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Diffstat (limited to 'src/crypto/mschapv2.c')
| -rw-r--r-- | src/crypto/mschapv2.c | 363 |
1 files changed, 363 insertions, 0 deletions
diff --git a/src/crypto/mschapv2.c b/src/crypto/mschapv2.c new file mode 100644 index 00000000..ac55fec1 --- /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" ); +} |