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Diffstat (limited to 'curve25519.c')
| -rw-r--r-- | curve25519.c | 497 |
1 files changed, 497 insertions, 0 deletions
diff --git a/curve25519.c b/curve25519.c new file mode 100644 index 0000000..51e0e76 --- /dev/null +++ b/curve25519.c @@ -0,0 +1,497 @@ +/* + * Dropbear - a SSH2 server + * + * Copyright (c) 2002,2003 Matt Johnston + * All rights reserved. + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. */ + +#include "includes.h" +#include "dbrandom.h" +#include "curve25519.h" + +#if DROPBEAR_CURVE25519 || DROPBEAR_ED25519 + +/* Modified TweetNaCl version 20140427, a self-contained public-domain C library. + * https://tweetnacl.cr.yp.to/ */ + +#define FOR(i,n) for (i = 0;i < n;++i) +#define sv static void + +typedef unsigned char u8; +typedef unsigned long u32; +typedef unsigned long long u64; +typedef long long i64; +typedef i64 gf[16]; + +#if DROPBEAR_CURVE25519 +static const gf + _121665 = {0xDB41,1}; +#endif /* DROPBEAR_CURVE25519 */ +#if DROPBEAR_ED25519 +static const gf + gf0, + gf1 = {1}, + D2 = {0xf159, 0x26b2, 0x9b94, 0xebd6, 0xb156, 0x8283, 0x149a, 0x00e0, 0xd130, 0xeef3, 0x80f2, 0x198e, 0xfce7, 0x56df, 0xd9dc, 0x2406}, + X = {0xd51a, 0x8f25, 0x2d60, 0xc956, 0xa7b2, 0x9525, 0xc760, 0x692c, 0xdc5c, 0xfdd6, 0xe231, 0xc0a4, 0x53fe, 0xcd6e, 0x36d3, 0x2169}, + Y = {0x6658, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666}; +#if DROPBEAR_SIGNKEY_VERIFY +static const gf + D = {0x78a3, 0x1359, 0x4dca, 0x75eb, 0xd8ab, 0x4141, 0x0a4d, 0x0070, 0xe898, 0x7779, 0x4079, 0x8cc7, 0xfe73, 0x2b6f, 0x6cee, 0x5203}, + I = {0xa0b0, 0x4a0e, 0x1b27, 0xc4ee, 0xe478, 0xad2f, 0x1806, 0x2f43, 0xd7a7, 0x3dfb, 0x0099, 0x2b4d, 0xdf0b, 0x4fc1, 0x2480, 0x2b83}; +#endif /* DROPBEAR_SIGNKEY_VERIFY */ +#endif /* DROPBEAR_ED25519 */ + +#if DROPBEAR_ED25519 +#if DROPBEAR_SIGNKEY_VERIFY +static int vn(const u8 *x,const u8 *y,u32 n) +{ + u32 i,d = 0; + FOR(i,n) d |= x[i]^y[i]; + return (1 & ((d - 1) >> 8)) - 1; +} + +static int crypto_verify_32(const u8 *x,const u8 *y) +{ + return vn(x,y,32); +} +#endif /* DROPBEAR_SIGNKEY_VERIFY */ + +sv set25519(gf r, const gf a) +{ + int i; + FOR(i,16) r[i]=a[i]; +} +#endif /* DROPBEAR_ED25519 */ + +sv car25519(gf o) +{ + int i; + i64 c; + FOR(i,16) { + o[i]+=(1LL<<16); + c=o[i]>>16; + o[(i+1)*(i<15)]+=c-1+37*(c-1)*(i==15); + o[i]-=c<<16; + } +} + +sv sel25519(gf p,gf q,int b) +{ + i64 t,i,c=~(b-1); + FOR(i,16) { + t= c&(p[i]^q[i]); + p[i]^=t; + q[i]^=t; + } +} + +sv pack25519(u8 *o,const gf n) +{ + int i,j,b; + gf m,t; + FOR(i,16) t[i]=n[i]; + car25519(t); + car25519(t); + car25519(t); + FOR(j,2) { + m[0]=t[0]-0xffed; + for(i=1;i<15;i++) { + m[i]=t[i]-0xffff-((m[i-1]>>16)&1); + m[i-1]&=0xffff; + } + m[15]=t[15]-0x7fff-((m[14]>>16)&1); + b=(m[15]>>16)&1; + m[14]&=0xffff; + sel25519(t,m,1-b); + } + FOR(i,16) { + o[2*i]=t[i]&0xff; + o[2*i+1]=t[i]>>8; + } +} + +#if DROPBEAR_ED25519 +#if DROPBEAR_SIGNKEY_VERIFY +static int neq25519(const gf a, const gf b) +{ + u8 c[32],d[32]; + pack25519(c,a); + pack25519(d,b); + return crypto_verify_32(c,d); +} +#endif /* DROPBEAR_SIGNKEY_VERIFY */ + +static u8 par25519(const gf a) +{ + u8 d[32]; + pack25519(d,a); + return d[0]&1; +} +#endif /* DROPBEAR_ED25519 */ + +sv unpack25519(gf o, const u8 *n) +{ + int i; + FOR(i,16) o[i]=n[2*i]+((i64)n[2*i+1]<<8); + o[15]&=0x7fff; +} + +sv A(gf o,const gf a,const gf b) +{ + int i; + FOR(i,16) o[i]=a[i]+b[i]; +} + +sv Z(gf o,const gf a,const gf b) +{ + int i; + FOR(i,16) o[i]=a[i]-b[i]; +} + +sv M(gf o,const gf a,const gf b) +{ + i64 i,j,t[31]; + FOR(i,31) t[i]=0; + FOR(i,16) FOR(j,16) t[i+j]+=a[i]*b[j]; + FOR(i,15) t[i]+=38*t[i+16]; + FOR(i,16) o[i]=t[i]; + car25519(o); + car25519(o); +} + +sv S(gf o,const gf a) +{ + M(o,a,a); +} + +sv inv25519(gf o,const gf i) +{ + gf c; + int a; + FOR(a,16) c[a]=i[a]; + for(a=253;a>=0;a--) { + S(c,c); + if(a!=2&&a!=4) M(c,c,i); + } + FOR(a,16) o[a]=c[a]; +} + +#if DROPBEAR_ED25519 && DROPBEAR_SIGNKEY_VERIFY +sv pow2523(gf o,const gf i) +{ + gf c; + int a; + FOR(a,16) c[a]=i[a]; + for(a=250;a>=0;a--) { + S(c,c); + if(a!=1) M(c,c,i); + } + FOR(a,16) o[a]=c[a]; +} +#endif /* DROPBEAR_ED25519 && DROPBEAR_SIGNKEY_VERIFY */ + +#if DROPBEAR_CURVE25519 +void dropbear_curve25519_scalarmult(u8 *q,const u8 *n,const u8 *p) +{ + u8 z[32]; + i64 x[80],r,i; + gf a,b,c,d,e,f; + FOR(i,31) z[i]=n[i]; + z[31]=(n[31]&127)|64; + z[0]&=248; + unpack25519(x,p); + FOR(i,16) { + b[i]=x[i]; + d[i]=a[i]=c[i]=0; + } + a[0]=d[0]=1; + for(i=254;i>=0;--i) { + r=(z[i>>3]>>(i&7))&1; + sel25519(a,b,r); + sel25519(c,d,r); + A(e,a,c); + Z(a,a,c); + A(c,b,d); + Z(b,b,d); + S(d,e); + S(f,a); + M(a,c,a); + M(c,b,e); + A(e,a,c); + Z(a,a,c); + S(b,a); + Z(c,d,f); + M(a,c,_121665); + A(a,a,d); + M(c,c,a); + M(a,d,f); + M(d,b,x); + S(b,e); + sel25519(a,b,r); + sel25519(c,d,r); + } + FOR(i,16) { + x[i+16]=a[i]; + x[i+32]=c[i]; + x[i+48]=b[i]; + x[i+64]=d[i]; + } + inv25519(x+32,x+32); + M(x+16,x+16,x+32); + pack25519(q,x+16); +} +#endif /* DROPBEAR_CURVE25519 */ + +#if DROPBEAR_ED25519 +static int crypto_hash(u8 *out,const u8 *m,u64 n) +{ + hash_state hs; + + sha512_init(&hs); + sha512_process(&hs, m, n); + return sha512_done(&hs, out); +} + +sv add(gf p[4],gf q[4]) +{ + gf a,b,c,d,t,e,f,g,h; + + Z(a, p[1], p[0]); + Z(t, q[1], q[0]); + M(a, a, t); + A(b, p[0], p[1]); + A(t, q[0], q[1]); + M(b, b, t); + M(c, p[3], q[3]); + M(c, c, D2); + M(d, p[2], q[2]); + A(d, d, d); + Z(e, b, a); + Z(f, d, c); + A(g, d, c); + A(h, b, a); + + M(p[0], e, f); + M(p[1], h, g); + M(p[2], g, f); + M(p[3], e, h); +} + +sv cswap(gf p[4],gf q[4],u8 b) +{ + int i; + FOR(i,4) + sel25519(p[i],q[i],b); +} + +sv pack(u8 *r,gf p[4]) +{ + gf tx, ty, zi; + inv25519(zi, p[2]); + M(tx, p[0], zi); + M(ty, p[1], zi); + pack25519(r, ty); + r[31] ^= par25519(tx) << 7; +} + +sv scalarmult(gf p[4],gf q[4],const u8 *s) +{ + int i; + set25519(p[0],gf0); + set25519(p[1],gf1); + set25519(p[2],gf1); + set25519(p[3],gf0); + for (i = 255;i >= 0;--i) { + u8 b = (s[i/8]>>(i&7))&1; + cswap(p,q,b); + add(q,p); + add(p,p); + cswap(p,q,b); + } +} + +sv scalarbase(gf p[4],const u8 *s) +{ + gf q[4]; + set25519(q[0],X); + set25519(q[1],Y); + set25519(q[2],gf1); + M(q[3],X,Y); + scalarmult(p,q,s); +} + +void dropbear_ed25519_make_key(u8 *pk,u8 *sk) +{ + u8 d[64]; + gf p[4]; + + genrandom(sk, 32); + + crypto_hash(d, sk, 32); + d[0] &= 248; + d[31] &= 127; + d[31] |= 64; + + scalarbase(p,d); + pack(pk,p); +} + +static const u64 L[32] = {0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x10}; + +sv modL(u8 *r,i64 x[64]) +{ + i64 carry,i,j; + for (i = 63;i >= 32;--i) { + carry = 0; + for (j = i - 32;j < i - 12;++j) { + x[j] += carry - 16 * x[i] * L[j - (i - 32)]; + carry = (x[j] + 128) >> 8; + x[j] -= carry << 8; + } + x[j] += carry; + x[i] = 0; + } + carry = 0; + FOR(j,32) { + x[j] += carry - (x[31] >> 4) * L[j]; + carry = x[j] >> 8; + x[j] &= 255; + } + FOR(j,32) x[j] -= carry * L[j]; + FOR(i,32) { + x[i+1] += x[i] >> 8; + r[i] = x[i] & 255; + } +} + +sv reduce(u8 *r) +{ + i64 x[64],i; + FOR(i,64) x[i] = (u64) r[i]; + FOR(i,64) r[i] = 0; + modL(r,x); +} + +void dropbear_ed25519_sign(const u8 *m,u32 mlen,u8 *s,u32 *slen,const u8 *sk, const u8 *pk) +{ + hash_state hs; + u8 d[64],h[64],r[64]; + i64 x[64]; + gf p[4]; + u32 i,j; + + crypto_hash(d, sk, 32); + d[0] &= 248; + d[31] &= 127; + d[31] |= 64; + + *slen = 64; + + sha512_init(&hs); + sha512_process(&hs,d + 32,32); + sha512_process(&hs,m,mlen); + sha512_done(&hs,r); + reduce(r); + scalarbase(p,r); + pack(s,p); + + sha512_init(&hs); + sha512_process(&hs,s,32); + sha512_process(&hs,pk,32); + sha512_process(&hs,m,mlen); + sha512_done(&hs,h); + reduce(h); + + FOR(i,64) x[i] = 0; + FOR(i,32) x[i] = (u64) r[i]; + FOR(i,32) FOR(j,32) x[i+j] += h[i] * (u64) d[j]; + modL(s + 32,x); +} + +#if DROPBEAR_SIGNKEY_VERIFY +static int unpackneg(gf r[4],const u8 p[32]) +{ + gf t, chk, num, den, den2, den4, den6; + set25519(r[2],gf1); + unpack25519(r[1],p); + S(num,r[1]); + M(den,num,D); + Z(num,num,r[2]); + A(den,r[2],den); + + S(den2,den); + S(den4,den2); + M(den6,den4,den2); + M(t,den6,num); + M(t,t,den); + + pow2523(t,t); + M(t,t,num); + M(t,t,den); + M(t,t,den); + M(r[0],t,den); + + S(chk,r[0]); + M(chk,chk,den); + if (neq25519(chk, num)) M(r[0],r[0],I); + + S(chk,r[0]); + M(chk,chk,den); + if (neq25519(chk, num)) return -1; + + if (par25519(r[0]) == (p[31]>>7)) Z(r[0],gf0,r[0]); + + M(r[3],r[0],r[1]); + return 0; +} + +int dropbear_ed25519_verify(const u8 *m,u32 mlen,const u8 *s,u32 slen,const u8 *pk) +{ + hash_state hs; + u8 t[32],h[64]; + gf p[4],q[4]; + + if (slen < 64) return -1; + + if (unpackneg(q,pk)) return -1; + + sha512_init(&hs); + sha512_process(&hs,s,32); + sha512_process(&hs,pk,32); + sha512_process(&hs,m,mlen); + sha512_done(&hs,h); + + reduce(h); + scalarmult(p,q,h); + + scalarbase(q,s + 32); + add(p,q); + pack(t,p); + + if (crypto_verify_32(s, t)) + return -1; + + return 0; +} +#endif /* DROPBEAR_SIGNKEY_VERIFY */ + +#endif /* DROPBEAR_ED25519 */ + +#endif /* DROPBEAR_CURVE25519 || DROPBEAR_ED25519 */ |