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compat-openssl098.29205
openssl-CVE-2022-4304.patch
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File openssl-CVE-2022-4304.patch of Package compat-openssl098.29205
From aefe424d7695ed13b240673298d340bc552365fe Mon Sep 17 00:00:00 2001 From: Bernd Edlinger <bernd.edlinger@hotmail.de> Date: Mon, 13 Feb 2023 17:46:41 +0100 Subject: [PATCH] Alternative fix for CVE-2022-4304 This is about a timing leak in the topmost limb of the internal result of RSA_private_decrypt, before the padding check. There are in fact at least three bugs together that caused the timing leak: First and probably most important is the fact that the blinding did not use the constant time code path at all when the RSA object was used for a private decrypt, due to the fact that the Montgomery context rsa->_method_mod_n was not set up early enough in rsa_ossl_private_decrypt, when BN_BLINDING_create_param needed it, and that was persisted as blinding->m_ctx, although the RSA object creates the Montgomery context just a bit later. Then the infamous bn_correct_top was used on the secret value right after the blinding was removed. And finally the function BN_bn2binpad did not use the constant-time code path since the BN_FLG_CONSTTIME was not set on the secret value. In order to address the first problem, this patch makes sure that the rsa->_method_mod_n is initialized right before the blinding context. And to fix the second problem, we add a new utility function bn_correct_top_consttime, a const-time variant of bn_correct_top. Together with the fact, that BN_bn2binpad is already constant time if the flag BN_FLG_CONSTTIME is set, this should eliminate the timing oracle completely. In addition the no-asm variant may also have branches that depend on secret values, because the last invocation of bn_sub_words in bn_from_montgomery_word had branches when the function is compiled by certain gcc compiler versions, due to the clumsy coding style. So additionally this patch stream-lined the no-asm C-code in order to avoid branches where possible and improve the resulting code quality. --- CHANGES | 10 +++++ crypto/bn/bn_asm.c | 102 +++++++++++++++++++++++++++++---------------------- crypto/bn/bn_blind.c | 3 + crypto/bn/bn_lcl.h | 26 ++++++------- crypto/bn/bn_lib.c | 22 +++++++++++ crypto/rsa/rsa_eay.c | 8 ++-- 6 files changed, 111 insertions(+), 60 deletions(-) --- a/CHANGES +++ b/CHANGES @@ -4,6 +4,16 @@ Changes between 0.9.8i and 0.9.8j [07 Jan 2009] + *) Reworked the Fix for the Timing Oracle in RSA Decryption (CVE-2022-4304). + The previous fix for this timing side channel turned out to cause + a severe 2-3x performance regression in the typical use case + compared to 1.1.1s. The new fix uses existing constant time + code paths, and restores the previous performance level while + fully eliminating all existing timing side channels. + The fix was developed by Bernd Edlinger with testing support + by Hubert Kario. + [Bernd Edlinger] + *) Properly check EVP_VerifyFinal() and similar return values (CVE-2008-5077). [Ben Laurie, Bodo Moeller, Google Security Team] --- a/crypto/bn/bn_asm.c +++ b/crypto/bn/bn_asm.c @@ -392,24 +392,40 @@ BN_ULONG bn_sub_words(BN_ULONG *r, const for (;;) { - t1=a[0]; t2=b[0]; - r[0]=(t1-t2-c)&BN_MASK2; - if (t1 != t2) c=(t1 < t2); + t1=a[0]; + t2 = (t1 - c) & BN_MASK2; + c = (t2 > t1); + t1 = b[0]; + t1 = (t2 - t1) & BN_MASK2; + r[0] = t1; + c += (t1 > t2); if (--n <= 0) break; - t1=a[1]; t2=b[1]; - r[1]=(t1-t2-c)&BN_MASK2; - if (t1 != t2) c=(t1 < t2); + t1=a[1]; + t2 = (t1 - c) & BN_MASK2; + c = (t2 > t1); + t1 = b[1]; + t1 = (t2 - t1) & BN_MASK2; + r[1] = t1; + c += (t1 > t2); if (--n <= 0) break; - t1=a[2]; t2=b[2]; - r[2]=(t1-t2-c)&BN_MASK2; - if (t1 != t2) c=(t1 < t2); + t1=a[2]; + t2 = (t1 - c) & BN_MASK2; + c = (t2 > t1); + t1 = b[2]; + t1 = (t2 - t1) & BN_MASK2; + r[2] = t1; + c += (t1 > t2); if (--n <= 0) break; - t1=a[3]; t2=b[3]; - r[3]=(t1-t2-c)&BN_MASK2; - if (t1 != t2) c=(t1 < t2); + t1=a[3]; + t2 = (t1 - c) & BN_MASK2; + c = (t2 > t1); + t1 = b[3]; + t1 = (t2 - t1) & BN_MASK2; + r[3] = t1; + c += (t1 > t2); if (--n <= 0) break; a+=4; @@ -440,25 +456,25 @@ BN_ULONG bn_sub_words(BN_ULONG *r, const t=(BN_ULLONG)a*b; \ t1=(BN_ULONG)Lw(t); \ t2=(BN_ULONG)Hw(t); \ - c0=(c0+t1)&BN_MASK2; if ((c0) < t1) t2++; \ - c1=(c1+t2)&BN_MASK2; if ((c1) < t2) c2++; + c0=(c0+t1)&BN_MASK2; t2 += ((c0) < t1); \ + c1=(c1+t2)&BN_MASK2; c2 += ((c1) < t2); #define mul_add_c2(a,b,c0,c1,c2) \ t=(BN_ULLONG)a*b; \ tt=(t+t)&BN_MASK; \ - if (tt < t) c2++; \ + c2 += (tt < t); \ t1=(BN_ULONG)Lw(tt); \ t2=(BN_ULONG)Hw(tt); \ c0=(c0+t1)&BN_MASK2; \ - if ((c0 < t1) && (((++t2)&BN_MASK2) == 0)) c2++; \ - c1=(c1+t2)&BN_MASK2; if ((c1) < t2) c2++; + c2 += ((c0 < t1) && (((++t2)&BN_MASK2) == 0)); \ + c1=(c1+t2)&BN_MASK2; c2 += ((c1) < t2); #define sqr_add_c(a,i,c0,c1,c2) \ t=(BN_ULLONG)a[i]*a[i]; \ t1=(BN_ULONG)Lw(t); \ t2=(BN_ULONG)Hw(t); \ - c0=(c0+t1)&BN_MASK2; if ((c0) < t1) t2++; \ - c1=(c1+t2)&BN_MASK2; if ((c1) < t2) c2++; + c0=(c0+t1)&BN_MASK2; t2 += ((c0) < t1); \ + c1=(c1+t2)&BN_MASK2; c2 += ((c1) < t2); #define sqr_add_c2(a,i,j,c0,c1,c2) \ mul_add_c2((a)[i],(a)[j],c0,c1,c2) @@ -468,24 +484,24 @@ BN_ULONG bn_sub_words(BN_ULONG *r, const #define mul_add_c(a,b,c0,c1,c2) { \ BN_ULONG ta=(a),tb=(b); \ BN_UMULT_LOHI(t1,t2,ta,tb); \ - c0 += t1; t2 += (c0<t1)?1:0; \ - c1 += t2; c2 += (c1<t2)?1:0; \ + c0 += t1; t2 += (c0<t1); \ + c1 += t2; c2 += (c1<t2); \ } #define mul_add_c2(a,b,c0,c1,c2) { \ BN_ULONG ta=(a),tb=(b),t0; \ BN_UMULT_LOHI(t0,t1,ta,tb); \ - c0 += t0; t2 = t1+((c0<t0)?1:0);\ - c1 += t2; c2 += (c1<t2)?1:0; \ - c0 += t0; t1 += (c0<t0)?1:0; \ - c1 += t1; c2 += (c1<t1)?1:0; \ + c0 += t0; t2 = t1+((c0<t0));\ + c1 += t2; c2 += (c1<t2); \ + c0 += t0; t1 += (c0<t0); \ + c1 += t1; c2 += (c1<t1); \ } #define sqr_add_c(a,i,c0,c1,c2) { \ BN_ULONG ta=(a)[i]; \ BN_UMULT_LOHI(t1,t2,ta,ta); \ - c0 += t1; t2 += (c0<t1)?1:0; \ - c1 += t2; c2 += (c1<t2)?1:0; \ + c0 += t1; t2 += (c0<t1); \ + c1 += t2; c2 += (c1<t2); \ } #define sqr_add_c2(a,i,j,c0,c1,c2) \ @@ -497,26 +513,26 @@ BN_ULONG bn_sub_words(BN_ULONG *r, const BN_ULONG ta=(a),tb=(b); \ t1 = ta * tb; \ t2 = BN_UMULT_HIGH(ta,tb); \ - c0 += t1; t2 += (c0<t1)?1:0; \ - c1 += t2; c2 += (c1<t2)?1:0; \ + c0 += t1; t2 += (c0<t1); \ + c1 += t2; c2 += (c1<t2); \ } #define mul_add_c2(a,b,c0,c1,c2) { \ BN_ULONG ta=(a),tb=(b),t0; \ t1 = BN_UMULT_HIGH(ta,tb); \ t0 = ta * tb; \ - c0 += t0; t2 = t1+((c0<t0)?1:0);\ - c1 += t2; c2 += (c1<t2)?1:0; \ - c0 += t0; t1 += (c0<t0)?1:0; \ - c1 += t1; c2 += (c1<t1)?1:0; \ + c0 += t0; t2 = t1+((c0<t0));\ + c1 += t2; c2 += (c1<t2); \ + c0 += t0; t1 += (c0<t0); \ + c1 += t1; c2 += (c1<t1); \ } #define sqr_add_c(a,i,c0,c1,c2) { \ BN_ULONG ta=(a)[i]; \ t1 = ta * ta; \ t2 = BN_UMULT_HIGH(ta,ta); \ - c0 += t1; t2 += (c0<t1)?1:0; \ - c1 += t2; c2 += (c1<t2)?1:0; \ + c0 += t1; t2 += (c0<t1); \ + c1 += t2; c2 += (c1<t2); \ } #define sqr_add_c2(a,i,j,c0,c1,c2) \ @@ -527,25 +543,25 @@ BN_ULONG bn_sub_words(BN_ULONG *r, const t1=LBITS(a); t2=HBITS(a); \ bl=LBITS(b); bh=HBITS(b); \ mul64(t1,t2,bl,bh); \ - c0=(c0+t1)&BN_MASK2; if ((c0) < t1) t2++; \ - c1=(c1+t2)&BN_MASK2; if ((c1) < t2) c2++; + c0=(c0+t1)&BN_MASK2; t2 += ((c0) < t1); \ + c1=(c1+t2)&BN_MASK2; c2 += ((c1) < t2); #define mul_add_c2(a,b,c0,c1,c2) \ t1=LBITS(a); t2=HBITS(a); \ bl=LBITS(b); bh=HBITS(b); \ mul64(t1,t2,bl,bh); \ - if (t2 & BN_TBIT) c2++; \ + c2 += !!(t2 & BN_TBIT); \ t2=(t2+t2)&BN_MASK2; \ - if (t1 & BN_TBIT) t2++; \ + t2 += !!(t1 & BN_TBIT); \ t1=(t1+t1)&BN_MASK2; \ c0=(c0+t1)&BN_MASK2; \ - if ((c0 < t1) && (((++t2)&BN_MASK2) == 0)) c2++; \ - c1=(c1+t2)&BN_MASK2; if ((c1) < t2) c2++; + c2 += ((c0 < t1) && (((++t2)&BN_MASK2) == 0)); \ + c1=(c1+t2)&BN_MASK2; c2 += ((c1) < t2); #define sqr_add_c(a,i,c0,c1,c2) \ sqr64(t1,t2,(a)[i]); \ - c0=(c0+t1)&BN_MASK2; if ((c0) < t1) t2++; \ - c1=(c1+t2)&BN_MASK2; if ((c1) < t2) c2++; + c0=(c0+t1)&BN_MASK2; t2 += ((c0) < t1); \ + c1=(c1+t2)&BN_MASK2; c2 += ((c1) < t2); #define sqr_add_c2(a,i,j,c0,c1,c2) \ mul_add_c2((a)[i],(a)[j],c0,c1,c2) --- a/crypto/bn/bn_blind.c +++ b/crypto/bn/bn_blind.c @@ -270,7 +270,8 @@ int BN_BLINDING_invert_ex(BIGNUM *n, con n->top = (int)(rtop & ~mask) | (ntop & mask); n->flags |= (BN_FLG_FIXED_TOP & ~mask); } - ret = BN_mod_mul_montgomery(n, n, r, b->m_ctx, ctx); + ret = bn_mul_mont_fixed_top(n, n, r, b->m_ctx, ctx); + bn_correct_top_consttime(n); } else { ret = BN_mod_mul(n, n, r, b->mod, ctx); } --- a/crypto/bn/bn_lcl.h +++ b/crypto/bn/bn_lcl.h @@ -328,10 +328,10 @@ extern "C" { ret = (r); \ BN_UMULT_LOHI(low,high,w,tmp); \ ret += (c); \ - (c) = (ret<(c))?1:0; \ + (c) = (ret<(c)); \ (c) += high; \ ret += low; \ - (c) += (ret<low)?1:0; \ + (c) += (ret<low); \ (r) = ret; \ } @@ -340,7 +340,7 @@ extern "C" { BN_UMULT_LOHI(low,high,w,ta); \ ret = low + (c); \ (c) = high; \ - (c) += (ret<low)?1:0; \ + (c) += (ret<low); \ (r) = ret; \ } @@ -356,10 +356,10 @@ extern "C" { high= BN_UMULT_HIGH(w,tmp); \ ret += (c); \ low = (w) * tmp; \ - (c) = (ret<(c))?1:0; \ + (c) = (ret<(c)); \ (c) += high; \ ret += low; \ - (c) += (ret<low)?1:0; \ + (c) += (ret<low); \ (r) = ret; \ } @@ -369,7 +369,7 @@ extern "C" { high= BN_UMULT_HIGH(w,ta); \ ret = low + (c); \ (c) = high; \ - (c) += (ret<low)?1:0; \ + (c) += (ret<low); \ (r) = ret; \ } @@ -402,10 +402,10 @@ extern "C" { lt=(bl)*(lt); \ m1=(bl)*(ht); \ ht =(bh)*(ht); \ - m=(m+m1)&BN_MASK2; if (m < m1) ht+=L2HBITS((BN_ULONG)1); \ + m=(m+m1)&BN_MASK2; ht += L2HBITS((BN_ULONG)(m < m1)); \ ht+=HBITS(m); \ m1=L2HBITS(m); \ - lt=(lt+m1)&BN_MASK2; if (lt < m1) ht++; \ + lt=(lt+m1)&BN_MASK2; ht += (lt < m1); \ (l)=lt; \ (h)=ht; \ } @@ -422,7 +422,7 @@ extern "C" { h*=h; \ h+=(m&BN_MASK2h1)>>(BN_BITS4-1); \ m =(m&BN_MASK2l)<<(BN_BITS4+1); \ - l=(l+m)&BN_MASK2; if (l < m) h++; \ + l=(l+m)&BN_MASK2; h += (l < m); \ (lo)=l; \ (ho)=h; \ } @@ -436,9 +436,9 @@ extern "C" { mul64(l,h,(bl),(bh)); \ \ /* non-multiply part */ \ - l=(l+(c))&BN_MASK2; if (l < (c)) h++; \ + l=(l+(c))&BN_MASK2; h += (l < (c)); \ (c)=(r); \ - l=(l+(c))&BN_MASK2; if (l < (c)) h++; \ + l=(l+(c))&BN_MASK2; h += (l < (c)); \ (c)=h&BN_MASK2; \ (r)=l; \ } @@ -452,7 +452,7 @@ extern "C" { mul64(l,h,(bl),(bh)); \ \ /* non-multiply part */ \ - l+=(c); if ((l&BN_MASK2) < (c)) h++; \ + l+=(c); h += ((l&BN_MASK2) < (c)); \ (c)=h&BN_MASK2; \ (r)=l&BN_MASK2; \ } @@ -482,7 +482,7 @@ BN_ULONG bn_add_part_words(BN_ULONG *r, BN_ULONG bn_sub_part_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b, int cl, int dl); int bn_mul_mont(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp, const BN_ULONG *np,const BN_ULONG *n0, int num); - +void bn_correct_top_consttime(BIGNUM *a); #ifdef __cplusplus } #endif --- a/crypto/bn/bn_lib.c +++ b/crypto/bn/bn_lib.c @@ -66,6 +66,7 @@ #include <stdio.h> #include "cryptlib.h" #include "bn_lcl.h" +#include "constant_time_locl.h" const char BN_version[]="Big Number" OPENSSL_VERSION_PTEXT; @@ -957,3 +958,24 @@ void BN_consttime_swap(BN_ULONG conditio #undef BN_CONSTTIME_SWAP } +void bn_correct_top_consttime(BIGNUM *a) +{ + int j, atop; + BN_ULONG limb; + unsigned int mask; + + for (j = 0, atop = 0; j < a->dmax; j++) { + limb = a->d[j]; + limb |= 0 - limb; + limb >>= BN_BITS2 - 1; + limb = 0 - limb; + mask = (unsigned int)limb; + mask &= constant_time_msb(j - a->top); + atop = constant_time_select_int(mask, j + 1, atop); + } + + mask = constant_time_eq_int(atop, 0); + a->top = atop; + a->neg = constant_time_select_int(mask, 0, a->neg); + a->flags &= ~BN_FLG_FIXED_TOP; +} --- a/crypto/rsa/rsa_eay.c +++ b/crypto/rsa/rsa_eay.c @@ -328,6 +328,7 @@ static int rsa_blinding_convert(BN_BLIND static int rsa_blinding_invert(BN_BLINDING *b, int local, BIGNUM *f, BIGNUM *r, BN_CTX *ctx) { + BN_set_flags(f, BN_FLG_CONSTTIME); if (local) return BN_BLINDING_invert_ex(f, NULL, b, ctx); else @@ -510,6 +511,10 @@ static int RSA_eay_private_decrypt(int f goto err; } + if (rsa->flags & RSA_FLAG_CACHE_PUBLIC) + if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, CRYPTO_LOCK_RSA, rsa->n, ctx)) + goto err; + if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) { blinding = rsa_get_blinding(rsa, &local_blinding, ctx); @@ -547,9 +552,6 @@ static int RSA_eay_private_decrypt(int f else d = rsa->d; - if (rsa->flags & RSA_FLAG_CACHE_PUBLIC) - if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, CRYPTO_LOCK_RSA, rsa->n, ctx)) - goto err; if (!rsa->meth->bn_mod_exp(ret,f,d,rsa->n,ctx, rsa->_method_mod_n)) goto err;
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