Attachment #2515 for bug #2322

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Lines 37-42 Link Here

(-)usr.bin/ssh/auth.h (+7 lines)
37	#include <krb5.h>	37	#include <krb5.h>
38	#endif	38	#endif
39		39
		40	struct sshkey;
		41
40	typedef struct Authctxt Authctxt;	42	typedef struct Authctxt Authctxt;
41	typedef struct Authmethod Authmethod;	43	typedef struct Authmethod Authmethod;
42	typedef struct KbdintDevice KbdintDevice;	44	typedef struct KbdintDevice KbdintDevice;
Lines 66-71 struct Authctxt { Link Here
66	char *krb5_ticket_file;	68	char *krb5_ticket_file;
67	#endif	69	#endif
68	void *methoddata;	70	void *methoddata;
		71
		72	struct sshkey **prev_userkeys;
		73	u_int nprev_userkeys;
69	};	74	};
70	/*	75	/*
71	* Every authentication method has to handle authentication requests for	76	* Every authentication method has to handle authentication requests for
Lines 114-119 int hostbased_key_allowed(struct passwd Link Here
114	int user_key_allowed(struct passwd , Key );	119	int user_key_allowed(struct passwd , Key );
115	void pubkey_auth_info(Authctxt , const Key , const char *, ...)	120	void pubkey_auth_info(Authctxt , const Key , const char *, ...)
116	__attribute__((__format__ (printf, 3, 4)));	121	__attribute__((__format__ (printf, 3, 4)));
		122	void auth2_record_userkey(Authctxt , struct sshkey );
		123	int auth2_userkey_already_used(Authctxt , struct sshkey );
117		124
118	struct stat;	125	struct stat;
119	int auth_secure_path(const char , struct stat , const char *, uid_t,	126	int auth_secure_path(const char , struct stat , const char *, uid_t,

Lines 38-43 Link Here

(-)usr.bin/ssh/auth2-pubkey.c (-1 / +39 lines)
38	#include <string.h>	38	#include <string.h>
39	#include <time.h>	39	#include <time.h>
40	#include <unistd.h>	40	#include <unistd.h>
		41	#include <limits.h>
41		42
42	#include "xmalloc.h"	43	#include "xmalloc.h"
43	#include "ssh.h"	44	#include "ssh.h"
Lines 119-124 userauth_pubkey(Authctxt *authctxt) Link Here
119	"signature scheme");	120	"signature scheme");
120	goto done;	121	goto done;
121	}	122	}
		123	if (auth2_userkey_already_used(authctxt, key)) {
		124	logit("refusing previously-used %s key", key_type(key));
		125	goto done;
		126	}
122	if (have_sig) {	127	if (have_sig) {
123	sig = packet_get_string(&slen);	128	sig = packet_get_string(&slen);
124	packet_check_eom();	129	packet_check_eom();
Lines 156-163 userauth_pubkey(Authctxt *authctxt) Link Here
156	authenticated = 0;	161	authenticated = 0;
157	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&	162	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
158	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),	163	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
159	buffer_len(&b))) == 1)	164	buffer_len(&b))) == 1) {
160	authenticated = 1;	165	authenticated = 1;
		166	/* Record the successful key to prevent reuse */
		167	auth2_record_userkey(authctxt, key);
		168	key = NULL; /* Don't free below */
		169	}
161	buffer_free(&b);	170	buffer_free(&b);
162	free(sig);	171	free(sig);
163	} else {	172	} else {
Lines 675-680 user_key_allowed(struct passwd *pw, Key Link Here
675	}	684	}
676		685
677	return success;	686	return success;
		687	}
		688
		689	/* Records a public key in the list of previously-successful keys */
		690	void
		691	auth2_record_userkey(Authctxt authctxt, struct sshkey key)
		692	{
		693	struct sshkey **tmp;
		694
		695	if (authctxt->nprev_userkeys >= INT_MAX \|\|
		696	(tmp = reallocarray(authctxt->prev_userkeys,
		697	authctxt->nprev_userkeys + 1, sizeof(*tmp))) == NULL)
		698	fatal("%s: reallocarray failed", __func__);
		699	authctxt->prev_userkeys = tmp;
		700	authctxt->prev_userkeys[authctxt->nprev_userkeys] = key;
		701	authctxt->nprev_userkeys++;
		702	}
		703
		704	/* Checks whether a key has already been used successfully for authentication */
		705	int
		706	auth2_userkey_already_used(Authctxt authctxt, struct sshkey key)
		707	{
		708	u_int i;
		709
		710	for (i = 0; i < authctxt->nprev_userkeys; i++) {
		711	if (sshkey_equal_public(key, authctxt->prev_userkeys[i])) {
		712	return 1;
		713	}
		714	}
		715	return 0;
678	}	716	}
679		717
680	Authmethod method_pubkey = {	718	Authmethod method_pubkey = {

Lines 884-889 mm_answer_keyallowed(int sock, Buffer *m Link Here

(-)usr.bin/ssh/monitor.c (-1 / +7 lines)
884	switch (type) {	884	switch (type) {
885	case MM_USERKEY:	885	case MM_USERKEY:
886	allowed = options.pubkey_authentication &&	886	allowed = options.pubkey_authentication &&
		887	!auth2_userkey_already_used(authctxt, key) &&
887	user_key_allowed(authctxt->pw, key);	888	user_key_allowed(authctxt->pw, key);
888	pubkey_auth_info(authctxt, key, NULL);	889	pubkey_auth_info(authctxt, key, NULL);
889	auth_method = "publickey";	890	auth_method = "publickey";
Lines 1111-1117 mm_answer_keyverify(int sock, Buffer *m) Link Here
1111	debug3("%s: key %p signature %s",	1112	debug3("%s: key %p signature %s",
1112	__func__, key, (verified == 1) ? "verified" : "unverified");	1113	__func__, key, (verified == 1) ? "verified" : "unverified");
1113		1114
1114	key_free(key);	1115	/* If auth was successful then record key to ensure it isn't reused */
		1116	if (verified == 1)
		1117	auth2_record_userkey(authctxt, key);
		1118	else
		1119	key_free(key);
		1120
1115	free(blob);	1121	free(blob);
1116	free(signature);	1122	free(signature);
1117	free(data);	1123	free(data);




.Dq bsdauth
device.
.Pp
If the
.Dq publickey
method is listed more than one,
.Xr sshd 8
verifies that keys that have been successfully are not reused for subsequent
authentications.
For example, an
.Cm AuthenticationMethods
of
.Dq publickey,publickey
will require successful authentication using two different public keys.
.Pp
This option is only available for SSH protocol 2 and will yield a fatal
error if enabled if protocol 1 is also enabled.
Note that each authentication method listed should also be explicitly enabled

Lines 58-64 LTESTS= connect \ Link Here

(-)regress/usr.bin/ssh/Makefile (-1 / +2 lines)
58	keys-command \	58	keys-command \
59	forward-control \	59	forward-control \
60	integrity \	60	integrity \
61	krl	61	krl \
		62	multipubkey
62		63
63	INTEROP_TESTS= putty-transfer putty-ciphers putty-kex conch-ciphers	64	INTEROP_TESTS= putty-transfer putty-ciphers putty-kex conch-ciphers
64	#INTEROP_TESTS+=ssh-com ssh-com-client ssh-com-keygen ssh-com-sftp	65	#INTEROP_TESTS+=ssh-com ssh-com-client ssh-com-keygen ssh-com-sftp




#	$OpenBSD$
#	Placed in the Public Domain.

tid="multiple pubkey"

rm -f $OBJ/authorized_keys_$USER $OBJ/user_ca_key* $OBJ/user_key*
rm -f $OBJ/authorized_principals_$USER $OBJ/cert_user_key*

mv $OBJ/sshd_proxy $OBJ/sshd_proxy.orig
mv $OBJ/ssh_proxy $OBJ/ssh_proxy.orig

# Create a CA key
${SSHKEYGEN} -q -N '' -t ed25519  -f $OBJ/user_ca_key ||\
	fatal "ssh-keygen failed"

# Make some keys and a certificate.
${SSHKEYGEN} -q -N '' -t ed25519 -f $OBJ/user_key1 || \
	fatal "ssh-keygen failed"
${SSHKEYGEN} -q -N '' -t ed25519 -f $OBJ/user_key2 || \
	fatal "ssh-keygen failed"
${SSHKEYGEN} -q -s $OBJ/user_ca_key -I "regress user key for $USER" \
	-z $$ -n ${USER},mekmitasdigoat $OBJ/user_key1 ||
		fail "couldn't sign user_key1"
# Copy the private key alongside the cert to allow better control of when
# it is offered.
mv $OBJ/user_key1-cert.pub $OBJ/cert_user_key1.pub
cp -p $OBJ/user_key1 $OBJ/cert_user_key1

grep -v IdentityFile $OBJ/ssh_proxy.orig > $OBJ/ssh_proxy

opts="-oProtocol=2 -F $OBJ/ssh_proxy -oIdentitiesOnly=yes"
opts="$opts -i $OBJ/cert_user_key1 -i $OBJ/user_key1 -i $OBJ/user_key2"

for privsep in no yes; do
	(
		grep -v "Protocol"  $OBJ/sshd_proxy.orig
		echo "Protocol 2"
		echo "UsePrivilegeSeparation $privsep"
		echo "AuthenticationMethods publickey,publickey"
		echo "TrustedUserCAKeys $OBJ/user_ca_key.pub"
		echo "AuthorizedPrincipalsFile $OBJ/authorized_principals_%u"
 	) > $OBJ/sshd_proxy

	# Single key should fail.
	rm -f $OBJ/authorized_principals_$USER
	cat $OBJ/user_key1.pub > $OBJ/authorized_keys_$USER
	${SSH} $opts proxy true && fail "ssh succeeded with key"

	# Single key with same-public cert should fail.
	echo mekmitasdigoat > $OBJ/authorized_principals_$USER
	cat $OBJ/user_key1.pub > $OBJ/authorized_keys_$USER
	${SSH} $opts proxy true && fail "ssh succeeded with key+cert"

	# Multiple plain keys should succeed.
	rm -f $OBJ/authorized_principals_$USER
	cat $OBJ/user_key1.pub $OBJ/user_key2.pub > \
	    $OBJ/authorized_keys_$USER
	${SSH} $opts proxy true || fail "ssh failed with multiple keys"
	# Cert and different key should succeed

	# Key and different-public cert should succeed.
	echo mekmitasdigoat > $OBJ/authorized_principals_$USER
	cat $OBJ/user_key2.pub > $OBJ/authorized_keys_$USER
	${SSH} $opts proxy true || fail "ssh failed with key/cert"
done


Return to bug 2322

Lines 210-215 would restrict keyboard interactive auth Link Here

(-)usr.bin/ssh/sshd_config.5 (+12 lines)
210	.Dq bsdauth	210	.Dq bsdauth
211	device.	211	device.
212	.Pp	212	.Pp
		213	If the
		214	.Dq publickey
		215	method is listed more than one,
		216	.Xr sshd 8
		217	verifies that keys that have been successfully are not reused for subsequent
		218	authentications.
		219	For example, an
		220	.Cm AuthenticationMethods
		221	of
		222	.Dq publickey,publickey
		223	will require successful authentication using two different public keys.
		224	.Pp
213	This option is only available for SSH protocol 2 and will yield a fatal	225	This option is only available for SSH protocol 2 and will yield a fatal
214	error if enabled if protocol 1 is also enabled.	226	error if enabled if protocol 1 is also enabled.
215	Note that each authentication method listed should also be explicitly enabled	227	Note that each authentication method listed should also be explicitly enabled

Added Link Here

(-)regress/usr.bin/ssh/multipubkey.sh (+66 lines)
1	# $OpenBSD$
2	# Placed in the Public Domain.
3
4	tid="multiple pubkey"
5
6	rm -f $OBJ/authorized_keys_$USER $OBJ/user_ca_key* $OBJ/user_key*
7	rm -f $OBJ/authorized_principals_$USER $OBJ/cert_user_key*
8
9	mv $OBJ/sshd_proxy $OBJ/sshd_proxy.orig
10	mv $OBJ/ssh_proxy $OBJ/ssh_proxy.orig
11
12	# Create a CA key
13	${SSHKEYGEN} -q -N '' -t ed25519 -f $OBJ/user_ca_key \|\|\
14	fatal "ssh-keygen failed"
15
16	# Make some keys and a certificate.
17	${SSHKEYGEN} -q -N '' -t ed25519 -f $OBJ/user_key1 \|\| \
18	fatal "ssh-keygen failed"
19	${SSHKEYGEN} -q -N '' -t ed25519 -f $OBJ/user_key2 \|\| \
20	fatal "ssh-keygen failed"
21	${SSHKEYGEN} -q -s $OBJ/user_ca_key -I "regress user key for $USER" \
22	-z $$ -n ${USER},mekmitasdigoat $OBJ/user_key1 \|\|
23	fail "couldn't sign user_key1"
24	# Copy the private key alongside the cert to allow better control of when
25	# it is offered.
26	mv $OBJ/user_key1-cert.pub $OBJ/cert_user_key1.pub
27	cp -p $OBJ/user_key1 $OBJ/cert_user_key1
28
29	grep -v IdentityFile $OBJ/ssh_proxy.orig > $OBJ/ssh_proxy
30
31	opts="-oProtocol=2 -F $OBJ/ssh_proxy -oIdentitiesOnly=yes"
32	opts="$opts -i $OBJ/cert_user_key1 -i $OBJ/user_key1 -i $OBJ/user_key2"
33
34	for privsep in no yes; do
35	(
36	grep -v "Protocol" $OBJ/sshd_proxy.orig
37	echo "Protocol 2"
38	echo "UsePrivilegeSeparation $privsep"
39	echo "AuthenticationMethods publickey,publickey"
40	echo "TrustedUserCAKeys $OBJ/user_ca_key.pub"
41	echo "AuthorizedPrincipalsFile $OBJ/authorized_principals_%u"
42	) > $OBJ/sshd_proxy
43
44	# Single key should fail.
45	rm -f $OBJ/authorized_principals_$USER
46	cat $OBJ/user_key1.pub > $OBJ/authorized_keys_$USER
47	${SSH} $opts proxy true && fail "ssh succeeded with key"
48
49	# Single key with same-public cert should fail.
50	echo mekmitasdigoat > $OBJ/authorized_principals_$USER
51	cat $OBJ/user_key1.pub > $OBJ/authorized_keys_$USER
52	${SSH} $opts proxy true && fail "ssh succeeded with key+cert"
53
54	# Multiple plain keys should succeed.
55	rm -f $OBJ/authorized_principals_$USER
56	cat $OBJ/user_key1.pub $OBJ/user_key2.pub > \
57	$OBJ/authorized_keys_$USER
58	${SSH} $opts proxy true \|\| fail "ssh failed with multiple keys"
59	# Cert and different key should succeed
60
61	# Key and different-public cert should succeed.
62	echo mekmitasdigoat > $OBJ/authorized_principals_$USER
63	cat $OBJ/user_key2.pub > $OBJ/authorized_keys_$USER
64	${SSH} $opts proxy true \|\| fail "ssh failed with key/cert"
65	done
66