hostapd: Verify availability of random data when using WPA/WPA2
On Linux, verify that the kernel entropy pool is capable of providing strong random data before allowing WPA/WPA2 connection to be established. If 20 bytes of data cannot be read from /dev/random, force first two 4-way handshakes to fail while collecting entropy into the internal pool in hostapd. After that, give up on /dev/random and allow the AP to function based on the combination of /dev/urandom and whatever data has been collected into the internal entropy pool.
This commit is contained in:
parent
dbb6ed7e75
commit
08704cd885
4 changed files with 118 additions and 1 deletions
|
@ -29,6 +29,9 @@
|
|||
*/
|
||||
|
||||
#include "utils/includes.h"
|
||||
#ifdef __linux__
|
||||
#include <fcntl.h>
|
||||
#endif /* __linux__ */
|
||||
|
||||
#include "utils/common.h"
|
||||
#include "sha1.h"
|
||||
|
@ -42,14 +45,18 @@
|
|||
#define POOL_TAP4 7
|
||||
#define POOL_TAP5 1
|
||||
#define EXTRACT_LEN 16
|
||||
#define MIN_READY_MARK 2
|
||||
|
||||
static u32 pool[POOL_WORDS];
|
||||
static unsigned int input_rotate = 0;
|
||||
static unsigned int pool_pos = 0;
|
||||
static const u8 dummy_key[20];
|
||||
static u8 dummy_key[20];
|
||||
static size_t dummy_key_avail = 0;
|
||||
static unsigned int own_pool_ready = 0;
|
||||
|
||||
#define MIN_COLLECT_ENTROPY 1000
|
||||
static unsigned int entropy = 0;
|
||||
static unsigned int total_collected = 0;
|
||||
|
||||
|
||||
static u32 __ROL32(u32 x, u32 y)
|
||||
|
@ -135,6 +142,7 @@ void random_add_randomness(const void *buf, size_t len)
|
|||
wpa_hexdump_key(MSG_EXCESSIVE, "random pool",
|
||||
(const u8 *) pool, sizeof(pool));
|
||||
entropy++;
|
||||
total_collected++;
|
||||
}
|
||||
|
||||
|
||||
|
@ -174,3 +182,77 @@ int random_get_bytes(void *buf, size_t len)
|
|||
|
||||
return ret;
|
||||
}
|
||||
|
||||
|
||||
int random_pool_ready(void)
|
||||
{
|
||||
#ifdef __linux__
|
||||
int fd;
|
||||
ssize_t res;
|
||||
|
||||
/*
|
||||
* Make sure that there is reasonable entropy available before allowing
|
||||
* some key derivation operations to proceed.
|
||||
*/
|
||||
|
||||
if (dummy_key_avail == sizeof(dummy_key))
|
||||
return 1; /* Already initialized - good to continue */
|
||||
|
||||
/*
|
||||
* Try to fetch some more data from the kernel high quality
|
||||
* /dev/random. There may not be enough data available at this point,
|
||||
* so use non-blocking read to avoid blocking the application
|
||||
* completely.
|
||||
*/
|
||||
fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
|
||||
if (fd < 0) {
|
||||
int error = errno;
|
||||
perror("open(/dev/random)");
|
||||
wpa_printf(MSG_ERROR, "random: Cannot open /dev/random: %s",
|
||||
strerror(error));
|
||||
return -1;
|
||||
}
|
||||
|
||||
res = read(fd, dummy_key + dummy_key_avail,
|
||||
sizeof(dummy_key) - dummy_key_avail);
|
||||
if (res < 0) {
|
||||
wpa_printf(MSG_ERROR, "random: Cannot read from /dev/random: "
|
||||
"%s", strerror(errno));
|
||||
res = 0;
|
||||
}
|
||||
wpa_printf(MSG_DEBUG, "random: Got %u/%u bytes from "
|
||||
"/dev/random", (unsigned) res,
|
||||
(unsigned) (sizeof(dummy_key) - dummy_key_avail));
|
||||
dummy_key_avail += res;
|
||||
close(fd);
|
||||
|
||||
if (dummy_key_avail == sizeof(dummy_key))
|
||||
return 1;
|
||||
|
||||
wpa_printf(MSG_INFO, "random: Only %u/%u bytes of strong "
|
||||
"random data available from /dev/random",
|
||||
(unsigned) dummy_key_avail, (unsigned) sizeof(dummy_key));
|
||||
|
||||
if (own_pool_ready >= MIN_READY_MARK ||
|
||||
total_collected + 10 * own_pool_ready > MIN_COLLECT_ENTROPY) {
|
||||
wpa_printf(MSG_INFO, "random: Allow operation to proceed "
|
||||
"based on internal entropy");
|
||||
return 1;
|
||||
}
|
||||
|
||||
wpa_printf(MSG_INFO, "random: Not enough entropy pool available for "
|
||||
"secure operations");
|
||||
return 0;
|
||||
#else /* __linux__ */
|
||||
/* TODO: could do similar checks on non-Linux platforms */
|
||||
return 1;
|
||||
#endif /* __linux__ */
|
||||
}
|
||||
|
||||
|
||||
void random_mark_pool_ready(void)
|
||||
{
|
||||
own_pool_ready++;
|
||||
wpa_printf(MSG_DEBUG, "random: Mark internal entropy pool to be "
|
||||
"ready (count=%u/%u)", own_pool_ready, MIN_READY_MARK);
|
||||
}
|
||||
|
|
Loading…
Add table
Add a link
Reference in a new issue