On Tue, Oct 16, 2018 at 9:49 PM Brandon Enochs <[email protected]> wrote:
> Here's the git format-patch:
See my version attached.
> +//config:config FEATURE_NTP_AUTH_MD5
> +//config: bool "Make ntpd support MD5 authentication"
> +//config: default n
> +//config: depends on FEATURE_NTP_AUTH
> +//config: help
> +//config: Make ntpd support MD5 authentication"
> +//config:config FEATURE_NTP_AUTH_SHA1
> +//config: bool "Make ntpd support SHA1 authentication"
> +//config: default n
> +//config: depends on FEATURE_NTP_AUTH
> +//config: help
> +//config: Make ntpd support SHA1 authentication"
If FEATURE_NTP_AUTH is selected, there is little benefit to have even more
granular choices (md5/sha1). Let's just support both.
> //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)"
The interplay between -p and -K is rather hard to code.
Since -p is busybox's invention anyway, there is no compatibility
to support, and we can, say, just include keys into -p ARG.
Then we don't need -K.
Brainstorming. How about -p [ALGO:KEYNO:]PEER ?
Also, code which parses of "server" lines in /etc/ntp.conf
probably needs to be extended to understand "key KEYNO" arg?
> + 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 = HASH_NONE;
> + size_t key_length;
> + key_entry_t *key_entry = (key_entry_t *)
> xzalloc(sizeof(key_entry_t));
> +
> +#if ENABLE_FEATURE_NTP_AUTH_MD5
> + if (strcasecmp(tokens[1], "MD5") == 0) {
manpages and other documents seem to suggest "M" also should mean MD5?
> + } else if ((key_length & 1) == 0 && key_length <= 64) {
manpage says "The key is a hex-encoded ASCII string of 40 characters,
which is truncated as necessary."
Why 64?
diff --git a/networking/ntpd.c b/networking/ntpd.c
index 1ebdc34c3..453345f99 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -62,6 +62,12 @@
//config: help
//config: Make ntpd look in /etc/ntp.conf for peers. Only "server address"
//config: is supported.
+//config:config FEATURE_NTP_AUTH
+//config: bool "Make ntpd support authentication"
+//config: default n
+//config: depends on NTPD
+//config: help
+//config: Make ntpd support authentication"
//applet:IF_NTPD(APPLET(ntpd, BB_DIR_USR_SBIN, BB_SUID_DROP))
@@ -78,6 +84,10 @@
//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: IF_FEATURE_NTP_AUTH(
+//usage: "\n -K key number for preceding PEER (may be repeated)"
+//usage: "\n -k key file (ntp.keys compatible)"
+//usage: )
//usage: IF_FEATURE_NTPD_CONF(
//usage: "\n If -p is not given, 'server HOST' lines"
//usage: "\n from /etc/ntp.conf are used"
@@ -228,14 +238,24 @@
/* Parameter averaging constant */
#define AVG 4
+#define MAX_KEY_NUMBER 65535
+#define KEYID_SIZE sizeof(uint32_t)
enum {
NTP_VERSION = 4,
NTP_MAXSTRATUM = 15,
+#if ENABLE_FEATURE_NTP_AUTH
+ 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,
+#else
NTP_DIGESTSIZE = 16,
NTP_MSGSIZE_NOAUTH = 48,
- NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + 4 + NTP_DIGESTSIZE),
+ NTP_MSGSIZE = (NTP_MSGSIZE_NOAUTH + KEYID_SIZE + NTP_DIGESTSIZE),
+#endif
/* Status Masks */
MODE_MASK = (7 << 0),
@@ -288,7 +308,11 @@ typedef struct {
l_fixedpt_t m_rectime;
l_fixedpt_t m_xmttime;
uint32_t m_keyid;
+#if ENABLE_FEATURE_NTP_AUTH
+ uint8_t m_digest[NTP_SHA1_DIGESTSIZE];
+#else
uint8_t m_digest[NTP_DIGESTSIZE];
+#endif
} msg_t;
typedef struct {
@@ -297,6 +321,20 @@ typedef struct {
double d_dispersion;
} datapoint_t;
+#if ENABLE_FEATURE_NTP_AUTH
+enum {
+ HASH_MD5,
+ HASH_SHA1,
+};
+typedef struct {
+ unsigned id; //try uint16?
+ smalluint type;
+ smalluint msg_size;
+ smalluint key_length;
+ char key[0];
+} key_entry_t;
+#endif
+
typedef struct {
len_and_sockaddr *p_lsa;
char *p_dotted;
@@ -326,6 +364,9 @@ typedef struct {
/* last sent packet: */
msg_t p_xmt_msg;
char p_hostname[1];
+#if ENABLE_FEATURE_NTP_AUTH
+ key_entry_t *key_entry;
+#endif
} peer_t;
@@ -337,13 +378,25 @@ enum {
OPT_q = (1 << 1),
OPT_N = (1 << 2),
OPT_x = (1 << 3),
+#if ENABLE_FEATURE_NTP_AUTH
+ OPT_k = (1 << 4),
+ OPT_K = (1 << 5),
+#endif
/* Insert new options above this line. */
/* Non-compat options: */
+#if ENABLE_FEATURE_NTP_AUTH
+ 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,
+#else
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,
+#endif
/* We hijack some bits for other purposes */
OPT_qq = (1 << 31),
};
@@ -816,8 +869,12 @@ resolve_peer_hostname(peer_t *p)
return lsa;
}
+#if !ENABLE_FEATURE_NTP_AUTH
+#define add_peers(s, key_entry) \
+ add_peers(s)
+#endif
static void
-add_peers(const char *s)
+add_peers(const char *s, key_entry_t *key_entry)
{
llist_t *item;
peer_t *p;
@@ -846,6 +903,9 @@ add_peers(const char *s)
}
}
+#if ENABLE_FEATURE_NTP_AUTH
+ p->key_entry = key_entry;
+#endif
llist_add_to(&G.ntp_peers, p);
G.peer_cnt++;
}
@@ -870,6 +930,49 @@ do_sendto(int fd,
return 0;
}
+#if ENABLE_FEATURE_NTP_AUTH
+static void
+hash(key_entry_t *key_entry, const msg_t *msg, uint8_t *output)
+{
+ union {
+ md5_ctx_t m;
+ sha1_ctx_t s;
+ } ctx;
+ unsigned hash_size = sizeof(*msg) - sizeof(msg->m_keyid) - sizeof(msg->m_digest);
+
+ switch (key_entry->type) {
+ case HASH_MD5:
+ md5_begin(&ctx.m);
+ md5_hash(&ctx.m, key_entry->key, key_entry->key_length);
+ md5_hash(&ctx.m, msg, hash_size);
+ md5_end(&ctx.m, output);
+ break;
+ default: /* it's HASH_SHA1 */
+ sha1_begin(&ctx.s);
+ sha1_hash(&ctx.s, key_entry->key, key_entry->key_length);
+ sha1_hash(&ctx.s, msg, hash_size);
+ sha1_end(&ctx.s, output);
+ break;
+ }
+}
+
+static void
+hash_peer(peer_t *p)
+{
+ p->p_xmt_msg.m_keyid = htonl(p->key_entry->id);
+ hash(p->key_entry, &p->p_xmt_msg, p->p_xmt_msg.m_digest);
+}
+
+static int
+hashes_differ(peer_t *p, const msg_t *msg)
+{
+ uint8_t digest[NTP_SHA1_DIGESTSIZE];
+
+ hash(p->key_entry, msg, digest);
+ return memcmp(digest, msg->m_digest, p->key_entry->msg_size - NTP_MSGSIZE_NOAUTH - KEYID_SIZE);
+}
+#endif
+
static void
send_query_to_peer(peer_t *p)
{
@@ -946,9 +1049,18 @@ send_query_to_peer(peer_t *p)
*/
p->reachable_bits <<= 1;
+#if ENABLE_FEATURE_NTP_AUTH
+ if (p->key_entry)
+ hash_peer(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 ? NTP_MSGSIZE_NOAUTH : p->key_entry->msg_size) == -1
+ )
+#else
+ 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
+ )
+#endif
+ {
close(p->p_fd);
p->p_fd = -1;
/*
@@ -1924,10 +2036,21 @@ recv_and_process_peer_pkt(peer_t *p)
bb_perror_msg_and_die("recv(%s) error", p->p_dotted);
}
+#if ENABLE_FEATURE_NTP_AUTH
+ 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 && hashes_differ(p, &msg)) {
+ bb_error_msg("invalid cryptographic hash received from %s", p->p_dotted);
+ return;
+ }
+#else
if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE) {
bb_error_msg("malformed packet received from %s", p->p_dotted);
return;
}
+#endif
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 +2258,12 @@ 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 ENABLE_FEATURE_NTP_AUTH
+ if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE_SHA1_AUTH && size != NTP_MSGSIZE_MD5_AUTH)
+#else
+ if (size != NTP_MSGSIZE_NOAUTH && size != NTP_MSGSIZE)
+#endif
+ {
char *addr;
if (size < 0) {
if (errno == EAGAIN)
@@ -2278,6 +2406,19 @@ recv_and_process_client_pkt(void /*int fd*/)
* with the -g and -q options. See the tinker command for other options.
* Note: The kernel time discipline is disabled with this option.
*/
+#if ENABLE_FEATURE_NTP_AUTH
+static key_entry_t *
+find_key_entry(llist_t *key_entries, unsigned id)
+{
+ while (key_entries) {
+ key_entry_t *cur = (key_entry_t*) key_entries->data;
+ if (cur->id == id)
+ return cur;
+ key_entries = key_entries->link;
+ }
+ return NULL;
+}
+#endif
/* By doing init in a separate function we decrease stack usage
* in main loop.
@@ -2286,6 +2427,11 @@ static NOINLINE void ntp_init(char **argv)
{
unsigned opts;
llist_t *peers;
+#if ENABLE_FEATURE_NTP_AUTH
+ llist_t *key_ids;
+ llist_t *key_entries = NULL;
+ char *key_file_path = NULL;
+#endif
srand(getpid());
@@ -2304,6 +2450,7 @@ static NOINLINE void ntp_init(char **argv)
peers = NULL;
opts = getopt32(argv, "^"
"nqNx" /* compat */
+ IF_FEATURE_NTP_AUTH("K:*k:")
"wp:*S:"IF_FEATURE_NTPD_SERVER("l") /* NOT compat */
IF_FEATURE_NTPD_SERVER("I:") /* compat */
"d" /* compat */
@@ -2311,6 +2458,10 @@ 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 */
+ IF_FEATURE_NTP_AUTH(":K?k") /* -k is required if -K appears */
+#if ENABLE_FEATURE_NTP_AUTH
+ , &key_ids, &key_file_path
+#endif
, &peers, &G.script_name,
#if ENABLE_FEATURE_NTPD_SERVER
&G.if_name,
@@ -2341,9 +2492,84 @@ static NOINLINE void ntp_init(char **argv)
logmode = LOGMODE_NONE;
}
+#if ENABLE_FEATURE_NTP_AUTH
+ if (opts & OPT_k) {
+ char *tokens[4];
+ parser_t *parser;
+
+ parser = config_open(key_file_path);
+ while (config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL | PARSE_MIN_DIE) == 3) {
+ key_entry_t *key_entry;
+ char buffer[64];
+ smalluint hash_type;
+ smalluint msg_size;
+ smalluint key_length;
+ char *key;
+
+ if ((tokens[1][0] | 0x20) == 'm')
+ /* supports 'M' and 'md5' formats */
+ hash_type = HASH_MD5;
+ else
+ if (strncasecmp(tokens[1], "sha", 3) == 0)
+ /* supports 'sha' and 'sha1' formats */
+ hash_type = HASH_SHA1;
+ else
+ bb_error_msg_and_die("only MD5 and SHA1 keys supported");
+
+/* man ntp.keys:
+ * MD5 The key is 1 to 16 printable characters terminated by an EOL,
+ * whitespace, or a # (which is the "start of comment" character).
+ * SHA
+ * SHA1
+ * RMD160 The key is a hex-encoded ASCII string of 40 characters, which
+ * is truncated as necessary.
+ */
+ key_length = strnlen(tokens[2], 41);
+ if (key_length >= 41) {
+ err:
+ bb_error_msg_and_die("malformed key at line %u", parser->lineno);
+ }
+
+ if (hash_type == HASH_MD5) {
+ key = tokens[2];
+ msg_size = NTP_MSGSIZE_MD5_AUTH;
+ } else /* it's hash_type == HASH_SHA1 */
+ if (!(key_length & 1)) {
+ key_length >>= 1;
+ if (!hex2bin(buffer, tokens[2], key_length))
+ goto err;
+ key = buffer;
+ msg_size = NTP_MSGSIZE_SHA1_AUTH;
+ } else {
+ goto err;
+ }
+ key_entry = xzalloc(sizeof(*key_entry) + key_length);
+ key_entry->type = hash_type;
+ key_entry->msg_size = msg_size;
+ key_entry->key_length = key_length;
+ memcpy(key_entry->key, key, key_length);
+ key_entry->id = xatou_range(tokens[0], 1, MAX_KEY_NUMBER);
+ llist_add_to(&key_entries, key_entry);
+ }
+ config_close(parser);
+ }
+#endif
if (peers) {
+#if ENABLE_FEATURE_NTP_AUTH
+ 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);
+//error if not found?
+ }
+ add_peers(llist_pop(&peers), key_entry);
+ }
+#else
while (peers)
add_peers(llist_pop(&peers));
+#endif
}
#if ENABLE_FEATURE_NTPD_CONF
else {
@@ -2353,7 +2579,7 @@ 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 +2620,7 @@ static NOINLINE void ntp_init(char **argv)
| (1 << SIGCHLD)
, SIG_IGN
);
+//TODO: free unused elements of key_entries?
}
int ntpd_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
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