This patches adds support for MD5 and SHA1 authentication to ntpd. I tried
to key the code style as consistent as possible with what I say in busybox.
diff --git a/networking/ntpd.c b/networking/ntpd.c
index 1ebdc34..d05c6ab 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -78,6 +78,8 @@
//usage: "\n -w Do not set time (only query peers), implies -n"
//usage: "\n -S PROG Run PROG after stepping time, stratum
change, and every 11 mins"
//usage: "\n -p PEER Obtain time from PEER (may be repeated)"
+//usage: "\n -K key number for preceding PEER (may be repeated)"
+//usage: "\n -k key file (see man 5 ntp.keys)"
//usage: IF_FEATURE_NTPD_CONF(
//usage: "\n If -p is not given, 'server HOST' lines"
//usage: "\n from /etc/ntp.conf are used"
@@ -227,15 +229,18 @@
#define FLL (MAXPOLL + 1)
/* Parameter averaging constant */
#define AVG 4
-
+#define MAX_KEY_NUMBER 65535
+#define KEYID_SIZE sizeof(uint32_t)
enum {
NTP_VERSION = 4,
NTP_MAXSTRATUM = 15,
- NTP_DIGESTSIZE = 16,
- NTP_MSGSIZE_NOAUTH = 48,
- NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
+ NTP_MD5_DIGESTSIZE = 16,
+ NTP_SHA1_DIGESTSIZE = 20,
+ NTP_MSGSIZE_NOAUTH = 48,
+ NTP_MSGSIZE_MD5_AUTH = NTP_MSGSIZE_NOAUTH + NTP_MD5_DIGESTSIZE +
KEYID_SIZE,
+ NTP_MSGSIZE_SHA1_AUTH = NTP_MSGSIZE_NOAUTH + NTP_SHA1_DIGESTSIZE +
KEYID_SIZE,
/* Status Masks */
MODE_MASK = (7 << 0),
@@ -288,7 +293,7 @@ typedef struct {
l_fixedpt_t m_rectime;
l_fixedpt_t m_xmttime;
uint32_t m_keyid;
- uint8_t m_digest[NTP_DIGESTSIZE];
+ uint8_t m_digest[NTP_SHA1_DIGESTSIZE];
} msg_t;
typedef struct {
@@ -297,6 +302,19 @@ typedef struct {
double d_dispersion;
} datapoint_t;
+enum hash_type {
+ HASH_MD5,
+ HASH_SHA1
+};
+
+typedef struct {
+ unsigned id;
+ enum hash_type type;
+ char *key;
+ size_t key_length;
+ size_t msg_size;
+} key_entry_t;
+
typedef struct {
len_and_sockaddr *p_lsa;
char *p_dotted;
@@ -326,6 +344,7 @@ typedef struct {
/* last sent packet: */
msg_t p_xmt_msg;
char p_hostname[1];
+ key_entry_t *key_entry;
} peer_t;
@@ -337,13 +356,15 @@ enum {
OPT_q = (1 << 1),
OPT_N = (1 << 2),
OPT_x = (1 << 3),
+ OPT_k = (1 << 4),
+ OPT_K = (1 << 5),
/* Insert new options above this line. */
/* Non-compat options: */
- OPT_w = (1 << 4),
- OPT_p = (1 << 5),
- OPT_S = (1 << 6),
- OPT_l = (1 << 7) * ENABLE_FEATURE_NTPD_SERVER,
- OPT_I = (1 << 8) * ENABLE_FEATURE_NTPD_SERVER,
+ OPT_w = (1 << 6),
+ OPT_p = (1 << 7),
+ OPT_S = (1 << 8),
+ OPT_l = (1 << 9) * ENABLE_FEATURE_NTPD_SERVER,
+ OPT_I = (1 << 10) * ENABLE_FEATURE_NTPD_SERVER,
/* We hijack some bits for other purposes */
OPT_qq = (1 << 31),
};
@@ -817,7 +838,15 @@ resolve_peer_hostname(peer_t *p)
}
static void
-add_peers(const char *s)
+free_key_entry(void *data) {
+ key_entry_t *key_entry = (key_entry_t *) data;
+
+ free(key_entry->key);
+ free(key_entry);
+}
+
+static void
+add_peers(const char *s, key_entry_t *key_entry)
{
llist_t *item;
peer_t *p;
@@ -840,12 +869,15 @@ add_peers(const char *s)
bb_error_msg("duplicate peer %s (%s)", s, p->p_dotted);
free(p->p_lsa);
free(p->p_dotted);
+ if (p->key_entry != NULL) {
+ free_key_entry(p->key_entry);
+ }
free(p);
return;
}
}
}
-
+ p->key_entry = key_entry;
llist_add_to(&G.ntp_peers, p);
G.peer_cnt++;
}
@@ -871,6 +903,65 @@ do_sendto(int fd,
}
static void
+hash(peer_t *p) {
+ size_t hash_size = sizeof(msg_t) - sizeof(p->p_xmt_msg.m_keyid) -
sizeof(p->p_xmt_msg.m_digest);
+
+ p->p_xmt_msg.m_keyid = htonl(p->key_entry->id);
+ switch (p->key_entry->type) {
+ case HASH_MD5: {
+ md5_ctx_t ctx;
+
+ md5_begin(&ctx);
+ md5_hash(&ctx, p->key_entry->key, p->key_entry->key_length);
+ md5_hash(&ctx, &p->p_xmt_msg, hash_size);
+ md5_end(&ctx, &p->p_xmt_msg.m_digest);
+ }
+ break;
+ case HASH_SHA1: {
+ sha1_ctx_t ctx;
+
+ sha1_begin(&ctx);
+ sha1_hash(&ctx, p->key_entry->key, p->key_entry->key_length);
+ sha1_hash(&ctx, &p->p_xmt_msg, hash_size);
+ sha1_end(&ctx, &p->p_xmt_msg.m_digest);
+ }
+ break;
+ }
+}
+
+static int compare_hashes(peer_t *p, const msg_t *msg) {
+ size_t hash_size = sizeof(msg_t) - sizeof(msg->m_keyid) -
sizeof(msg->m_digest);
+ key_entry_t *key_entry = p->key_entry;
+ int result = 1;
+
+ switch (p->key_entry->type) {
+ case HASH_MD5: {
+ md5_ctx_t ctx;
+ char digest[NTP_MD5_DIGESTSIZE];
+
+ md5_begin(&ctx);
+ md5_hash(&ctx, key_entry->key, key_entry->key_length);
+ md5_hash(&ctx, msg, hash_size);
+ md5_end(&ctx, &digest);
+ result = memcmp(digest, msg->m_digest, NTP_MD5_DIGESTSIZE);
+ }
+ break;
+ case HASH_SHA1: {
+ sha1_ctx_t ctx;
+ char digest[NTP_SHA1_DIGESTSIZE];
+
+ sha1_begin(&ctx);
+ sha1_hash(&ctx, key_entry->key, key_entry->key_length);
+ sha1_hash(&ctx, msg, hash_size);
+ sha1_end(&ctx, &digest);
+ result = memcmp(digest, msg->m_digest, NTP_SHA1_DIGESTSIZE);
+ }
+ break;
+ }
+ return result;
+}
+
+static void
send_query_to_peer(peer_t *p)
{
if (!p->p_lsa)
@@ -945,9 +1036,11 @@ send_query_to_peer(peer_t *p)
* We still need to declare "unsync" if this condition persists.
*/
p->reachable_bits <<= 1;
-
+ if (p->key_entry != NULL) {
+ hash(p);
+ }
if (do_sendto(p->p_fd, /*from:*/ NULL, /*to:*/ &p->p_lsa->u.sa,
/*addrlen:*/ p->p_lsa->len,
- &p->p_xmt_msg, NTP_MSGSIZE_NOAUTH) == -1
+ &p->p_xmt_msg, p->key_entry == NULL ? NTP_MSGSIZE_NOAUTH :
p->key_entry->msg_size) == -1
) {
close(p->p_fd);
p->p_fd = -1;
@@ -1924,10 +2017,14 @@ recv_and_process_peer_pkt(peer_t *p)
bb_perror_msg_and_die("recv(%s) error", p->p_dotted);
}
- if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
+ if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_MD5_AUTH && size
!= NTP_MSGSIZE_SHA1_AUTH) {
bb_error_msg("malformed packet received from %s", p->p_dotted);
return;
}
+ if (p->key_entry != NULL && compare_hashes(p, &msg) != 0) {
+ bb_error_msg("invalid cryptographic hash received from %s",
p->p_dotted);
+ return;
+ }
if (msg.m_orgtime.int_partl != p->p_xmt_msg.m_xmttime.int_partl
|| msg.m_orgtime.fractionl != p->p_xmt_msg.m_xmttime.fractionl
@@ -2135,7 +2232,7 @@ recv_and_process_client_pkt(void /*int fd*/)
from = xzalloc(to->len);
size = recv_from_to(G_listen_fd, &msg, sizeof(msg), MSG_DONTWAIT,
from, &to->u.sa, to->len);
- if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
+ if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_SHA1_AUTH &&
size != NTP_MSGSIZE_MD5_AUTH) {
char *addr;
if (size < 0) {
if (errno == EAGAIN)
@@ -2279,6 +2376,27 @@ recv_and_process_client_pkt(void /*int fd*/)
* Note: The kernel time discipline is disabled with this option.
*/
+static key_entry_t *
+find_key_entry(llist_t *key_entries, unsigned id) {
+ key_entry_t *result = NULL;
+ llist_t *iterator = key_entries;
+ key_entry_t *temporary;
+
+ while(iterator != NULL && result == NULL) {
+ temporary = (key_entry_t *) iterator->data;
+ if(temporary->id == id) {
+ result = xzalloc(sizeof(key_entry_t));
+ result->id = temporary->id;
+ result->type = temporary->type;
+ result->key = xstrdup(temporary->key);
+ result->key_length = temporary->key_length;
+ result->msg_size = temporary->msg_size;
+ }
+ iterator = iterator->link;
+ }
+ return result;
+}
+
/* By doing init in a separate function we decrease stack usage
* in main loop.
*/
@@ -2286,6 +2404,9 @@ static NOINLINE void ntp_init(char **argv)
{
unsigned opts;
llist_t *peers;
+ llist_t *key_ids;
+ llist_t *key_entries = NULL;
+ char *key_file_path = NULL;
srand(getpid());
@@ -2304,6 +2425,7 @@ static NOINLINE void ntp_init(char **argv)
peers = NULL;
opts = getopt32(argv, "^"
"nqNx" /* compat */
+ "K:*k:"
"wp:*S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
IF_FEATURE_NTPD_SERVER("I:") /* compat */
"d" /* compat */
@@ -2311,7 +2433,7 @@ static NOINLINE void ntp_init(char **argv)
"\0"
"dd:wn" /* -d: counter; -p: list; -w implies -n */
IF_FEATURE_NTPD_SERVER(":Il") /* -I implies -l */
- , &peers, &G.script_name,
+ , &key_ids, &key_file_path, &peers, &G.script_name,
#if ENABLE_FEATURE_NTPD_SERVER
&G.if_name,
#endif
@@ -2341,9 +2463,67 @@ static NOINLINE void ntp_init(char **argv)
logmode = LOGMODE_NONE;
}
+ if (key_ids && !(opts & OPT_k)) {
+ bb_error_msg_and_die("A key file (-k) is required to use a key
(-K) option");
+ }
+
+ if (opts & OPT_k) {
+ char *tokens[4];
+ parser_t *key_file_parser;
+ int token_count;
+
+ key_file_parser = config_open(key_file_path);
+ while ((token_count = config_read(key_file_parser, tokens, 4, 3,
"# \t", PARSE_NORMAL | PARSE_MIN_DIE)) == 3) {
+ enum hash_type hash_type;
+ size_t key_length;
+ key_entry_t *key_entry = (key_entry_t *)
xzalloc(sizeof(key_entry_t));
+
+ if (strcasecmp(tokens[1], "MD5") == 0) {
+ hash_type = HASH_MD5;
+ key_entry->msg_size = NTP_MSGSIZE_MD5_AUTH;
+ } else if (strcasecmp(tokens[1], "SHA1") == 0) {
+ hash_type = HASH_SHA1;
+ key_entry->msg_size = NTP_MSGSIZE_SHA1_AUTH;
+ } else {
+ bb_error_msg_and_die("busybox only supports MD5 and SHA1
NTP keys");
+ }
+ key_entry->type = hash_type;
+ key_entry->id = xatou_range(tokens[0], 1, MAX_KEY_NUMBER);
+ key_length = strlen(tokens[2]);
+ if (key_length <= 20) {
+ key_entry->key = xstrdup(tokens[2]);
+ key_entry->key_length = key_length;
+ } else if ((key_length & 1) == 0) {
+ char buffer[64];
+ char *key;
+ size_t byte_count = key_length / 2;
+
+ memset(buffer, 0, sizeof(buffer));
+ key = hex2bin(buffer, tokens[2], byte_count);
+ if (key == NULL) {
+ bb_error_msg_and_die("key #%d is malformed",
key_entry->id);
+ }
+ key_entry->key = xstrdup(buffer);
+ key_entry->key_length = byte_count;
+ } else {
+ bb_error_msg_and_die("key #%d is malformed",
key_entry->id);
+ }
+ llist_add_to(&key_entries, key_entry);
+ }
+ config_close(key_file_parser);
+ }
+
if (peers) {
- while (peers)
- add_peers(llist_pop(&peers));
+ while (peers) {
+ key_entry_t *key_entry = NULL;
+
+ if (key_ids) {
+ int key_id = xatou_range(llist_pop(&key_ids), 1,
MAX_KEY_NUMBER);
+
+ key_entry = find_key_entry(key_entries, key_id);
+ }
+ add_peers(llist_pop(&peers), key_entry);
+ }
}
#if ENABLE_FEATURE_NTPD_CONF
else {
@@ -2353,7 +2533,7 @@ static NOINLINE void ntp_init(char **argv)
parser = config_open("/etc/ntp.conf");
while (config_read(parser, token, 3, 1, "# \t", PARSE_NORMAL)) {
if (strcmp(token[0], "server") == 0 && token[1]) {
- add_peers(token[1]);
+ add_peers(token[1], NULL);
continue;
}
bb_error_msg("skipping %s:%u: unimplemented command '%s'",
@@ -2394,6 +2574,7 @@ static NOINLINE void ntp_init(char **argv)
| (1 << SIGCHLD)
, SIG_IGN
);
+ llist_free(key_entries, free_key_entry);
}
int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
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