ATR statistics: TA2 - Global, specific mode byte

Article from the series "ATR statistics"

TA2 - Global, specific mode byte

The ISO 7816-3 specification is not public. So I can't copy/paste part of the text. I will use Wikipedia instead.

From Wikipedia https://en.wikipedia.org/wiki/Answer_to_reset#Interface_byte_TA2

Interface byte TA₂, if present, is global, and is named the specific mode byte.

Presence of TA₂ commands that the reader use specific mode as defined by TA₂ and earlier global bytes, rather than negotiable mode when TA₂ is absent.

TA₂ encodes in its 4 low-order bits an integer T defining the protocol required by the card, in the convention used for TD₁ (EMV prescribes that a card which T encoded in TA₂ does not match that in TD₁ shall be rejected).

The 5th bit is 0 to encodes that the required ETU duration is F_i/D_i clock cycles as defined by TA₁ (or its default value if absent); or 1 to indicate that the ETU duration is implicitly known (by some convention, or setting of the reader; EMV prescribes that such card shall be rejected).

The 6th and 7th bit are reserved for future use; 0 indicates not used.

The 8th bit is 1 to indicate that the card is unable to change the negotiable/specific mode (that is, does not propose other settings); or 0 to indicate that card has that ability (perhaps after a warm ATR).

Historical note: Provision for specific mode did not exist in ISO/IEC 7816-3:1989. Back then, the interface character TA₂ had no particular name or function, and was specific (to the protocol introduced by TD₁). ISO/IEC 7816-3:1997 introduced the specific mode and the specific mode byte, with interim note helping cards with specific mode byte TA₂ in their ATR dealing with a reader that did not implement specific mode.

TA2	#	%
	1983	95.70 %
0x81	48	2.32 %
0x80	31	1.50 %
0x00	10	0.48 %

TA₂ is used by only 4.30% of cards. 95.70% of smart cards in my list have no TA₂ defined.

• 0x81 indicates "Protocol to be used in spec mode: T=1 - Unable to change - defined by interface bytes".
• The 4 low-order bits are set to 0001b so T=1 protocol.
• The 8th bit set to 1 to indicate unable to change the negotiable/specific mode
• 0x80 indicates "Protocol to be used in spec mode: T=0 - Unable to change - defined by interface bytes"
• The 4 low-order bits are set to 0000b so T=0 protocol.
• The 8th bit set to 1 to indicate unable to change the negotiable/specific mode
• 0x00 indicates "Protocol to be used in spec mode: T=0 - Capable to change - defined by interface bytes"
• The 4 low-order bits are set to 0000b so T=0 protocol.
• The 8th bit set to 0 to indicate the card is able to change the negotiable/specific mode

New version of pcsc-lite: 1.8.19

I just released a new version of pcsc-lite 1.8.19.
pcsc-lite is a Free Software implementation of the PC/SC (or WinSCard) API for Unix systems.

Changes:
1.8.19: Ludovic Rousseau
9 December 2016

• SCardGetStatusChange(): Fix a (rare) race condition
• Doxygen:
• SCardGetStatusChange() may return SCARD_E_UNKNOWN_READER
• SCardConnect() and SCardReconnect() will never return SCARD_E_NOT_READY
• pcsc-spy:
• fix display of execution time
• log the thread number in the results
• Some other minor improvements

macOS Sierra and pam_smartcard

In Sierra a new smart card component has been introduced: pam_smartcard. PAM is Pluggable Authentication Modules.

The source code is available at macOS 10.12 Source and is part of the pam_modules component.

pam_smartcard

The pam_smartcard(8) manage is:

pam_smartcard(8)          BSD System Manager's Manual         pam_smartcard(8)

NAME
     pam_smartcard -- Smartcard PAM module

SYNOPSIS
     [service-name] function-class control-flag pam_smartcard [options]

DESCRIPTION
     The Smartcard PAM module supports authentication function class.  In
     terms of the function-class parameter, this is ``auth.''

   The Smartcard Authentication Module
     This module permits or denies users based on smartcard authentication
     support in the Open Directory database, and the presence of an appropri-
     ate smartcard in the reader attached to the local machine. When a card is
     locked, the user is asked to unlock it with his PIN.

   The following options may be passed to this account management module:
     no_check_shell
             Continues evaluation even if user's shell is not valid. Normally,
             users with a shell like /usr/bin/false are considered as dis-
             abled.

EXAMPLE
     Adding the following line on the top of the /etc/pam.d/sudo enables smartcard support for sudo:
             auth   sufficient     pam_smartcard.so

SEE ALSO
     pam.conf(5), pam(8) SmartCardServices(7)

BSD                             August 27, 2015                            BSD

I guess this is related to the introduction of the native support of PIV cards in Sierra. See "macOS Sierra and PIVToken source code".

The pam_smartcard PAM module is used by two services by default:

• authorization_ctk
• screensaver_ctk

$ grep pam_smartcard /etc/pam.d/*
/etc/pam.d/authorization_ctk:auth       required       pam_smartcard.so  use_first_pass
/etc/pam.d/screensaver_ctk:auth       required       pam_smartcard.so  use_first_pass

$ cat /etc/pam.d/authorization_ctk 
# ctk: auth 
auth       required       pam_smartcard.so   use_first_pass
account    required       pam_opendirectory.so

$ cat /etc/pam.d/screensaver_ctk 
# ctk: auth 
auth       required       pam_smartcard.so  use_first_pass
account    required       pam_opendirectory.so
account    sufficient     pam_self.so
account    required       pam_group.so no_warn group=admin,wheel fail_safe
account    required       pam_group.so no_warn deny group=admin,wheel ruser fail_safe

SmartCardServices

Another interesting man page is SmartCardServices(7). Here is an extract:

SmartCardServices(7) BSD Miscellaneous Information Manual SmartCardServices(7)

NAME
     SmartCardServices -- overview of smart card support

DESCRIPTION
     SmartCardServices is a set of components for OS X smart card support.

     Any smart card which supports the PIV standard is supported natively by
     OS X. Access to smart card items is possible using the keychain inter-
     face. Applications can install additional drivers for smart cards that
     are not natively supported.

     Smart card certificates are automatically added to user's keychain when a
     smart card is inserted. Smart card certificates can be listed with
     security using the list-smartcards or export-smartcard commands. Keychain
     Access GUI cannot be used to manipulate or list these certificates.

SETUP
     To associate users with smart cards, the system can be set up for either
     fixed key mapping or attribute based mapping. For fixed key use
     sc_auth(8) or use the dialog which appears automatically when an unasso-
     ciated smartcard is inserted into a reader. This dialog can be globally
     suppressed by:

           sudo defaults write /Library/Preferences/com.apple.security.smartcard UserPairing -bool NO

     Attribute matching can be set up using the appropriate AttributeMapping
     section in the configuration file as described below. There is no default
     configuration. If no AttributeMapping exists or the configuration file is
     missing, attribute matching is not used. If both fixed key mapping and
     attribute mapping are able to associate the inserted smart card with a
     user, attribute mapping takes precedence.

     By default certificates do not need to be trusted to allow association.
     Certificate trust can be globally enforced by setting:

           sudo defaults write /Library/Preferences/com.apple.security.smartcard checkCertificateTrust -bool YES

[...]

PAM PKCS#11?

Since PAM is available in macOS maybe the PAM PKCS#11 module can be used without too much changes? This module is for GNU/Linux but may be adapted for macOS.

In this case, adding support for smart card login in macOS, if you already have a PKCS#11 library for your card, should be easy.

Conclusion

The use of smart card in macOS for high level services (like authentication) is easier in Sierra, at least for PIV smart cards.

I imagine that the support of other smart cards models will be proposed by third parties "soon".

macOS Sierra and smart card source code

Apple released the source code of the open source components they use in Sierra (OS X 10.12 released in September 2016). The components are available at OS X 10.12 Source.

As I did for El Capitan in "OS X El Capitan and smart card source code" I will document what I found.

The smart card related components are:

• SecurityTokend
• SmartcardCCID

See "macOS Sierra and smart cards status" for a general discussion of the changes in El Capitan.

SecurityTokend

The version changed from 55108 in El Capitan to 55111 in Sierra.

The changes are very limited:

• the Xcode project uses Security.framework
• 1 bug fixed "to prevent uninitialized value when following CALL ends with exception" according to the source code comment

diffstat:

 SecurityTokend-55111/SecurityTokend.xcodeproj/project.pbxproj    |    6 ++++++
 SecurityTokend-55111/lib/transition.cpp                          |    1 +
 SecurityTokend-55111/security_tokend_client/transition.cpp       |    1 +
 3 files changed, 8 insertions(+)

SmartcardCCID

The version changed from 55008.40.1 in El Capitan (10.11.4) to 55013 in Sierra.

Changes:

• CCID driver upgraded from 1.4.21 (released 21 October 2015) to 1.4.24 (released 22 May 2016)
• two Apple patches (RSA_SecurID_getpasswd.c.patch, scardcontrol.c.patch) are no more needed since the problem is fixed upstream

No change:

• the same libusb version 1.0.9 is used. This version was released in 2012-04-02. The latest libusb version is 1.0.21 released in 2016-10-01.
• the CCID driver provided by Apple has 4 patches. These patches are related to the way Apple builds the driver.

Conclusion

No disruptive changes this time.

The source code of CryptoTokenKit (introduced in Yosemite. See "OS X Yosemite BETA and smart cards status") is not provided. That is not surprising since this it is an Apple only component and not a fork of an existing free software.

OS X El Capitan and CCID evolution

In a previous blog article "OS X El Capitan and CCID driver upgrades" I mentioned the evolution of the CCID driver for the same major release of OS X 10.11.x.

With the availability of the source code at Apple Open Source it is easy to see what happened.

OS X Version	SmartcardCCID	CCID
10.11	SmartcardCCID-55008	1.4.14
10.11.1	SmartcardCCID-55008	1.4.14
10.11.2	SmartcardCCID-55008.20.1	1.4.20
10.11.3	SmartcardCCID-55008.20.1	1.4.20
10.11.4	SmartcardCCID-55008.40.1	1.4.21
10.11.5	SmartcardCCID-55008.40.1	1.4.21
10.11.6	SmartcardCCID-55008.40.1	1.4.21

I will try to closely follow the evolution of macOS Sierra (10.12) source code to avoid surprises in the future.

Bitcoins received for this blog: 2 years later

Two years ago (November 2014) I proposed to send me bitcoins in "How to help my projects? Send me bitcoins!".

Bitcoin

After 2 years I got 3 donations for a total amount of 0.02858649 BTC (or approximately 19.37€). The 3 transactions are public and can be seen at https://blockchain.info/address/14iqwd2wEATig6JJD6zwkpvq7AYaECgtng. A great thanks to my 3 donors.

This is not a huge amount. In comparison I received 100.27€ from Flattr in 6 years (see "How to help my projects?").

System	Duration	Total amount	Mean
Flattr	6 years	100.27 €	16.71 €/year
Bitcoin	2 years	19.37 €	9.67 €/year

The problem with Flattr (as I explained in "My Flattr experience") is that the funds are automatically "reinvested" so the real result after 6 years is 0€ in my pockets.

Adsense? No!

Google just proposed me to enrol in the AdSense program. Their estimation is a gain of 10,18 € per month.

Bonne nouvelle ! Votre compte répond aux critères requis pour bénéficier du traitement AdSense accéléré.
Vous devriez pouvoir gagner jusqu'à 10,18 € par mois*. Faites en sorte que votre blog vienne grossir les rangs de ces millions d'autres qui rapportent de l'argent grâce à AdSense. S'inscrire

*Les revenus mentionnés ne sont que des estimations basées sur le trafic récemment enregistré par votre blog. Nous ne pouvons en garantir le montant. Les comptes et les revenus AdSense doivent également respecter le Règlement du programme et les Conditions d'utilisation AdSense.

But since I do not like ads in web pages (and I use an advertisement blocker) I will not use AdSense or any other advertising system.

Conclusion

Please continue sending bitcoins. My bitcoin address is at the bottom of each blog page.

ATR statistics: TD1 - Structural, encodes Y2 and T

Article from the series "ATR statistics"

TD1 - Structural, encodes Y2 and T

The ISO 7816-3 specification is not public. So I can't copy/paste part of the text. I will use Wikipedia instead.

From Wikipedia https://en.wikipedia.org/wiki/Answer_to_reset#Interface_bytes_TDi:

Interfaces bytes TD_i for i≥1, if present, are structural.
TD_i encodes in its 4 high-order bits the presence of at most 4 other interface bytes: TA_i+1 (resp. TB_i+1, TC_i+1, TD_i+1) follow, in that order, if the 5th (resp. 6th, 7th, 8th) bit of TD_i is 1.
TD_i encodes in its 4 low-order bits (4th MSbit to 1st LSbit) an integer T, in range [0..15]. T = 15 is invalid in TD₁, and in other TD_i qualifies the following TA_i+1 TB_i+1, TC_i+1, TD_i+1 (if present) as global interface bytes. Other values of T indicates a protocol that the card is willing to use, and that TA_i+1 TB_i+1, TC_i+1, TD_i+1 (if present) are specific interface bytes applying only to that protocol. T = 0 is a character-oriented protocol. T = 1 is a block-oriented protocol. T in the range [3..14] is RFU.
Historical note: provision for dynamically qualifying interface bytes as global using T = 15 did not exist in ISO/IEC 7816-3:1989.

TD1	#	%
	899	43.39 %
0x80	459	22.15 %
0x81	372	17.95 %
0x40	95	4.58 %
0x00	69	3.33 %
0x91	46	2.22 %
0xC0	45	2.17 %
0xC1	27	1.30 %
0x10	22	1.06 %
0x50	16	0.77 %
0x01	9	0.43 %
0x0E	8	0.39 %
0x11	2	0.10 %
0x1F	1	0.05 %
0x31	1	0.05 %
0x3F	1	0.05 %

TD1 (as the other TDi bytes) is structural and indicates:

• How to interpret the other ATR bytes
• What communication protocol the card wants to use

For 43% of the ATRs no TD₁ is present. So no other TA₂, TB₂, TC₂ or TD₂ is present and no protocol is defined so the default T=0 will be used.

For 22% of ATRs TD₁ = 0x80 so bit 8 is set to indicate that a TD₂ is present and T=0 is used. One such ATR is 3B 80 80 01 01.

For 17% of ATRs TD₁ = 0x81 so, as in the previous case, TD₂ is present but T=1 is used. One such ATR is 3B 82 81 31 76 43 C0 02 C5

For 5% of ATRs TD₁ = 0x40 so TC₂ is present and T=0 is used. One such ATR is 3B 85 40 20 68 01 01 00 00

I will not document all the other cases. I let this exercise to the reader.

One special case is TD₁ = 0x?E to indicate the T=14 protocol.

From ISO 7816-3:

The type T refers to a transmission protocol and/or qualifies interface bytes.

• T=0 refers to the half-duplex transmission of characters specified in clause 10.
• T=1 refers to the half-duplex transmission of blocks specified in clause 11.
• T=2 and T=3 are reserved for future full-duplex operations.
• T=4 is reserved for an enhanced half-duplex transmission of characters.
• T=5 to T=13 are reserved for future use by ISO/IEC JTC 1/SC 17.
• T=14 refers to transmission protocols not standardized by ISO/IEC JTC 1/SC 17.
• T=15 does not refer to a transmission protocol, but only qualifies global interface bytes.

As you can see in the list above "T=14 refers to transmission protocols not standardized by ISO/IEC JTC 1/SC 17." In my list T=14 is used only by pay TV cards like 3B 9F 21 0E 49 52 44 45 54 4F 20 41 43 53 03 83 95 00 80 55.

TD₁ = 0x?F is also another special case to indicate T=15, which is not a protocol, and will change the interpretation of the following ATR bytes.