/* * Support rsync daemon authentication. * * Copyright (C) 1998-2000 Andrew Tridgell * Copyright (C) 2002-2022 Wayne Davison * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, visit the http://fsf.org website. */ #include "rsync.h"#include "itypes.h"#include "ifuncs.h" /* O_CLOEXEC is absent on some still-supported targets.  The random-source fd * is read and closed synchronously, so the established zero-value fallback is * sufficient without adding a configure dependency. */#ifndef O_CLOEXEC#define O_CLOEXEC 0#endif extern int read_only;extern char *password_file;extern struct name_num_obj valid_auth_checksums; /***************************************************************************encode a buffer using base64 - simple and slow algorithm. null terminatesthe result.  ***************************************************************************/void base64_encode(const char *buf, int len, char *out, int pad){	char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";	int bit_offset, byte_offset, idx, i;	const uchar *d = (const uchar *)buf;	int bytes = (len*8 + 5)/6; 	for (i = 0; i < bytes; i++) {		byte_offset = (i*6)/8;		bit_offset = (i*6)%8;		if (bit_offset < 3) {			idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;		} else {			idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;			if (byte_offset+1 < len) {				idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));			}		}		out[i] = b64[idx];	} 	while (pad && (i % 4))		out[i++] = '='; 	out[i] = '\0';} /* Fill buf with len bytes from the kernel CSPRNG.  Returns 1 on success. * We read /dev/urandom directly rather than depending on getrandom()/ * arc4random_buf() availability so this works on every platform rsync * targets without new configure probes. */static int get_random_bytes(char *buf, int len){	int fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);	int got = 0;	if (fd < 0)		return 0;	while (got < len) {		int n = read(fd, buf + got, len - got);		if (n <= 0)			break;		got += n;	}	close(fd);	return got == len;} /* Generate a challenge buffer and return it base64-encoded. */static void gen_challenge(const char *addr, char *challenge){	char input[32];	char rnd[32];	char digest[MAX_DIGEST_LEN];	struct timeval tv;	int len; 	memset(input, 0, sizeof input); 	strlcpy(input, addr, 17);	sys_gettimeofday(&tv);	SIVAL(input, 16, tv.tv_sec);	SIVAL(input, 20, tv.tv_usec);	SIVAL(input, 24, getpid()); 	len = sum_init(valid_auth_checksums.negotiated_nni, 0);	/* The challenge must be unpredictable to a network observer; addr+time	 * +pid alone is ~35 bits and lets an attacker enumerate the preimage	 * offline.  Hash 32 bytes from the kernel RNG first so the digest	 * carries full entropy, keeping the legacy inputs as a mix-in so a	 * urandom failure degrades to (never below) the old behaviour. */	if (get_random_bytes(rnd, sizeof rnd))		sum_update(rnd, sizeof rnd);	else		rprintf(FWARNING, "gen_challenge: /dev/urandom unavailable, "			"falling back to time-based challenge\n");	sum_update(input, sizeof input);	sum_end(digest); 	base64_encode(digest, len, challenge, 0);} /* Generate an MD4 hash created from the combination of the password * and the challenge string and return it base64-encoded. */static void generate_hash(const char *in, const char *challenge, char *out){	char buf[MAX_DIGEST_LEN];	int len; 	len = sum_init(valid_auth_checksums.negotiated_nni, 0);	sum_update(in, strlen(in));	sum_update(challenge, strlen(challenge));	sum_end(buf); 	base64_encode(buf, len, out, 0);} /* Return the secret for a user from the secret file, null terminated. * Maximum length is len (not counting the null). */static const char *check_secret(int module, const char *user, const char *group,				const char *challenge, const char *pass){	char line[1024];	char pass2[MAX_DIGEST_LEN*2];	const char *fname = lp_secrets_file(module);	STRUCT_STAT st;	int ok = 1;	int user_len = strlen(user);	int group_len = group ? strlen(group) : 0;	char *err;	FILE *fh; 	/* Daemon 'secrets file = PATH' open.  A planted symlink would be	 * followed and the strict-modes fstat() check below runs on the target	 * inode, so a symlink to /etc/shadow (0640 root:shadow) would pass and	 * the daemon would auth against shadow hashes.  Refuse symlinks not	 * owned by uid 0 or our euid. */	if (!fname || !*fname)		return "no secrets file";	{		int fd = open_no_attacker_symlinks(fname, O_RDONLY, 0);		if (fd < 0)			return "no secrets file";		fh = fdopen(fd, "r");		if (!fh) {			close(fd);			return "no secrets file";		}	} 	if (do_fstat(fileno(fh), &st) == -1) {		rsyserr(FLOG, errno, "fstat(%s)", fname);		ok = 0;	} else if (lp_strict_modes(module)) {		if ((st.st_mode & 06) != 0) {			rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");			ok = 0;		} else if (MY_UID() == ROOT_UID && st.st_uid != ROOT_UID) {			rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");			ok = 0;		}	}	if (!ok) {		fclose(fh);		return "ignoring secrets file";	} 	if (*user == '#') {		/* Reject attempt to match a comment. */		fclose(fh);		return "invalid username";	} 	/* Try to find a line that starts with the user (or @group) name and a ':'. */	err = "secret not found";	while ((user || group) && fgets(line, sizeof line, fh) != NULL) {		const char **ptr, *s = strtok(line, "\n\r");		int len;		if (!s)			continue;		if (*s == '@') {			ptr = &group;			len = group_len;			s++;		} else {			ptr = &user;			len = user_len;		}		if (!*ptr || strncmp(s, *ptr, len) != 0 || s[len] != ':')			continue;		generate_hash(s+len+1, challenge, pass2);		if (strcmp(pass, pass2) == 0) {			err = NULL;			break;		}		err = "password mismatch";		*ptr = NULL; /* Don't look for name again. */	} 	fclose(fh); 	force_memzero(line, sizeof line);	force_memzero(pass2, sizeof pass2); 	return err;} static const char *getpassf(const char *filename){	STRUCT_STAT st;	char buffer[512], *p;	int n; 	if (!filename)		return NULL; 	if (strcmp(filename, "-") == 0) {		n = fgets(buffer, sizeof buffer, stdin) == NULL ? -1 : (int)strlen(buffer);	} else {		int fd; 		/* --password-file=PATH client open.  Its first line is sent as the		 * auth response, so a planted symlink leaks the target's content		 * (e.g. shadow hashes) to a malicious daemon; the do_stat()		 * other-access check runs on the target mode and passes 0640		 * root:shadow.  Refuse symlinks not owned by uid 0 or our euid. */		if ((fd = open_no_attacker_symlinks(filename, O_RDONLY, 0)) < 0) {			rsyserr(FERROR, errno, "could not open password file %s", filename);			exit_cleanup(RERR_SYNTAX);		} 		/* fstat the opened fd, not the pathname: a same-object check		 * (matching check_secret() above) so an attacker who swaps the		 * path between open and check can't make the owner/mode test		 * validate a different inode than the one we read the password		 * from. */		if (do_fstat(fd, &st) == -1) {			rsyserr(FERROR, errno, "fstat(%s)", filename);			exit_cleanup(RERR_SYNTAX);		}		if ((st.st_mode & 06) != 0) {			rprintf(FERROR, "ERROR: password file must not be other-accessible\n");			exit_cleanup(RERR_SYNTAX);		}		if (MY_UID() == ROOT_UID && st.st_uid != ROOT_UID) {			rprintf(FERROR, "ERROR: password file must be owned by root when running as root\n");			exit_cleanup(RERR_SYNTAX);		} 		n = read(fd, buffer, sizeof buffer - 1);		close(fd);	} 	if (n > 0) {		buffer[n] = '\0';		if ((p = strtok(buffer, "\n\r")) != NULL)			return strdup(p);	} 	rprintf(FERROR, "ERROR: failed to read a password from %s\n", filename);	exit_cleanup(RERR_SYNTAX);} /* Possibly negotiate authentication with the client.  Use "leader" to * start off the auth if necessary. * * Return NULL if authentication failed.  Return "" if anonymous access. * Otherwise return username. */char *auth_server(int f_in, int f_out, int module, const char *host,		  const char *addr, const char *leader){	char *users = lp_auth_users(module);	char challenge[MAX_DIGEST_LEN*2];	char line[BIGPATHBUFLEN];	const char **auth_uid_groups = NULL;	int auth_uid_groups_cnt = -1;	const char *err = NULL;	int group_match = -1;	char *tok, *pass;	char opt_ch = '\0'; 	/* if no auth list then allow anyone in! */	if (!users || !*users)		return ""; 	negotiate_daemon_auth(f_out, 0); 	/* Enforce a configured minimum auth digest (default: none).  This refuses	 * a peer that negotiated -- or, via an omitted digest list / old protocol,	 * fell back to -- a digest weaker than the operator-required floor, e.g. a	 * client downgraded to md5/md4.  Lower rank == stronger (the auth list is	 * ordered strongest-first), so a higher rank than the floor is too weak. */	{		const char *min_digest = lp_auth_digest(module);		if (min_digest && *min_digest) {			int floor_rank = auth_digest_rank(min_digest);			int got_rank = auth_digest_rank(valid_auth_checksums.negotiated_nni->name);			if (floor_rank < 0) {				rprintf(FLOG, "auth failed on module %s from %s (%s): the "					"configured 'auth digest = %s' is not a supported digest "					"on this build\n",					lp_name(module), host, addr, min_digest);				return NULL;			}			if (got_rank < 0 || got_rank > floor_rank) {				rprintf(FLOG, "auth failed on module %s from %s (%s): negotiated "					"auth digest %s is weaker than the required "					"'auth digest = %s'\n",					lp_name(module), host, addr,					valid_auth_checksums.negotiated_nni->name, min_digest);				return NULL;			}		}	} 	gen_challenge(addr, challenge); 	io_printf(f_out, "%s%s\n", leader, challenge); 	if (!read_line_old(f_in, line, sizeof line, 0)	 || (pass = strchr(line, ' ')) == NULL) {		rprintf(FLOG, "auth failed on module %s from %s (%s): "			"invalid challenge response\n",			lp_name(module), host, addr);		return NULL;	}	*pass++ = '\0'; 	users = strdup(users); 	/* conf_strtok() honours the documented leading-comma form: a value that	 * starts with a comma splits on commas ALONE, so an entry may contain	 * spaces -- which is how a group name with a space is written.  Splitting	 * on whitespace here tore such an entry apart, so the rule the admin wrote	 * never matched and a rule they never wrote appeared from its tail.  The	 * daemon's gid field already uses this parser (clientserver.c). */	for (tok = conf_strtok(users); tok; tok = conf_strtok(NULL)) {		char *opts;		/* See if the user appended :deny, :ro, or :rw. */		if ((opts = strchr(tok, ':')) != NULL) {			*opts++ = '\0';			opt_ch = isUpper(opts) ? toLower(opts) : *opts;			if (opt_ch == 'r') { /* handle ro and rw */				opt_ch = isUpper(opts+1) ? toLower(opts+1) : opts[1];				if (opt_ch == 'o')					opt_ch = 'r';				else if (opt_ch != 'w')					opt_ch = '\0';			} else if (opt_ch != 'd') /* if it's not deny, ignore it */				opt_ch = '\0';		} else			opt_ch = '\0';		if (*tok != '@') {			/* Match the username */			if (wildmatch(tok, line))				break;		} else {#ifdef HAVE_GETGROUPLIST			int j;			/* See if authorizing user is a real user, and if so, see			 * if it is in a group that matches tok+1 wildmat. */			if (auth_uid_groups_cnt < 0) {				item_list gid_list = EMPTY_ITEM_LIST;				uid_t auth_uid;				if (!user_to_uid(line, &auth_uid, False)				 || getallgroups(auth_uid, &gid_list) != NULL)					auth_uid_groups_cnt = 0;				else {					gid_t *gid_array = gid_list.items;					auth_uid_groups_cnt = gid_list.count;					auth_uid_groups = new_array(const char *, auth_uid_groups_cnt);					for (j = 0; j < auth_uid_groups_cnt; j++)						auth_uid_groups[j] = gid_to_group(gid_array[j]);				}			}			for (j = 0; j < auth_uid_groups_cnt; j++) {				if (auth_uid_groups[j] && wildmatch(tok+1, auth_uid_groups[j])) {					group_match = j;					break;				}			}			if (group_match >= 0)				break;#else			rprintf(FLOG, "your computer doesn't support getgrouplist(), so no @group authorization is possible.\n");#endif		}	} 	free(users); 	if (!tok)		err = "no matching rule";	else if (opt_ch == 'd')		err = "denied by rule";	else {		const char *group = group_match >= 0 ? auth_uid_groups[group_match] : NULL;		err = check_secret(module, line, group, challenge, pass);	} 	force_memzero(challenge, sizeof challenge);	force_memzero(pass, strlen(pass)); 	if (auth_uid_groups) {		int j;		for (j = 0; j < auth_uid_groups_cnt; j++) {			if (auth_uid_groups[j])				free((char*)auth_uid_groups[j]);		}		free(auth_uid_groups);	} 	if (err) {		rprintf(FLOG, "auth failed on module %s from %s (%s) for %s: %s\n",			lp_name(module), host, addr, line, err);		return NULL;	} 	if (opt_ch == 'r')		read_only = 1;	else if (opt_ch == 'w')		read_only = 0; 	return strdup(line);} void auth_client(int fd, const char *user, const char *challenge){	const char *pass;	char pass2[MAX_DIGEST_LEN*2]; 	if (!user || !*user)		user = "nobody";	negotiate_daemon_auth(-1, 1); 	if (!(pass = getpassf(password_file))	 && !(pass = getenv("RSYNC_PASSWORD"))) {		/* XXX: cyeoh says that getpass is deprecated, because		 * it may return a truncated password on some systems,		 * and it is not in the LSB.		 *		 * Andrew Klein says that getpassphrase() is present		 * on Solaris and reads up to 256 characters.		 *		 * OpenBSD has a readpassphrase() that might be more suitable.		 */		pass = getpass("Password: ");	} 	if (!pass)		pass = ""; 	generate_hash(pass, challenge, pass2);	io_printf(fd, "%s %s\n", user, pass2);}