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ntp: fix length check of NTPv4 extension fields

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Don't allow extension fields shorter than 16 bytes.
This commit is contained in:
Miroslav Lichvar 2015-01-07 13:58:11 +01:00
parent 52e12e42e5
commit 35e11ffe60
1 changed files with 2 additions and 1 deletions
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3
ntp_core.c
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@ -1040,7 +1040,8 @@ check_packet_auth(NTP_Packet *pkt, int length, int *has_auth, uint32_t *key_id)
16-bit length of the whole field aligned to 32 bits and data. */ 16-bit length of the whole field aligned to 32 bits and data. */
if (remainder >= NTP_MIN_EXTENSION_LENGTH) { if (remainder >= NTP_MIN_EXTENSION_LENGTH) {
ext_length = ntohs(*(uint16_t *)(data + i + 2)); ext_length = ntohs(*(uint16_t *)(data + i + 2));
if (ext_length % 4 == 0 && ext_length <= remainder) { if (ext_length >= NTP_MIN_EXTENSION_LENGTH &&
ext_length <= remainder && ext_length % 4 == 0) {
i += ext_length; i += ext_length;
continue; continue;
} }