdef DEBUG_PK
                buffer_dump(&b);
#endif
                pubkey_auth_info(authctxt, key, NULL);

                /* test for correct signature */
                authenticated = 0;
                if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
                    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
                    buffer_len(&b))) == 1)
                        authenticated = 1;
                buffer_free(&b);
                free(sig);
        } else {
                debug("test whether pkalg/pkblob are acceptable");
                packet_check_eom();

                /* XXX fake reply and always send PK_OK ? */
                /*
                 * XXX this allows testing whether a user is allowed
                 * to login: if you happen to have a valid pubkey this
                 * message is sent. the message is NEVER sent at all
                 * if a user is not allowed to login. is this an
                 * issue? -markus
                 */
                if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
                        packet_start(SSH2_MSG_USERAUTH_PK_OK);
                        packet_put_string(pkalg, alen);
                        packet_put_string(pkblob, blen);
                        packet_send();
                        packet_write_wait();
                        authctxt->postponed = 1;
                }
        }
        if (authenticated != 1)
                auth_clear_options();
done:
        debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
        if (key != NULL)
                key_free(key);
        free(pkalg);
        free(pkblob);
        return authenticated;
}

void
pubkey_auth_info(Authctxt *authctxt, const Key *key, const char *fmt, ...)
{
        char *fp, *extra;
        va_list ap;
        int i;

        extra = NULL;
        if (fmt != NULL) {
                va_start(ap, fmt);
                i = vasprintf(&extra, fmt, ap);
                va_end(ap);
                if (i < 0 || extra == NULL)
                        fatal("%s: vasprintf failed", __func__);        
        }

        if (key_is_cert(key)) {
                fp = key_fingerprint(key->cert->signature_key,
                    SSH_FP_MD5, SSH_FP_HEX);
                auth_info(authctxt, "%s ID %s (serial %llu) CA %s %s%s%s", 
                    key_type(key), key->cert->key_id,
                    (unsigned long long)key->cert->serial,
                    key_type(key->cert->signature_key), fp,
                    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
                free(fp);
        } else {
                fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
                auth_info(authctxt, "%s %s%s%s", key_type(key), fp,
                    extra == NULL ? "" : ", ", extra == NULL ? "" : extra);
                free(fp);
        }
        free(extra);
}

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;
}

static int
match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert)
{
        FILE *f;
        char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts;
        u_long linenum = 0;
        u_int i;

        temporarily_use_uid(pw);
        debug("trying authorized principals file %s", file);
        if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
                restore_uid();
                return 0;
        }
        while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
                /* 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;
                /* 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;
                }
                for (i = 0; i < cert->nprincipals; i++) {
                        if (strcmp(cp, cert->principals[i]) == 0) {
                                debug3("matched principal \"%.100s\" "
                                    "from file \"%s\" on line %lu",
                                    cert->principals[i], file, linenum);
                                if (auth_parse_options(pw, line_opts,
                                    file, linenum) != 1)
                                        continue;
                                fclose(f);
                                restore_uid();
                                return 1;
                        }
                }
        }
        fclose(f);
        restore_uid();
        return 0;
}

/*
 * Checks whether key is allowed in authorized_keys-format file,
 * returns 1 if the key is allowed or 0 otherwise.
 */
static int
check_authkeys_file(FILE *f, char *file, Key* key, struct passwd *pw)
{
        char line[SSH_MAX_PUBKEY_BYTES];
        const char *reason;
        int found_key = 0;
        u_long linenum = 0;
        Key *found;
        char *fp;

        found_key = 0;

        found = NULL;
        while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
                char *cp, *key_options = NULL;
                if (found != NULL)
                        key_free(found);
                found = key_new(key_is_cert(key) ? KEY_UNSPEC : key->type);
                auth_clear_options();

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

                if (key_read(found, &cp) != 1) {
                        /* no key?  check if there are options for this key */
                        int quoted = 0;
                        debug2("user_key_allowed: check options: '%s'", cp);
                        key_options = cp;
                        for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
                                if (*cp == '\\' && cp[1] == '"')
                                        cp++;   /* Skip both */
                                else if (*cp == '"')
                                        quoted = !quoted;
                        }
                        /* Skip remaining whitespace. */
                        for (; *cp == ' ' || *cp == '\t'; cp++)
                                ;
                        if (key_read(found, &cp) != 1) {
                                debug2("user_key_allowed: advance: '%s'", cp);
                                /* still no key?  advance to next line*/
                                continue;
                        }
                }
                if (key_is_cert(key)) {
                        if (!key_equal(found, key->cert->signature_key))
                                continue;
                        if (auth_parse_options(pw, key_options, file,
                            linenum) != 1)
                                continue;
                        if (!key_is_cert_authority)
                                continue;
                        fp = key_fingerprint(found, SSH_FP_MD5,
                            SSH_FP_HEX);
                        debug("matching CA found: file %s, line %lu, %s %s",
                            file, linenum, key_type(found), fp);
                        /*
                         * 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 (authorized_principals != NULL &&
                            !match_principals_option(authorized_principals,
                            key->cert)) {
                                reason = "Certificate does not contain an "
                                    "authorized principal";
 fail_reason:
                                free(fp);
                                error("%s", reason);
                                auth_debug_add("%s", reason);
                                continue;
                        }
                        if (key_cert_check_authority(key, 0, 0,
                            authorized_principals == NULL ? pw->pw_name : NULL,
                            &reason) != 0)
                                goto fail_reason;
                        if (auth_cert_options(key, pw) != 0) {
                                free(fp);
                                continue;
                        }
                        verbose("Accepted certificate ID \"%s\" "
                            "signed by %s CA %s via %s", key->cert->key_id,
                            key_type(found), fp, file);
                        free(fp);
                        found_key = 1;
                        break;
                } else if (key_equal(found, key)) {
                        if (auth_parse_options(pw, key_options, file,
                            linenum) != 1)
                                continue;
                        if (key_is_cert_authority)
                                continue;
                        found_key = 1;
                        fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
                        debug("matching key found: file %s, line %lu %s %s",
                            file, linenum, key_type(found), fp);
                        free(fp);
                        break;
                }
        }
        if (found != NULL)
                key_free(found);
        if (!found_key)
                debug2("key not found");
        return found_key;
}

/* Authenticate a certificate key against TrustedUserCAKeys */
static int
user_cert_trusted_ca(struct passwd *pw, Key *key)
{
        char *ca_fp, *principals_file = NULL;
        const char *reason;
        int ret = 0;

        if (!key_is_cert(key) || options.trusted_user_ca_keys == NULL)
                return 0;

        ca_fp = key_fingerprint(key->cert->signature_key,
            SSH_FP_MD5, SSH_FP_HEX);

        if (key_in_file(key->cert->signature_key,
            options.trusted_user_ca_keys, 1) != 1) {
                debug2("%s: CA %s %s is not listed in %s", __func__,
                    key_type(key->cert->signature_key), ca_fp,
                    options.trusted_user_ca_keys);
                goto out;
        }
        /*
         * If AuthorizedPrincipals is in use, then compare the certificate
         * principals against the names in that file rather than matching
         * against the username.
         */
        if ((principals_file = authorized_principals_file(pw)) != NULL) {
                if (!match_principals_file(principals_file, pw, key->cert)) {
                        reason = "Certificate does not contain an "
                            "authorized principal";
 fail_reason:
                        error("%s", reason);
                        auth_debug_add("%s", reason);
                        goto out;
                }
        }
        if (key_cert_check_authority(key, 0, 1,
            principals_file == NULL ? pw->pw_name : NULL, &reason) != 0)
                goto fail_reason;
        if (auth_cert_options(key, pw) != 0)
                goto out;

        verbose("Accepted certificate ID \"%s\" signed by %s CA %s via %s",
            key->cert->key_id, key_type(key->cert->signature_key), ca_fp,
            options.trusted_user_ca_keys);
        ret = 1;

 out:
        free(principals_file);
        free(ca_fp);
        return ret;
}

/*
 * Checks whether key is allowed in file.
 * returns 1 if the key is allowed or 0 otherwise.
 */
static int
user_key_allowed2(struct passwd *pw, Key *key, char *file)
{
        FILE *f;
        int found_key = 0;

        /* Temporarily use the user's uid. */
        temporarily_use_uid(pw);

        debug("trying public key file %s", file);
        if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
                found_key = check_authkeys_file(f, file, key, pw);
                fclose(f);
        }

        restore_uid();
        return found_key;
}

/*
 * Checks whether key is allowed in output of command.
 * returns 1 if the key is allowed or 0 otherwise.
 */
static int
user_key_command_allowed2(struct passwd *user_pw, Key *key)
{
        FILE *f;
        int ok, found_key = 0;
        struct passwd *pw;
        struct stat st;
        int status, devnull, p[2], i;
        pid_t pid;
        char *username, errmsg[512];

        if (options.authorized_keys_command == NULL ||
            options.authorized_keys_command[0] != '/')
                return 0;

        if (options.authorized_keys_command_user == NULL) {
                error("No user for AuthorizedKeysCommand specified, skipping");
                return 0;
        }

        username = percent_expand(options.authorized_keys_command_user,
            "u", user_pw->pw_name, (char *)NULL);
        pw = getpwnam(username);
        if (pw == NULL) {
                error("AuthorizedKeysCommandUser \"%s\" not found: %s",
                    username, strerror(errno));
                free(username);
                return 0;
        }
        free(username);

        temporarily_use_uid(pw);

        if (stat(options.authorized_keys_command, &st) < 0) {
                error("Could not stat AuthorizedKeysCommand \"%s\": %s",
                    options.authorized_keys_command, strerror(errno));
                goto out;
        }
        if (auth_secure_path(options.authorized_keys_command, &st, NULL, 0,
            errmsg, sizeof(errmsg)) != 0) {
                error("Unsafe AuthorizedKeysCommand: %s", errmsg);
                goto out;
        }

        if (pipe(p) != 0) {
                error("%s: pipe: %s", __func__, strerror(errno));
                goto out;
        }

        debug3("Running AuthorizedKeysCommand: \"%s %s\" as \"%s\"",
            options.authorized_keys_command, user_pw->pw_name, pw->pw_name);

        /*
         * Don't want to call this in the child, where it can fatal() and
         * run cleanup_exit() code.
         */
        restore_uid();

        switch ((pid = fork())) {
        case -1: /* error */
                error("%s: fork: %s", __func__, strerror(errno));
                close(p[0]);
                close(p[1]);
                return 0;
        case 0: /* child */
                for (i = 0; i < NSIG; i++)
                        signal(i, SIG_DFL);

                if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
                        error("%s: open %s: %s", __func__, _PATH_DEVNULL,
                            strerror(errno));
                        _exit(1);
                }
                /* Keep stderr around a while longer to catch errors */
                if (dup2(devnull, STDIN_FILENO) == -1 ||
                    dup2(p[1], STDOUT_FILENO) == -1) {
                        error("%s: dup2: %s", __func__, strerror(errno));
                        _exit(1);
                }
                closefrom(STDERR_FILENO + 1);

                /* Don't use permanently_set_uid() here to avoid fatal() */
                if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
                        error("setresgid %u: %s", (u_int)pw->pw_gid,
                            strerror(errno));
                        _exit(1);
                }
                if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
                        error("setresuid %u: %s", (u_int)pw->pw_uid,
                            strerror(errno));
                        _exit(1);
                }
                /* stdin is pointed to /dev/null at this point */
                if (dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
                        error("%s: dup2: %s", __func__, strerror(errno));
                        _exit(1);
                }

                execl(options.authorized_keys_command,
                    options.authorized_keys_command, user_pw->pw_name, NULL);

                error("AuthorizedKeysCommand %s exec failed: %s",
                    options.authorized_keys_command, strerror(errno));
                _exit(127);
        default: /* parent */
                break;
        }

        temporarily_use_uid(pw);

        close(p[1]);
        if ((f = fdopen(p[0], "r")) == NULL) {
                error("%s: fdopen: %s", __func__, strerror(errno));
                close(p[0]);
                /* Don't leave zombie child */
                kill(pid, SIGTERM);
                while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
                        ;
                goto out;
        }
        ok = check_authkeys_file(f, options.authorized_keys_command, key, pw);
        fclose(f);

        while (waitpid(pid, &status, 0) == -1) {
                if (errno != EINTR) {
                        error("%s: waitpid: %s", __func__, strerror(errno));
                        goto out;
                }
        }
        if (WIFSIGNALED(status)) {
                error("AuthorizedKeysCommand %s exited on signal %d",
                    options.authorized_keys_command, WTERMSIG(status));
                goto out;
        } else if (WEXITSTATUS(status) != 0) {
                error("AuthorizedKeysCommand %s returned status %d",
                    options.authorized_keys_command, WEXITSTATUS(status));
                goto out;
        }
        found_key = ok;
 out:
        restore_uid();
        return found_key;
}

/*
 * Check whether key authenticates and authorises the user.
 */
int
user_key_allowed(struct passwd *pw, Key *key)
{
        u_int success, i;
        char *file;

        if (auth_key_is_revoked(key))
                return 0;
        if (key_is_cert(key) && auth_key_is_revoked(key->cert->signature_key))
                return 0;

        success = user_cert_trusted_ca(pw, key);
        if (success)
                return success;

        success = user_key_command_allowed2(pw, key);
        if (success > 0)
                return success;

        for (i = 0; !success && i < options.num_authkeys_files; i++) {

                if (strcasecmp(options.authorized_keys_files[i], "none") == 0)
                        continue;
                file = expand_authorized_keys(
                    options.authorized_keys_files[i], pw);

                success = user_key_allowed2(pw, key, file);
                free(file);
        }

        return success;
}

Authmethod method_pubkey = {
        "publickey",
        userauth_pubkey,
        &options.pubkey_authentication
};