Mercurial > dropbear
view curve25519.c @ 1788:1fc0012b9c38
Fix handling of replies to global requests (#112)
The current code assumes that all global requests want / need a reply.
This isn't always true and the request itself indicates if it wants a
reply or not.
It causes a specific problem with [email protected] messages.
These are sent by OpenSSH after authentication to inform the client of
potential other host keys for the host. This can be used to add a new
type of host key or to rotate host keys.
The initial information message from the server is sent as a global
request, but with want_reply set to false. This means that the server
doesn't expect an answer to this message. Instead the client needs to
send a prove request as a reply if it wants to receive proof of
ownership for the host keys.
The bug doesn't cause any current problems with due to how OpenSSH
treats receiving the failure message. It instead treats it as a
keepalive message and further ignores it.
Arguably this is a protocol violation though of Dropbear and it is only
accidental that it doesn't cause a problem with OpenSSH.
The bug was found when adding host keys support to libssh, which is more
strict protocol wise and treats the unexpected failure message an error,
also see https://gitlab.com/libssh/libssh-mirror/-/merge_requests/145
for more information.
The fix here is to honor the want_reply flag in the global request and
to only send a reply if the other side expects a reply.
author | Dirkjan Bussink <d.bussink@gmail.com> |
---|---|
date | Thu, 10 Dec 2020 16:13:13 +0100 |
parents | 41a0ff8d5a89 |
children |
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/* * 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 */