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[src/trunk]: src/crypto/external/bsd/openssh/dist OpenSSH 8.4 was released on...



details:   https://anonhg.NetBSD.org/src/rev/b40b5ef65b8a
branches:  trunk
changeset: 946612:b40b5ef65b8a
user:      christos <christos%NetBSD.org@localhost>
date:      Fri Dec 04 18:40:04 2020 +0000

description:
OpenSSH 8.4 was released on 2020-09-27. It is available from the
mirrors listed at https://www.openssh.com/.

OpenSSH is a 100% complete SSH protocol 2.0 implementation and
includes sftp client and server support.

Once again, we would like to thank the OpenSSH community for their
continued support of the project, especially those who contributed
code or patches, reported bugs, tested snapshots or donated to the
project. More information on donations may be found at:
https://www.openssh.com/donations.html

Future deprecation notice
=========================

It is now possible[1] to perform chosen-prefix attacks against the
SHA-1 algorithm for less than USD$50K. For this reason, we will be
disabling the "ssh-rsa" public key signature algorithm by default in a
near-future release.

This algorithm is unfortunately still used widely despite the
existence of better alternatives, being the only remaining public key
signature algorithm specified by the original SSH RFCs.

The better alternatives include:

 * The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These
   algorithms have the advantage of using the same key type as
   "ssh-rsa" but use the safe SHA-2 hash algorithms. These have been
   supported since OpenSSH 7.2 and are already used by default if the
   client and server support them.

 * The ssh-ed25519 signature algorithm. It has been supported in
   OpenSSH since release 6.5.

 * The RFC5656 ECDSA algorithms: ecdsa-sha2-nistp256/384/521. These
   have been supported by OpenSSH since release 5.7.

To check whether a server is using the weak ssh-rsa public key
algorithm, for host authentication, try to connect to it after
removing the ssh-rsa algorithm from ssh(1)'s allowed list:

    ssh -oHostKeyAlgorithms=-ssh-rsa user@host

If the host key verification fails and no other supported host key
types are available, the server software on that host should be
upgraded.

We intend to enable UpdateHostKeys by default in the next OpenSSH
release. This will assist the client by automatically migrating to
better algorithms. Users may consider enabling this option manually.

[1] "SHA-1 is a Shambles: First Chosen-Prefix Collision on SHA-1 and
    Application to the PGP Web of Trust" Leurent, G and Peyrin, T
    (2020) https://eprint.iacr.org/2020/014.pdf

Security
========

 * ssh-agent(1): restrict ssh-agent from signing web challenges for
   FIDO/U2F keys.

   When signing messages in ssh-agent using a FIDO key that has an
   application string that does not start with "ssh:", ensure that the
   message being signed is one of the forms expected for the SSH protocol
   (currently public key authentication and sshsig signatures).

   This prevents ssh-agent forwarding on a host that has FIDO keys
   attached granting the ability for the remote side to sign challenges
   for web authentication using those keys too.

   Note that the converse case of web browsers signing SSH challenges is
   already precluded because no web RP can have the "ssh:" prefix in the
   application string that we require.

 * ssh-keygen(1): Enable FIDO 2.1 credProtect extension when generating
   a FIDO resident key.

   The recent FIDO 2.1 Client to Authenticator Protocol introduced a
   "credProtect" feature to better protect resident keys. We use this
   option to require a PIN prior to all operations that may retrieve
   a resident key from a FIDO token.

Potentially-incompatible changes
================================

This release includes a number of changes that may affect existing
configurations:

 * For FIDO/U2F support, OpenSSH recommends the use of libfido2 1.5.0
   or greater. Older libraries have limited support at the expense of
   disabling particular features. These include resident keys, PIN-
   required keys and multiple attached tokens.

 * ssh-keygen(1): the format of the attestation information optionally
   recorded when a FIDO key is generated has changed. It now includes
   the authenticator data needed to validate attestation signatures.

 * The API between OpenSSH and the FIDO token middleware has changed
   and the SSH_SK_VERSION_MAJOR version has been incremented as a
   result. Third-party middleware libraries must support the current
   API version (7) to work with OpenSSH 8.4.

 * The portable OpenSSH distribution now requires automake to rebuild
   the configure script and supporting files. This is not required when
   simply building portable OpenSSH from a release tar file.

Changes since OpenSSH 8.3
=========================

New features
------------

 * ssh(1), ssh-keygen(1): support for FIDO keys that require a PIN for
   each use. These keys may be generated using ssh-keygen using a new
   "verify-required" option. When a PIN-required key is used, the user
   will be prompted for a PIN to complete the signature operation.

 * sshd(8): authorized_keys now supports a new "verify-required"
   option to require FIDO signatures assert that the token verified
   that the user was present before making the signature. The FIDO
   protocol supports multiple methods for user-verification, but
   currently OpenSSH only supports PIN verification.

 * sshd(8), ssh-keygen(1): add support for verifying FIDO webauthn
   signatures. Webauthn is a standard for using FIDO keys in web
   browsers. These signatures are a slightly different format to plain
   FIDO signatures and thus require explicit support.

 * ssh(1): allow some keywords to expand shell-style ${ENV}
   environment variables. The supported keywords are CertificateFile,
   ControlPath, IdentityAgent and IdentityFile, plus LocalForward and
   RemoteForward when used for Unix domain socket paths. bz#3140

 * ssh(1), ssh-agent(1): allow some additional control over the use of
   ssh-askpass via a new $SSH_ASKPASS_REQUIRE environment variable,
   including forcibly enabling and disabling its use. bz#69

 * ssh(1): allow ssh_config(5)'s AddKeysToAgent keyword accept a time
   limit for keys in addition to its current flag options. Time-
   limited keys will automatically be removed from ssh-agent after
   their expiry time has passed.

 * scp(1), sftp(1): allow the -A flag to explicitly enable agent
   forwarding in scp and sftp. The default remains to not forward an
   agent, even when ssh_config enables it.

 * ssh(1): add a '%k' TOKEN that expands to the effective HostKey of
   the destination. This allows, e.g., keeping host keys in individual
   files using "UserKnownHostsFile ~/.ssh/known_hosts.d/%k". bz#1654

 * ssh(1): add %-TOKEN, environment variable and tilde expansion to
   the UserKnownHostsFile directive, allowing the path to be
   completed by the configuration (e.g. bz#1654)

 * ssh-keygen(1): allow "ssh-add -d -" to read keys to be deleted
   from stdin. bz#3180

 * sshd(8): improve logging for MaxStartups connection throttling.
   sshd will now log when it starts and stops throttling and periodically
   while in this state. bz#3055

Bugfixes
--------

 * ssh(1), ssh-keygen(1): better support for multiple attached FIDO
   tokens. In cases where OpenSSH cannot unambiguously determine which
   token to direct a request to, the user is now required to select a
   token by touching it. In cases of operations that require a PIN to
   be verified, this avoids sending the wrong PIN to the wrong token
   and incrementing the token's PIN failure counter (tokens
   effectively erase their keys after too many PIN failures).

 * sshd(8): fix Include before Match in sshd_config; bz#3122

 * ssh(1): close stdin/out/error when forking after authentication
   completes ("ssh -f ...") bz#3137

 * ssh(1), sshd(8): limit the amount of channel input data buffered,
   avoiding peers that advertise large windows but are slow to read
   from causing high memory consumption.

 * ssh-agent(1): handle multiple requests sent in a single write() to
   the agent.

 * sshd(8): allow sshd_config longer than 256k

 * sshd(8): avoid spurious "Unable to load host key" message when sshd
   load a private key but no public counterpart

 * ssh(1): prefer the default hostkey algorithm list whenever we have
   a hostkey that matches its best-preference algorithm.

 * sshd(1): when ordering the hostkey algorithms to request from a
   server, prefer certificate types if the known_hosts files contain a key
   marked as a @cert-authority; bz#3157

 * ssh(1): perform host key fingerprint comparisons for the "Are you
   sure you want to continue connecting (yes/no/[fingerprint])?"
   prompt with case sensitivity.

 * sshd(8): ensure that address/masklen mismatches in sshd_config
   yield fatal errors at daemon start time rather than later when
   they are evaluated.

 * ssh-keygen(1): ensure that certificate extensions are lexically
   sorted. Previously if the user specified a custom extension then
   the everything would be in order except the custom ones. bz#3198

 * ssh(1): also compare username when checking for JumpHost loops.
   bz#3057

 * ssh-keygen(1): preserve group/world read permission on known_hosts
   files across runs of "ssh-keygen -Rf /path". The old behaviour was
   to remove all rights for group/other. bz#3146

 * ssh-keygen(1): Mention the [-a rounds] flag in the ssh-keygen
   manual page and usage().

 * sshd(8): explicitly construct path to ~/.ssh/rc rather than
   relying on it being relative to the current directory, so that it
   can still be found if the shell startup changes its directory.
   bz#3185

 * sshd(8): when redirecting sshd's log output to a file, undo this
   redirection after the session child process is forked(). Fixes
   missing log messages when using this feature under some
   circumstances.

 * sshd(8): start ClientAliveInterval bookkeeping before first pass
   through select() loop; fixed theoretical case where busy sshd may
   ignore timeouts from client.

 * ssh(1): only reset the ServerAliveInterval check when we receive
   traffic from the server and ignore traffic from a port forwarding
   client, preventing a client from keeping a connection alive when
   it should be terminated. bz#2265

 * ssh-keygen(1): avoid spurious error message when ssh-keygen
   creates files outside ~/.ssh

 * sftp-client(1): fix off-by-one error that caused sftp downloads to
   make one more concurrent request that desired. This prevented using
   sftp(1) in unpipelined request/response mode, which is useful when
   debugging. bz#3054

 * ssh(1), sshd(8): handle EINTR in waitfd() and timeout_connect()
   helpers. bz#3071

 * ssh(1), ssh-keygen(1): defer creation of ~/.ssh until we attempt to
   write to it so we don't leave an empty .ssh directory when it's not
   needed. bz#3156

 * ssh(1), sshd(8): fix multiplier when parsing time specifications
   when handling seconds after other units. bz#3171

Portability
-----------

 * sshd(8): always send any PAM account messages. If the PAM account
   stack returns any messages, always send them to the user and not
   just if the check succeeds. bz#2049

 * Implement some backwards compatibility for libfido2 libraries
   older than 1.5.0. Note that use of an older library will result
   in the loss of certain features including resident key support,
   PIN support and support for multiple attached tokens.

 * configure fixes for XCode 12

 * gnome-ssh-askpass3: ensure the "close" button is not focused by
   default for SSH_ASKPASS_PROMPT=none prompts. Avoids space/enter
   accidentally dismissing FIDO touch notifications.

 * gnome-ssh-askpass3: allow some control over textarea colour via
   $GNOME_SSH_ASKPASS_FG_COLOR and $GNOME_SSH_ASKPASS_BG_COLOR
   environment variables.

 * sshd(8): document another PAM spec problem in a frustrated comment

 * sshd(8): support NetBSD's utmpx.ut_ss address field. bz#960

 * Add the ssh-sk-helper binary and its manpage to the RPM spec file

 * Detect the Frankenstein monster of Linux/X32 and allow the sandbox
   to function there. bz#3085

diffstat:

 crypto/external/bsd/openssh/dist/PROTOCOL.sshsig |    3 +-
 crypto/external/bsd/openssh/dist/PROTOCOL.u2f    |  130 +++++++++-------------
 crypto/external/bsd/openssh/dist/sk-api.h        |    7 +-
 crypto/external/bsd/openssh/dist/sshsig.h        |    9 +-
 4 files changed, 64 insertions(+), 85 deletions(-)

diffs (256 lines):

diff -r 103f695801f4 -r b40b5ef65b8a crypto/external/bsd/openssh/dist/PROTOCOL.sshsig
--- a/crypto/external/bsd/openssh/dist/PROTOCOL.sshsig  Fri Dec 04 18:28:55 2020 +0000
+++ b/crypto/external/bsd/openssh/dist/PROTOCOL.sshsig  Fri Dec 04 18:40:04 2020 +0000
@@ -71,7 +71,7 @@
 signature algorithm must be "rsa-sha2-512" or "rsa-sha2-256" (i.e.
 not the legacy RSA-SHA1 "ssh-rsa").
 
-This blob is encoded as a string using the RFC4243 encoding
+This blob is encoded as a string using the RFC4253 encoding
 rules and base64 encoded to form the middle part of the
 armored signature.
 
@@ -97,3 +97,4 @@
 The data is concatenated and passed to the SSH signing
 function.
 
+$OpenBSD: PROTOCOL.sshsig,v 1.4 2020/08/31 00:17:41 djm Exp $
diff -r 103f695801f4 -r b40b5ef65b8a crypto/external/bsd/openssh/dist/PROTOCOL.u2f
--- a/crypto/external/bsd/openssh/dist/PROTOCOL.u2f     Fri Dec 04 18:28:55 2020 +0000
+++ b/crypto/external/bsd/openssh/dist/PROTOCOL.u2f     Fri Dec 04 18:40:04 2020 +0000
@@ -39,6 +39,13 @@
 primarily use ECDSA signatures in the NIST-P256 field, though the FIDO2
 standard specifies additional key types, including one based on Ed25519.
 
+Use of U2F security keys does not automatically imply multi-factor
+authentication. From sshd's perspective, a security key constitutes a
+single factor of authentication, even if protected by a PIN or biometric
+authentication.  To enable multi-factor authentication in ssh, please
+refer to the AuthenticationMethods option in sshd_config(5).
+
+
 SSH U2F Key formats
 -------------------
 
@@ -147,6 +154,16 @@
 case, OpenSSH optionally allows retaining the attestation information
 at the time of key generation. It will take the following format:
 
+       string          "ssh-sk-attest-v01"
+       string          attestation certificate
+       string          enrollment signature
+       string          authenticator data (CBOR encoded)
+       uint32          reserved flags
+       string          reserved string
+
+A previous version of this format, emitted prior to OpenSSH 8.4 omitted
+the authenticator data.
+
        string          "ssh-sk-attest-v00"
        string          attestation certificate
        string          enrollment signature
@@ -202,6 +219,32 @@
        byte            flags
        uint32          counter
 
+webauthn signatures
+-------------------
+
+The W3C/FIDO webauthn[1] standard defines a mechanism for a web browser to
+interact with FIDO authentication tokens. This standard builds upon the
+FIDO standards, but requires different signature contents to raw FIDO
+messages. OpenSSH supports ECDSA/p256 webauthn signatures through the
+"webauthn-sk-ecdsa-sha2-nistp256%openssh.com@localhost" signature algorithm.
+
+The wire encoding for a webauthn-sk-ecdsa-sha2-nistp256%openssh.com@localhost
+signature is similar to the sk-ecdsa-sha2-nistp256%openssh.com@localhost format:
+
+       string          "webauthn-sk-ecdsa-sha2-nistp256%openssh.com@localhost"
+       string          ecdsa_signature
+       byte            flags
+       uint32          counter
+       string          origin
+       string          clientData
+       string          extensions
+
+Where "origin" is the HTTP origin making the signature, "clientData" is
+the JSON-like structure signed by the browser and "extensions" are any
+extensions used in making the signature.
+
+[1] https://www.w3.org/TR/webauthn-2/
+
 ssh-agent protocol extensions
 -----------------------------
 
@@ -234,87 +277,15 @@
 loaded middleware libraries to communicate with security keys, but offer
 support for the common case of USB HID security keys internally.
 
-The middleware library need only expose a handful of functions:
-
-       #define SSH_SK_VERSION_MAJOR            0x00050000 /* API version */
-       #define SSH_SK_VERSION_MAJOR_MASK       0xffff0000
-
-       /* Flags */
-       #define SSH_SK_USER_PRESENCE_REQD       0x01
-       #define SSH_SK_USER_VERIFICATION_REQD   0x04
-       #define SSH_SK_RESIDENT_KEY             0x20
-
-       /* Algs */
-       #define SSH_SK_ECDSA                   0x00
-       #define SSH_SK_ED25519                 0x01
-
-       /* Error codes */
-       #define SSH_SK_ERR_GENERAL              -1
-       #define SSH_SK_ERR_UNSUPPORTED          -2
-       #define SSH_SK_ERR_PIN_REQUIRED         -3
-       #define SSH_SK_ERR_DEVICE_NOT_FOUND     -4
-
-       struct sk_enroll_response {
-               uint8_t *public_key;
-               size_t public_key_len;
-               uint8_t *key_handle;
-               size_t key_handle_len;
-               uint8_t *signature;
-               size_t signature_len;
-               uint8_t *attestation_cert;
-               size_t attestation_cert_len;
-       };
-
-       struct sk_sign_response {
-               uint8_t flags;
-               uint32_t counter;
-               uint8_t *sig_r;
-               size_t sig_r_len;
-               uint8_t *sig_s;
-               size_t sig_s_len;
-       };
-
-       struct sk_resident_key {
-               uint32_t alg;
-               size_t slot;
-               char *application;
-               struct sk_enroll_response key;
-       };
-
-       struct sk_option {
-               char *name;
-               char *value;
-               uint8_t important;
-       };
-
-       /* Return the version of the middleware API */
-       uint32_t sk_api_version(void);
-
-       /* Enroll a U2F key (private key generation) */
-       int sk_enroll(uint32_t alg,
-           const uint8_t *challenge, size_t challenge_len,
-           const char *application, uint8_t flags, const char *pin,
-           struct sk_option **options,
-           struct sk_enroll_response **enroll_response);
-
-       /* Sign a challenge */
-       int sk_sign(uint32_t alg, const uint8_t *message, size_t message_len,
-           const char *application,
-           const uint8_t *key_handle, size_t key_handle_len,
-           uint8_t flags, const char *pin, struct sk_option **options,
-           struct sk_sign_response **sign_response);
-
-       /* Enumerate all resident keys */
-       int sk_load_resident_keys(const char *pin, struct sk_option **options,
-           struct sk_resident_key ***rks, size_t *nrks);
-
-The SSH_SK_VERSION_MAJOR should be incremented for each incompatible
+The middleware library need only expose a handful of functions and
+numbers listed in sk-api.h. Included in the defined numbers is a
+SSH_SK_VERSION_MAJOR that should be incremented for each incompatible
 API change.
 
-The options may be used to pass miscellaneous options to the middleware
-as a NULL-terminated array of pointers to struct sk_option. The middleware
-may ignore unsupported or unknown options unless the "important" flag is
-set, in which case it should return failure if an unsupported option is
+miscellaneous options may be passed to the middleware as a NULL-
+terminated array of pointers to struct sk_option. The middleware may
+ignore unsupported or unknown options unless the "required" flag is set,
+in which case it should return failure if an unsupported option is
 requested.
 
 At present the following options names are supported:
@@ -335,3 +306,4 @@
 ssh-pkcs11-helper to provide address-space containment of the
 middleware from ssh-agent.
 
+$OpenBSD: PROTOCOL.u2f,v 1.26 2020/09/09 03:08:01 djm Exp $
diff -r 103f695801f4 -r b40b5ef65b8a crypto/external/bsd/openssh/dist/sk-api.h
--- a/crypto/external/bsd/openssh/dist/sk-api.h Fri Dec 04 18:28:55 2020 +0000
+++ b/crypto/external/bsd/openssh/dist/sk-api.h Fri Dec 04 18:40:04 2020 +0000
@@ -1,4 +1,4 @@
-/* $OpenBSD: sk-api.h,v 1.9 2020/04/28 04:02:29 djm Exp $ */
+/* $OpenBSD: sk-api.h,v 1.11 2020/09/09 03:08:01 djm Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -45,6 +45,8 @@
        size_t signature_len;
        uint8_t *attestation_cert;
        size_t attestation_cert_len;
+       uint8_t *authdata;
+       size_t authdata_len;
 };
 
 struct sk_sign_response {
@@ -61,6 +63,7 @@
        size_t slot;
        char *application;
        struct sk_enroll_response key;
+       uint8_t flags;
 };
 
 struct sk_option {
@@ -69,7 +72,7 @@
        uint8_t required;
 };
 
-#define SSH_SK_VERSION_MAJOR           0x00050000 /* current API version */
+#define SSH_SK_VERSION_MAJOR           0x00070000 /* current API version */
 #define SSH_SK_VERSION_MAJOR_MASK      0xffff0000
 
 /* Return the version of the middleware API */
diff -r 103f695801f4 -r b40b5ef65b8a crypto/external/bsd/openssh/dist/sshsig.h
--- a/crypto/external/bsd/openssh/dist/sshsig.h Fri Dec 04 18:28:55 2020 +0000
+++ b/crypto/external/bsd/openssh/dist/sshsig.h Fri Dec 04 18:40:04 2020 +0000
@@ -1,3 +1,4 @@
+/* $OpenBSD: sshsig.h,v 1.9 2020/08/31 00:17:41 djm Exp $ */
 /*
  * Copyright (c) 2019 Google LLC
  *
@@ -23,7 +24,8 @@
 struct sshkey_sig_details;
 
 typedef int sshsig_signer(struct sshkey *, u_char **, size_t *,
-    const u_char *, size_t, const char *, const char *, u_int, void *);
+    const u_char *, size_t, const char *, const char *, const char *,
+    u_int, void *);
 
 /* Buffer-oriented API */
 
@@ -33,7 +35,7 @@
  * out is populated with the detached signature, or NULL on failure.
  */
 int sshsig_signb(struct sshkey *key, const char *hashalg,
-    const char *sk_provider, const struct sshbuf *message,
+    const char *sk_provider, const char *sk_pin, const struct sshbuf *message,
     const char *sig_namespace, struct sshbuf **out,
     sshsig_signer *signer, void *signer_ctx);
 
@@ -54,7 +56,8 @@
  * out is populated with the detached signature, or NULL on failure.
  */
 int sshsig_sign_fd(struct sshkey *key, const char *hashalg,
-    const char *sk_provider, int fd, const char *sig_namespace,
+    const char *sk_provider, const char *sk_pin,
+    int fd, const char *sig_namespace,
     struct sshbuf **out, sshsig_signer *signer, void *signer_ctx);
 
 /*



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