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-rw-r--r--crypto/openssh/auth2.c467
1 files changed, 467 insertions, 0 deletions
diff --git a/crypto/openssh/auth2.c b/crypto/openssh/auth2.c
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+++ b/crypto/openssh/auth2.c
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+/*
+ * 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.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by Markus Friedl.
+ * 4. 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 ``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"
+RCSID("$OpenBSD: auth2.c,v 1.8 2000/05/08 17:42:24 markus Exp $");
+
+#include <openssl/dsa.h>
+#include <openssl/rsa.h>
+#include <openssl/evp.h>
+
+#include "xmalloc.h"
+#include "rsa.h"
+#include "ssh.h"
+#include "pty.h"
+#include "packet.h"
+#include "buffer.h"
+#include "cipher.h"
+#include "servconf.h"
+#include "compat.h"
+#include "channels.h"
+#include "bufaux.h"
+#include "ssh2.h"
+#include "auth.h"
+#include "session.h"
+#include "dispatch.h"
+#include "auth.h"
+#include "key.h"
+#include "kex.h"
+
+#include "dsa.h"
+#include "uidswap.h"
+
+/* import */
+extern ServerOptions options;
+extern unsigned char *session_id2;
+extern int session_id2_len;
+
+/* protocol */
+
+void input_service_request(int type, int plen);
+void input_userauth_request(int type, int plen);
+void protocol_error(int type, int plen);
+
+/* auth */
+int ssh2_auth_none(struct passwd *pw);
+int ssh2_auth_password(struct passwd *pw);
+int ssh2_auth_pubkey(struct passwd *pw, unsigned char *raw, unsigned int rlen);
+
+/* helper */
+struct passwd* auth_set_user(char *u, char *s);
+int user_dsa_key_allowed(struct passwd *pw, Key *key);
+
+typedef struct Authctxt Authctxt;
+struct Authctxt {
+ char *user;
+ char *service;
+ struct passwd pw;
+ int valid;
+};
+static Authctxt *authctxt = NULL;
+static int userauth_success = 0;
+
+/*
+ * loop until userauth_success == TRUE
+ */
+
+void
+do_authentication2()
+{
+ /* turn off skey/kerberos, not supported by SSH2 */
+#ifdef SKEY
+ options.skey_authentication = 0;
+#endif
+#ifdef KRB4
+ options.kerberos_authentication = 0;
+#endif
+
+ dispatch_init(&protocol_error);
+ dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
+ dispatch_run(DISPATCH_BLOCK, &userauth_success);
+ do_authenticated2();
+}
+
+void
+protocol_error(int type, int plen)
+{
+ log("auth: protocol error: type %d plen %d", type, plen);
+ packet_start(SSH2_MSG_UNIMPLEMENTED);
+ packet_put_int(0);
+ packet_send();
+ packet_write_wait();
+}
+
+void
+input_service_request(int type, int plen)
+{
+ unsigned int len;
+ int accept = 0;
+ char *service = packet_get_string(&len);
+ packet_done();
+
+ if (strcmp(service, "ssh-userauth") == 0) {
+ if (!userauth_success) {
+ accept = 1;
+ /* now we can handle user-auth requests */
+ dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
+ }
+ }
+ /* XXX all other service requests are denied */
+
+ if (accept) {
+ packet_start(SSH2_MSG_SERVICE_ACCEPT);
+ packet_put_cstring(service);
+ packet_send();
+ packet_write_wait();
+ } else {
+ debug("bad service request %s", service);
+ packet_disconnect("bad service request %s", service);
+ }
+ xfree(service);
+}
+
+void
+input_userauth_request(int type, int plen)
+{
+ static void (*authlog) (const char *fmt,...) = verbose;
+ static int attempt = 0;
+ unsigned int len, rlen;
+ int authenticated = 0;
+ char *raw, *user, *service, *method, *authmsg = NULL;
+ struct passwd *pw;
+
+ if (++attempt == AUTH_FAIL_MAX)
+ packet_disconnect("too many failed userauth_requests");
+
+ raw = packet_get_raw(&rlen);
+ if (plen != rlen)
+ fatal("plen != rlen");
+ user = packet_get_string(&len);
+ service = packet_get_string(&len);
+ method = packet_get_string(&len);
+ debug("userauth-request for user %s service %s method %s", user, service, method);
+
+ /* XXX we only allow the ssh-connection service */
+ pw = auth_set_user(user, service);
+ if (pw && strcmp(service, "ssh-connection")==0) {
+ if (strcmp(method, "none") == 0) {
+ authenticated = ssh2_auth_none(pw);
+ } else if (strcmp(method, "password") == 0) {
+ authenticated = ssh2_auth_password(pw);
+ } else if (strcmp(method, "publickey") == 0) {
+ authenticated = ssh2_auth_pubkey(pw, raw, rlen);
+ }
+ }
+ if (authenticated && pw && pw->pw_uid == 0 && !options.permit_root_login) {
+ authenticated = 0;
+ log("ROOT LOGIN REFUSED FROM %.200s",
+ get_canonical_hostname());
+ }
+
+ /* Raise logging level */
+ if (authenticated == 1 ||
+ attempt == AUTH_FAIL_LOG ||
+ strcmp(method, "password") == 0)
+ authlog = log;
+
+ /* Log before sending the reply */
+ if (authenticated == 1) {
+ authmsg = "Accepted";
+ } else if (authenticated == 0) {
+ authmsg = "Failed";
+ } else {
+ authmsg = "Postponed";
+ }
+ authlog("%s %s for %.200s from %.200s port %d ssh2",
+ authmsg,
+ method,
+ pw && pw->pw_uid == 0 ? "ROOT" : user,
+ get_remote_ipaddr(),
+ get_remote_port());
+
+ /* XXX todo: check if multiple auth methods are needed */
+ if (authenticated == 1) {
+ /* turn off userauth */
+ dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
+ packet_start(SSH2_MSG_USERAUTH_SUCCESS);
+ packet_send();
+ packet_write_wait();
+ /* now we can break out */
+ userauth_success = 1;
+ } else if (authenticated == 0) {
+ packet_start(SSH2_MSG_USERAUTH_FAILURE);
+ packet_put_cstring("publickey,password"); /* XXX dynamic */
+ packet_put_char(0); /* XXX partial success, unused */
+ packet_send();
+ packet_write_wait();
+ }
+
+ xfree(service);
+ xfree(user);
+ xfree(method);
+}
+
+int
+ssh2_auth_none(struct passwd *pw)
+{
+ packet_done();
+ return auth_password(pw, "");
+}
+int
+ssh2_auth_password(struct passwd *pw)
+{
+ char *password;
+ int authenticated = 0;
+ int change;
+ unsigned int len;
+ change = packet_get_char();
+ if (change)
+ log("password change not supported");
+ password = packet_get_string(&len);
+ packet_done();
+ if (options.password_authentication &&
+ auth_password(pw, password) == 1)
+ authenticated = 1;
+ memset(password, 0, len);
+ xfree(password);
+ return authenticated;
+}
+int
+ssh2_auth_pubkey(struct passwd *pw, unsigned char *raw, unsigned int rlen)
+{
+ Buffer b;
+ Key *key;
+ char *pkalg, *pkblob, *sig;
+ unsigned int alen, blen, slen;
+ int have_sig;
+ int authenticated = 0;
+
+ if (options.dsa_authentication == 0) {
+ debug("pubkey auth disabled");
+ return 0;
+ }
+ if (datafellows & SSH_BUG_PUBKEYAUTH) {
+ log("bug compatibility with ssh-2.0.13 pubkey not implemented");
+ return 0;
+ }
+ have_sig = packet_get_char();
+ pkalg = packet_get_string(&alen);
+ if (strcmp(pkalg, KEX_DSS) != 0) {
+ xfree(pkalg);
+ log("bad pkalg %s", pkalg); /*XXX*/
+ return 0;
+ }
+ pkblob = packet_get_string(&blen);
+ key = dsa_key_from_blob(pkblob, blen);
+ if (key != NULL) {
+ if (have_sig) {
+ sig = packet_get_string(&slen);
+ packet_done();
+ buffer_init(&b);
+ buffer_append(&b, session_id2, session_id2_len);
+ buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
+ if (slen + 4 > rlen)
+ fatal("bad rlen/slen");
+ buffer_append(&b, raw, rlen - slen - 4);
+#ifdef DEBUG_DSS
+ buffer_dump(&b);
+#endif
+ /* test for correct signature */
+ if (user_dsa_key_allowed(pw, key) &&
+ dsa_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
+ authenticated = 1;
+ buffer_clear(&b);
+ xfree(sig);
+ } else {
+ packet_done();
+ debug("test key...");
+ /* test whether pkalg/pkblob are acceptable */
+ /* 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 (user_dsa_key_allowed(pw, key)) {
+ packet_start(SSH2_MSG_USERAUTH_PK_OK);
+ packet_put_string(pkalg, alen);
+ packet_put_string(pkblob, blen);
+ packet_send();
+ packet_write_wait();
+ authenticated = -1;
+ }
+ }
+ key_free(key);
+ }
+ xfree(pkalg);
+ xfree(pkblob);
+ return authenticated;
+}
+
+/* set and get current user */
+
+struct passwd*
+auth_get_user(void)
+{
+ return (authctxt != NULL && authctxt->valid) ? &authctxt->pw : NULL;
+}
+
+struct passwd*
+auth_set_user(char *u, char *s)
+{
+ struct passwd *pw, *copy;
+
+ if (authctxt == NULL) {
+ authctxt = xmalloc(sizeof(*authctxt));
+ authctxt->valid = 0;
+ authctxt->user = xstrdup(u);
+ authctxt->service = xstrdup(s);
+ setproctitle("%s", u);
+ pw = getpwnam(u);
+ if (!pw || !allowed_user(pw)) {
+ log("auth_set_user: illegal user %s", u);
+ return NULL;
+ }
+ copy = &authctxt->pw;
+ memset(copy, 0, sizeof(*copy));
+ copy->pw_name = xstrdup(pw->pw_name);
+ copy->pw_passwd = xstrdup(pw->pw_passwd);
+ copy->pw_uid = pw->pw_uid;
+ copy->pw_gid = pw->pw_gid;
+ copy->pw_dir = xstrdup(pw->pw_dir);
+ copy->pw_shell = xstrdup(pw->pw_shell);
+ authctxt->valid = 1;
+ } else {
+ if (strcmp(u, authctxt->user) != 0 ||
+ strcmp(s, authctxt->service) != 0) {
+ log("auth_set_user: missmatch: (%s,%s)!=(%s,%s)",
+ u, s, authctxt->user, authctxt->service);
+ return NULL;
+ }
+ }
+ return auth_get_user();
+}
+
+/* return 1 if user allows given key */
+int
+user_dsa_key_allowed(struct passwd *pw, Key *key)
+{
+ char line[8192], file[1024];
+ int found_key = 0;
+ unsigned int bits = -1;
+ FILE *f;
+ unsigned long linenum = 0;
+ struct stat st;
+ Key *found;
+
+ /* Temporarily use the user's uid. */
+ temporarily_use_uid(pw->pw_uid);
+
+ /* The authorized keys. */
+ snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
+ SSH_USER_PERMITTED_KEYS2);
+
+ /* Fail quietly if file does not exist */
+ if (stat(file, &st) < 0) {
+ /* Restore the privileged uid. */
+ restore_uid();
+ return 0;
+ }
+ /* Open the file containing the authorized keys. */
+ f = fopen(file, "r");
+ if (!f) {
+ /* Restore the privileged uid. */
+ restore_uid();
+ return 0;
+ }
+ if (options.strict_modes) {
+ int fail = 0;
+ char buf[1024];
+ /* Check open file in order to avoid open/stat races */
+ if (fstat(fileno(f), &st) < 0 ||
+ (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
+ (st.st_mode & 022) != 0) {
+ snprintf(buf, sizeof buf, "DSA authentication refused for %.100s: "
+ "bad ownership or modes for '%s'.", pw->pw_name, file);
+ fail = 1;
+ } else {
+ /* Check path to SSH_USER_PERMITTED_KEYS */
+ int i;
+ static const char *check[] = {
+ "", SSH_USER_DIR, NULL
+ };
+ for (i = 0; check[i]; i++) {
+ snprintf(line, sizeof line, "%.500s/%.100s",
+ pw->pw_dir, check[i]);
+ if (stat(line, &st) < 0 ||
+ (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
+ (st.st_mode & 022) != 0) {
+ snprintf(buf, sizeof buf,
+ "DSA authentication refused for %.100s: "
+ "bad ownership or modes for '%s'.",
+ pw->pw_name, line);
+ fail = 1;
+ break;
+ }
+ }
+ }
+ if (fail) {
+ log(buf);
+ fclose(f);
+ restore_uid();
+ return 0;
+ }
+ }
+ found_key = 0;
+ found = key_new(KEY_DSA);
+
+ while (fgets(line, sizeof(line), f)) {
+ char *cp;
+ linenum++;
+ /* Skip leading whitespace, empty and comment lines. */
+ for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
+ ;
+ if (!*cp || *cp == '\n' || *cp == '#')
+ continue;
+ bits = key_read(found, &cp);
+ if (bits == 0)
+ continue;
+ if (key_equal(found, key)) {
+ found_key = 1;
+ debug("matching key found: file %s, line %ld",
+ file, linenum);
+ break;
+ }
+ }
+ restore_uid();
+ fclose(f);
+ key_free(found);
+ return found_key;
+}
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