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wg: use key_is_zero for comparing to zeros

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Maybe an attacker on the system could use the infoleak in /proc to gauge
how long a wg(8) process takes to complete and determine the number of
leading zeros. This is somewhat ridiculous, but it's possible somebody
somewhere might at somepoint care in the future, so alright.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2017-09-22 04:04:00 +02:00
parent 6c7d67acfe
commit 9ef84af8c0
6 changed files with 24 additions and 22 deletions
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10
src/config.c
View file

@ -387,17 +387,11 @@ bool config_read_init(struct config_ctx *ctx, struct wgdevice **device, bool app
return true; return true;
} }
static inline bool key_is_valid(uint8_t key[WG_KEY_LEN])
{
static const uint8_t zero[WG_KEY_LEN] = { 0 };
return !!memcmp(key, zero, WG_KEY_LEN);
}
bool config_read_finish(struct config_ctx *ctx) bool config_read_finish(struct config_ctx *ctx)
{ {
size_t i; size_t i;
struct wgpeer *peer; struct wgpeer *peer;
if (ctx->buf.dev->flags & WGDEVICE_REPLACE_PEERS && !key_is_valid(ctx->buf.dev->private_key)) { if (ctx->buf.dev->flags & WGDEVICE_REPLACE_PEERS && key_is_zero(ctx->buf.dev->private_key)) {
fprintf(stderr, "No private key configured\n"); fprintf(stderr, "No private key configured\n");
goto err; goto err;
} }
@ -405,7 +399,7 @@ bool config_read_finish(struct config_ctx *ctx)
ctx->buf.dev->flags |= WGDEVICE_REMOVE_FWMARK; ctx->buf.dev->flags |= WGDEVICE_REMOVE_FWMARK;
for_each_wgpeer(ctx->buf.dev, peer, i) { for_each_wgpeer(ctx->buf.dev, peer, i) {
if (!key_is_valid(peer->public_key)) { if (key_is_zero(peer->public_key)) {
fprintf(stderr, "A peer is missing a public key\n"); fprintf(stderr, "A peer is missing a public key\n");
goto err; goto err;
} }

14
src/encoding.c
View file

@ -77,12 +77,12 @@ void key_to_hex(char hex[static WG_KEY_LEN_HEX], const uint8_t key[static WG_KEY
bool key_from_hex(uint8_t key[static WG_KEY_LEN], const char *hex) bool key_from_hex(uint8_t key[static WG_KEY_LEN], const char *hex)
{ {
uint8_t i, c, c_acc = 0, c_alpha0, c_alpha, c_num0, c_num, c_val, state = 0; uint8_t c, c_acc = 0, c_alpha0, c_alpha, c_num0, c_num, c_val, state = 0;
if (strlen(hex) != WG_KEY_LEN_HEX - 1) if (strlen(hex) != WG_KEY_LEN_HEX - 1)
return false; return false;
for (i = 0; i < WG_KEY_LEN_HEX - 1; ++i) { for (unsigned int i = 0; i < WG_KEY_LEN_HEX - 1; ++i) {
c = (uint8_t)hex[i]; c = (uint8_t)hex[i];
c_num = c ^ 48U; c_num = c ^ 48U;
c_num0 = (c_num - 10U) >> 8; c_num0 = (c_num - 10U) >> 8;
@ -99,3 +99,13 @@ bool key_from_hex(uint8_t key[static WG_KEY_LEN], const char *hex)
} }
return true; return true;
} }
bool key_is_zero(const uint8_t key[static WG_KEY_LEN])
{
uint8_t acc = 0;
for (unsigned int i = 0; i < WG_KEY_LEN; ++i) {
acc |= key[i];
__asm__ ("" : "=r" (acc) : "0" (acc));
}
return acc == 0;
}

2
src/encoding.h
View file

@ -16,4 +16,6 @@ bool key_from_base64(uint8_t key[static WG_KEY_LEN], const char *base64);
void key_to_hex(char hex[static WG_KEY_LEN_HEX], const uint8_t key[static WG_KEY_LEN]); void key_to_hex(char hex[static WG_KEY_LEN_HEX], const uint8_t key[static WG_KEY_LEN]);
bool key_from_hex(uint8_t key[static WG_KEY_LEN], const char *hex); bool key_from_hex(uint8_t key[static WG_KEY_LEN], const char *hex);
bool key_is_zero(const uint8_t key[static WG_KEY_LEN]);
#endif #endif

5
src/ipc.c
View file

@ -170,7 +170,6 @@ out:
static int userspace_set_device(struct wgdevice *dev) static int userspace_set_device(struct wgdevice *dev)
{ {
static const uint8_t zero[WG_KEY_LEN] = { 0 };
char hex[WG_KEY_LEN_HEX], ip[INET6_ADDRSTRLEN], host[4096 + 1], service[512 + 1]; char hex[WG_KEY_LEN_HEX], ip[INET6_ADDRSTRLEN], host[4096 + 1], service[512 + 1];
struct wgpeer *peer; struct wgpeer *peer;
struct wgipmask *ipmask; struct wgipmask *ipmask;
@ -186,7 +185,7 @@ static int userspace_set_device(struct wgdevice *dev)
if (dev->flags & WGDEVICE_REMOVE_PRIVATE_KEY) if (dev->flags & WGDEVICE_REMOVE_PRIVATE_KEY)
fprintf(f, "private_key=\n"); fprintf(f, "private_key=\n");
else if (memcmp(dev->private_key, zero, WG_KEY_LEN)) { else if (!key_is_zero(dev->private_key)) {
key_to_hex(hex, dev->private_key); key_to_hex(hex, dev->private_key);
fprintf(f, "private_key=%s\n", hex); fprintf(f, "private_key=%s\n", hex);
} }
@ -208,7 +207,7 @@ static int userspace_set_device(struct wgdevice *dev)
} }
if (peer->flags & WGPEER_REMOVE_PRESHARED_KEY) if (peer->flags & WGPEER_REMOVE_PRESHARED_KEY)
fprintf(f, "preshared_key=\n"); fprintf(f, "preshared_key=\n");
else if (memcmp(peer->preshared_key, zero, WG_KEY_LEN)) { else if (!key_is_zero(peer->preshared_key)) {
key_to_hex(hex, peer->preshared_key); key_to_hex(hex, peer->preshared_key);
fprintf(f, "preshared_key=%s\n", hex); fprintf(f, "preshared_key=%s\n", hex);
} }

10
src/show.c
View file

@ -75,12 +75,10 @@ static void sort_peers(struct wgdevice *device)
free(new_device); free(new_device);
} }
static const uint8_t zero[WG_KEY_LEN] = { 0 };
static char *key(const uint8_t key[static WG_KEY_LEN]) static char *key(const uint8_t key[static WG_KEY_LEN])
{ {
static char base64[WG_KEY_LEN_BASE64]; static char base64[WG_KEY_LEN_BASE64];
if (!memcmp(key, zero, WG_KEY_LEN)) if (key_is_zero(key))
return "(none)"; return "(none)";
key_to_base64(base64, key); key_to_base64(base64, key);
return base64; return base64;
@ -212,9 +210,9 @@ static void pretty_print(struct wgdevice *device)
terminal_printf(TERMINAL_RESET); terminal_printf(TERMINAL_RESET);
terminal_printf(TERMINAL_FG_GREEN TERMINAL_BOLD "interface" TERMINAL_RESET ": " TERMINAL_FG_GREEN "%s" TERMINAL_RESET "\n", device->interface); terminal_printf(TERMINAL_FG_GREEN TERMINAL_BOLD "interface" TERMINAL_RESET ": " TERMINAL_FG_GREEN "%s" TERMINAL_RESET "\n", device->interface);
if (memcmp(device->public_key, zero, WG_KEY_LEN)) if (!key_is_zero(device->public_key))
terminal_printf(" " TERMINAL_BOLD "public key" TERMINAL_RESET ": %s\n", key(device->public_key)); terminal_printf(" " TERMINAL_BOLD "public key" TERMINAL_RESET ": %s\n", key(device->public_key));
if (memcmp(device->private_key, zero, WG_KEY_LEN)) if (!key_is_zero(device->private_key))
terminal_printf(" " TERMINAL_BOLD "private key" TERMINAL_RESET ": %s\n", masked_key(device->private_key)); terminal_printf(" " TERMINAL_BOLD "private key" TERMINAL_RESET ": %s\n", masked_key(device->private_key));
if (device->port) if (device->port)
terminal_printf(" " TERMINAL_BOLD "listening port" TERMINAL_RESET ": %u\n", device->port); terminal_printf(" " TERMINAL_BOLD "listening port" TERMINAL_RESET ": %u\n", device->port);
@ -226,7 +224,7 @@ static void pretty_print(struct wgdevice *device)
} }
for_each_wgpeer(device, peer, i) { for_each_wgpeer(device, peer, i) {
terminal_printf(TERMINAL_FG_YELLOW TERMINAL_BOLD "peer" TERMINAL_RESET ": " TERMINAL_FG_YELLOW "%s" TERMINAL_RESET "\n", key(peer->public_key)); terminal_printf(TERMINAL_FG_YELLOW TERMINAL_BOLD "peer" TERMINAL_RESET ": " TERMINAL_FG_YELLOW "%s" TERMINAL_RESET "\n", key(peer->public_key));
if (memcmp(peer->preshared_key, zero, WG_KEY_LEN)) if (!key_is_zero(peer->preshared_key))
terminal_printf(" " TERMINAL_BOLD "preshared key" TERMINAL_RESET ": %s\n", masked_key(peer->preshared_key)); terminal_printf(" " TERMINAL_BOLD "preshared key" TERMINAL_RESET ": %s\n", masked_key(peer->preshared_key));
if (peer->endpoint.addr.sa_family == AF_INET || peer->endpoint.addr.sa_family == AF_INET6) if (peer->endpoint.addr.sa_family == AF_INET || peer->endpoint.addr.sa_family == AF_INET6)
terminal_printf(" " TERMINAL_BOLD "endpoint" TERMINAL_RESET ": %s\n", endpoint(&peer->endpoint.addr)); terminal_printf(" " TERMINAL_BOLD "endpoint" TERMINAL_RESET ": %s\n", endpoint(&peer->endpoint.addr));

5
src/showconf.c
View file

@ -16,7 +16,6 @@
int showconf_main(int argc, char *argv[]) int showconf_main(int argc, char *argv[])
{ {
static const uint8_t zero[WG_KEY_LEN] = { 0 };
char base64[WG_KEY_LEN_BASE64]; char base64[WG_KEY_LEN_BASE64];
char ip[INET6_ADDRSTRLEN]; char ip[INET6_ADDRSTRLEN];
struct wgdevice *device = NULL; struct wgdevice *device = NULL;
@ -46,7 +45,7 @@ int showconf_main(int argc, char *argv[])
printf("ListenPort = %u\n", device->port); printf("ListenPort = %u\n", device->port);
if (device->fwmark) if (device->fwmark)
printf("FwMark = 0x%x\n", device->fwmark); printf("FwMark = 0x%x\n", device->fwmark);
if (memcmp(device->private_key, zero, WG_KEY_LEN)) { if (!key_is_zero(device->private_key)) {
key_to_base64(base64, device->private_key); key_to_base64(base64, device->private_key);
printf("PrivateKey = %s\n", base64); printf("PrivateKey = %s\n", base64);
} }
@ -54,7 +53,7 @@ int showconf_main(int argc, char *argv[])
for_each_wgpeer(device, peer, i) { for_each_wgpeer(device, peer, i) {
key_to_base64(base64, peer->public_key); key_to_base64(base64, peer->public_key);
printf("[Peer]\nPublicKey = %s\n", base64); printf("[Peer]\nPublicKey = %s\n", base64);
if (memcmp(peer->preshared_key, zero, WG_KEY_LEN)) { if (!key_is_zero(peer->preshared_key)) {
key_to_base64(base64, peer->preshared_key); key_to_base64(base64, peer->preshared_key);
printf("PresharedKey = %s\n", base64); printf("PresharedKey = %s\n", base64);
} }