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transport2: make kexlists dynamically allocated.

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The list of kex methods recently ran out of space due to the addition
of NTRU (at least, if you have GSSAPI enabled). It's time to stop
having an arbitrary limit on those arrays and switch to doing it
properly.
This commit is contained in:
Simon Tatham 2022-04-21 05:11:58 +01:00
parent 6a9e4ba24a
commit 7d44e35bb3
2 changed files with 49 additions and 44 deletions
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86
ssh/transport2.c
View File

@ -216,6 +216,8 @@ static void ssh2_transport_free(PacketProtocolLayer *ppl)
ssh_key_free(s->hkey);
s->hkey = NULL;
}
for (size_t i = 0; i < NKEXLIST; i++)
sfree(s->kexlists[i].algs);
if (s->f) mp_free(s->f);
if (s->p) mp_free(s->p);
if (s->g) mp_free(s->g);
@ -307,21 +309,20 @@ static void ssh2_mkkey(
* of.
*/
static struct kexinit_algorithm *ssh2_kexinit_addalg_pl(
struct kexinit_algorithm *list, ptrlen name)
struct kexinit_algorithm_list *list, ptrlen name)
{
int i;
for (size_t i = 0; i < list->nalgs; i++)
if (ptrlen_eq_ptrlen(list->algs[i].name, name))
return &list->algs[i];
for (i = 0; i < MAXKEXLIST; i++)
if (list[i].name.ptr == NULL || ptrlen_eq_ptrlen(list[i].name, name)) {
list[i].name = name;
return &list[i];
}
unreachable("Should never run out of space in KEXINIT list");
sgrowarray(list->algs, list->algsize, list->nalgs);
struct kexinit_algorithm *entry = &list->algs[list->nalgs++];
entry->name = name;
return entry;
}
static struct kexinit_algorithm *ssh2_kexinit_addalg(
struct kexinit_algorithm *list, const char *name)
struct kexinit_algorithm_list *list, const char *name)
{
return ssh2_kexinit_addalg_pl(list, ptrlen_from_asciz(name));
}
@ -489,7 +490,7 @@ PktIn *ssh2_transport_pop(struct ssh2_transport_state *s)
static void ssh2_write_kexinit_lists(
BinarySink *pktout,
struct kexinit_algorithm kexlists[NKEXLIST][MAXKEXLIST],
struct kexinit_algorithm_list kexlists[NKEXLIST],
Conf *conf, const SshServerConfig *ssc, int remote_bugs,
const char *hk_host, int hk_port, const ssh_keyalg *hk_prev,
ssh_transient_hostkey_cache *thc,
@ -611,15 +612,14 @@ static void ssh2_write_kexinit_lists(
preferred_comp = &ssh_comp_none;
for (i = 0; i < NKEXLIST; i++)
for (j = 0; j < MAXKEXLIST; j++)
kexlists[i][j].name = make_ptrlen(NULL, 0);
kexlists[i].nalgs = 0;
/* List key exchange algorithms. */
warn = false;
for (i = 0; i < n_preferred_kex; i++) {
const ssh_kexes *k = preferred_kex[i];
if (!k) warn = true;
else for (j = 0; j < k->nkexes; j++) {
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_KEX],
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_KEX],
k->list[j]->name);
alg->u.kex.kex = k->list[j];
alg->u.kex.warn = warn;
@ -634,20 +634,20 @@ static void ssh2_write_kexinit_lists(
for (i = 0; i < our_nhostkeys; i++) {
const ssh_keyalg *keyalg = ssh_key_alg(our_hostkeys[i]);
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY],
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY],
keyalg->ssh_id);
alg->u.hk.hostkey = keyalg;
alg->u.hk.hkflags = 0;
alg->u.hk.warn = false;
if (keyalg == &ssh_rsa) {
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY],
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY],
"rsa-sha2-256");
alg->u.hk.hostkey = keyalg;
alg->u.hk.hkflags = SSH_AGENT_RSA_SHA2_256;
alg->u.hk.warn = false;
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY],
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY],
"rsa-sha2-512");
alg->u.hk.hostkey = keyalg;
alg->u.hk.hkflags = SSH_AGENT_RSA_SHA2_512;
@ -678,7 +678,7 @@ static void ssh2_write_kexinit_lists(
if (conf_get_bool(conf, CONF_ssh_prefer_known_hostkeys) &&
have_ssh_host_key(hk_host, hk_port,
ssh2_hostkey_algs[j].alg->cache_id)) {
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY],
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY],
ssh2_hostkey_algs[j].alg->ssh_id);
alg->u.hk.hostkey = ssh2_hostkey_algs[j].alg;
alg->u.hk.warn = warn;
@ -692,7 +692,7 @@ static void ssh2_write_kexinit_lists(
for (j = 0; j < lenof(ssh2_hostkey_algs); j++) {
if (ssh2_hostkey_algs[j].id != preferred_hk[i])
continue;
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY],
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY],
ssh2_hostkey_algs[j].alg->ssh_id);
alg->u.hk.hostkey = ssh2_hostkey_algs[j].alg;
alg->u.hk.warn = warn;
@ -721,7 +721,7 @@ static void ssh2_write_kexinit_lists(
continue;
if (ssh_transient_hostkey_cache_has(
thc, ssh2_hostkey_algs[j].alg)) {
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY],
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY],
ssh2_hostkey_algs[j].alg->ssh_id);
alg->u.hk.hostkey = ssh2_hostkey_algs[j].alg;
alg->u.hk.warn = warn;
@ -738,19 +738,19 @@ static void ssh2_write_kexinit_lists(
* reverification.
*/
assert(hk_prev);
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY], hk_prev->ssh_id);
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY], hk_prev->ssh_id);
alg->u.hk.hostkey = hk_prev;
alg->u.hk.warn = false;
}
if (can_gssapi_keyex) {
alg = ssh2_kexinit_addalg(kexlists[KEXLIST_HOSTKEY], "null");
alg = ssh2_kexinit_addalg(&kexlists[KEXLIST_HOSTKEY], "null");
alg->u.hk.hostkey = NULL;
}
/* List encryption algorithms (client->server then server->client). */
for (k = KEXLIST_CSCIPHER; k <= KEXLIST_SCCIPHER; k++) {
warn = false;
#ifdef FUZZING
alg = ssh2_kexinit_addalg(kexlists[k], "none");
alg = ssh2_kexinit_addalg(&kexlists[K], "none");
alg->u.cipher.cipher = NULL;
alg->u.cipher.warn = warn;
#endif /* FUZZING */
@ -758,7 +758,7 @@ static void ssh2_write_kexinit_lists(
const ssh2_ciphers *c = preferred_ciphers[i];
if (!c) warn = true;
else for (j = 0; j < c->nciphers; j++) {
alg = ssh2_kexinit_addalg(kexlists[k],
alg = ssh2_kexinit_addalg(&kexlists[k],
c->list[j]->ssh2_id);
alg->u.cipher.cipher = c->list[j];
alg->u.cipher.warn = warn;
@ -785,7 +785,7 @@ static void ssh2_write_kexinit_lists(
alg->u.mac.etm = false;
#endif /* FUZZING */
for (i = 0; i < nmacs; i++) {
alg = ssh2_kexinit_addalg(kexlists[j], maclist[i]->name);
alg = ssh2_kexinit_addalg(&kexlists[j], maclist[i]->name);
alg->u.mac.mac = maclist[i];
alg->u.mac.etm = false;
}
@ -793,7 +793,7 @@ static void ssh2_write_kexinit_lists(
/* For each MAC, there may also be an ETM version,
* which we list second. */
if (maclist[i]->etm_name) {
alg = ssh2_kexinit_addalg(kexlists[j], maclist[i]->etm_name);
alg = ssh2_kexinit_addalg(&kexlists[j], maclist[i]->etm_name);
alg->u.mac.mac = maclist[i];
alg->u.mac.etm = true;
}
@ -806,22 +806,22 @@ static void ssh2_write_kexinit_lists(
for (j = KEXLIST_CSCOMP; j <= KEXLIST_SCCOMP; j++) {
assert(lenof(compressions) > 1);
/* Prefer non-delayed versions */
alg = ssh2_kexinit_addalg(kexlists[j], preferred_comp->name);
alg = ssh2_kexinit_addalg(&kexlists[j], preferred_comp->name);
alg->u.comp.comp = preferred_comp;
alg->u.comp.delayed = false;
if (preferred_comp->delayed_name) {
alg = ssh2_kexinit_addalg(kexlists[j],
alg = ssh2_kexinit_addalg(&kexlists[j],
preferred_comp->delayed_name);
alg->u.comp.comp = preferred_comp;
alg->u.comp.delayed = true;
}
for (i = 0; i < lenof(compressions); i++) {
const ssh_compression_alg *c = compressions[i];
alg = ssh2_kexinit_addalg(kexlists[j], c->name);
alg = ssh2_kexinit_addalg(&kexlists[j], c->name);
alg->u.comp.comp = c;
alg->u.comp.delayed = false;
if (c->delayed_name) {
alg = ssh2_kexinit_addalg(kexlists[j], c->delayed_name);
alg = ssh2_kexinit_addalg(&kexlists[j], c->delayed_name);
alg->u.comp.comp = c;
alg->u.comp.delayed = true;
}
@ -837,10 +837,8 @@ static void ssh2_write_kexinit_lists(
if (ssc && ssc->kex_override[i].ptr) {
put_datapl(list, ssc->kex_override[i]);
} else {
for (j = 0; j < MAXKEXLIST; j++) {
if (kexlists[i][j].name.ptr == NULL) break;
add_to_commasep_pl(list, kexlists[i][j].name);
}
for (j = 0; j < kexlists[i].nalgs; j++)
add_to_commasep_pl(list, kexlists[i].algs[j].name);
}
if (i == KEXLIST_KEX && first_time) {
if (our_hostkeys) /* we're the server */
@ -858,12 +856,12 @@ static void ssh2_write_kexinit_lists(
static bool ssh2_scan_kexinits(
ptrlen client_kexinit, ptrlen server_kexinit,
struct kexinit_algorithm kexlists[NKEXLIST][MAXKEXLIST],
struct kexinit_algorithm_list kexlists[NKEXLIST],
const ssh_kex **kex_alg, const ssh_keyalg **hostkey_alg,
transport_direction *cs, transport_direction *sc,
bool *warn_kex, bool *warn_hk, bool *warn_cscipher, bool *warn_sccipher,
Ssh *ssh, bool *ignore_guess_cs_packet, bool *ignore_guess_sc_packet,
int *n_server_hostkeys, int server_hostkeys[MAXKEXLIST], unsigned *hkflags,
int *n_server_hostkeys, int *server_hostkeys, unsigned *hkflags,
bool *can_send_ext_info)
{
BinarySource client[1], server[1];
@ -928,10 +926,9 @@ static bool ssh2_scan_kexinits(
found_match:
selected[i] = NULL;
for (j = 0; j < MAXKEXLIST; j++) {
if (kexlists[i][j].name.ptr &&
ptrlen_eq_ptrlen(found, kexlists[i][j].name)) {
selected[i] = &kexlists[i][j];
for (j = 0; j < kexlists[i].nalgs; j++) {
if (ptrlen_eq_ptrlen(found, kexlists[i].algs[j].name)) {
selected[i] = &kexlists[i].algs[j];
break;
}
}
@ -1241,7 +1238,8 @@ static void ssh2_transport_process_queue(PacketProtocolLayer *ppl)
* selected algorithm identifiers.
*/
{
int nhk, hks[MAXKEXLIST], i, j;
int nhk, i, j;
int *hks = snewn(s->kexlists[KEXLIST_HOSTKEY].nalgs, int);
if (!ssh2_scan_kexinits(
ptrlen_from_strbuf(s->client_kexinit),
@ -1249,8 +1247,10 @@ static void ssh2_transport_process_queue(PacketProtocolLayer *ppl)
s->kexlists, &s->kex_alg, &s->hostkey_alg, s->cstrans,
s->sctrans, &s->warn_kex, &s->warn_hk, &s->warn_cscipher,
&s->warn_sccipher, s->ppl.ssh, NULL, &s->ignorepkt, &nhk, hks,
&s->hkflags, &s->can_send_ext_info))
&s->hkflags, &s->can_send_ext_info)) {
sfree(hks);
return; /* false means a fatal error function was called */
}
/*
* In addition to deciding which host key we're actually going
@ -1272,6 +1272,8 @@ static void ssh2_transport_process_queue(PacketProtocolLayer *ppl)
s->uncert_hostkeys[s->n_uncert_hostkeys++] = j;
}
}
sfree(hks);
}
if (s->warn_kex) {

7
ssh/transport2.h
View File

@ -18,7 +18,6 @@
#define DH_MIN_SIZE 1024
#define DH_MAX_SIZE 8192
#define MAXKEXLIST 16
struct kexinit_algorithm {
ptrlen name;
union {
@ -45,6 +44,10 @@ struct kexinit_algorithm {
} comp;
} u;
};
struct kexinit_algorithm_list {
struct kexinit_algorithm *algs;
size_t nalgs, algsize;
};
#define HOSTKEY_ALGORITHMS(X) \
X(HK_ED25519, ssh_ecdsa_ed25519) \
@ -190,7 +193,7 @@ struct ssh2_transport_state {
SeatPromptResult spr;
bool guessok;
bool ignorepkt;
struct kexinit_algorithm kexlists[NKEXLIST][MAXKEXLIST];
struct kexinit_algorithm_list kexlists[NKEXLIST];
#ifndef NO_GSSAPI
Ssh_gss_buf gss_buf;
Ssh_gss_buf gss_rcvtok, gss_sndtok;