summaryrefslogtreecommitdiffstats
path: root/auth2-pubkey.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--auth2-pubkey.c1045
1 files changed, 1045 insertions, 0 deletions
diff --git a/auth2-pubkey.c b/auth2-pubkey.c
new file mode 100644
index 0000000..2fb5950
--- /dev/null
+++ b/auth2-pubkey.c
@@ -0,0 +1,1045 @@
+/* $OpenBSD: auth2-pubkey.c,v 1.86 2018/09/20 03:28:06 djm 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 <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 <limits.h>
+
+#include "xmalloc.h"
+#include "ssh.h"
+#include "ssh2.h"
+#include "packet.h"
+#include "sshbuf.h"
+#include "log.h"
+#include "misc.h"
+#include "servconf.h"
+#include "compat.h"
+#include "sshkey.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"
+#include "ssherr.h"
+#include "channels.h" /* XXX for session.h */
+#include "session.h" /* XXX for child_set_env(); refactor? */
+
+/* import */
+extern ServerOptions options;
+extern u_char *session_id2;
+extern u_int session_id2_len;
+
+static char *
+format_key(const struct sshkey *key)
+{
+ char *ret, *fp = sshkey_fingerprint(key,
+ options.fingerprint_hash, SSH_FP_DEFAULT);
+
+ xasprintf(&ret, "%s %s", sshkey_type(key), fp);
+ free(fp);
+ return ret;
+}
+
+static int
+userauth_pubkey(struct ssh *ssh)
+{
+ Authctxt *authctxt = ssh->authctxt;
+ struct passwd *pw = authctxt->pw;
+ struct sshbuf *b = NULL;
+ struct sshkey *key = NULL;
+ char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
+ u_char *pkblob = NULL, *sig = NULL, have_sig;
+ size_t blen, slen;
+ int r, pktype;
+ int authenticated = 0;
+ struct sshauthopt *authopts = NULL;
+
+ if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
+ (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
+ (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
+ fatal("%s: parse request failed: %s", __func__, ssh_err(r));
+ pktype = sshkey_type_from_name(pkalg);
+ if (pktype == KEY_UNSPEC) {
+ /* this is perfectly legal */
+ verbose("%s: unsupported public key algorithm: %s",
+ __func__, pkalg);
+ goto done;
+ }
+ if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
+ error("%s: could not parse key: %s", __func__, ssh_err(r));
+ goto done;
+ }
+ if (key == NULL) {
+ error("%s: cannot decode key: %s", __func__, pkalg);
+ goto done;
+ }
+ if (key->type != pktype) {
+ error("%s: type mismatch for decoded key "
+ "(received %d, expected %d)", __func__, key->type, pktype);
+ goto done;
+ }
+ if (sshkey_type_plain(key->type) == KEY_RSA &&
+ (ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
+ logit("Refusing RSA key because client uses unsafe "
+ "signature scheme");
+ goto done;
+ }
+ if (auth2_key_already_used(authctxt, key)) {
+ logit("refusing previously-used %s key", sshkey_type(key));
+ goto done;
+ }
+ if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) {
+ logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
+ __func__, sshkey_ssh_name(key));
+ goto done;
+ }
+ if ((r = sshkey_check_cert_sigtype(key,
+ options.ca_sign_algorithms)) != 0) {
+ logit("%s: certificate signature algorithm %s: %s", __func__,
+ (key->cert == NULL || key->cert->signature_type == NULL) ?
+ "(null)" : key->cert->signature_type, ssh_err(r));
+ goto done;
+ }
+ key_s = format_key(key);
+ if (sshkey_is_cert(key))
+ ca_s = format_key(key->cert->signature_key);
+
+ if (have_sig) {
+ debug3("%s: have %s signature for %s%s%s",
+ __func__, pkalg, key_s,
+ ca_s == NULL ? "" : " CA ",
+ ca_s == NULL ? "" : ca_s);
+ if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
+ (r = sshpkt_get_end(ssh)) != 0)
+ fatal("%s: %s", __func__, ssh_err(r));
+ if ((b = sshbuf_new()) == NULL)
+ fatal("%s: sshbuf_new failed", __func__);
+ if (ssh->compat & SSH_OLD_SESSIONID) {
+ if ((r = sshbuf_put(b, session_id2,
+ session_id2_len)) != 0)
+ fatal("%s: sshbuf_put session id: %s",
+ __func__, ssh_err(r));
+ } else {
+ if ((r = sshbuf_put_string(b, session_id2,
+ session_id2_len)) != 0)
+ fatal("%s: sshbuf_put_string session id: %s",
+ __func__, ssh_err(r));
+ }
+ if (!authctxt->valid || authctxt->user == NULL) {
+ debug2("%s: disabled because of invalid user",
+ __func__);
+ goto done;
+ }
+ /* reconstruct packet */
+ xasprintf(&userstyle, "%s%s%s", authctxt->user,
+ authctxt->style ? ":" : "",
+ authctxt->style ? authctxt->style : "");
+ if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
+ (r = sshbuf_put_cstring(b, userstyle)) != 0 ||
+ (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
+ (r = sshbuf_put_cstring(b, "publickey")) != 0 ||
+ (r = sshbuf_put_u8(b, have_sig)) != 0 ||
+ (r = sshbuf_put_cstring(b, pkalg)) != 0 ||
+ (r = sshbuf_put_string(b, pkblob, blen)) != 0)
+ fatal("%s: build packet failed: %s",
+ __func__, ssh_err(r));
+#ifdef DEBUG_PK
+ sshbuf_dump(b, stderr);
+#endif
+ /* test for correct signature */
+ authenticated = 0;
+ if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
+ PRIVSEP(sshkey_verify(key, sig, slen,
+ sshbuf_ptr(b), sshbuf_len(b),
+ (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
+ ssh->compat)) == 0) {
+ authenticated = 1;
+ }
+ auth2_record_key(authctxt, authenticated, key);
+ } else {
+ debug("%s: test pkalg %s pkblob %s%s%s",
+ __func__, pkalg, key_s,
+ ca_s == NULL ? "" : " CA ",
+ ca_s == NULL ? "" : ca_s);
+
+ if ((r = sshpkt_get_end(ssh)) != 0)
+ fatal("%s: %s", __func__, ssh_err(r));
+
+ if (!authctxt->valid || authctxt->user == NULL) {
+ debug2("%s: disabled because of invalid user",
+ __func__);
+ goto done;
+ }
+ /* 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(ssh, pw, key, 0, NULL))) {
+ if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
+ != 0 ||
+ (r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
+ (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
+ (r = sshpkt_send(ssh)) != 0 ||
+ (r = ssh_packet_write_wait(ssh)) != 0)
+ fatal("%s: %s", __func__, ssh_err(r));
+ authctxt->postponed = 1;
+ }
+ }
+done:
+ if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
+ debug("%s: key options inconsistent with existing", __func__);
+ authenticated = 0;
+ }
+ debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
+
+ sshbuf_free(b);
+ sshauthopt_free(authopts);
+ sshkey_free(key);
+ free(userstyle);
+ free(pkalg);
+ free(pkblob);
+ free(key_s);
+ free(ca_s);
+ free(sig);
+ return authenticated;
+}
+
+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.
+ */
+static int
+check_principals_line(struct ssh *ssh, 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;
+}
+
+static int
+process_principals(struct ssh *ssh, 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;
+ 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;
+
+ snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
+ if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
+ found_principal = 1;
+ }
+ free(line);
+ return found_principal;
+}
+
+/* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
+
+static int
+match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
+ struct sshkey_cert *cert, struct sshauthopt **authoptsp)
+{
+ FILE *f;
+ int success;
+
+ if (authoptsp != NULL)
+ *authoptsp = NULL;
+
+ 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;
+ }
+ success = process_principals(ssh, f, file, cert, authoptsp);
+ fclose(f);
+ restore_uid();
+ return success;
+}
+
+/*
+ * Checks whether principal is allowed in output of command.
+ * returns 1 if the principal is allowed or 0 otherwise.
+ */
+static int
+match_principals_command(struct ssh *ssh, struct passwd *user_pw,
+ const struct sshkey *key, struct sshauthopt **authoptsp)
+{
+ struct passwd *runas_pw = NULL;
+ const struct sshkey_cert *cert = key->cert;
+ FILE *f = NULL;
+ int r, ok, found_principal = 0;
+ int i, ac = 0, uid_swapped = 0;
+ pid_t pid;
+ char *tmp, *username = NULL, *command = NULL, **av = NULL;
+ char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
+ char serial_s[16], uidstr[32];
+ void (*osigchld)(int);
+
+ if (authoptsp != NULL)
+ *authoptsp = NULL;
+ if (options.authorized_principals_command == NULL)
+ return 0;
+ if (options.authorized_principals_command_user == NULL) {
+ error("No user for AuthorizedPrincipalsCommand specified, "
+ "skipping");
+ return 0;
+ }
+
+ /*
+ * NB. all returns later this function should go via "out" to
+ * ensure the original SIGCHLD handler is restored properly.
+ */
+ osigchld = signal(SIGCHLD, SIG_DFL);
+
+ /* Prepare and verify the user for the command */
+ username = percent_expand(options.authorized_principals_command_user,
+ "u", user_pw->pw_name, (char *)NULL);
+ runas_pw = getpwnam(username);
+ if (runas_pw == NULL) {
+ error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
+ username, strerror(errno));
+ goto out;
+ }
+
+ /* Turn the command into an argument vector */
+ if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
+ error("AuthorizedPrincipalsCommand \"%s\" contains "
+ "invalid quotes", command);
+ goto out;
+ }
+ if (ac == 0) {
+ error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
+ command);
+ goto out;
+ }
+ if ((ca_fp = sshkey_fingerprint(cert->signature_key,
+ options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
+ error("%s: sshkey_fingerprint failed", __func__);
+ goto out;
+ }
+ if ((key_fp = sshkey_fingerprint(key,
+ options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
+ error("%s: sshkey_fingerprint failed", __func__);
+ goto out;
+ }
+ if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
+ error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
+ goto out;
+ }
+ if ((r = sshkey_to_base64(key, &keytext)) != 0) {
+ error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
+ goto out;
+ }
+ snprintf(serial_s, sizeof(serial_s), "%llu",
+ (unsigned long long)cert->serial);
+ snprintf(uidstr, sizeof(uidstr), "%llu",
+ (unsigned long long)user_pw->pw_uid);
+ for (i = 1; i < ac; i++) {
+ tmp = percent_expand(av[i],
+ "U", uidstr,
+ "u", user_pw->pw_name,
+ "h", user_pw->pw_dir,
+ "t", sshkey_ssh_name(key),
+ "T", sshkey_ssh_name(cert->signature_key),
+ "f", key_fp,
+ "F", ca_fp,
+ "k", keytext,
+ "K", catext,
+ "i", cert->key_id,
+ "s", serial_s,
+ (char *)NULL);
+ if (tmp == NULL)
+ fatal("%s: percent_expand failed", __func__);
+ free(av[i]);
+ av[i] = tmp;
+ }
+ /* Prepare a printable command for logs, etc. */
+ command = argv_assemble(ac, av);
+
+ if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
+ ac, av, &f,
+ SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
+ goto out;
+
+ uid_swapped = 1;
+ temporarily_use_uid(runas_pw);
+
+ ok = process_principals(ssh, f, "(command)", cert, authoptsp);
+
+ fclose(f);
+ f = NULL;
+
+ if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
+ goto out;
+
+ /* Read completed successfully */
+ found_principal = ok;
+ out:
+ if (f != NULL)
+ fclose(f);
+ signal(SIGCHLD, osigchld);
+ for (i = 0; i < ac; i++)
+ free(av[i]);
+ free(av);
+ if (uid_swapped)
+ restore_uid();
+ free(command);
+ free(username);
+ free(ca_fp);
+ free(key_fp);
+ free(catext);
+ free(keytext);
+ return found_principal;
+}
+
+static void
+skip_space(char **cpp)
+{
+ char *cp;
+
+ for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
+ ;
+ *cpp = cp;
+}
+
+/*
+ * Advanced *cpp past the end of key options, defined as the first unquoted
+ * whitespace character. Returns 0 on success or -1 on failure (e.g.
+ * unterminated quotes).
+ */
+static int
+advance_past_options(char **cpp)
+{
+ char *cp = *cpp;
+ int quoted = 0;
+
+ for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
+ if (*cp == '\\' && cp[1] == '"')
+ cp++; /* Skip both */
+ else if (*cp == '"')
+ quoted = !quoted;
+ }
+ *cpp = cp;
+ /* return failure for unterminated quotes */
+ return (*cp == '\0' && quoted) ? -1 : 0;
+}
+
+/*
+ * 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.
+ */
+static int
+check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
+ char *cp, 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("%s: keytype %d failed", __func__, 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 (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,
+ options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
+ fatal("%s: fingerprint failed", __func__);
+
+ debug("%s: matching %s found: %s %s", loc,
+ sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
+
+ if (auth_authorise_keyopts(ssh, pw, keyopts,
+ sshkey_is_cert(key), 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(ssh, pw, certopts, 0, 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(key, 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("%s: internal error: missing options", __func__);
+ 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.
+ */
+static int
+check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
+ char *file, struct sshkey *key, struct sshauthopt **authoptsp)
+{
+ char *cp, *line = NULL, loc[256];
+ size_t linesize = 0;
+ int found_key = 0;
+ u_long linenum = 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;
+ snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
+ if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
+ found_key = 1;
+ }
+ free(line);
+ return found_key;
+}
+
+/* Authenticate a certificate key against TrustedUserCAKeys */
+static int
+user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
+ struct sshauthopt **authoptsp)
+{
+ char *ca_fp, *principals_file = NULL;
+ const char *reason;
+ struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
+ struct sshauthopt *final_opts = NULL;
+ int r, ret = 0, found_principal = 0, use_authorized_principals;
+
+ if (authoptsp != NULL)
+ *authoptsp = NULL;
+
+ if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
+ return 0;
+
+ if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
+ options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
+ return 0;
+
+ if ((r = sshkey_in_file(key->cert->signature_key,
+ options.trusted_user_ca_keys, 1, 0)) != 0) {
+ debug2("%s: CA %s %s is not listed in %s: %s", __func__,
+ sshkey_type(key->cert->signature_key), ca_fp,
+ options.trusted_user_ca_keys, ssh_err(r));
+ 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(ssh, pw, principals_file,
+ key->cert, &principals_opts))
+ found_principal = 1;
+ }
+ /* Try querying command if specified */
+ if (!found_principal && match_principals_command(ssh, pw, key,
+ &principals_opts))
+ found_principal = 1;
+ /* If principals file or command is specified, then require a match */
+ use_authorized_principals = principals_file != NULL ||
+ options.authorized_principals_command != NULL;
+ if (!found_principal && use_authorized_principals) {
+ reason = "Certificate does not contain an authorized principal";
+ goto fail_reason;
+ }
+ if (use_authorized_principals && principals_opts == NULL)
+ fatal("%s: internal error: missing principals_opts", __func__);
+ if (sshkey_cert_check_authority(key, 0, 1,
+ use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
+ goto fail_reason;
+
+ /* Check authority from options in key and from principals file/cmd */
+ if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
+ reason = "Invalid certificate options";
+ goto fail_reason;
+ }
+ if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
+ reason = "Refused by certificate options";
+ goto fail_reason;
+ }
+ if (principals_opts == NULL) {
+ final_opts = cert_opts;
+ cert_opts = NULL;
+ } else {
+ if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
+ "principals") != 0) {
+ reason = "Refused by certificate principals options";
+ goto fail_reason;
+ }
+ if ((final_opts = sshauthopt_merge(principals_opts,
+ cert_opts, &reason)) == NULL) {
+ fail_reason:
+ error("%s", reason);
+ auth_debug_add("%s", reason);
+ goto out;
+ }
+ }
+
+ /* Success */
+ verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
+ "%s CA %s via %s", key->cert->key_id,
+ (unsigned long long)key->cert->serial,
+ sshkey_type(key->cert->signature_key), ca_fp,
+ options.trusted_user_ca_keys);
+ if (authoptsp != NULL) {
+ *authoptsp = final_opts;
+ final_opts = NULL;
+ }
+ ret = 1;
+ out:
+ sshauthopt_free(principals_opts);
+ sshauthopt_free(cert_opts);
+ sshauthopt_free(final_opts);
+ 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 ssh *ssh, struct passwd *pw, struct sshkey *key,
+ char *file, struct sshauthopt **authoptsp)
+{
+ FILE *f;
+ int found_key = 0;
+
+ if (authoptsp != NULL)
+ *authoptsp = NULL;
+
+ /* 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(ssh, pw, f, file,
+ key, authoptsp);
+ 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 ssh *ssh, struct passwd *user_pw,
+ struct sshkey *key, struct sshauthopt **authoptsp)
+{
+ struct passwd *runas_pw = NULL;
+ FILE *f = NULL;
+ int r, ok, found_key = 0;
+ int i, uid_swapped = 0, ac = 0;
+ pid_t pid;
+ char *username = NULL, *key_fp = NULL, *keytext = NULL;
+ char uidstr[32], *tmp, *command = NULL, **av = NULL;
+ void (*osigchld)(int);
+
+ if (authoptsp != NULL)
+ *authoptsp = NULL;
+ if (options.authorized_keys_command == NULL)
+ return 0;
+ if (options.authorized_keys_command_user == NULL) {
+ error("No user for AuthorizedKeysCommand specified, skipping");
+ return 0;
+ }
+
+ /*
+ * NB. all returns later this function should go via "out" to
+ * ensure the original SIGCHLD handler is restored properly.
+ */
+ osigchld = signal(SIGCHLD, SIG_DFL);
+
+ /* Prepare and verify the user for the command */
+ username = percent_expand(options.authorized_keys_command_user,
+ "u", user_pw->pw_name, (char *)NULL);
+ runas_pw = getpwnam(username);
+ if (runas_pw == NULL) {
+ error("AuthorizedKeysCommandUser \"%s\" not found: %s",
+ username, strerror(errno));
+ goto out;
+ }
+
+ /* Prepare AuthorizedKeysCommand */
+ if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
+ SSH_FP_DEFAULT)) == NULL) {
+ error("%s: sshkey_fingerprint failed", __func__);
+ goto out;
+ }
+ if ((r = sshkey_to_base64(key, &keytext)) != 0) {
+ error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
+ goto out;
+ }
+
+ /* Turn the command into an argument vector */
+ if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
+ error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
+ command);
+ goto out;
+ }
+ if (ac == 0) {
+ error("AuthorizedKeysCommand \"%s\" yielded no arguments",
+ command);
+ goto out;
+ }
+ snprintf(uidstr, sizeof(uidstr), "%llu",
+ (unsigned long long)user_pw->pw_uid);
+ for (i = 1; i < ac; i++) {
+ tmp = percent_expand(av[i],
+ "U", uidstr,
+ "u", user_pw->pw_name,
+ "h", user_pw->pw_dir,
+ "t", sshkey_ssh_name(key),
+ "f", key_fp,
+ "k", keytext,
+ (char *)NULL);
+ if (tmp == NULL)
+ fatal("%s: percent_expand failed", __func__);
+ free(av[i]);
+ av[i] = tmp;
+ }
+ /* Prepare a printable command for logs, etc. */
+ command = argv_assemble(ac, av);
+
+ /*
+ * If AuthorizedKeysCommand was run without arguments
+ * then fall back to the old behaviour of passing the
+ * target username as a single argument.
+ */
+ if (ac == 1) {
+ av = xreallocarray(av, ac + 2, sizeof(*av));
+ av[1] = xstrdup(user_pw->pw_name);
+ av[2] = NULL;
+ /* Fix up command too, since it is used in log messages */
+ free(command);
+ xasprintf(&command, "%s %s", av[0], av[1]);
+ }
+
+ if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
+ ac, av, &f,
+ SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
+ goto out;
+
+ uid_swapped = 1;
+ temporarily_use_uid(runas_pw);
+
+ ok = check_authkeys_file(ssh, user_pw, f,
+ options.authorized_keys_command, key, authoptsp);
+
+ fclose(f);
+ f = NULL;
+
+ if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
+ goto out;
+
+ /* Read completed successfully */
+ found_key = ok;
+ out:
+ if (f != NULL)
+ fclose(f);
+ signal(SIGCHLD, osigchld);
+ for (i = 0; i < ac; i++)
+ free(av[i]);
+ free(av);
+ if (uid_swapped)
+ restore_uid();
+ free(command);
+ free(username);
+ free(key_fp);
+ free(keytext);
+ return found_key;
+}
+
+/*
+ * Check whether key authenticates and authorises the user.
+ */
+int
+user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
+ int auth_attempt, struct sshauthopt **authoptsp)
+{
+ u_int success, i;
+ char *file;
+ struct sshauthopt *opts = NULL;
+ if (authoptsp != NULL)
+ *authoptsp = NULL;
+
+ if (auth_key_is_revoked(key))
+ return 0;
+ if (sshkey_is_cert(key) &&
+ auth_key_is_revoked(key->cert->signature_key))
+ return 0;
+
+ if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0)
+ goto out;
+ sshauthopt_free(opts);
+ opts = NULL;
+
+ if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0)
+ goto out;
+ sshauthopt_free(opts);
+ opts = NULL;
+
+ 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(ssh, pw, key, file, &opts);
+ free(file);
+ }
+
+ out:
+ if (success && authoptsp != NULL) {
+ *authoptsp = opts;
+ opts = NULL;
+ }
+ sshauthopt_free(opts);
+ return success;
+}
+
+Authmethod method_pubkey = {
+ "publickey",
+ userauth_pubkey,
+ &options.pubkey_authentication
+};