[crypto] Add implementation of MS-CHAPv2 authentication
Add an implementation of the authentication portions of the MS-CHAPv2
algorithm as defined in RFC 2759, along with the single test vector
provided therein.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
diff --git a/src/crypto/mschapv2.c b/src/crypto/mschapv2.c
new file mode 100644
index 0000000..ac55fec
--- /dev/null
+++ b/src/crypto/mschapv2.c
@@ -0,0 +1,363 @@
+/*
+ * Copyright (C) 2024 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * MS-CHAPv2 authentication
+ *
+ * The algorithms used for MS-CHAPv2 authentication are defined in
+ * RFC 2759 section 8.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <byteswap.h>
+#include <ipxe/md4.h>
+#include <ipxe/sha1.h>
+#include <ipxe/des.h>
+#include <ipxe/mschapv2.h>
+
+/**
+ * MS-CHAPv2 context block
+ *
+ * For no particularly discernible reason, MS-CHAPv2 uses two
+ * different digest algorithms and one block cipher. The uses do not
+ * overlap, so share the context storage between these to reduce stack
+ * usage.
+ */
+union mschapv2_context {
+ /** SHA-1 digest context */
+ uint8_t sha1[SHA1_CTX_SIZE];
+ /** MD4 digest context */
+ uint8_t md4[MD4_CTX_SIZE];
+ /** DES cipher context */
+ uint8_t des[DES_CTX_SIZE];
+};
+
+/**
+ * MS-CHAPv2 challenge hash
+ *
+ * MS-CHAPv2 calculates the SHA-1 digest of the peer challenge, the
+ * authenticator challenge, and the username, and then uses only the
+ * first 8 bytes of the result (as a DES plaintext block).
+ */
+union mschapv2_challenge_hash {
+ /** SHA-1 digest */
+ uint8_t sha1[SHA1_DIGEST_SIZE];
+ /** DES plaintext block */
+ uint8_t des[DES_BLOCKSIZE];
+};
+
+/**
+ * MS-CHAPv2 password hash
+ *
+ * MS-CHAPv2 calculates the MD4 digest of an unspecified two-byte
+ * little-endian Unicode encoding (presumably either UCS-2LE or
+ * UTF-16LE) of the password.
+ *
+ * For constructing the challenge response, the MD4 digest is then
+ * zero-padded to 21 bytes and used as three separate 56-bit DES keys.
+ *
+ * For constructing the authenticator response, the MD4 digest is then
+ * used as an input to a SHA-1 digest along with the NT response and a
+ * magic constant.
+ */
+union mschapv2_password_hash {
+ /** MD4 digest */
+ uint8_t md4[MD4_DIGEST_SIZE];
+ /** SHA-1 digest */
+ uint8_t sha1[SHA1_DIGEST_SIZE];
+ /** DES keys */
+ uint8_t des[3][DES_BLOCKSIZE];
+ /** DES key expansion */
+ uint8_t expand[ 3 * DES_BLOCKSIZE ];
+};
+
+/** MS-CHAPv2 magic constant 1 */
+static const char mschapv2_magic1[39] =
+ "Magic server to client signing constant";
+
+/** MS-CHAPv2 magic constant 2 */
+static const char mschapv2_magic2[41] =
+ "Pad to make it do more than one iteration";
+
+/**
+ * Calculate MS-CHAPv2 challenge hash
+ *
+ * @v ctx Context block
+ * @v challenge Authenticator challenge
+ * @v peer Peer challenge
+ * @v username User name (or NULL to use empty string)
+ * @v chash Challenge hash to fill in
+ *
+ * This is the ChallengeHash() function as documented in RFC 2759
+ * section 8.2.
+ */
+static void
+mschapv2_challenge_hash ( union mschapv2_context *ctx,
+ const struct mschapv2_challenge *challenge,
+ const struct mschapv2_challenge *peer,
+ const char *username,
+ union mschapv2_challenge_hash *chash ) {
+ struct digest_algorithm *sha1 = &sha1_algorithm;
+
+ /* Calculate SHA-1 hash of challenges and username */
+ digest_init ( sha1, ctx->sha1 );
+ digest_update ( sha1, ctx->sha1, peer, sizeof ( *peer ) );
+ digest_update ( sha1, ctx->sha1, challenge, sizeof ( *challenge ) );
+ if ( username ) {
+ digest_update ( sha1, ctx->sha1, username,
+ strlen ( username ) );
+ }
+ digest_final ( sha1, ctx->sha1, chash->sha1 );
+ DBGC ( ctx, "MSCHAPv2 authenticator challenge:\n" );
+ DBGC_HDA ( ctx, 0, challenge, sizeof ( *challenge ) );
+ DBGC ( ctx, "MSCHAPv2 peer challenge:\n" );
+ DBGC_HDA ( ctx, 0, peer, sizeof ( *peer ) );
+ DBGC ( ctx, "MSCHAPv2 challenge hash:\n" );
+ DBGC_HDA ( ctx, 0, chash->des, sizeof ( chash->des ) );
+}
+
+/**
+ * Calculate MS-CHAPv2 password hash
+ *
+ * @v ctx Context block
+ * @v password Password (or NULL to use empty string)
+ * @v phash Password hash to fill in
+ *
+ * This is the NtPasswordHash() function as documented in RFC 2759
+ * section 8.3.
+ */
+static void mschapv2_password_hash ( union mschapv2_context *ctx,
+ const char *password,
+ union mschapv2_password_hash *phash ) {
+ struct digest_algorithm *md4 = &md4_algorithm;
+ uint16_t wc;
+ uint8_t c;
+
+ /* Construct zero-padded MD4 hash of encoded password */
+ memset ( phash, 0, sizeof ( *phash ) );
+ digest_init ( md4, ctx->md4 );
+ if ( password ) {
+ while ( ( c = *(password++) ) ) {
+ wc = cpu_to_le16 ( c );
+ digest_update ( md4, ctx->md4, &wc, sizeof ( wc ) );
+ }
+ }
+ digest_final ( md4, ctx->md4, phash->md4 );
+ DBGC ( ctx, "MSCHAPv2 password hash:\n" );
+ DBGC_HDA ( ctx, 0, phash->md4, sizeof ( phash->md4 ) );
+}
+
+/**
+ * Hash the MS-CHAPv2 password hash
+ *
+ * @v ctx Context block
+ * @v phash Password hash to be rehashed
+ *
+ * This is the HashNtPasswordHash() function as documented in RFC 2759
+ * section 8.4.
+ */
+static void mschapv2_hash_hash ( union mschapv2_context *ctx,
+ union mschapv2_password_hash *phash ) {
+ struct digest_algorithm *md4 = &md4_algorithm;
+
+ /* Calculate MD4 hash of existing MD4 hash */
+ digest_init ( md4, ctx->md4 );
+ digest_update ( md4, ctx->md4, phash->md4, sizeof ( phash->md4 ) );
+ digest_final ( md4, ctx->md4, phash->md4 );
+ DBGC ( ctx, "MSCHAPv2 password hash hash:\n" );
+ DBGC_HDA ( ctx, 0, phash->md4, sizeof ( phash->md4 ) );
+}
+
+/**
+ * Expand MS-CHAPv2 password hash by inserting DES dummy parity bits
+ *
+ * @v ctx Context block
+ * @v phash Password hash to expand
+ *
+ * This is part of the DesEncrypt() function as documented in RFC 2759
+ * section 8.6.
+ */
+static void mschapv2_expand_hash ( union mschapv2_context *ctx,
+ union mschapv2_password_hash *phash ) {
+ uint8_t *dst;
+ uint8_t *src;
+ unsigned int i;
+
+ /* Expand password hash by inserting (unused) DES parity bits */
+ for ( i = ( sizeof ( phash->expand ) - 1 ) ; i > 0 ; i-- ) {
+ dst = &phash->expand[i];
+ src = ( dst - ( i / 8 ) );
+ *dst = ( ( ( src[-1] << 8 ) | src[0] ) >> ( i % 8 ) );
+ }
+ DBGC ( ctx, "MSCHAPv2 expanded password hash:\n" );
+ DBGC_HDA ( ctx, 0, phash->expand, sizeof ( phash->expand ) );
+}
+
+/**
+ * Calculate MS-CHAPv2 challenge response
+ *
+ * @v ctx Context block
+ * @v chash Challenge hash
+ * @v phash Password hash (after expansion)
+ * @v nt NT response to fill in
+ *
+ * This is the ChallengeResponse() function as documented in RFC 2759
+ * section 8.5.
+ */
+static void
+mschapv2_challenge_response ( union mschapv2_context *ctx,
+ const union mschapv2_challenge_hash *chash,
+ const union mschapv2_password_hash *phash,
+ struct mschapv2_nt_response *nt ) {
+ struct cipher_algorithm *des = &des_algorithm;
+ unsigned int i;
+ int rc;
+
+ /* Construct response. The design of the algorithm here is
+ * interesting, suggesting that an intern at Microsoft had
+ * heard the phrase "Triple DES" and hazarded a blind guess at
+ * what it might mean.
+ */
+ for ( i = 0 ; i < ( sizeof ( phash->des ) /
+ sizeof ( phash->des[0] ) ) ; i++ ) {
+ rc = cipher_setkey ( des, ctx->des, phash->des[i],
+ sizeof ( phash->des[i] ) );
+ assert ( rc == 0 ); /* no failure mode exists */
+ cipher_encrypt ( des, ctx->des, chash->des, nt->block[i],
+ sizeof ( chash->des ) );
+ }
+ DBGC ( ctx, "MSCHAPv2 NT response:\n" );
+ DBGC_HDA ( ctx, 0, nt, sizeof ( *nt ) );
+}
+
+/**
+ * Calculate MS-CHAPv2 challenge response
+ *
+ * @v username User name (or NULL to use empty string)
+ * @v password Password (or NULL to use empty string)
+ * @v challenge Authenticator challenge
+ * @v peer Peer challenge
+ * @v response Challenge response to fill in
+ *
+ * This is essentially the GenerateNTResponse() function as documented
+ * in RFC 2759 section 8.1.
+ */
+void mschapv2_response ( const char *username, const char *password,
+ const struct mschapv2_challenge *challenge,
+ const struct mschapv2_challenge *peer,
+ struct mschapv2_response *response ) {
+ union mschapv2_context ctx;
+ union mschapv2_challenge_hash chash;
+ union mschapv2_password_hash phash;
+
+ /* Zero reserved fields */
+ memset ( response, 0, sizeof ( *response ) );
+
+ /* Copy peer challenge to response */
+ memcpy ( &response->peer, peer, sizeof ( response->peer ) );
+
+ /* Construct challenge hash */
+ mschapv2_challenge_hash ( &ctx, challenge, peer, username, &chash );
+
+ /* Construct expanded password hash */
+ mschapv2_password_hash ( &ctx, password, &phash );
+ mschapv2_expand_hash ( &ctx, &phash );
+
+ /* Construct NT response */
+ mschapv2_challenge_response ( &ctx, &chash, &phash, &response->nt );
+ DBGC ( &ctx, "MSCHAPv2 challenge response:\n" );
+ DBGC_HDA ( &ctx, 0, response, sizeof ( *response ) );
+}
+
+/**
+ * Calculate MS-CHAPv2 authenticator response
+ *
+ * @v username User name (or NULL to use empty string)
+ * @v password Password (or NULL to use empty string)
+ * @v challenge Authenticator challenge
+ * @v response Challenge response
+ * @v auth Authenticator response to fill in
+ *
+ * This is essentially the GenerateAuthenticatorResponse() function as
+ * documented in RFC 2759 section 8.7.
+ */
+void mschapv2_auth ( const char *username, const char *password,
+ const struct mschapv2_challenge *challenge,
+ const struct mschapv2_response *response,
+ struct mschapv2_auth *auth ) {
+ struct digest_algorithm *sha1 = &sha1_algorithm;
+ union mschapv2_context ctx;
+ union mschapv2_challenge_hash chash;
+ union mschapv2_password_hash phash;
+ char tmp[3];
+ char *wtf;
+ unsigned int i;
+
+ /* Construct hash of password hash */
+ mschapv2_password_hash ( &ctx, password, &phash );
+ mschapv2_hash_hash ( &ctx, &phash );
+
+ /* Construct unnamed intermediate hash */
+ digest_init ( sha1, ctx.sha1 );
+ digest_update ( sha1, ctx.sha1, phash.md4, sizeof ( phash.md4 ) );
+ digest_update ( sha1, ctx.sha1, &response->nt,
+ sizeof ( response->nt ) );
+ digest_update ( sha1, ctx.sha1, mschapv2_magic1,
+ sizeof ( mschapv2_magic1 ) );
+ digest_final ( sha1, ctx.sha1, phash.sha1 );
+ DBGC ( &ctx, "MSCHAPv2 NT response:\n" );
+ DBGC_HDA ( &ctx, 0, &response->nt, sizeof ( response->nt ) );
+ DBGC ( &ctx, "MSCHAPv2 unnamed intermediate hash:\n" );
+ DBGC_HDA ( &ctx, 0, phash.sha1, sizeof ( phash.sha1 ) );
+
+ /* Construct challenge hash */
+ mschapv2_challenge_hash ( &ctx, challenge, &response->peer,
+ username, &chash );
+
+ /* Construct authenticator response hash */
+ digest_init ( sha1, ctx.sha1 );
+ digest_update ( sha1, ctx.sha1, phash.sha1, sizeof ( phash.sha1 ) );
+ digest_update ( sha1, ctx.sha1, chash.des, sizeof ( chash.des ) );
+ digest_update ( sha1, ctx.sha1, mschapv2_magic2,
+ sizeof ( mschapv2_magic2 ) );
+ digest_final ( sha1, ctx.sha1, phash.sha1 );
+ DBGC ( &ctx, "MSCHAPv2 authenticator response hash:\n" );
+ DBGC_HDA ( &ctx, 0, phash.sha1, sizeof ( phash.sha1 ) );
+
+ /* Encode authenticator response hash */
+ wtf = auth->wtf;
+ *(wtf++) = 'S';
+ *(wtf++) = '=';
+ DBGC ( &ctx, "MSCHAPv2 authenticator response: S=" );
+ for ( i = 0 ; i < sizeof ( phash.sha1 ) ; i++ ) {
+ snprintf ( tmp, sizeof ( tmp ), "%02X", phash.sha1[i] );
+ *(wtf++) = tmp[0];
+ *(wtf++) = tmp[1];
+ DBGC ( &ctx, "%s", tmp );
+ }
+ DBGC ( &ctx, "\n" );
+}
diff --git a/src/include/ipxe/mschapv2.h b/src/include/ipxe/mschapv2.h
new file mode 100644
index 0000000..59cf37e
--- /dev/null
+++ b/src/include/ipxe/mschapv2.h
@@ -0,0 +1,59 @@
+#ifndef _IPXE_MSCHAPV2_H
+#define _IPXE_MSCHAPV2_H
+
+/** @file
+ *
+ * MS-CHAPv2 authentication
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+
+/** An MS-CHAPv2 challenge */
+struct mschapv2_challenge {
+ /** Raw bytes */
+ uint8_t byte[16];
+} __attribute__ (( packed ));
+
+/** An MS-CHAPv2 NT response */
+struct mschapv2_nt_response {
+ /** DES-encrypted blocks */
+ uint8_t block[3][8];
+} __attribute__ (( packed ));
+
+/** An MS-CHAPv2 challenge response */
+struct mschapv2_response {
+ /** Peer challenge */
+ struct mschapv2_challenge peer;
+ /** Reserved, must be zero */
+ uint8_t reserved[8];
+ /** NT response */
+ struct mschapv2_nt_response nt;
+ /** Flags, must be zero */
+ uint8_t flags;
+} __attribute__ (( packed ));
+
+/** An MS-CHAPv2 authenticator response */
+struct mschapv2_auth {
+ /** Authenticator response string
+ *
+ * This is an unterminated 42-byte string of the form
+ * "S=<auth_string>" where <auth_string> is the upper-cased
+ * hexadecimal encoding of the actual authenticator response
+ * value. Joy.
+ */
+ char wtf[42];
+} __attribute__ (( packed ));
+
+extern void mschapv2_response ( const char *username, const char *password,
+ const struct mschapv2_challenge *challenge,
+ const struct mschapv2_challenge *peer,
+ struct mschapv2_response *response );
+extern void mschapv2_auth ( const char *username, const char *password,
+ const struct mschapv2_challenge *challenge,
+ const struct mschapv2_response *response,
+ struct mschapv2_auth *auth );
+
+#endif /* _IPXE_MSCHAPV2_H */
diff --git a/src/tests/mschapv2_test.c b/src/tests/mschapv2_test.c
new file mode 100644
index 0000000..3d10ed1
--- /dev/null
+++ b/src/tests/mschapv2_test.c
@@ -0,0 +1,144 @@
+/*
+ * Copyright (C) 2024 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * MS-CHAPv2 authentication self-tests
+ *
+ */
+
+/* Forcibly enable assertions */
+#undef NDEBUG
+
+#include <stdlib.h>
+#include <string.h>
+#include <ipxe/mschapv2.h>
+#include <ipxe/test.h>
+
+/** An MS-CHAPv2 test */
+struct mschapv2_test {
+ /** Username */
+ const char *username;
+ /** Password */
+ const char *password;
+ /** Authenticator challenge */
+ const struct mschapv2_challenge *challenge;
+ /** Peer challenge */
+ const struct mschapv2_challenge *peer;
+ /** Expected challenge response */
+ const struct mschapv2_response *response;
+ /** Expected authenticator response */
+ const struct mschapv2_auth *auth;
+};
+
+/** Define inline data */
+#define DATA(...) { __VA_ARGS__ }
+
+/** Define an MS-CHAPv2 test */
+#define MSCHAPV2_TEST( name, USERNAME, PASSWORD, CHALLENGE, PEER, \
+ RESPONSE, AUTH ) \
+ static const struct mschapv2_challenge name ## _challenge = { \
+ .byte = CHALLENGE, \
+ }; \
+ static const struct mschapv2_challenge name ## _peer = { \
+ .byte = PEER, \
+ }; \
+ static const union { \
+ struct mschapv2_response response; \
+ uint8_t byte[ sizeof ( struct mschapv2_response ) ]; \
+ } name ## _response = { \
+ .byte = RESPONSE, \
+ }; \
+ static const union { \
+ struct mschapv2_auth auth; \
+ uint8_t byte[ sizeof ( struct mschapv2_auth ) ]; \
+ } name ## _auth = { \
+ .byte = AUTH, \
+ }; \
+ static struct mschapv2_test name = { \
+ .username = USERNAME, \
+ .password = PASSWORD, \
+ .challenge = &name ## _challenge, \
+ .peer = &name ## _peer, \
+ .response = &name ## _response.response, \
+ .auth = &name ## _auth.auth, \
+ };
+
+/** RFC 2759 section 9.2 test case */
+MSCHAPV2_TEST ( rfc2759_test,
+ "User", "clientPass",
+ DATA ( 0x5b, 0x5d, 0x7c, 0x7d, 0x7b, 0x3f, 0x2f, 0x3e,
+ 0x3c, 0x2c, 0x60, 0x21, 0x32, 0x26, 0x26, 0x28 ),
+ DATA ( 0x21, 0x40, 0x23, 0x24, 0x25, 0x5e, 0x26, 0x2a,
+ 0x28, 0x29, 0x5f, 0x2b, 0x3a, 0x33, 0x7c, 0x7e ),
+ DATA ( 0x21, 0x40, 0x23, 0x24, 0x25, 0x5e, 0x26, 0x2a,
+ 0x28, 0x29, 0x5f, 0x2b, 0x3a, 0x33, 0x7c, 0x7e,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x82, 0x30, 0x9e, 0xcd, 0x8d, 0x70, 0x8b, 0x5e,
+ 0xa0, 0x8f, 0xaa, 0x39, 0x81, 0xcd, 0x83, 0x54,
+ 0x42, 0x33, 0x11, 0x4a, 0x3d, 0x85, 0xd6, 0xdf,
+ 0x00 ),
+ "S=407A5589115FD0D6209F510FE9C04566932CDA56" );
+
+/**
+ * Report an MS-CHAPv2 test result
+ *
+ * @v test Authentication test
+ * @v file Test code file
+ * @v line Test code line
+ */
+static void mschapv2_okx ( struct mschapv2_test *test,
+ const char *file, unsigned int line ) {
+ struct mschapv2_response response;
+ struct mschapv2_auth auth;
+
+ /* Compute challenge response */
+ mschapv2_response ( test->username, test->password, test->challenge,
+ test->peer, &response );
+ okx ( memcmp ( &response, test->response, sizeof ( response ) ) == 0,
+ file, line );
+
+ /* Compute authenticator response */
+ mschapv2_auth ( test->username, test->password, test->challenge,
+ test->response, &auth );
+ okx ( memcmp ( &auth, test->auth, sizeof ( auth ) ) == 0, file, line );
+}
+#define mschapv2_ok( test ) \
+ mschapv2_okx ( test, __FILE__, __LINE__ )
+
+/**
+ * Perform MS-CHAPv2 self-test
+ *
+ */
+static void mschapv2_test_exec ( void ) {
+
+ mschapv2_ok ( &rfc2759_test );
+}
+
+/** MS-CHAPv2 self-test */
+struct self_test mschapv2_test __self_test = {
+ .name = "mschapv2",
+ .exec = mschapv2_test_exec,
+};
diff --git a/src/tests/tests.c b/src/tests/tests.c
index 282d2eb..90cec94 100644
--- a/src/tests/tests.c
+++ b/src/tests/tests.c
@@ -83,3 +83,4 @@
REQUIRE_OBJECT ( nap_test );
REQUIRE_OBJECT ( x25519_test );
REQUIRE_OBJECT ( des_test );
+REQUIRE_OBJECT ( mschapv2_test );
