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annotate libtomcrypt/src/encauth/ocb3/ocb3_decrypt_last.c @ 1930:299f4f19ba19

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Add /usr/sbin and /sbin to default root PATH When dropbear is used in a very restricted environment (such as in a initrd), the default user shell is often also very restricted and doesn't take care of setting the PATH so the user ends up with the PATH set by dropbear. Unfortunately, dropbear always sets "/usr/bin:/bin" as default PATH even for the root user which should have /usr/sbin and /sbin too. For a concrete instance of this problem, see the "Remote Unlocking" section in this tutorial: https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/ It speaks of a bug in the initramfs script because it's written "blkid" instead of "/sbin/blkid"... this is just because the scripts from the initramfs do not expect to have a PATH without the sbin directories and because dropbear is not setting the PATH appropriately for the root user. I'm thus suggesting to use the attached patch to fix this misbehaviour (I did not test it, but it's easy enough). It might seem anecdotic but multiple Kali users have been bitten by this. From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403
author Raphael Hertzog <hertzog@debian.org>
date Mon, 09 Jul 2018 16:27:53 +0200
parents 6dba84798cd5
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
1471
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9
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10 /**
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11 @file ocb3_decrypt_last.c
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12 OCB implementation, internal helper, by Karel Miko
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13 */
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14 #include "tomcrypt.h"
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15
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16 #ifdef LTC_OCB3_MODE
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17
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18 /**
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19 Finish an OCB (decryption) stream
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20 @param ocb The OCB state
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21 @param ct The remaining ciphertext
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22 @param ctlen The length of the ciphertext (octets)
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23 @param pt [out] The output buffer
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24 @return CRYPT_OK if successful
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25 */
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26 int ocb3_decrypt_last(ocb3_state *ocb, const unsigned char *ct, unsigned long ctlen, unsigned char *pt)
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27 {
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28 unsigned char iOffset_star[MAXBLOCKSIZE];
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29 unsigned char iPad[MAXBLOCKSIZE];
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30 int err, x, full_blocks, full_blocks_len, last_block_len;
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31
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32 LTC_ARGCHK(ocb != NULL);
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33 if (ct == NULL) LTC_ARGCHK(ctlen == 0);
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34 if (ctlen != 0) {
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35 LTC_ARGCHK(ct != NULL);
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36 LTC_ARGCHK(pt != NULL);
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37 }
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38
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39 if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
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40 goto LBL_ERR;
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41 }
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42
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43 full_blocks = ctlen/ocb->block_len;
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44 full_blocks_len = full_blocks * ocb->block_len;
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45 last_block_len = ctlen - full_blocks_len;
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46
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47 /* process full blocks first */
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48 if (full_blocks>0) {
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49 if ((err = ocb3_decrypt(ocb, ct, full_blocks_len, pt)) != CRYPT_OK) {
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50 goto LBL_ERR;
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51 }
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52 }
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53
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54 if (last_block_len>0) {
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55 /* Offset_* = Offset_m xor L_* */
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56 ocb3_int_xor_blocks(iOffset_star, ocb->Offset_current, ocb->L_star, ocb->block_len);
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57
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58 /* Pad = ENCIPHER(K, Offset_*) */
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59 if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(iOffset_star, iPad, &ocb->key)) != CRYPT_OK) {
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60 goto LBL_ERR;
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61 }
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62
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63 /* P_* = C_* xor Pad[1..bitlen(C_*)] */
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64 ocb3_int_xor_blocks(pt+full_blocks_len, (unsigned char *)ct+full_blocks_len, iPad, last_block_len);
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65
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66 /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
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67 ocb3_int_xor_blocks(ocb->checksum, ocb->checksum, pt+full_blocks_len, last_block_len);
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68 for(x=last_block_len; x<ocb->block_len; x++) {
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69 if (x == last_block_len)
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70 ocb->checksum[x] ^= 0x80;
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71 else
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72 ocb->checksum[x] ^= 0x00;
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73 }
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74
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75 /* Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A) */
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76 /* at this point we calculate only: Tag_part = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) */
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77 for(x=0; x<ocb->block_len; x++) {
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78 ocb->tag_part[x] = (ocb->checksum[x] ^ iOffset_star[x]) ^ ocb->L_dollar[x];
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79 }
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80 if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(ocb->tag_part, ocb->tag_part, &ocb->key)) != CRYPT_OK) {
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81 goto LBL_ERR;
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82 }
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83 }
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84 else {
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85 /* Tag = ENCIPHER(K, Checksum_m xor Offset_m xor L_$) xor HASH(K,A) */
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86 /* at this point we calculate only: Tag_part = ENCIPHER(K, Checksum_m xor Offset_m xor L_$) */
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87 for(x=0; x<ocb->block_len; x++) {
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88 ocb->tag_part[x] = (ocb->checksum[x] ^ ocb->Offset_current[x]) ^ ocb->L_dollar[x];
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89 }
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90 if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(ocb->tag_part, ocb->tag_part, &ocb->key)) != CRYPT_OK) {
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91 goto LBL_ERR;
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92 }
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93 }
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94
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95 err = CRYPT_OK;
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96
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97 LBL_ERR:
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98 #ifdef LTC_CLEAN_STACK
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99 zeromem(iOffset_star, MAXBLOCKSIZE);
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100 zeromem(iPad, MAXBLOCKSIZE);
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101 #endif
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102
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103 return err;
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104 }
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105
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106 #endif
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107
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108 /* ref: $Format:%D$ */
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109 /* git commit: $Format:%H$ */
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110 /* commit time: $Format:%ai$ */