/* * HMAC_DRBG implementation (NIST SP 800-90) * * Copyright (C) 2014, ARM Limited, All Rights Reserved * * This file is part of mbed TLS (https://tls.mbed.org) * * 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 * (at your option) 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. */ /* * The NIST SP 800-90A DRBGs are described in the following publication. * http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf * References below are based on rev. 1 (January 2012). */ #if !defined(POLARSSL_CONFIG_FILE) #include "mbedtls/config.h" #else #include POLARSSL_CONFIG_FILE #endif #if defined(POLARSSL_HMAC_DRBG_C) #include "mbedtls/hmac_drbg.h" #include #if defined(POLARSSL_FS_IO) #include #endif #if defined(POLARSSL_SELF_TEST) #if defined(POLARSSL_PLATFORM_C) #include "mbedtls/platform.h" #else #include #define polarssl_printf printf #endif /* POLARSSL_SELF_TEST */ #endif /* POLARSSL_PLATFORM_C */ /* Implementation that should never be optimized out by the compiler */ static void polarssl_zeroize( void *v, size_t n ) { volatile unsigned char *p = v; while( n-- ) *p++ = 0; } /* * HMAC_DRBG update, using optional additional data (10.1.2.2) */ void hmac_drbg_update( hmac_drbg_context *ctx, const unsigned char *additional, size_t add_len ) { size_t md_len = md_get_size( ctx->md_ctx.md_info ); unsigned char rounds = ( additional != NULL && add_len != 0 ) ? 2 : 1; unsigned char sep[1]; unsigned char K[POLARSSL_MD_MAX_SIZE]; for( sep[0] = 0; sep[0] < rounds; sep[0]++ ) { /* Step 1 or 4 */ md_hmac_reset( &ctx->md_ctx ); md_hmac_update( &ctx->md_ctx, ctx->V, md_len ); md_hmac_update( &ctx->md_ctx, sep, 1 ); if( rounds == 2 ) md_hmac_update( &ctx->md_ctx, additional, add_len ); md_hmac_finish( &ctx->md_ctx, K ); /* Step 2 or 5 */ md_hmac_starts( &ctx->md_ctx, K, md_len ); md_hmac_update( &ctx->md_ctx, ctx->V, md_len ); md_hmac_finish( &ctx->md_ctx, ctx->V ); } } /* * Simplified HMAC_DRBG initialisation (for use with deterministic ECDSA) */ int hmac_drbg_init_buf( hmac_drbg_context *ctx, const md_info_t * md_info, const unsigned char *data, size_t data_len ) { int ret; memset( ctx, 0, sizeof( hmac_drbg_context ) ); md_init( &ctx->md_ctx ); if( ( ret = md_setup( &ctx->md_ctx, md_info, 1 ) ) != 0 ) return( ret ); /* * Set initial working state. * Use the V memory location, which is currently all 0, to initialize the * MD context with an all-zero key. Then set V to its initial value. */ md_hmac_starts( &ctx->md_ctx, ctx->V, md_get_size( md_info ) ); memset( ctx->V, 0x01, md_get_size( md_info ) ); hmac_drbg_update( ctx, data, data_len ); return( 0 ); } /* * HMAC_DRBG reseeding: 10.1.2.4 (arabic) + 9.2 (Roman) */ int hmac_drbg_reseed( hmac_drbg_context *ctx, const unsigned char *additional, size_t len ) { unsigned char seed[POLARSSL_HMAC_DRBG_MAX_SEED_INPUT]; size_t seedlen; /* III. Check input length */ if( len > POLARSSL_HMAC_DRBG_MAX_INPUT || ctx->entropy_len + len > POLARSSL_HMAC_DRBG_MAX_SEED_INPUT ) { return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG ); } memset( seed, 0, POLARSSL_HMAC_DRBG_MAX_SEED_INPUT ); /* IV. Gather entropy_len bytes of entropy for the seed */ if( ctx->f_entropy( ctx->p_entropy, seed, ctx->entropy_len ) != 0 ) return( POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED ); seedlen = ctx->entropy_len; /* 1. Concatenate entropy and additional data if any */ if( additional != NULL && len != 0 ) { memcpy( seed + seedlen, additional, len ); seedlen += len; } /* 2. Update state */ hmac_drbg_update( ctx, seed, seedlen ); /* 3. Reset reseed_counter */ ctx->reseed_counter = 1; /* 4. Done */ return( 0 ); } /* * HMAC_DRBG initialisation (10.1.2.3 + 9.1) */ int hmac_drbg_init( hmac_drbg_context *ctx, const md_info_t * md_info, int (*f_entropy)(void *, unsigned char *, size_t), void *p_entropy, const unsigned char *custom, size_t len ) { int ret; size_t entropy_len, md_size; memset( ctx, 0, sizeof( hmac_drbg_context ) ); md_init( &ctx->md_ctx ); if( ( ret = md_setup( &ctx->md_ctx, md_info, 1 ) ) != 0 ) return( ret ); md_size = md_get_size( md_info ); /* * Set initial working state. * Use the V memory location, which is currently all 0, to initialize the * MD context with an all-zero key. Then set V to its initial value. */ md_hmac_starts( &ctx->md_ctx, ctx->V, md_size ); memset( ctx->V, 0x01, md_size ); ctx->f_entropy = f_entropy; ctx->p_entropy = p_entropy; ctx->reseed_interval = POLARSSL_HMAC_DRBG_RESEED_INTERVAL; /* * See SP800-57 5.6.1 (p. 65-66) for the security strength provided by * each hash function, then according to SP800-90A rev1 10.1 table 2, * min_entropy_len (in bits) is security_strength. * * (This also matches the sizes used in the NIST test vectors.) */ entropy_len = md_size <= 20 ? 16 : /* 160-bits hash -> 128 bits */ md_size <= 28 ? 24 : /* 224-bits hash -> 192 bits */ 32; /* better (256+) -> 256 bits */ /* * For initialisation, use more entropy to emulate a nonce * (Again, matches test vectors.) */ ctx->entropy_len = entropy_len * 3 / 2; if( ( ret = hmac_drbg_reseed( ctx, custom, len ) ) != 0 ) return( ret ); ctx->entropy_len = entropy_len; return( 0 ); } /* * Set prediction resistance */ void hmac_drbg_set_prediction_resistance( hmac_drbg_context *ctx, int resistance ) { ctx->prediction_resistance = resistance; } /* * Set entropy length grabbed for reseeds */ void hmac_drbg_set_entropy_len( hmac_drbg_context *ctx, size_t len ) { ctx->entropy_len = len; } /* * Set reseed interval */ void hmac_drbg_set_reseed_interval( hmac_drbg_context *ctx, int interval ) { ctx->reseed_interval = interval; } /* * HMAC_DRBG random function with optional additional data: * 10.1.2.5 (arabic) + 9.3 (Roman) */ int hmac_drbg_random_with_add( void *p_rng, unsigned char *output, size_t out_len, const unsigned char *additional, size_t add_len ) { int ret; hmac_drbg_context *ctx = (hmac_drbg_context *) p_rng; size_t md_len = md_get_size( ctx->md_ctx.md_info ); size_t left = out_len; unsigned char *out = output; /* II. Check request length */ if( out_len > POLARSSL_HMAC_DRBG_MAX_REQUEST ) return( POLARSSL_ERR_HMAC_DRBG_REQUEST_TOO_BIG ); /* III. Check input length */ if( add_len > POLARSSL_HMAC_DRBG_MAX_INPUT ) return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG ); /* 1. (aka VII and IX) Check reseed counter and PR */ if( ctx->f_entropy != NULL && /* For no-reseeding instances */ ( ctx->prediction_resistance == POLARSSL_HMAC_DRBG_PR_ON || ctx->reseed_counter > ctx->reseed_interval ) ) { if( ( ret = hmac_drbg_reseed( ctx, additional, add_len ) ) != 0 ) return( ret ); add_len = 0; /* VII.4 */ } /* 2. Use additional data if any */ if( additional != NULL && add_len != 0 ) hmac_drbg_update( ctx, additional, add_len ); /* 3, 4, 5. Generate bytes */ while( left != 0 ) { size_t use_len = left > md_len ? md_len : left; md_hmac_reset( &ctx->md_ctx ); md_hmac_update( &ctx->md_ctx, ctx->V, md_len ); md_hmac_finish( &ctx->md_ctx, ctx->V ); memcpy( out, ctx->V, use_len ); out += use_len; left -= use_len; } /* 6. Update */ hmac_drbg_update( ctx, additional, add_len ); /* 7. Update reseed counter */ ctx->reseed_counter++; /* 8. Done */ return( 0 ); } /* * HMAC_DRBG random function */ int hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len ) { return( hmac_drbg_random_with_add( p_rng, output, out_len, NULL, 0 ) ); } /* * Free an HMAC_DRBG context */ void hmac_drbg_free( hmac_drbg_context *ctx ) { if( ctx == NULL ) return; md_free( &ctx->md_ctx ); polarssl_zeroize( ctx, sizeof( hmac_drbg_context ) ); } #if defined(POLARSSL_FS_IO) int hmac_drbg_write_seed_file( hmac_drbg_context *ctx, const char *path ) { int ret; FILE *f; unsigned char buf[ POLARSSL_HMAC_DRBG_MAX_INPUT ]; if( ( f = fopen( path, "wb" ) ) == NULL ) return( POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR ); if( ( ret = hmac_drbg_random( ctx, buf, sizeof( buf ) ) ) != 0 ) goto exit; if( fwrite( buf, 1, sizeof( buf ), f ) != sizeof( buf ) ) { ret = POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR; goto exit; } ret = 0; exit: fclose( f ); return( ret ); } int hmac_drbg_update_seed_file( hmac_drbg_context *ctx, const char *path ) { FILE *f; size_t n; unsigned char buf[ POLARSSL_HMAC_DRBG_MAX_INPUT ]; if( ( f = fopen( path, "rb" ) ) == NULL ) return( POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR ); fseek( f, 0, SEEK_END ); n = (size_t) ftell( f ); fseek( f, 0, SEEK_SET ); if( n > POLARSSL_HMAC_DRBG_MAX_INPUT ) { fclose( f ); return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG ); } if( fread( buf, 1, n, f ) != n ) { fclose( f ); return( POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR ); } fclose( f ); hmac_drbg_update( ctx, buf, n ); return( hmac_drbg_write_seed_file( ctx, path ) ); } #endif /* POLARSSL_FS_IO */ #if defined(POLARSSL_SELF_TEST) #if !defined(POLARSSL_SHA1_C) /* Dummy checkup routine */ int hmac_drbg_self_test( int verbose ) { if( verbose != 0 ) polarssl_printf( "\n" ); return( 0 ); } #else #define OUTPUT_LEN 80 /* From a NIST PR=true test vector */ static const unsigned char entropy_pr[] = { 0xa0, 0xc9, 0xab, 0x58, 0xf1, 0xe2, 0xe5, 0xa4, 0xde, 0x3e, 0xbd, 0x4f, 0xf7, 0x3e, 0x9c, 0x5b, 0x64, 0xef, 0xd8, 0xca, 0x02, 0x8c, 0xf8, 0x11, 0x48, 0xa5, 0x84, 0xfe, 0x69, 0xab, 0x5a, 0xee, 0x42, 0xaa, 0x4d, 0x42, 0x17, 0x60, 0x99, 0xd4, 0x5e, 0x13, 0x97, 0xdc, 0x40, 0x4d, 0x86, 0xa3, 0x7b, 0xf5, 0x59, 0x54, 0x75, 0x69, 0x51, 0xe4 }; static const unsigned char result_pr[OUTPUT_LEN] = { 0x9a, 0x00, 0xa2, 0xd0, 0x0e, 0xd5, 0x9b, 0xfe, 0x31, 0xec, 0xb1, 0x39, 0x9b, 0x60, 0x81, 0x48, 0xd1, 0x96, 0x9d, 0x25, 0x0d, 0x3c, 0x1e, 0x94, 0x10, 0x10, 0x98, 0x12, 0x93, 0x25, 0xca, 0xb8, 0xfc, 0xcc, 0x2d, 0x54, 0x73, 0x19, 0x70, 0xc0, 0x10, 0x7a, 0xa4, 0x89, 0x25, 0x19, 0x95, 0x5e, 0x4b, 0xc6, 0x00, 0x1d, 0x7f, 0x4e, 0x6a, 0x2b, 0xf8, 0xa3, 0x01, 0xab, 0x46, 0x05, 0x5c, 0x09, 0xa6, 0x71, 0x88, 0xf1, 0xa7, 0x40, 0xee, 0xf3, 0xe1, 0x5c, 0x02, 0x9b, 0x44, 0xaf, 0x03, 0x44 }; /* From a NIST PR=false test vector */ static const unsigned char entropy_nopr[] = { 0x79, 0x34, 0x9b, 0xbf, 0x7c, 0xdd, 0xa5, 0x79, 0x95, 0x57, 0x86, 0x66, 0x21, 0xc9, 0x13, 0x83, 0x11, 0x46, 0x73, 0x3a, 0xbf, 0x8c, 0x35, 0xc8, 0xc7, 0x21, 0x5b, 0x5b, 0x96, 0xc4, 0x8e, 0x9b, 0x33, 0x8c, 0x74, 0xe3, 0xe9, 0x9d, 0xfe, 0xdf }; static const unsigned char result_nopr[OUTPUT_LEN] = { 0xc6, 0xa1, 0x6a, 0xb8, 0xd4, 0x20, 0x70, 0x6f, 0x0f, 0x34, 0xab, 0x7f, 0xec, 0x5a, 0xdc, 0xa9, 0xd8, 0xca, 0x3a, 0x13, 0x3e, 0x15, 0x9c, 0xa6, 0xac, 0x43, 0xc6, 0xf8, 0xa2, 0xbe, 0x22, 0x83, 0x4a, 0x4c, 0x0a, 0x0a, 0xff, 0xb1, 0x0d, 0x71, 0x94, 0xf1, 0xc1, 0xa5, 0xcf, 0x73, 0x22, 0xec, 0x1a, 0xe0, 0x96, 0x4e, 0xd4, 0xbf, 0x12, 0x27, 0x46, 0xe0, 0x87, 0xfd, 0xb5, 0xb3, 0xe9, 0x1b, 0x34, 0x93, 0xd5, 0xbb, 0x98, 0xfa, 0xed, 0x49, 0xe8, 0x5f, 0x13, 0x0f, 0xc8, 0xa4, 0x59, 0xb7 }; /* "Entropy" from buffer */ static size_t test_offset; static int hmac_drbg_self_test_entropy( void *data, unsigned char *buf, size_t len ) { const unsigned char *p = data; memcpy( buf, p + test_offset, len ); test_offset += len; return( 0 ); } #define CHK( c ) if( (c) != 0 ) \ { \ if( verbose != 0 ) \ polarssl_printf( "failed\n" ); \ return( 1 ); \ } /* * Checkup routine for HMAC_DRBG with SHA-1 */ int hmac_drbg_self_test( int verbose ) { hmac_drbg_context ctx; unsigned char buf[OUTPUT_LEN]; const md_info_t *md_info = md_info_from_type( POLARSSL_MD_SHA1 ); /* * PR = True */ if( verbose != 0 ) polarssl_printf( " HMAC_DRBG (PR = True) : " ); test_offset = 0; CHK( hmac_drbg_init( &ctx, md_info, hmac_drbg_self_test_entropy, (void *) entropy_pr, NULL, 0 ) ); hmac_drbg_set_prediction_resistance( &ctx, POLARSSL_HMAC_DRBG_PR_ON ); CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) ); CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) ); CHK( memcmp( buf, result_pr, OUTPUT_LEN ) ); hmac_drbg_free( &ctx ); if( verbose != 0 ) polarssl_printf( "passed\n" ); /* * PR = False */ if( verbose != 0 ) polarssl_printf( " HMAC_DRBG (PR = False) : " ); test_offset = 0; CHK( hmac_drbg_init( &ctx, md_info, hmac_drbg_self_test_entropy, (void *) entropy_nopr, NULL, 0 ) ); CHK( hmac_drbg_reseed( &ctx, NULL, 0 ) ); CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) ); CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) ); CHK( memcmp( buf, result_nopr, OUTPUT_LEN ) ); hmac_drbg_free( &ctx ); if( verbose != 0 ) polarssl_printf( "passed\n" ); if( verbose != 0 ) polarssl_printf( "\n" ); return( 0 ); } #endif /* POLARSSL_SHA1_C */ #endif /* POLARSSL_SELF_TEST */ #endif /* POLARSSL_HMAC_DRBG_C */