[openssh.git] / auth-rsa.c

/*
 *
 * auth-rsa.c
 *
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 *
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 *
 * Created: Mon Mar 27 01:46:52 1995 ylo
 *
 * RSA-based authentication.  This code determines whether to admit a login
 * based on RSA authentication.  This file also contains functions to check
 * validity of the host key.
 *
 */

#include "includes.h"
RCSID("$Id$");

#include "rsa.h"
#include "packet.h"
#include "xmalloc.h"
#include "ssh.h"
#include "mpaux.h"
#include "uidswap.h"
#include "match.h"
#include "servconf.h"

#include <openssl/rsa.h>
#include <openssl/md5.h>

/* Flags that may be set in authorized_keys options. */
extern int no_port_forwarding_flag;
extern int no_agent_forwarding_flag;
extern int no_x11_forwarding_flag;
extern int no_pty_flag;
extern char *forced_command;
extern struct envstring *custom_environment;

/*
 * Session identifier that is used to bind key exchange and authentication
 * responses to a particular session.
 */
extern unsigned char session_id[16];

/*
 * The .ssh/authorized_keys file contains public keys, one per line, in the
 * following format:
 *   options bits e n comment
 * where bits, e and n are decimal numbers,
 * and comment is any string of characters up to newline.  The maximum
 * length of a line is 8000 characters.  See the documentation for a
 * description of the options.
 */

/*
 * Performs the RSA authentication challenge-response dialog with the client,
 * and returns true (non-zero) if the client gave the correct answer to
 * our challenge; returns zero if the client gives a wrong answer.
 */

int
auth_rsa_challenge_dialog(RSA *pk)
{
	BIGNUM *challenge, *encrypted_challenge;
	BN_CTX *ctx;
	unsigned char buf[32], mdbuf[16], response[16];
	MD5_CTX md;
	unsigned int i;
	int plen, len;

	encrypted_challenge = BN_new();
	challenge = BN_new();

	/* Generate a random challenge. */
	BN_rand(challenge, 256, 0, 0);
	ctx = BN_CTX_new();
	BN_mod(challenge, challenge, pk->n, ctx);
	BN_CTX_free(ctx);

	/* Encrypt the challenge with the public key. */
	rsa_public_encrypt(encrypted_challenge, challenge, pk);

	/* Send the encrypted challenge to the client. */
	packet_start(SSH_SMSG_AUTH_RSA_CHALLENGE);
	packet_put_bignum(encrypted_challenge);
	packet_send();
	BN_clear_free(encrypted_challenge);
	packet_write_wait();

	/* Wait for a response. */
	packet_read_expect(&plen, SSH_CMSG_AUTH_RSA_RESPONSE);
	packet_integrity_check(plen, 16, SSH_CMSG_AUTH_RSA_RESPONSE);
	for (i = 0; i < 16; i++)
		response[i] = packet_get_char();

	/* The response is MD5 of decrypted challenge plus session id. */
	len = BN_num_bytes(challenge);
	if (len <= 0 || len > 32)
		fatal("auth_rsa_challenge_dialog: bad challenge length %d", len);
	memset(buf, 0, 32);
	BN_bn2bin(challenge, buf + 32 - len);
	MD5_Init(&md);
	MD5_Update(&md, buf, 32);
	MD5_Update(&md, session_id, 16);
	MD5_Final(mdbuf, &md);
	BN_clear_free(challenge);

	/* Verify that the response is the original challenge. */
	if (memcmp(response, mdbuf, 16) != 0) {
		/* Wrong answer. */
		return 0;
	}
	/* Correct answer. */
	return 1;
}

/*
 * Performs the RSA authentication dialog with the client.  This returns
 * 0 if the client could not be authenticated, and 1 if authentication was
 * successful.  This may exit if there is a serious protocol violation.
 */

int
auth_rsa(struct passwd *pw, BIGNUM *client_n)
{
	extern ServerOptions options;
	char line[8192], file[1024];
	int authenticated;
	unsigned int bits;
	FILE *f;
	unsigned long linenum = 0;
	struct stat st;
	RSA *pk;
	int mname, mip;

	/* 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_KEYS);

	/* 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();
		packet_send_debug("Could not open %.900s for reading.", file);
		packet_send_debug("If your home is on an NFS volume, it may need to be world-readable.");
		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, "RSA 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, "RSA authentication refused for %.100s: "
						 "bad ownership or modes for '%s'.", pw->pw_name, line);
					fail = 1;
					break;
				}
			}
		}
		if (fail) {
			fclose(f);
			log(buf);
			packet_send_debug(buf);
			restore_uid();
			return 0;
		}
	}
	/* Flag indicating whether authentication has succeeded. */
	authenticated = 0;

	pk = RSA_new();
	pk->e = BN_new();
	pk->n = BN_new();

	/*
	 * Go though the accepted keys, looking for the current key.  If
	 * found, perform a challenge-response dialog to verify that the
	 * user really has the corresponding private key.
	 */
	while (fgets(line, sizeof(line), f)) {
		char *cp;
		char *options;

		linenum++;

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

		/*
		 * Check if there are options for this key, and if so,
		 * save their starting address and skip the option part
		 * for now.  If there are no options, set the starting
		 * address to NULL.
		 */
		if (*cp < '0' || *cp > '9') {
			int quoted = 0;
			options = cp;
			for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
				if (*cp == '\\' && cp[1] == '"')
					cp++;	/* Skip both */
				else if (*cp == '"')
					quoted = !quoted;
			}
		} else
			options = NULL;

		/* Parse the key from the line. */
		if (!auth_rsa_read_key(&cp, &bits, pk->e, pk->n)) {
			debug("%.100s, line %lu: bad key syntax",
			      SSH_USER_PERMITTED_KEYS, linenum);
			packet_send_debug("%.100s, line %lu: bad key syntax",
					  SSH_USER_PERMITTED_KEYS, linenum);
			continue;
		}
		/* cp now points to the comment part. */

		/* Check if the we have found the desired key (identified by its modulus). */
		if (BN_cmp(pk->n, client_n) != 0)
			continue;

		/* check the real bits  */
		if (bits != BN_num_bits(pk->n))
			log("Warning: %s, line %ld: keysize mismatch: "
			    "actual %d vs. announced %d.",
			    file, linenum, BN_num_bits(pk->n), bits);

		/* We have found the desired key. */

		/* Perform the challenge-response dialog for this key. */
		if (!auth_rsa_challenge_dialog(pk)) {
			/* Wrong response. */
			verbose("Wrong response to RSA authentication challenge.");
			packet_send_debug("Wrong response to RSA authentication challenge.");
			continue;
		}
		/*
		 * Correct response.  The client has been successfully
		 * authenticated. Note that we have not yet processed the
		 * options; this will be reset if the options cause the
		 * authentication to be rejected.
		 */
		authenticated = 1;

		/* RSA part of authentication was accepted.  Now process the options. */
		if (options) {
			while (*options && *options != ' ' && *options != '\t') {
				cp = "no-port-forwarding";
				if (strncmp(options, cp, strlen(cp)) == 0) {
					packet_send_debug("Port forwarding disabled.");
					no_port_forwarding_flag = 1;
					options += strlen(cp);
					goto next_option;
				}
				cp = "no-agent-forwarding";
				if (strncmp(options, cp, strlen(cp)) == 0) {
					packet_send_debug("Agent forwarding disabled.");
					no_agent_forwarding_flag = 1;
					options += strlen(cp);
					goto next_option;
				}
				cp = "no-X11-forwarding";
				if (strncmp(options, cp, strlen(cp)) == 0) {
					packet_send_debug("X11 forwarding disabled.");
					no_x11_forwarding_flag = 1;
					options += strlen(cp);
					goto next_option;
				}
				cp = "no-pty";
				if (strncmp(options, cp, strlen(cp)) == 0) {
					packet_send_debug("Pty allocation disabled.");
					no_pty_flag = 1;
					options += strlen(cp);
					goto next_option;
				}
				cp = "command=\"";
				if (strncmp(options, cp, strlen(cp)) == 0) {
					int i;
					options += strlen(cp);
					forced_command = xmalloc(strlen(options) + 1);
					i = 0;
					while (*options) {
						if (*options == '"')
							break;
						if (*options == '\\' && options[1] == '"') {
							options += 2;
							forced_command[i++] = '"';
							continue;
						}
						forced_command[i++] = *options++;
					}
					if (!*options) {
						debug("%.100s, line %lu: missing end quote",
						      SSH_USER_PERMITTED_KEYS, linenum);
						packet_send_debug("%.100s, line %lu: missing end quote",
								  SSH_USER_PERMITTED_KEYS, linenum);
						continue;
					}
					forced_command[i] = 0;
					packet_send_debug("Forced command: %.900s", forced_command);
					options++;
					goto next_option;
				}
				cp = "environment=\"";
				if (strncmp(options, cp, strlen(cp)) == 0) {
					int i;
					char *s;
					struct envstring *new_envstring;
					options += strlen(cp);
					s = xmalloc(strlen(options) + 1);
					i = 0;
					while (*options) {
						if (*options == '"')
							break;
						if (*options == '\\' && options[1] == '"') {
							options += 2;
							s[i++] = '"';
							continue;
						}
						s[i++] = *options++;
					}
					if (!*options) {
						debug("%.100s, line %lu: missing end quote",
						      SSH_USER_PERMITTED_KEYS, linenum);
						packet_send_debug("%.100s, line %lu: missing end quote",
								  SSH_USER_PERMITTED_KEYS, linenum);
						continue;
					}
					s[i] = 0;
					packet_send_debug("Adding to environment: %.900s", s);
					debug("Adding to environment: %.900s", s);
					options++;
					new_envstring = xmalloc(sizeof(struct envstring));
					new_envstring->s = s;
					new_envstring->next = custom_environment;
					custom_environment = new_envstring;
					goto next_option;
				}
				cp = "from=\"";
				if (strncmp(options, cp, strlen(cp)) == 0) {
					char *patterns = xmalloc(strlen(options) + 1);
					int i;
					options += strlen(cp);
					i = 0;
					while (*options) {
						if (*options == '"')
							break;
						if (*options == '\\' && options[1] == '"') {
							options += 2;
							patterns[i++] = '"';
							continue;
						}
						patterns[i++] = *options++;
					}
					if (!*options) {
						debug("%.100s, line %lu: missing end quote",
						      SSH_USER_PERMITTED_KEYS, linenum);
						packet_send_debug("%.100s, line %lu: missing end quote",
								  SSH_USER_PERMITTED_KEYS, linenum);
						continue;
					}
					patterns[i] = 0;
					options++;
					/*
					 * Deny access if we get a negative
					 * match for the hostname or the ip
					 * or if we get not match at all
					 */
					mname = match_hostname(get_canonical_hostname(),
					    patterns, strlen(patterns));
					mip = match_hostname(get_remote_ipaddr(),
					    patterns, strlen(patterns));
					if (mname == -1 || mip == -1 ||
					    (mname != 1 && mip != 1)) {
						log("RSA authentication tried for %.100s with correct key but not from a permitted host (host=%.200s, ip=%.200s).",
						    pw->pw_name, get_canonical_hostname(),
						    get_remote_ipaddr());
						packet_send_debug("Your host '%.200s' is not permitted to use this key for login.",
						get_canonical_hostname());
						xfree(patterns);
						/* key invalid for this host, reset flags */
						authenticated = 0;
						no_agent_forwarding_flag = 0;
						no_port_forwarding_flag = 0;
						no_pty_flag = 0;
						no_x11_forwarding_flag = 0;
						while (custom_environment) {
							struct envstring *ce = custom_environment;
							custom_environment = ce->next;
							xfree(ce->s);
							xfree(ce);
						}
						if (forced_command) {
							xfree(forced_command);
							forced_command = NULL;
						}
						break;
					}
					xfree(patterns);
					/* Host name matches. */
					goto next_option;
				}
		bad_option:
				log("Bad options in %.100s file, line %lu: %.50s",
				    SSH_USER_PERMITTED_KEYS, linenum, options);
				packet_send_debug("Bad options in %.100s file, line %lu: %.50s",
						  SSH_USER_PERMITTED_KEYS, linenum, options);
				authenticated = 0;
				break;

		next_option:
				/*
				 * Skip the comma, and move to the next option
				 * (or break out if there are no more).
				 */
				if (!*options)
					fatal("Bugs in auth-rsa.c option processing.");
				if (*options == ' ' || *options == '\t')
					break;		/* End of options. */
				if (*options != ',')
					goto bad_option;
				options++;
				/* Process the next option. */
				continue;
			}
		}
		/*
		 * Break out of the loop if authentication was successful;
		 * otherwise continue searching.
		 */
		if (authenticated)
			break;
	}

	/* Restore the privileged uid. */
	restore_uid();

	/* Close the file. */
	fclose(f);

	RSA_free(pk);

	if (authenticated)
		packet_send_debug("RSA authentication accepted.");

	/* Return authentication result. */
	return authenticated;
}
Commit	Line	Data
8efc0c15	1	/*
6ae2364d	2	*
5260325f	3	* auth-rsa.c
6ae2364d	4	*
5260325f	5	* Author: Tatu Ylonen <ylo@cs.hut.fi>
6ae2364d	6	*
5260325f	7	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5260325f	8	* All rights reserved
6ae2364d	9	*
5260325f	10	* Created: Mon Mar 27 01:46:52 1995 ylo
6ae2364d	11	*
5260325f	12	* RSA-based authentication. This code determines whether to admit a login
	13	* based on RSA authentication. This file also contains functions to check
	14	* validity of the host key.
6ae2364d	15	*
5260325f	16	*/
8efc0c15	17
	18	#include "includes.h"
	19	RCSID("$Id$");
	20
	21	#include "rsa.h"
	22	#include "packet.h"
	23	#include "xmalloc.h"
	24	#include "ssh.h"
	25	#include "mpaux.h"
	26	#include "uidswap.h"
4fe2af09	27	#include "match.h"
6fa724bc	28	#include "servconf.h"
8efc0c15	29
	30	#include <openssl/rsa.h>
	31	#include <openssl/md5.h>
	32
	33	/* Flags that may be set in authorized_keys options. */
	34	extern int no_port_forwarding_flag;
	35	extern int no_agent_forwarding_flag;
	36	extern int no_x11_forwarding_flag;
	37	extern int no_pty_flag;
	38	extern char *forced_command;
	39	extern struct envstring *custom_environment;
	40
aa3378df	41	/*
	42	* Session identifier that is used to bind key exchange and authentication
	43	* responses to a particular session.
	44	*/
8efc0c15	45	extern unsigned char session_id[16];
8efc0c15	46
aa3378df	47	/*
	48	* The .ssh/authorized_keys file contains public keys, one per line, in the
	49	* following format:
	50	* options bits e n comment
	51	* where bits, e and n are decimal numbers,
	52	* and comment is any string of characters up to newline. The maximum
	53	* length of a line is 8000 characters. See the documentation for a
	54	* description of the options.
	55	*/
8efc0c15	56
aa3378df	57	/*
	58	* Performs the RSA authentication challenge-response dialog with the client,
	59	* and returns true (non-zero) if the client gave the correct answer to
	60	* our challenge; returns zero if the client gives a wrong answer.
	61	*/
8efc0c15	62
8efc0c15	63	int
4fe2af09	64	auth_rsa_challenge_dialog(RSA *pk)
8efc0c15	65	{
c8d54615	66	BIGNUM challenge, encrypted_challenge;
c8d54615	67	BN_CTX *ctx;
5260325f	68	unsigned char buf[32], mdbuf[16], response[16];
	69	MD5_CTX md;
	70	unsigned int i;
	71	int plen, len;
	72
	73	encrypted_challenge = BN_new();
	74	challenge = BN_new();
5260325f	75
	76	/* Generate a random challenge. */
	77	BN_rand(challenge, 256, 0, 0);
c8d54615	78	ctx = BN_CTX_new();
4fe2af09	79	BN_mod(challenge, challenge, pk->n, ctx);
c8d54615	80	BN_CTX_free(ctx);
5260325f	81
5260325f	82	/* Encrypt the challenge with the public key. */
5260325f	83	rsa_public_encrypt(encrypted_challenge, challenge, pk);
5260325f	84
	85	/* Send the encrypted challenge to the client. */
	86	packet_start(SSH_SMSG_AUTH_RSA_CHALLENGE);
	87	packet_put_bignum(encrypted_challenge);
	88	packet_send();
c8d54615	89	BN_clear_free(encrypted_challenge);
5260325f	90	packet_write_wait();
5260325f	91
c8d54615	92	/* Wait for a response. */
	93	packet_read_expect(&plen, SSH_CMSG_AUTH_RSA_RESPONSE);
	94	packet_integrity_check(plen, 16, SSH_CMSG_AUTH_RSA_RESPONSE);
	95	for (i = 0; i < 16; i++)
	96	response[i] = packet_get_char();
	97
5260325f	98	/* The response is MD5 of decrypted challenge plus session id. */
	99	len = BN_num_bytes(challenge);
	100	if (len <= 0 \|\| len > 32)
	101	fatal("auth_rsa_challenge_dialog: bad challenge length %d", len);
	102	memset(buf, 0, 32);
	103	BN_bn2bin(challenge, buf + 32 - len);
	104	MD5_Init(&md);
	105	MD5_Update(&md, buf, 32);
	106	MD5_Update(&md, session_id, 16);
	107	MD5_Final(mdbuf, &md);
5260325f	108	BN_clear_free(challenge);
5260325f	109
	110	/* Verify that the response is the original challenge. */
	111	if (memcmp(response, mdbuf, 16) != 0) {
	112	/* Wrong answer. */
	113	return 0;
	114	}
	115	/* Correct answer. */
	116	return 1;
8efc0c15	117	}
8efc0c15	118
aa3378df	119	/*
	120	* Performs the RSA authentication dialog with the client. This returns
	121	* 0 if the client could not be authenticated, and 1 if authentication was
	122	* successful. This may exit if there is a serious protocol violation.
	123	*/
8efc0c15	124
8efc0c15	125	int
6fa724bc	126	auth_rsa(struct passwd pw, BIGNUM client_n)
8efc0c15	127	{
5260325f	128	extern ServerOptions options;
	129	char line[8192], file[1024];
	130	int authenticated;
	131	unsigned int bits;
	132	FILE *f;
	133	unsigned long linenum = 0;
	134	struct stat st;
4fe2af09	135	RSA *pk;
fa649821	136	int mname, mip;
5260325f	137
	138	/* Temporarily use the user's uid. */
	139	temporarily_use_uid(pw->pw_uid);
	140
	141	/* The authorized keys. */
	142	snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
	143	SSH_USER_PERMITTED_KEYS);
	144
	145	/* Fail quietly if file does not exist */
	146	if (stat(file, &st) < 0) {
	147	/* Restore the privileged uid. */
	148	restore_uid();
	149	return 0;
8efc0c15	150	}
5260325f	151	/* Open the file containing the authorized keys. */
	152	f = fopen(file, "r");
	153	if (!f) {
	154	/* Restore the privileged uid. */
	155	restore_uid();
	156	packet_send_debug("Could not open %.900s for reading.", file);
	157	packet_send_debug("If your home is on an NFS volume, it may need to be world-readable.");
	158	return 0;
8efc0c15	159	}
5260325f	160	if (options.strict_modes) {
	161	int fail = 0;
	162	char buf[1024];
	163	/* Check open file in order to avoid open/stat races */
	164	if (fstat(fileno(f), &st) < 0 \|\|
	165	(st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
	166	(st.st_mode & 022) != 0) {
	167	snprintf(buf, sizeof buf, "RSA authentication refused for %.100s: "
	168	"bad ownership or modes for '%s'.", pw->pw_name, file);
	169	fail = 1;
	170	} else {
	171	/* Check path to SSH_USER_PERMITTED_KEYS */
	172	int i;
	173	static const char *check[] = {
	174	"", SSH_USER_DIR, NULL
	175	};
	176	for (i = 0; check[i]; i++) {
	177	snprintf(line, sizeof line, "%.500s/%.100s", pw->pw_dir, check[i]);
	178	if (stat(line, &st) < 0 \|\|
	179	(st.st_uid != 0 && st.st_uid != pw->pw_uid) \|\|
	180	(st.st_mode & 022) != 0) {
	181	snprintf(buf, sizeof buf, "RSA authentication refused for %.100s: "
	182	"bad ownership or modes for '%s'.", pw->pw_name, line);
	183	fail = 1;
	184	break;
	185	}
	186	}
8efc0c15	187	}
5260325f	188	if (fail) {
a306f2dd	189	fclose(f);
5260325f	190	log(buf);
	191	packet_send_debug(buf);
	192	restore_uid();
	193	return 0;
8efc0c15	194	}
5260325f	195	}
	196	/* Flag indicating whether authentication has succeeded. */
	197	authenticated = 0;
	198
4fe2af09	199	pk = RSA_new();
	200	pk->e = BN_new();
	201	pk->n = BN_new();
5260325f	202
aa3378df	203	/*
	204	* Go though the accepted keys, looking for the current key. If
	205	* found, perform a challenge-response dialog to verify that the
	206	* user really has the corresponding private key.
	207	*/
5260325f	208	while (fgets(line, sizeof(line), f)) {
	209	char *cp;
	210	char *options;
	211
	212	linenum++;
	213
aa3378df	214	/* Skip leading whitespace, empty and comment lines. */
	215	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	216	;
5260325f	217	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	218	continue;
	219
aa3378df	220	/*
	221	* Check if there are options for this key, and if so,
	222	* save their starting address and skip the option part
	223	* for now. If there are no options, set the starting
	224	* address to NULL.
	225	*/
5260325f	226	if (cp < '0' \|\| cp > '9') {
	227	int quoted = 0;
	228	options = cp;
	229	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	230	if (*cp == '\\' && cp[1] == '"')
	231	cp++; /* Skip both */
	232	else if (*cp == '"')
	233	quoted = !quoted;
8efc0c15	234	}
5260325f	235	} else
	236	options = NULL;
	237
	238	/* Parse the key from the line. */
4fe2af09	239	if (!auth_rsa_read_key(&cp, &bits, pk->e, pk->n)) {
5260325f	240	debug("%.100s, line %lu: bad key syntax",
	241	SSH_USER_PERMITTED_KEYS, linenum);
	242	packet_send_debug("%.100s, line %lu: bad key syntax",
6ae2364d	243	SSH_USER_PERMITTED_KEYS, linenum);
5260325f	244	continue;
8efc0c15	245	}
5260325f	246	/* cp now points to the comment part. */
5260325f	247
5260325f	248	/* Check if the we have found the desired key (identified by its modulus). */
4fe2af09	249	if (BN_cmp(pk->n, client_n) != 0)
aa3378df	250	continue;
5260325f	251
57112b5a	252	/* check the real bits */
4fe2af09	253	if (bits != BN_num_bits(pk->n))
57112b5a	254	log("Warning: %s, line %ld: keysize mismatch: "
57112b5a	255	"actual %d vs. announced %d.",
4fe2af09	256	file, linenum, BN_num_bits(pk->n), bits);
57112b5a	257
5260325f	258	/* We have found the desired key. */
	259
	260	/* Perform the challenge-response dialog for this key. */
4fe2af09	261	if (!auth_rsa_challenge_dialog(pk)) {
5260325f	262	/* Wrong response. */
	263	verbose("Wrong response to RSA authentication challenge.");
	264	packet_send_debug("Wrong response to RSA authentication challenge.");
	265	continue;
8efc0c15	266	}
aa3378df	267	/*
	268	* Correct response. The client has been successfully
	269	* authenticated. Note that we have not yet processed the
	270	* options; this will be reset if the options cause the
	271	* authentication to be rejected.
	272	*/
5260325f	273	authenticated = 1;
	274
	275	/* RSA part of authentication was accepted. Now process the options. */
	276	if (options) {
	277	while (options && options != ' ' && *options != '\t') {
	278	cp = "no-port-forwarding";
	279	if (strncmp(options, cp, strlen(cp)) == 0) {
	280	packet_send_debug("Port forwarding disabled.");
	281	no_port_forwarding_flag = 1;
	282	options += strlen(cp);
	283	goto next_option;
	284	}
	285	cp = "no-agent-forwarding";
	286	if (strncmp(options, cp, strlen(cp)) == 0) {
	287	packet_send_debug("Agent forwarding disabled.");
	288	no_agent_forwarding_flag = 1;
	289	options += strlen(cp);
	290	goto next_option;
	291	}
	292	cp = "no-X11-forwarding";
	293	if (strncmp(options, cp, strlen(cp)) == 0) {
	294	packet_send_debug("X11 forwarding disabled.");
	295	no_x11_forwarding_flag = 1;
	296	options += strlen(cp);
	297	goto next_option;
	298	}
	299	cp = "no-pty";
	300	if (strncmp(options, cp, strlen(cp)) == 0) {
	301	packet_send_debug("Pty allocation disabled.");
	302	no_pty_flag = 1;
	303	options += strlen(cp);
	304	goto next_option;
	305	}
	306	cp = "command=\"";
	307	if (strncmp(options, cp, strlen(cp)) == 0) {
	308	int i;
	309	options += strlen(cp);
	310	forced_command = xmalloc(strlen(options) + 1);
	311	i = 0;
	312	while (*options) {
	313	if (*options == '"')
	314	break;
	315	if (*options == '\\' && options[1] == '"') {
	316	options += 2;
	317	forced_command[i++] = '"';
	318	continue;
	319	}
	320	forced_command[i++] = *options++;
	321	}
	322	if (!*options) {
	323	debug("%.100s, line %lu: missing end quote",
	324	SSH_USER_PERMITTED_KEYS, linenum);
	325	packet_send_debug("%.100s, line %lu: missing end quote",
	326	SSH_USER_PERMITTED_KEYS, linenum);
	327	continue;
	328	}
	329	forced_command[i] = 0;
	330	packet_send_debug("Forced command: %.900s", forced_command);
	331	options++;
	332	goto next_option;
	333	}
	334	cp = "environment=\"";
	335	if (strncmp(options, cp, strlen(cp)) == 0) {
	336	int i;
337	char *s;
338	struct envstring *new_envstring;
339	options += strlen(cp);
340	s = xmalloc(strlen(options) + 1);
341	i = 0;
342	while (*options) {
343	if (*options == '"')
344	break;
345	if (*options == '\\' && options[1] == '"') {
346	options += 2;
347	s[i++] = '"';
348	continue;
349	}
350	s[i++] = *options++;
351	}
352	if (!*options) {
353	debug("%.100s, line %lu: missing end quote",
354	SSH_USER_PERMITTED_KEYS, linenum);
355	packet_send_debug("%.100s, line %lu: missing end quote",
356	SSH_USER_PERMITTED_KEYS, linenum);
357	continue;
358	}
359	s[i] = 0;
360	packet_send_debug("Adding to environment: %.900s", s);
361	debug("Adding to environment: %.900s", s);
362	options++;
363	new_envstring = xmalloc(sizeof(struct envstring));
364	new_envstring->s = s;
365	new_envstring->next = custom_environment;
366	custom_environment = new_envstring;
367	goto next_option;
368	}
369	cp = "from=\"";
370	if (strncmp(options, cp, strlen(cp)) == 0) {
371	char *patterns = xmalloc(strlen(options) + 1);
372	int i;
373	options += strlen(cp);
374	i = 0;
375	while (*options) {
376	if (*options == '"')
377	break;
378	if (*options == '\\' && options[1] == '"') {
379	options += 2;
380	patterns[i++] = '"';
381	continue;
382	}
383	patterns[i++] = *options++;
384	}
385	if (!*options) {
386	debug("%.100s, line %lu: missing end quote",
387	SSH_USER_PERMITTED_KEYS, linenum);
388	packet_send_debug("%.100s, line %lu: missing end quote",
389	SSH_USER_PERMITTED_KEYS, linenum);
390	continue;
391	}
392	patterns[i] = 0;
393	options++;
fa649821	394	/*
	395	* Deny access if we get a negative
	396	* match for the hostname or the ip
	397	* or if we get not match at all
	398	*/
	399	mname = match_hostname(get_canonical_hostname(),
	400	patterns, strlen(patterns));
	401	mip = match_hostname(get_remote_ipaddr(),
	402	patterns, strlen(patterns));
	403	if (mname == -1 \|\| mip == -1 \|\|
	404	(mname != 1 && mip != 1)) {
5260325f	405	log("RSA authentication tried for %.100s with correct key but not from a permitted host (host=%.200s, ip=%.200s).",
	406	pw->pw_name, get_canonical_hostname(),
	407	get_remote_ipaddr());
	408	packet_send_debug("Your host '%.200s' is not permitted to use this key for login.",
	409	get_canonical_hostname());
	410	xfree(patterns);
7b2ea3a1	411	/* key invalid for this host, reset flags */
5260325f	412	authenticated = 0;
7b2ea3a1	413	no_agent_forwarding_flag = 0;
	414	no_port_forwarding_flag = 0;
	415	no_pty_flag = 0;
	416	no_x11_forwarding_flag = 0;
	417	while (custom_environment) {
	418	struct envstring *ce = custom_environment;
	419	custom_environment = ce->next;
	420	xfree(ce->s);
	421	xfree(ce);
	422	}
	423	if (forced_command) {
	424	xfree(forced_command);
	425	forced_command = NULL;
	426	}
5260325f	427	break;
	428	}
	429	xfree(patterns);
	430	/* Host name matches. */
	431	goto next_option;
	432	}
	433	bad_option:
5260325f	434	log("Bad options in %.100s file, line %lu: %.50s",
	435	SSH_USER_PERMITTED_KEYS, linenum, options);
	436	packet_send_debug("Bad options in %.100s file, line %lu: %.50s",
	437	SSH_USER_PERMITTED_KEYS, linenum, options);
	438	authenticated = 0;
	439	break;
	440
	441	next_option:
aa3378df	442	/*
	443	* Skip the comma, and move to the next option
	444	* (or break out if there are no more).
	445	*/
5260325f	446	if (!*options)
	447	fatal("Bugs in auth-rsa.c option processing.");
	448	if (options == ' ' \|\| options == '\t')
aa3378df	449	break; /* End of options. */
5260325f	450	if (*options != ',')
	451	goto bad_option;
	452	options++;
	453	/* Process the next option. */
	454	continue;
8efc0c15	455	}
8efc0c15	456	}
aa3378df	457	/*
	458	* Break out of the loop if authentication was successful;
	459	* otherwise continue searching.
	460	*/
5260325f	461	if (authenticated)
5260325f	462	break;
8efc0c15	463	}
8efc0c15	464
5260325f	465	/* Restore the privileged uid. */
5260325f	466	restore_uid();
8efc0c15	467
5260325f	468	/* Close the file. */
5260325f	469	fclose(f);
8efc0c15	470
4fe2af09	471	RSA_free(pk);
8efc0c15	472
5260325f	473	if (authenticated)
5260325f	474	packet_send_debug("RSA authentication accepted.");
8efc0c15	475
5260325f	476	/* Return authentication result. */
5260325f	477	return authenticated;
8efc0c15	478	}