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mirror of https://git.FreeBSD.org/src.git synced 2024-12-05 09:14:03 +00:00
freebsd/contrib/ntp/libntp/authkeys.c
2018-02-28 07:59:55 +00:00

930 lines
20 KiB
C

/*
* authkeys.c - routines to manage the storage of authentication keys
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <math.h>
#include <stdio.h>
#include "ntp.h"
#include "ntp_fp.h"
#include "ntpd.h"
#include "ntp_lists.h"
#include "ntp_string.h"
#include "ntp_malloc.h"
#include "ntp_stdlib.h"
#include "ntp_keyacc.h"
/*
* Structure to store keys in in the hash table.
*/
typedef struct savekey symkey;
struct savekey {
symkey * hlink; /* next in hash bucket */
DECL_DLIST_LINK(symkey, llink); /* for overall & free lists */
u_char * secret; /* shared secret */
KeyAccT * keyacclist; /* Private key access list */
u_long lifetime; /* remaining lifetime */
keyid_t keyid; /* key identifier */
u_short type; /* OpenSSL digest NID */
size_t secretsize; /* secret octets */
u_short flags; /* KEY_ flags that wave */
};
/* define the payload region of symkey beyond the list pointers */
#define symkey_payload secret
#define KEY_TRUSTED 0x001 /* this key is trusted */
#ifdef DEBUG
typedef struct symkey_alloc_tag symkey_alloc;
struct symkey_alloc_tag {
symkey_alloc * link;
void * mem; /* enable free() atexit */
};
symkey_alloc * authallocs;
#endif /* DEBUG */
static u_short auth_log2(size_t);
static void auth_resize_hashtable(void);
static void allocsymkey(keyid_t, u_short,
u_short, u_long, size_t, u_char *, KeyAccT *);
static void freesymkey(symkey *);
#ifdef DEBUG
static void free_auth_mem(void);
#endif
symkey key_listhead; /* list of all in-use keys */;
/*
* The hash table. This is indexed by the low order bits of the
* keyid. We make this fairly big for potentially busy servers.
*/
#define DEF_AUTHHASHSIZE 64
/*#define HASHMASK ((HASHSIZE)-1)*/
#define KEYHASH(keyid) ((keyid) & authhashmask)
int authhashdisabled;
u_short authhashbuckets = DEF_AUTHHASHSIZE;
u_short authhashmask = DEF_AUTHHASHSIZE - 1;
symkey **key_hash;
u_long authkeynotfound; /* keys not found */
u_long authkeylookups; /* calls to lookup keys */
u_long authnumkeys; /* number of active keys */
u_long authkeyexpired; /* key lifetime expirations */
u_long authkeyuncached; /* cache misses */
u_long authnokey; /* calls to encrypt with no key */
u_long authencryptions; /* calls to encrypt */
u_long authdecryptions; /* calls to decrypt */
/*
* Storage for free symkey structures. We malloc() such things but
* never free them.
*/
symkey *authfreekeys;
int authnumfreekeys;
#define MEMINC 16 /* number of new free ones to get */
/*
* The key cache. We cache the last key we looked at here.
* Note: this should hold the last *trusted* key. Also the
* cache is only loaded when the digest type / MAC algorithm
* is valid.
*/
keyid_t cache_keyid; /* key identifier */
u_char *cache_secret; /* secret */
size_t cache_secretsize; /* secret length */
int cache_type; /* OpenSSL digest NID */
u_short cache_flags; /* flags that wave */
KeyAccT *cache_keyacclist; /* key access list */
/* --------------------------------------------------------------------
* manage key access lists
* --------------------------------------------------------------------
*/
/* allocate and populate new access node and pushes it on the list.
* Returns the new head.
*/
KeyAccT*
keyacc_new_push(
KeyAccT * head,
const sockaddr_u * addr,
unsigned int subnetbits
)
{
KeyAccT * node = emalloc(sizeof(KeyAccT));
memcpy(&node->addr, addr, sizeof(sockaddr_u));
node->subnetbits = subnetbits;
node->next = head;
return node;
}
/* ----------------------------------------------------------------- */
/* pop and deallocate the first node of a list of access nodes, if
* the list is not empty. Returns the tail of the list.
*/
KeyAccT*
keyacc_pop_free(
KeyAccT *head
)
{
KeyAccT * next = NULL;
if (head) {
next = head->next;
free(head);
}
return next;
}
/* ----------------------------------------------------------------- */
/* deallocate the list; returns an empty list. */
KeyAccT*
keyacc_all_free(
KeyAccT * head
)
{
while (head)
head = keyacc_pop_free(head);
return head;
}
/* ----------------------------------------------------------------- */
/* scan a list to see if it contains a given address. Return the
* default result value in case of an empty list.
*/
int /*BOOL*/
keyacc_contains(
const KeyAccT *head,
const sockaddr_u *addr,
int defv)
{
if (head) {
do {
if (keyacc_amatch(&head->addr, addr,
head->subnetbits))
return TRUE;
} while (NULL != (head = head->next));
return FALSE;
} else {
return !!defv;
}
}
#if CHAR_BIT != 8
# error "don't know how to handle bytes with that bit size"
#endif
/* ----------------------------------------------------------------- */
/* check two addresses for a match, taking a prefix length into account
* when doing the compare.
*
* The ISC lib contains a similar function with not entirely specified
* semantics, so it seemed somewhat cleaner to do this from scratch.
*
* Note 1: It *is* assumed that the addresses are stored in network byte
* order, that is, most significant byte first!
*
* Note 2: "no address" compares unequal to all other addresses, even to
* itself. This has the same semantics as NaNs have for floats: *any*
* relational or equality operation involving a NaN returns FALSE, even
* equality with itself. "no address" is either a NULL pointer argument
* or an address of type AF_UNSPEC.
*/
int/*BOOL*/
keyacc_amatch(
const sockaddr_u * a1,
const sockaddr_u * a2,
unsigned int mbits
)
{
const uint8_t * pm1;
const uint8_t * pm2;
uint8_t msk;
unsigned int len;
/* 1st check: If any address is not an address, it's inequal. */
if ( !a1 || (AF_UNSPEC == AF(a1)) ||
!a2 || (AF_UNSPEC == AF(a2)) )
return FALSE;
/* We could check pointers for equality here and shortcut the
* other checks if we find object identity. But that use case is
* too rare to care for it.
*/
/* 2nd check: Address families must be the same. */
if (AF(a1) != AF(a2))
return FALSE;
/* type check: address family determines buffer & size */
switch (AF(a1)) {
case AF_INET:
/* IPv4 is easy: clamp size, get byte pointers */
if (mbits > sizeof(NSRCADR(a1)) * 8)
mbits = sizeof(NSRCADR(a1)) * 8;
pm1 = (const void*)&NSRCADR(a1);
pm2 = (const void*)&NSRCADR(a2);
break;
case AF_INET6:
/* IPv6 is slightly different: Both scopes must match,
* too, before we even consider doing a match!
*/
if ( ! SCOPE_EQ(a1, a2))
return FALSE;
if (mbits > sizeof(NSRCADR6(a1)) * 8)
mbits = sizeof(NSRCADR6(a1)) * 8;
pm1 = (const void*)&NSRCADR6(a1);
pm2 = (const void*)&NSRCADR6(a2);
break;
default:
/* don't know how to compare that!?! */
return FALSE;
}
/* Split bit length into byte length and partial byte mask.
* Note that the byte mask extends from the MSB of a byte down,
* and that zero shift (--> mbits % 8 == 0) results in an
* all-zero mask.
*/
msk = 0xFFu ^ (0xFFu >> (mbits & 7));
len = mbits >> 3;
/* 3rd check: Do memcmp() over full bytes, if any */
if (len && memcmp(pm1, pm2, len))
return FALSE;
/* 4th check: compare last incomplete byte, if any */
if (msk && ((pm1[len] ^ pm2[len]) & msk))
return FALSE;
/* If none of the above failed, we're successfully through. */
return TRUE;
}
/*
* init_auth - initialize internal data
*/
void
init_auth(void)
{
size_t newalloc;
/*
* Initialize hash table and free list
*/
newalloc = authhashbuckets * sizeof(key_hash[0]);
key_hash = erealloc(key_hash, newalloc);
memset(key_hash, '\0', newalloc);
INIT_DLIST(key_listhead, llink);
#ifdef DEBUG
atexit(&free_auth_mem);
#endif
}
/*
* free_auth_mem - assist in leak detection by freeing all dynamic
* allocations from this module.
*/
#ifdef DEBUG
static void
free_auth_mem(void)
{
symkey * sk;
symkey_alloc * alloc;
symkey_alloc * next_alloc;
while (NULL != (sk = HEAD_DLIST(key_listhead, llink))) {
freesymkey(sk);
}
free(key_hash);
key_hash = NULL;
cache_keyid = 0;
cache_flags = 0;
cache_keyacclist = NULL;
for (alloc = authallocs; alloc != NULL; alloc = next_alloc) {
next_alloc = alloc->link;
free(alloc->mem);
}
authfreekeys = NULL;
authnumfreekeys = 0;
}
#endif /* DEBUG */
/*
* auth_moremem - get some more free key structures
*/
void
auth_moremem(
int keycount
)
{
symkey * sk;
int i;
#ifdef DEBUG
void * base;
symkey_alloc * allocrec;
# define MOREMEM_EXTRA_ALLOC (sizeof(*allocrec))
#else
# define MOREMEM_EXTRA_ALLOC (0)
#endif
i = (keycount > 0)
? keycount
: MEMINC;
sk = eallocarrayxz(i, sizeof(*sk), MOREMEM_EXTRA_ALLOC);
#ifdef DEBUG
base = sk;
#endif
authnumfreekeys += i;
for (; i > 0; i--, sk++) {
LINK_SLIST(authfreekeys, sk, llink.f);
}
#ifdef DEBUG
allocrec = (void *)sk;
allocrec->mem = base;
LINK_SLIST(authallocs, allocrec, link);
#endif
}
/*
* auth_prealloc_symkeys
*/
void
auth_prealloc_symkeys(
int keycount
)
{
int allocated;
int additional;
allocated = authnumkeys + authnumfreekeys;
additional = keycount - allocated;
if (additional > 0)
auth_moremem(additional);
auth_resize_hashtable();
}
static u_short
auth_log2(size_t x)
{
/*
** bithack to calculate floor(log2(x))
**
** This assumes
** - (sizeof(size_t) is a power of two
** - CHAR_BITS is a power of two
** - returning zero for arguments <= 0 is OK.
**
** Does only shifts, masks and sums in integer arithmetic in
** log2(CHAR_BIT*sizeof(size_t)) steps. (that is, 5/6 steps for
** 32bit/64bit size_t)
*/
int s;
int r = 0;
size_t m = ~(size_t)0;
for (s = sizeof(size_t) / 2 * CHAR_BIT; s != 0; s >>= 1) {
m <<= s;
if (x & m)
r += s;
else
x <<= s;
}
return (u_short)r;
}
int/*BOOL*/
ipaddr_match_masked(const sockaddr_u *,const sockaddr_u *,
unsigned int mbits);
static void
authcache_flush_id(
keyid_t id
)
{
if (cache_keyid == id) {
cache_keyid = 0;
cache_type = 0;
cache_flags = 0;
cache_secret = NULL;
cache_secretsize = 0;
cache_keyacclist = NULL;
}
}
/*
* auth_resize_hashtable
*
* Size hash table to average 4 or fewer entries per bucket initially,
* within the bounds of at least 4 and no more than 15 bits for the hash
* table index. Populate the hash table.
*/
static void
auth_resize_hashtable(void)
{
u_long totalkeys;
u_short hashbits;
u_short hash;
size_t newalloc;
symkey * sk;
totalkeys = authnumkeys + authnumfreekeys;
hashbits = auth_log2(totalkeys / 4) + 1;
hashbits = max(4, hashbits);
hashbits = min(15, hashbits);
authhashbuckets = 1 << hashbits;
authhashmask = authhashbuckets - 1;
newalloc = authhashbuckets * sizeof(key_hash[0]);
key_hash = erealloc(key_hash, newalloc);
memset(key_hash, '\0', newalloc);
ITER_DLIST_BEGIN(key_listhead, sk, llink, symkey)
hash = KEYHASH(sk->keyid);
LINK_SLIST(key_hash[hash], sk, hlink);
ITER_DLIST_END()
}
/*
* allocsymkey - common code to allocate and link in symkey
*
* secret must be allocated with a free-compatible allocator. It is
* owned by the referring symkey structure, and will be free()d by
* freesymkey().
*/
static void
allocsymkey(
keyid_t id,
u_short flags,
u_short type,
u_long lifetime,
size_t secretsize,
u_char * secret,
KeyAccT * ka
)
{
symkey * sk;
symkey ** bucket;
bucket = &key_hash[KEYHASH(id)];
if (authnumfreekeys < 1)
auth_moremem(-1);
UNLINK_HEAD_SLIST(sk, authfreekeys, llink.f);
DEBUG_ENSURE(sk != NULL);
sk->keyid = id;
sk->flags = flags;
sk->type = type;
sk->secretsize = secretsize;
sk->secret = secret;
sk->keyacclist = ka;
sk->lifetime = lifetime;
LINK_SLIST(*bucket, sk, hlink);
LINK_TAIL_DLIST(key_listhead, sk, llink);
authnumfreekeys--;
authnumkeys++;
}
/*
* freesymkey - common code to remove a symkey and recycle its entry.
*/
static void
freesymkey(
symkey * sk
)
{
symkey ** bucket;
symkey * unlinked;
if (NULL == sk)
return;
authcache_flush_id(sk->keyid);
keyacc_all_free(sk->keyacclist);
bucket = &key_hash[KEYHASH(sk->keyid)];
if (sk->secret != NULL) {
memset(sk->secret, '\0', sk->secretsize);
free(sk->secret);
}
UNLINK_SLIST(unlinked, *bucket, sk, hlink, symkey);
DEBUG_ENSURE(sk == unlinked);
UNLINK_DLIST(sk, llink);
memset((char *)sk + offsetof(symkey, symkey_payload), '\0',
sizeof(*sk) - offsetof(symkey, symkey_payload));
LINK_SLIST(authfreekeys, sk, llink.f);
authnumkeys--;
authnumfreekeys++;
}
/*
* auth_findkey - find a key in the hash table
*/
struct savekey *
auth_findkey(
keyid_t id
)
{
symkey * sk;
for (sk = key_hash[KEYHASH(id)]; sk != NULL; sk = sk->hlink)
if (id == sk->keyid)
return sk;
return NULL;
}
/*
* auth_havekey - return TRUE if the key id is zero or known. The
* key needs not to be trusted.
*/
int
auth_havekey(
keyid_t id
)
{
return
(0 == id) ||
(cache_keyid == id) ||
(NULL != auth_findkey(id));
}
/*
* authhavekey - return TRUE and cache the key, if zero or both known
* and trusted.
*/
int
authhavekey(
keyid_t id
)
{
symkey * sk;
authkeylookups++;
if (0 == id || cache_keyid == id)
return !!(KEY_TRUSTED & cache_flags);
/*
* Search the bin for the key. If not found, or found but the key
* type is zero, somebody marked it trusted without specifying a
* key or key type. In this case consider the key missing.
*/
authkeyuncached++;
sk = auth_findkey(id);
if ((sk == NULL) || (sk->type == 0)) {
authkeynotfound++;
return FALSE;
}
/*
* If the key is not trusted, the key is not considered found.
*/
if ( ! (KEY_TRUSTED & sk->flags)) {
authnokey++;
return FALSE;
}
/*
* The key is found and trusted. Initialize the key cache.
*/
cache_keyid = sk->keyid;
cache_type = sk->type;
cache_flags = sk->flags;
cache_secret = sk->secret;
cache_secretsize = sk->secretsize;
cache_keyacclist = sk->keyacclist;
return TRUE;
}
/*
* authtrust - declare a key to be trusted/untrusted
*/
void
authtrust(
keyid_t id,
u_long trust
)
{
symkey * sk;
u_long lifetime;
/*
* Search bin for key; if it does not exist and is untrusted,
* forget it.
*/
sk = auth_findkey(id);
if (!trust && sk == NULL)
return;
/*
* There are two conditions remaining. Either it does not
* exist and is to be trusted or it does exist and is or is
* not to be trusted.
*/
if (sk != NULL) {
/*
* Key exists. If it is to be trusted, say so and update
* its lifetime. If no longer trusted, return it to the
* free list. Flush the cache first to be sure there are
* no discrepancies.
*/
authcache_flush_id(id);
if (trust > 0) {
sk->flags |= KEY_TRUSTED;
if (trust > 1)
sk->lifetime = current_time + trust;
else
sk->lifetime = 0;
} else {
freesymkey(sk);
}
return;
}
/*
* keyid is not present, but the is to be trusted. We allocate
* a new key, but do not specify a key type or secret.
*/
if (trust > 1) {
lifetime = current_time + trust;
} else {
lifetime = 0;
}
allocsymkey(id, KEY_TRUSTED, 0, lifetime, 0, NULL, NULL);
}
/*
* authistrusted - determine whether a key is trusted
*/
int
authistrusted(
keyid_t id
)
{
symkey * sk;
if (id == cache_keyid)
return !!(KEY_TRUSTED & cache_flags);
authkeyuncached++;
sk = auth_findkey(id);
if (sk == NULL || !(KEY_TRUSTED & sk->flags)) {
authkeynotfound++;
return FALSE;
}
return TRUE;
}
/*
* authistrustedip - determine if the IP is OK for the keyid
*/
int
authistrustedip(
keyid_t keyno,
sockaddr_u * sau
)
{
symkey * sk;
if (keyno == cache_keyid) {
return (KEY_TRUSTED & cache_flags) &&
keyacc_contains(cache_keyacclist, sau, TRUE);
}
if (NULL != (sk = auth_findkey(keyno))) {
authkeyuncached++;
return (KEY_TRUSTED & sk->flags) &&
keyacc_contains(sk->keyacclist, sau, TRUE);
}
authkeynotfound++;
return FALSE;
}
/* Note: There are two locations below where 'strncpy()' is used. While
* this function is a hazard by itself, it's essential that it is used
* here. Bug 1243 involved that the secret was filled with NUL bytes
* after the first NUL encountered, and 'strlcpy()' simply does NOT have
* this behaviour. So disabling the fix and reverting to the buggy
* behaviour due to compatibility issues MUST also fill with NUL and
* this needs 'strncpy'. Also, the secret is managed as a byte blob of a
* given size, and eventually truncating it and replacing the last byte
* with a NUL would be a bug.
* perlinger@ntp.org 2015-10-10
*/
void
MD5auth_setkey(
keyid_t keyno,
int keytype,
const u_char *key,
size_t secretsize,
KeyAccT *ka
)
{
symkey * sk;
u_char * secret;
DEBUG_ENSURE(keytype <= USHRT_MAX);
DEBUG_ENSURE(secretsize < 4 * 1024);
/*
* See if we already have the key. If so just stick in the
* new value.
*/
sk = auth_findkey(keyno);
if (sk != NULL && keyno == sk->keyid) {
/* TALOS-CAN-0054: make sure we have a new buffer! */
if (NULL != sk->secret) {
memset(sk->secret, 0, sk->secretsize);
free(sk->secret);
}
sk->secret = emalloc(secretsize + 1);
sk->type = (u_short)keytype;
sk->secretsize = secretsize;
/* make sure access lists don't leak here! */
if (ka != sk->keyacclist) {
keyacc_all_free(sk->keyacclist);
sk->keyacclist = ka;
}
#ifndef DISABLE_BUG1243_FIX
memcpy(sk->secret, key, secretsize);
#else
/* >MUST< use 'strncpy()' here! See above! */
strncpy((char *)sk->secret, (const char *)key,
secretsize);
#endif
authcache_flush_id(keyno);
return;
}
/*
* Need to allocate new structure. Do it.
*/
secret = emalloc(secretsize + 1);
#ifndef DISABLE_BUG1243_FIX
memcpy(secret, key, secretsize);
#else
/* >MUST< use 'strncpy()' here! See above! */
strncpy((char *)secret, (const char *)key, secretsize);
#endif
allocsymkey(keyno, 0, (u_short)keytype, 0,
secretsize, secret, ka);
#ifdef DEBUG
if (debug >= 4) {
size_t j;
printf("auth_setkey: key %d type %d len %d ", (int)keyno,
keytype, (int)secretsize);
for (j = 0; j < secretsize; j++) {
printf("%02x", secret[j]);
}
printf("\n");
}
#endif
}
/*
* auth_delkeys - delete non-autokey untrusted keys, and clear all info
* except the trusted bit of non-autokey trusted keys, in
* preparation for rereading the keys file.
*/
void
auth_delkeys(void)
{
symkey * sk;
ITER_DLIST_BEGIN(key_listhead, sk, llink, symkey)
if (sk->keyid > NTP_MAXKEY) { /* autokey */
continue;
}
/*
* Don't lose info as to which keys are trusted. Make
* sure there are no dangling pointers!
*/
if (KEY_TRUSTED & sk->flags) {
if (sk->secret != NULL) {
memset(sk->secret, 0, sk->secretsize);
free(sk->secret);
sk->secret = NULL; /* TALOS-CAN-0054 */
}
sk->keyacclist = keyacc_all_free(sk->keyacclist);
sk->secretsize = 0;
sk->lifetime = 0;
} else {
freesymkey(sk);
}
ITER_DLIST_END()
}
/*
* auth_agekeys - delete keys whose lifetimes have expired
*/
void
auth_agekeys(void)
{
symkey * sk;
ITER_DLIST_BEGIN(key_listhead, sk, llink, symkey)
if (sk->lifetime > 0 && current_time > sk->lifetime) {
freesymkey(sk);
authkeyexpired++;
}
ITER_DLIST_END()
DPRINTF(1, ("auth_agekeys: at %lu keys %lu expired %lu\n",
current_time, authnumkeys, authkeyexpired));
}
/*
* authencrypt - generate message authenticator
*
* Returns length of authenticator field, zero if key not found.
*/
size_t
authencrypt(
keyid_t keyno,
u_int32 * pkt,
size_t length
)
{
/*
* A zero key identifier means the sender has not verified
* the last message was correctly authenticated. The MAC
* consists of a single word with value zero.
*/
authencryptions++;
pkt[length / 4] = htonl(keyno);
if (0 == keyno) {
return 4;
}
if (!authhavekey(keyno)) {
return 0;
}
return MD5authencrypt(cache_type,
cache_secret, cache_secretsize,
pkt, length);
}
/*
* authdecrypt - verify message authenticator
*
* Returns TRUE if authenticator valid, FALSE if invalid or not found.
*/
int
authdecrypt(
keyid_t keyno,
u_int32 * pkt,
size_t length,
size_t size
)
{
/*
* A zero key identifier means the sender has not verified
* the last message was correctly authenticated. For our
* purpose this is an invalid authenticator.
*/
authdecryptions++;
if (0 == keyno || !authhavekey(keyno) || size < 4) {
return FALSE;
}
return MD5authdecrypt(cache_type,
cache_secret, cache_secretsize,
pkt, length, size);
}