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netdev: Clarify the PTK->TK to MIC key mapping

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Cite 802.11 in the comments and use nl80211.h constants to map the tx
and rx keys correctly.
This commit is contained in:
Andrew Zaborowski 2017-08-31 04:04:53 +02:00 committed by Denis Kenzior
parent 092ede1147
commit f659265000
1 changed files with 40 additions and 25 deletions
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65
src/netdev.c
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@ -1016,25 +1016,31 @@ static void netdev_set_gtk(uint32_t ifindex, uint8_t key_index,
switch (cipher) {
case CRYPTO_CIPHER_CCMP:
/*
* 802.11-2012 11.7.4 Mapping GTK to CCMP keys:
* "A STA shall use the temporal key as the CCMP key."
*/
memcpy(gtk_buf, gtk, 16);
break;
case CRYPTO_CIPHER_TKIP:
/*
* Swap the TX and RX MIC key portions for supplicant.
* WPA_80211_v3_1_090922 doc's 3.3.4:
* The MIC key used on the Client for transmit (TX) is in
* bytes 24-31, and the MIC key used on the Client for
* receive (RX) is in bytes 16-23 of the PTK. That is,
* assume that TX MIC and RX MIC referred to in Clause 8.7
* are referenced to the Authenticator. Similarly, on the AP,
* the MIC used for TX is in bytes 16-23, and the MIC key
* used for RX is in bytes 24-31 of the PTK.
* 802.11-2012 11.7.2 Mapping GTK to TKIP keys:
* "A STA shall use bits 0-127 of the temporal key as the
* input to the TKIP Phase 1 and Phase 2 mixing functions.
*
* Here apply this to the GTK instead of the PTK.
* A STA shall use bits 128-191 of the temporal key as
* the Michael key for MSDUs from the Authenticator's STA
* to the Supplicant's STA.
*
* A STA shall use bits 192-255 of the temporal key as
* the Michael key for MSDUs from the Supplicant's STA
* to the Authenticator's STA."
*/
memcpy(gtk_buf, gtk, 16);
memcpy(gtk_buf + 16, gtk + 24, 8);
memcpy(gtk_buf + 24, gtk + 16, 8);
memcpy(gtk_buf + NL80211_TKIP_DATA_OFFSET_ENCR_KEY, gtk, 16);
memcpy(gtk_buf + NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY,
gtk + 16, 8);
memcpy(gtk_buf + NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY,
gtk + 24, 8);
break;
default:
l_error("Unexpected cipher: %x", cipher);
@ -1192,23 +1198,32 @@ static void netdev_set_tk(uint32_t ifindex, const uint8_t *aa,
switch (cipher) {
case CRYPTO_CIPHER_CCMP:
/*
* 802.11-2012 11.7.3 Mapping PTK to CCMP keys:
* "A STA shall use the temporal key as the CCMP key
* for MPDUs between the two communicating STAs."
*/
memcpy(tk_buf, tk, 16);
break;
case CRYPTO_CIPHER_TKIP:
/*
* Swap the TX and RX MIC key portions for supplicant.
* WPA_80211_v3_1_090922 doc's 3.3.4:
* The MIC key used on the Client for transmit (TX) is in
* bytes 24-31, and the MIC key used on the Client for
* receive (RX) is in bytes 16-23 of the PTK. That is,
* assume that TX MIC and RX MIC referred to in Clause 8.7
* are referenced to the Authenticator. Similarly, on the AP,
* the MIC used for TX is in bytes 16-23, and the MIC key
* used for RX is in bytes 24-31 of the PTK.
* 802.11-2012 11.7.1 Mapping PTK to TKIP keys:
* "A STA shall use bits 0-127 of the temporal key as its
* input to the TKIP Phase 1 and Phase 2 mixing functions.
*
* A STA shall use bits 128-191 of the temporal key as
* the Michael key for MSDUs from the Authenticator's STA
* to the Supplicant's STA.
*
* A STA shall use bits 192-255 of the temporal key as
* the Michael key for MSDUs from the Supplicant's STA
* to the Authenticator's STA."
*/
memcpy(tk_buf, tk, 16);
memcpy(tk_buf + 16, tk + 24, 8);
memcpy(tk_buf + 24, tk + 16, 8);
memcpy(tk_buf + NL80211_TKIP_DATA_OFFSET_ENCR_KEY, tk, 16);
memcpy(tk_buf + NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY,
tk + 16, 8);
memcpy(tk_buf + NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY,
tk + 24, 8);
break;
default:
l_error("Unexpected cipher: %x", cipher);