split sshd.c -> auth.c session.c sshd.c plus cleanup and goto-removal

1 files changed, 554 insertions, 0 deletions

diff --git a/usr.bin/ssh/auth.c b/usr.bin/ssh/auth.c
new file mode 100644
index 00000000000..6fc799e08ce
--- /dev/null
+++ b/usr.bin/ssh/auth.c
@@ -0,0 +1,554 @@
+/*
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ *                    All rights reserved
+ */
+
+#include "includes.h"
+RCSID("$OpenBSD: auth.c,v 1.1 2000/03/28 21:15:45 markus Exp $");
+
+#include "xmalloc.h"
+#include "rsa.h"
+#include "ssh.h"
+#include "pty.h"
+#include "packet.h"
+#include "buffer.h"
+#include "cipher.h"
+#include "mpaux.h"
+#include "servconf.h"
+#include "channels.h"
+#include "match.h"
+
+#include "session.h"
+#include "dispatch.h"
+
+/* import */
+extern ServerOptions options;
+extern char *forced_command;
+
+/*
+ * Check if the user is allowed to log in via ssh. If user is listed in
+ * DenyUsers or user's primary group is listed in DenyGroups, false will
+ * be returned. If AllowUsers isn't empty and user isn't listed there, or
+ * if AllowGroups isn't empty and user isn't listed there, false will be
+ * returned. 
+ * If the user's shell is not executable, false will be returned.
+ * Otherwise true is returned. 
+ */
+static int
+allowed_user(struct passwd * pw)
+{
+	struct stat st;
+	struct group *grp;
+	int i;
+
+	/* Shouldn't be called if pw is NULL, but better safe than sorry... */
+	if (!pw)
+		return 0;
+
+	/* deny if shell does not exists or is not executable */
+	if (stat(pw->pw_shell, &st) != 0)
+		return 0;
+	if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP))))
+		return 0;
+
+	/* Return false if user is listed in DenyUsers */
+	if (options.num_deny_users > 0) {
+		if (!pw->pw_name)
+			return 0;
+		for (i = 0; i < options.num_deny_users; i++)
+			if (match_pattern(pw->pw_name, options.deny_users[i]))
+				return 0;
+	}
+	/* Return false if AllowUsers isn't empty and user isn't listed there */
+	if (options.num_allow_users > 0) {
+		if (!pw->pw_name)
+			return 0;
+		for (i = 0; i < options.num_allow_users; i++)
+			if (match_pattern(pw->pw_name, options.allow_users[i]))
+				break;
+		/* i < options.num_allow_users iff we break for loop */
+		if (i >= options.num_allow_users)
+			return 0;
+	}
+	/* Get the primary group name if we need it. Return false if it fails */
+	if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
+		grp = getgrgid(pw->pw_gid);
+		if (!grp)
+			return 0;
+
+		/* Return false if user's group is listed in DenyGroups */
+		if (options.num_deny_groups > 0) {
+			if (!grp->gr_name)
+				return 0;
+			for (i = 0; i < options.num_deny_groups; i++)
+				if (match_pattern(grp->gr_name, options.deny_groups[i]))
+					return 0;
+		}
+		/*
+		 * Return false if AllowGroups isn't empty and user's group
+		 * isn't listed there
+		 */
+		if (options.num_allow_groups > 0) {
+			if (!grp->gr_name)
+				return 0;
+			for (i = 0; i < options.num_allow_groups; i++)
+				if (match_pattern(grp->gr_name, options.allow_groups[i]))
+					break;
+			/* i < options.num_allow_groups iff we break for
+			   loop */
+			if (i >= options.num_allow_groups)
+				return 0;
+		}
+	}
+	/* We found no reason not to let this user try to log on... */
+	return 1;
+}
+
+/*
+ * convert ssh auth msg type into description
+ */
+char *
+get_authname(int type)
+{
+	static char buf[1024];
+	switch (type) {
+	case SSH_CMSG_AUTH_PASSWORD:
+		return "password";
+	case SSH_CMSG_AUTH_RSA:
+		return "rsa";
+	case SSH_CMSG_AUTH_RHOSTS_RSA:
+		return "rhosts-rsa";
+	case SSH_CMSG_AUTH_RHOSTS:
+		return "rhosts";
+#ifdef KRB4
+	case SSH_CMSG_AUTH_KERBEROS:
+		return "kerberos";
+#endif
+#ifdef SKEY
+	case SSH_CMSG_AUTH_TIS_RESPONSE:
+		return "s/key";
+#endif
+	}
+	snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
+	return buf;
+}
+
+#define AUTH_FAIL_MAX 6
+#define AUTH_FAIL_LOG (AUTH_FAIL_MAX/2)
+#define AUTH_FAIL_MSG "Too many authentication failures for %.100s"
+
+/*
+ * The user does not exist or access is denied,
+ * but fake indication that authentication is needed.
+ */
+void
+do_fake_authloop1(char *user)
+{
+	int attempt = 0;
+
+	log("Faking authloop for illegal user %.200s from %.200s port %d",
+	    user,
+	    get_remote_ipaddr(),
+	    get_remote_port());
+
+	/* Indicate that authentication is needed. */
+	packet_start(SSH_SMSG_FAILURE);
+	packet_send();
+	packet_write_wait();
+
+	/*
+	 * Keep reading packets, and always respond with a failure.  This is
+	 * to avoid disclosing whether such a user really exists.
+	 */
+	for (attempt = 1;; attempt++) {
+		/* Read a packet.  This will not return if the client disconnects. */
+		int plen;
+		int type = packet_read(&plen);
+#ifdef SKEY
+		unsigned int dlen;
+		char *password, *skeyinfo;
+		password = NULL;
+		/* Try to send a fake s/key challenge. */
+		if (options.skey_authentication == 1 &&
+		    (skeyinfo = skey_fake_keyinfo(user)) != NULL) {
+			if (type == SSH_CMSG_AUTH_TIS) {
+				packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
+				packet_put_string(skeyinfo, strlen(skeyinfo));
+				packet_send();
+				packet_write_wait();
+				continue;
+			} else if (type == SSH_CMSG_AUTH_PASSWORD &&
+			           options.password_authentication &&
+			           (password = packet_get_string(&dlen)) != NULL &&
+			           dlen == 5 &&
+			           strncasecmp(password, "s/key", 5) == 0 ) {
+				packet_send_debug(skeyinfo);
+			}
+		}
+		if (password != NULL)
+			xfree(password);
+#endif
+		if (attempt > AUTH_FAIL_MAX)
+			packet_disconnect(AUTH_FAIL_MSG, user);
+
+		/*
+		 * Send failure.  This should be indistinguishable from a
+		 * failed authentication.
+		 */
+		packet_start(SSH_SMSG_FAILURE);
+		packet_send();
+		packet_write_wait();
+	}
+	/* NOTREACHED */
+	abort();
+}
+
+/*
+ * read packets and try to authenticate local user *pw.
+ * return if authentication is successfull
+ */
+void
+do_authloop(struct passwd * pw)
+{
+	int attempt = 0;
+	unsigned int bits;
+	RSA *client_host_key;
+	BIGNUM *n;
+	char *client_user, *password;
+	char user[1024];
+	unsigned int dlen;
+	int plen, nlen, elen;
+	unsigned int ulen;
+	int type = 0;
+	void (*authlog) (const char *fmt,...) = verbose;
+
+	/* Indicate that authentication is needed. */
+	packet_start(SSH_SMSG_FAILURE);
+	packet_send();
+	packet_write_wait();
+
+	for (attempt = 1;; attempt++) {
+		int authenticated = 0;
+		strlcpy(user, "", sizeof user);
+
+		/* Get a packet from the client. */
+		type = packet_read(&plen);
+
+		/* Process the packet. */
+		switch (type) {
+#ifdef AFS
+		case SSH_CMSG_HAVE_KERBEROS_TGT:
+			if (!options.kerberos_tgt_passing) {
+				/* packet_get_all(); */
+				verbose("Kerberos tgt passing disabled.");
+				break;
+			} else {
+				/* Accept Kerberos tgt. */
+				char *tgt = packet_get_string(&dlen);
+				packet_integrity_check(plen, 4 + dlen, type);
+				if (!auth_kerberos_tgt(pw, tgt))
+					verbose("Kerberos tgt REFUSED for %s", pw->pw_name);
+				xfree(tgt);
+			}
+			continue;
+
+		case SSH_CMSG_HAVE_AFS_TOKEN:
+			if (!options.afs_token_passing || !k_hasafs()) {
+				/* packet_get_all(); */
+				verbose("AFS token passing disabled.");
+				break;
+			} else {
+				/* Accept AFS token. */
+				char *token_string = packet_get_string(&dlen);
+				packet_integrity_check(plen, 4 + dlen, type);
+				if (!auth_afs_token(pw, token_string))
+					verbose("AFS token REFUSED for %s", pw->pw_name);
+				xfree(token_string);
+			}
+			continue;
+#endif /* AFS */
+#ifdef KRB4
+		case SSH_CMSG_AUTH_KERBEROS:
+			if (!options.kerberos_authentication) {
+				/* packet_get_all(); */
+				verbose("Kerberos authentication disabled.");
+				break;
+			} else {
+				/* Try Kerberos v4 authentication. */
+				KTEXT_ST auth;
+				char *tkt_user = NULL;
+				char *kdata = packet_get_string((unsigned int *) &auth.length);
+				packet_integrity_check(plen, 4 + auth.length, type);
+
+				if (auth.length < MAX_KTXT_LEN)
+					memcpy(auth.dat, kdata, auth.length);
+				xfree(kdata);
+
+				authenticated = auth_krb4(pw->pw_name, &auth, &tkt_user);
+
+				if (authenticated) {
+					snprintf(user, sizeof user, " tktuser %s", tkt_user);
+					xfree(tkt_user);
+				}
+			}
+			break;
+#endif /* KRB4 */
+
+		case SSH_CMSG_AUTH_RHOSTS:
+			if (!options.rhosts_authentication) {
+				verbose("Rhosts authentication disabled.");
+				break;
+			}
+			/*
+			 * Get client user name.  Note that we just have to
+			 * trust the client; this is one reason why rhosts
+			 * authentication is insecure. (Another is
+			 * IP-spoofing on a local network.)
+			 */
+			client_user = packet_get_string(&ulen);
+			packet_integrity_check(plen, 4 + ulen, type);
+
+			/* Try to authenticate using /etc/hosts.equiv and
+			   .rhosts. */
+			authenticated = auth_rhosts(pw, client_user);
+
+			snprintf(user, sizeof user, " ruser %s", client_user);
+			xfree(client_user);
+			break;
+
+		case SSH_CMSG_AUTH_RHOSTS_RSA:
+			if (!options.rhosts_rsa_authentication) {
+				verbose("Rhosts with RSA authentication disabled.");
+				break;
+			}
+			/*
+			 * Get client user name.  Note that we just have to
+			 * trust the client; root on the client machine can
+			 * claim to be any user.
+			 */
+			client_user = packet_get_string(&ulen);
+
+			/* Get the client host key. */
+			client_host_key = RSA_new();
+			if (client_host_key == NULL)
+				fatal("RSA_new failed");
+			client_host_key->e = BN_new();
+			client_host_key->n = BN_new();
+			if (client_host_key->e == NULL || client_host_key->n == NULL)
+				fatal("BN_new failed");
+			bits = packet_get_int();
+			packet_get_bignum(client_host_key->e, &elen);
+			packet_get_bignum(client_host_key->n, &nlen);
+
+			if (bits != BN_num_bits(client_host_key->n))
+				error("Warning: keysize mismatch for client_host_key: "
+				      "actual %d, announced %d", BN_num_bits(client_host_key->n), bits);
+			packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
+
+			authenticated = auth_rhosts_rsa(pw, client_user, client_host_key);
+			RSA_free(client_host_key);
+
+			snprintf(user, sizeof user, " ruser %s", client_user);
+			xfree(client_user);
+			break;
+
+		case SSH_CMSG_AUTH_RSA:
+			if (!options.rsa_authentication) {
+				verbose("RSA authentication disabled.");
+				break;
+			}
+			/* RSA authentication requested. */
+			n = BN_new();
+			packet_get_bignum(n, &nlen);
+			packet_integrity_check(plen, nlen, type);
+			authenticated = auth_rsa(pw, n);
+			BN_clear_free(n);
+			break;
+
+		case SSH_CMSG_AUTH_PASSWORD:
+			if (!options.password_authentication) {
+				verbose("Password authentication disabled.");
+				break;
+			}
+			/*
+			 * Read user password.  It is in plain text, but was
+			 * transmitted over the encrypted channel so it is
+			 * not visible to an outside observer.
+			 */
+			password = packet_get_string(&dlen);
+			packet_integrity_check(plen, 4 + dlen, type);
+
+			/* Try authentication with the password. */
+			authenticated = auth_password(pw, password);
+
+			memset(password, 0, strlen(password));
+			xfree(password);
+			break;
+
+#ifdef SKEY
+		case SSH_CMSG_AUTH_TIS:
+			debug("rcvd SSH_CMSG_AUTH_TIS");
+			if (options.skey_authentication == 1) {
+				char *skeyinfo = skey_keyinfo(pw->pw_name);
+				if (skeyinfo == NULL) {
+					debug("generating fake skeyinfo for %.100s.", pw->pw_name);
+					skeyinfo = skey_fake_keyinfo(pw->pw_name);
+				}
+				if (skeyinfo != NULL) {
+					/* we send our s/key- in tis-challenge messages */
+					debug("sending challenge '%s'", skeyinfo);
+					packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
+					packet_put_string(skeyinfo, strlen(skeyinfo));
+					packet_send();
+					packet_write_wait();
+					continue;
+				}
+			}
+			break;
+		case SSH_CMSG_AUTH_TIS_RESPONSE:
+			debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
+			if (options.skey_authentication == 1) {
+				char *response = packet_get_string(&dlen);
+				debug("skey response == '%s'", response);
+				packet_integrity_check(plen, 4 + dlen, type);
+				authenticated = (skey_haskey(pw->pw_name) == 0 &&
+						 skey_passcheck(pw->pw_name, response) != -1);
+				xfree(response);
+			}
+			break;
+#else
+		case SSH_CMSG_AUTH_TIS:
+			/* TIS Authentication is unsupported */
+			log("TIS authentication unsupported.");
+			break;
+#endif
+
+		default:
+			/*
+			 * Any unknown messages will be ignored (and failure
+			 * returned) during authentication.
+			 */
+			log("Unknown message during authentication: type %d", type);
+			break;
+		}
+ 
+ 		/*
+ 		 * Check if the user is logging in as root and root logins
+ 		 * are disallowed.
+ 		 * Note that root login is allowed for forced commands.
+ 		 */
+ 		if (authenticated && pw->pw_uid == 0 && !options.permit_root_login) {
+ 			if (forced_command) {
+ 				log("Root login accepted for forced command.");
+ 			} else {
+ 				authenticated = 0;
+ 				log("ROOT LOGIN REFUSED FROM %.200s",
+ 				    get_canonical_hostname());
+ 			}
+  		}
+
+		/* Raise logging level */
+		if (authenticated ||
+		    attempt == AUTH_FAIL_LOG ||
+		    type == SSH_CMSG_AUTH_PASSWORD)
+			authlog = log;
+
+		authlog("%s %s for %.200s from %.200s port %d%s",
+			authenticated ? "Accepted" : "Failed",
+			get_authname(type),
+			pw->pw_uid == 0 ? "ROOT" : pw->pw_name,
+			get_remote_ipaddr(),
+			get_remote_port(),
+			user);
+
+		if (authenticated)
+			return;
+
+		if (attempt > AUTH_FAIL_MAX)
+			packet_disconnect(AUTH_FAIL_MSG, pw->pw_name);
+
+		/* Send a message indicating that the authentication attempt failed. */
+		packet_start(SSH_SMSG_FAILURE);
+		packet_send();
+		packet_write_wait();
+	}
+}
+
+/*
+ * Performs authentication of an incoming connection.  Session key has already
+ * been exchanged and encryption is enabled.
+ */
+void
+do_authentication()
+{
+	struct passwd *pw, pwcopy;
+	int plen;
+	unsigned int ulen;
+	char *user;
+
+	/* Get the name of the user that we wish to log in as. */
+	packet_read_expect(&plen, SSH_CMSG_USER);
+
+	/* Get the user name. */
+	user = packet_get_string(&ulen);
+	packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
+
+	setproctitle("%s", user);
+
+#ifdef AFS
+	/* If machine has AFS, set process authentication group. */
+	if (k_hasafs()) {
+		k_setpag();
+		k_unlog();
+	}
+#endif /* AFS */
+
+	/* Verify that the user is a valid user. */
+	pw = getpwnam(user);
+	if (!pw || !allowed_user(pw))
+		do_fake_authloop1(user);
+	xfree(user);
+
+	/* Take a copy of the returned structure. */
+	memset(&pwcopy, 0, sizeof(pwcopy));
+	pwcopy.pw_name = xstrdup(pw->pw_name);
+	pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
+	pwcopy.pw_uid = pw->pw_uid;
+	pwcopy.pw_gid = pw->pw_gid;
+	pwcopy.pw_dir = xstrdup(pw->pw_dir);
+	pwcopy.pw_shell = xstrdup(pw->pw_shell);
+	pw = &pwcopy;
+
+	/*
+	 * If we are not running as root, the user must have the same uid as
+	 * the server.
+	 */
+	if (getuid() != 0 && pw->pw_uid != getuid())
+		packet_disconnect("Cannot change user when server not running as root.");
+
+	debug("Attempting authentication for %.100s.", pw->pw_name);
+
+	/* If the user has no password, accept authentication immediately. */
+	if (options.password_authentication &&
+#ifdef KRB4
+	    (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
+#endif /* KRB4 */
+	    auth_password(pw, "")) {
+		/* Authentication with empty password succeeded. */
+		log("Login for user %s from %.100s, accepted without authentication.",
+		    pw->pw_name, get_remote_ipaddr());
+	} else {
+		/* Loop until the user has been authenticated or the
+		   connection is closed, do_authloop() returns only if
+		   authentication is successfull */
+		do_authloop(pw);
+	}
+
+	/* The user has been authenticated and accepted. */
+	packet_start(SSH_SMSG_SUCCESS);
+	packet_send();
+	packet_write_wait();
+
+	/* Perform session preparation. */
+	do_authenticated(pw);
+}