/* * Copyright 1985, 1986, 1987, 1988 by the Massachusetts Institute * of Technology. * * For copying and distribution information, please see the file * . * * These routines perform encryption and decryption using the DES * private key algorithm, or else a subset of it-- fewer inner loops. * ( AUTH_DES_ITER defaults to 16, may be less) * * Under U.S. law, this software may not be exported outside the US * without license from the U.S. Commerce department. * * The key schedule is passed as an arg, as well as the cleartext or * ciphertext. The cleartext and ciphertext should be in host order. * * These routines form the library interface to the des facilities. * * spm 8/85 MIT project athena */ #include #include #include #include #include "des_internal.h" #define XPRT_PCBC_ENCRYPT extern int des_debug; extern int des_debug_print(); extern int des_ecb_encrypt(); /* * pcbc_encrypt is an "error propagation chaining" encrypt operation * for DES, similar to CBC, but that, on encryption, "xor"s the * plaintext of block N with the ciphertext resulting from block N, * then "xor"s that result with the plaintext of block N+1 prior to * encrypting block N+1. (decryption the appropriate inverse. This * "pcbc" mode propagates a single bit error anywhere in either the * cleartext or ciphertext chain all the way through to the end. In * contrast, CBC mode limits a single bit error in the ciphertext to * affect only the current (8byte) block and the subsequent block. * * performs pcbc error-propagation chaining operation by xor-ing block * N+1 with both the plaintext (block N) and the ciphertext from block * N. Either encrypts from cleartext to ciphertext, if encrypt != 0 * or decrypts from ciphertext to cleartext, if encrypt == 0 * * NOTE-- the output is ALWAYS an multiple of 8 bytes long. If not * enough space was provided, your program will get trashed. * * For encryption, the cleartext string is null padded, at the end, to * an integral multiple of eight bytes. * * For decryption, the ciphertext will be used in integral multiples * of 8 bytes, but only the first "length" bytes returned into the * cleartext. * * This is NOT a standard mode of operation. * */ afs_int32 des_pcbc_encrypt(in,out,length,key,iv,encrypt) des_cblock *in; /* >= length bytes of inputtext */ des_cblock *out; /* >= length bytes of outputtext */ register afs_int32 length; /* in bytes */ int encrypt; /* 0 ==> decrypt, else encrypt */ des_key_schedule key; /* precomputed key schedule */ des_cblock *iv; /* 8 bytes of ivec */ { register afs_uint32 *input = (afs_uint32 *) in; register afs_uint32 *output = (afs_uint32 *) out; register afs_uint32 *ivec = (afs_uint32 *) iv; afs_uint32 i,j; afs_uint32 t_input[2]; afs_uint32 t_output[2]; unsigned char *t_in_p = (unsigned char *) t_input; afs_uint32 xor_0, xor_1; if (encrypt) { #ifdef MUSTALIGN if ((afs_int32) ivec & 3) { bcopy((char *)ivec++,(char *)&xor_0,sizeof(xor_0)); bcopy((char *)ivec,(char *)&xor_1,sizeof(xor_1)); } else #endif { xor_0 = *ivec++; xor_1 = *ivec; } for (i = 0; length > 0; i++, length -= 8) { /* get input */ #ifdef MUSTALIGN if ((afs_int32) input & 3) { bcopy((char *)input,(char *)&t_input[0],sizeof(t_input[0])); bcopy((char *)(input+1),(char *)&t_input[1],sizeof(t_input[1])); } else #endif { t_input[0] = *input; t_input[1] = *(input+1); } /* zero pad */ if (length < 8) { for (j = length; j <= 7; j++) *(t_in_p+j)= 0; } #ifdef DEBUG if (des_debug) des_debug_print("clear",length,t_input[0],t_input[1]); #endif /* do the xor for cbc into the temp */ t_input[0] ^= xor_0 ; t_input[1] ^= xor_1 ; /* encrypt */ (void) des_ecb_encrypt(t_input,t_output,key,encrypt); /* * We want to XOR with both the plaintext and ciphertext * of the previous block, before we write the output, in * case both input and output are the same space. */ #ifdef MUSTALIGN if ((afs_int32) input & 3) { bcopy((char *)input++,(char *)&xor_0,sizeof(xor_0)); xor_0 ^= t_output[0]; bcopy((char *)input++,(char *)&xor_1,sizeof(xor_1)); xor_1 ^= t_output[1]; } else #endif { xor_0 = *input++ ^ t_output[0]; xor_1 = *input++ ^ t_output[1]; } /* copy temp output and save it for cbc */ #ifdef MUSTALIGN if ((afs_int32) output & 3) { bcopy((char *)&t_output[0],(char *)output++, sizeof(t_output[0])); bcopy((char *)&t_output[1],(char *)output++, sizeof(t_output[1])); } else #endif { *output++ = t_output[0]; *output++ = t_output[1]; } #ifdef DEBUG if (des_debug) { des_debug_print("xor'ed",i,t_input[0],t_input[1]); des_debug_print("cipher",i,t_output[0],t_output[1]); } #endif } t_output[0] = 0; t_output[1] = 0; xor_0 = 0; xor_1 = 0; return 0; } else { /* decrypt */ #ifdef MUSTALIGN if ((afs_int32) ivec & 3) { bcopy((char *)ivec++,(char *)&xor_0,sizeof(xor_0)); bcopy((char *)ivec,(char *)&xor_1,sizeof(xor_1)); } else #endif { xor_0 = *ivec++; xor_1 = *ivec; } for (i = 0; length > 0; i++, length -= 8) { /* get input */ #ifdef MUSTALIGN if ((afs_int32) input & 3) { bcopy((char *)input++,(char *)&t_input[0],sizeof(t_input[0])); bcopy((char *)input++,(char *)&t_input[1],sizeof(t_input[1])); } else #endif { t_input[0] = *input++; t_input[1] = *input++; } /* no padding for decrypt */ #ifdef DEBUG if (des_debug) des_debug_print("cipher",i,t_input[0],t_input[1]); #else #ifdef lint i = i; #endif #endif /* encrypt */ (void) des_ecb_encrypt(t_input,t_output,key,encrypt); #ifdef DEBUG if (des_debug) des_debug_print("out pre xor",i,t_output[0],t_output[1]); #endif /* do the xor for cbc into the output */ t_output[0] ^= xor_0 ; t_output[1] ^= xor_1 ; /* copy temp output */ #ifdef MUSTALIGN if ((afs_int32) output & 3) { bcopy((char *)&t_output[0],(char *)output++, sizeof(t_output[0])); bcopy((char *)&t_output[1],(char *)output++, sizeof(t_output[1])); } else #endif { *output++ = t_output[0]; *output++ = t_output[1]; } /* save xor value for next round */ xor_0 = t_output[0] ^ t_input[0]; xor_1 = t_output[1] ^ t_input[1]; #ifdef DEBUG if (des_debug) des_debug_print("clear",i,t_output[0],t_output[1]); #endif } return 0; } }