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libsec: add chacha20 poly1305 aead, allow 64 bit iv's for chacha, add tsmemcmp()

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chacha20 comes in two variants: ietf rfc7539, using 96 bit iv and 32 bit counter
and draft-agl-tls-chacha20poly1305 using 64 bit iv and a 64 bit counter. so
setupChachastate() now takes a ivlen argument which sets the mode.

add ccpoly_encrypt()/ccpoly_decrypt() routines.

to implement timing safe ccpoly_decrypt(), a constant time memcmp was needed, so
adding tsmemcmp() to libsec.
This commit is contained in:
cinap_lenrek 2015-11-26 15:25:10 +01:00
parent 90695e2eb2
commit 254031cf70
7 changed files with 244 additions and 20 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
sys/include/libsec.h
View file

@ -94,13 +94,18 @@ struct Chachastate
};
};
int rounds;
int ivwords;
};
void setupChachastate(Chachastate*, uchar*, ulong, uchar*, int);
void chacha_setblock(Chachastate*, u32int);
void setupChachastate(Chachastate*, uchar*, ulong, uchar*, ulong, int);
void chacha_setiv(Chachastate *, uchar*);
void chacha_setblock(Chachastate*, u64int);
void chacha_encrypt(uchar*, ulong, Chachastate*);
void chacha_encrypt2(uchar*, uchar*, ulong, Chachastate*);
void ccpoly_encrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs);
int ccpoly_decrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs);
/*
* DES definitions
*/
@ -505,3 +510,5 @@ void pbkdf2_x(uchar *p, ulong plen, uchar *s, ulong slen, ulong rounds, uchar *d
void hkdf_x(uchar *salt, ulong nsalt, uchar *info, ulong ninfo, uchar *key, ulong nkey, uchar *d, ulong dlen,
DigestState* (*x)(uchar*, ulong, uchar*, ulong, uchar*, DigestState*), int xlen);
/* timing safe memcmp() */
int tsmemcmp(void*, void*, ulong);

63
sys/man/2/chacha
View file

@ -1,17 +1,15 @@
.TH CHACHA 2
.SH NAME
setupChachastate, chacha_setblock, chacha_encrypt, chacha_encrypt2 - chacha encryption
setupChachastate, chacha_setblock, chacha_setiv, chacha_encrypt, chacha_encrypt2, ccpoly_encrypt, ccpoly_decrypt \- chacha encryption
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.br
.B #include <mp.h>
.br
.B #include <libsec.h>
.PP
.B
void setupChachastate(Chachastate *s, uchar key[], ulong keylen, uchar *nonce, int rounds)
void setupChachastate(Chachastate *s, uchar key[], ulong keylen, uchar *iv, ulong ivlen, int rounds)
.PP
.B
void chacha_encrypt(uchar *data, ulong len, Chachastate *s)
@ -20,7 +18,16 @@ void chacha_encrypt(uchar *data, ulong len, Chachastate *s)
void chacha_encrypt2(uchar *src, uchar *dst, ulong len, Chachastate *s)
.PP
.B
void chacha_setblock(Chachastate *s, u32int blockno)
void chacha_setblock(Chachastate *s, u64int blockno)
.PP
.B
void chacha_setiv(Chachastate *s, uchar *iv);
.PP
.B
void ccpoly_encrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs);
.PP
.B
int ccpoly_decrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs);
.SH DESCRIPTION
.PP
Chacha is D J Berstein's symmetric stream cipher, as modified by RFC7539. It supports
@ -38,14 +45,19 @@ of
bytes, which should normally be
.BR ChachaKeylen ,
a
.I nonce
or initialisation vector of
.B ChachaIVlen
bytes (set to all zeros if the argument is nil),
.I iv
or nonce of
.I ivlen
bytes (can be
.BR ChachaIVlen =12
or 8, set to all zeros if the
.I iv
argument is nil),
and the number of
.I rounds
(set to the default of 20 if the argument is zero).
With a keylength of 256 bits (32 bytes) and 20
With a key length of 256 bits (32 bytes), a nonce of 96 bits (12 bytes)
and 20
.IR rounds ,
the function implements the Chacha20 encryption function of RFC7539.
.PP
@ -77,6 +89,37 @@ without modifying
sets the Chacha block counter for the next encryption to
.IR blockno ,
allowing seeking in an encrypted stream.
.PP
.I Chacha_setiv
sets the the initialization vector (nonce) to
.IR iv .
.PP
.I Ccpoly_encrypt
and
.I ccpoly_decrypt
implement authenticated encryption with associated data (AEAD)
using Chacha cipher and Poly1305 message authentication code
as specified in RFC7539.
These routines require a
.I Chachastate
that has been setup with a new (per key unique) initialization
vector (nonce) on each invocation. The referenced data
.IR dat [ ndat ]
is in-place encrypted or decrypted.
.I Ccpoly_encrypt
produces a 16 byte authentication
.IR tag ,
while
.I ccpoly_decrypt
verifies the
.IR tag ,
returning zero on success or negative on a mismatch.
The
.IR aad [ naad ]
arguments refer to the additional authenticated data
that is included in the
.I tag
calculation, but not encrypted.
.SH SOURCE
.B /sys/src/libsec
.SH SEE ALSO

84
sys/src/libsec/port/ccpoly.c Normal file
View file

@ -0,0 +1,84 @@
#include <u.h>
#include <libc.h>
#include <libsec.h>
static void
ccpolyotk(Chachastate *cs, DigestState *ds)
{
uchar otk[ChachaBsize];
memset(ds, 0, sizeof(*ds));
memset(otk, 0, 32);
chacha_setblock(cs, 0);
chacha_encrypt(otk, ChachaBsize, cs);
poly1305(nil, 0, otk, 32, nil, ds);
}
static void
ccpolymac(uchar *buf, ulong nbuf, DigestState *ds)
{
static uchar zeros[16] = {0};
ulong npad;
if(nbuf == 0)
return;
poly1305(buf, nbuf, nil, 0, nil, ds);
npad = nbuf % 16;
if(npad == 0)
return;
poly1305(zeros, 16 - npad, nil, 0, nil, ds);
}
static void
ccpolytag(ulong ndat, ulong naad, uchar tag[16], DigestState *ds)
{
uchar info[16];
info[0] = naad;
info[1] = naad>>8;
info[2] = naad>>16;
info[3] = naad>>24;
info[4] = 0;
info[5] = 0;
info[6] = 0;
info[7] = 0;
info[8] = ndat;
info[9] = ndat>>8;
info[10] = ndat>>16;
info[11] = ndat>>24;
info[12] = 0;
info[13] = 0;
info[14] = 0;
info[15] = 0;
poly1305(info, 16, nil, 0, tag, ds);
}
void
ccpoly_encrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs)
{
DigestState ds;
ccpolyotk(cs, &ds);
ccpolymac(aad, naad, &ds);
chacha_encrypt(dat, ndat, cs);
ccpolymac(dat, ndat, &ds);
ccpolytag(ndat, naad, tag, &ds);
}
int
ccpoly_decrypt(uchar *dat, ulong ndat, uchar *aad, ulong naad, uchar tag[16], Chachastate *cs)
{
DigestState ds;
uchar tmp[16];
ccpolyotk(cs, &ds);
ccpolymac(aad, naad, &ds);
ccpolymac(dat, ndat, &ds);
ccpolytag(ndat, naad, tmp, &ds);
if(tsmemcmp(tag, tmp, 16) != 0)
return -1;
chacha_encrypt(dat, ndat, cs);
return 0;
}

22
sys/src/libsec/port/chacha.c
View file

@ -54,10 +54,12 @@ load(u32int *d, uchar *s, int nw)
}
void
setupChachastate(Chachastate *s, uchar *key, ulong keylen, uchar *iv, int rounds)
setupChachastate(Chachastate *s, uchar *key, ulong keylen, uchar *iv, ulong ivlen, int rounds)
{
if(keylen != 256/8 && keylen != 128/8)
sysfatal("invalid chacha key length");
if(ivlen != 96/8 && ivlen != 64/8)
sysfatal("invalid chacha iv length");
if(rounds == 0)
rounds = 20;
s->rounds = rounds;
@ -69,19 +71,28 @@ setupChachastate(Chachastate *s, uchar *key, ulong keylen, uchar *iv, int rounds
load(&s->input[4], key, 4);
load(&s->input[8], key, 4);
}
s->ivwords = ivlen/sizeof(u32int);
s->input[12] = 0;
s->input[13] = 0;
if(iv == nil){
s->input[13] = 0;
s->input[14] = 0;
s->input[15] = 0;
}else
load(&s->input[13], iv, 3);
chacha_setiv(s, iv);
}
void
chacha_setblock(Chachastate *s, u32int blockno)
chacha_setiv(Chachastate *s, uchar *iv)
{
load(&s->input[16 - s->ivwords], iv, s->ivwords);
}
void
chacha_setblock(Chachastate *s, u64int blockno)
{
s->input[12] = blockno;
if(s->ivwords == 2)
s->input[13] = blockno>>32;
}
static void
@ -148,7 +159,8 @@ encryptblock(Chachastate *s, uchar *src, uchar *dst)
}
#endif
s->input[12]++;
if(++s->input[12] == 0 && s->ivwords == 2)
s->input[13]++;
}
void

56
sys/src/libsec/port/chachatest.c
View file

@ -31,7 +31,7 @@ u32int rfccount = 1;
char rfctext[] = "Ladies and Gentlemen of the class of '99: If I could offer you only one tip for the future, "
"sunscreen would be it.";
uchar rfcout[3*ChachaBsize];
uchar rfcref[3*ChachaBsize] = {
uchar rfcref[] = {
0x6e, 0x2e, 0x35, 0x9a, 0x25, 0x68, 0xf9, 0x80, 0x41, 0xba, 0x07, 0x28, 0xdd, 0x0d, 0x69, 0x81,
0xe9, 0x7e, 0x7a, 0xec, 0x1d, 0x43, 0x60, 0xc2, 0x0a, 0x27, 0xaf, 0xcc, 0xfd, 0x9f, 0xae, 0x0b,
0xf9, 0x1b, 0x65, 0xc5, 0x52, 0x47, 0x33, 0xab, 0x8f, 0x59, 0x3d, 0xab, 0xcd, 0x62, 0xb3, 0x57,
@ -42,10 +42,26 @@ uchar rfcref[3*ChachaBsize] = {
0x87, 0x4d
};
uchar ccpaad[] = {
0x50, 0x51, 0x52, 0x53, 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
};
uchar ccpkey[] = {
0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
};
uchar ccpiv[] = {
0x07, 0x00, 0x00, 0x00,
0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
};
uchar ccptag[] = {
0x1a, 0xe1, 0x0b, 0x59, 0x4f, 0x09, 0xe2, 0x6a, 0x7e, 0x90, 0x2e, 0xcb, 0xd0, 0x60, 0x06, 0x91,
};
void
main(int argc, char **argv)
{
Chachastate s;
uchar tag[16];
int n;
ARGBEGIN{
@ -54,17 +70,51 @@ main(int argc, char **argv)
print("key:\n");
printblock(rfckey, sizeof(rfckey));
n = strlen(rfctext);
setupChachastate(&s, rfckey, sizeof(rfckey), rfcnonce, 0);
setupChachastate(&s, rfckey, sizeof(rfckey), rfcnonce, sizeof(rfcnonce), 0);
chacha_setblock(&s, rfccount);
print("rfc in:\n");
printblock((uchar*)rfctext, n);
chacha_encrypt2((uchar*)rfctext, rfcout, n, &s);
print("rfc out:\n");
printblock(rfcout, n);
if(memcmp(rfcout, rfcref, sizeof(rfcout)) != 0){
if(memcmp(rfcout, rfcref, sizeof(rfcref)) != 0){
print("failure of vision\n");
exits("wrong");
}
print("\n");
print("ccpoly key:\n");
printblock(ccpkey, sizeof(ccpkey));
print("ccpoly iv:\n");
printblock(ccpiv, sizeof(ccpiv));
setupChachastate(&s, ccpkey, sizeof(ccpkey), ccpiv, sizeof(ccpiv), 20);
memmove(rfcout, rfctext, sizeof(rfctext)-1);
ccpoly_encrypt(rfcout, sizeof(rfctext)-1, ccpaad, sizeof(ccpaad), tag, &s);
print("ccpoly cipher:\n");
printblock(rfcout, sizeof(rfctext)-1);
print("ccpoly tag:\n");
printblock(tag, sizeof(tag));
if(memcmp(tag, ccptag, sizeof(tag)) != 0){
print("bad ccpoly tag\n");
exits("wrong");
}
if(ccpoly_decrypt(rfcout, sizeof(rfctext)-1, ccpaad, sizeof(ccpaad), tag, &s) != 0){
print("ccpoly decryption failed\n");
exits("wrong");
}
if(memcmp(rfcout, rfctext, sizeof(rfctext)-1) != 0){
print("ccpoly bad decryption\n");
exits("wrong");
}
print("passed\n");
exits(nil);
}

2
sys/src/libsec/port/mkfile
View file

@ -27,6 +27,8 @@ CFILES = des.c desmodes.c desECB.c desCBC.c des3ECB.c des3CBC.c\
curve25519_dh.c\
pbkdf2.c\
hkdf.c\
ccpoly.c\
tsmemcmp.c\
ALLOFILES=${CFILES:%.c=%.$O}

26
sys/src/libsec/port/tsmemcmp.c Normal file
View file

@ -0,0 +1,26 @@
#include <u.h>
#include <libc.h>
#include <libsec.h>
/*
* timing safe memcmp()
*/
int
tsmemcmp(void *a1, void *a2, ulong n)
{
int lt, gt, c1, c2, r, m;
uchar *s1, *s2;
r = m = 0;
s1 = a1;
s2 = a2;
while(n--){
c1 = *s1++;
c2 = *s2++;
lt = (c1 - c2) >> 8;
gt = (c2 - c1) >> 8;
r |= (lt - gt) & ~m;
m |= lt | gt;
}
return r;
}