git: 5f3d952f6e6b - stable/13 - Fix a bug in BN_mod_sqrt() that can cause it to loop forever.
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Date: Tue, 15 Mar 2022 16:53:07 UTC
The branch stable/13 has been updated by gordon: URL: https://cgit.FreeBSD.org/src/commit/?id=5f3d952f6e6bce1151ab4a260c6922ba10d7a7ba commit 5f3d952f6e6bce1151ab4a260c6922ba10d7a7ba Author: Gordon Tetlow <gordon@FreeBSD.org> AuthorDate: 2022-03-15 16:48:59 +0000 Commit: Gordon Tetlow <gordon@FreeBSD.org> CommitDate: 2022-03-15 16:51:46 +0000 Fix a bug in BN_mod_sqrt() that can cause it to loop forever. Obtained from: OpenSSL Project Security: CVE-2022-0778 Security: FreeBSD-SA-22:03.openssl (cherry picked from commit fdc418f15e92732a3551832bcb625ba9b47242df) --- crypto/openssl/crypto/bn/bn_sqrt.c | 30 ++++++++++++++++++------------ crypto/openssl/doc/man3/BN_add.pod | 15 +++++++++++++-- 2 files changed, 31 insertions(+), 14 deletions(-) diff --git a/crypto/openssl/crypto/bn/bn_sqrt.c b/crypto/openssl/crypto/bn/bn_sqrt.c index 1723d5ded5a8..53b0f559855c 100644 --- a/crypto/openssl/crypto/bn/bn_sqrt.c +++ b/crypto/openssl/crypto/bn/bn_sqrt.c @@ -14,7 +14,8 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) /* * Returns 'ret' such that ret^2 == a (mod p), using the Tonelli/Shanks * algorithm (cf. Henri Cohen, "A Course in Algebraic Computational Number - * Theory", algorithm 1.5.1). 'p' must be prime! + * Theory", algorithm 1.5.1). 'p' must be prime, otherwise an error or + * an incorrect "result" will be returned. */ { BIGNUM *ret = in; @@ -301,18 +302,23 @@ BIGNUM *BN_mod_sqrt(BIGNUM *in, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx) goto vrfy; } - /* find smallest i such that b^(2^i) = 1 */ - i = 1; - if (!BN_mod_sqr(t, b, p, ctx)) - goto end; - while (!BN_is_one(t)) { - i++; - if (i == e) { - BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE); - goto end; + /* Find the smallest i, 0 < i < e, such that b^(2^i) = 1. */ + for (i = 1; i < e; i++) { + if (i == 1) { + if (!BN_mod_sqr(t, b, p, ctx)) + goto end; + + } else { + if (!BN_mod_mul(t, t, t, p, ctx)) + goto end; } - if (!BN_mod_mul(t, t, t, p, ctx)) - goto end; + if (BN_is_one(t)) + break; + } + /* If not found, a is not a square or p is not prime. */ + if (i >= e) { + BNerr(BN_F_BN_MOD_SQRT, BN_R_NOT_A_SQUARE); + goto end; } /* t := y^2^(e - i - 1) */ diff --git a/crypto/openssl/doc/man3/BN_add.pod b/crypto/openssl/doc/man3/BN_add.pod index dccd4790ede7..1f5e37a4d183 100644 --- a/crypto/openssl/doc/man3/BN_add.pod +++ b/crypto/openssl/doc/man3/BN_add.pod @@ -3,7 +3,7 @@ =head1 NAME BN_add, BN_sub, BN_mul, BN_sqr, BN_div, BN_mod, BN_nnmod, BN_mod_add, -BN_mod_sub, BN_mod_mul, BN_mod_sqr, BN_exp, BN_mod_exp, BN_gcd - +BN_mod_sub, BN_mod_mul, BN_mod_sqr, BN_mod_sqrt, BN_exp, BN_mod_exp, BN_gcd - arithmetic operations on BIGNUMs =head1 SYNOPSIS @@ -36,6 +36,8 @@ arithmetic operations on BIGNUMs int BN_mod_sqr(BIGNUM *r, BIGNUM *a, const BIGNUM *m, BN_CTX *ctx); + BIGNUM *BN_mod_sqrt(BIGNUM *in, BIGNUM *a, const BIGNUM *p, BN_CTX *ctx); + int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx); int BN_mod_exp(BIGNUM *r, BIGNUM *a, const BIGNUM *p, @@ -87,6 +89,12 @@ L<BN_mod_mul_reciprocal(3)>. BN_mod_sqr() takes the square of I<a> modulo B<m> and places the result in I<r>. +BN_mod_sqrt() returns the modular square root of I<a> such that +C<in^2 = a (mod p)>. The modulus I<p> must be a +prime, otherwise an error or an incorrect "result" will be returned. +The result is stored into I<in> which can be NULL. The result will be +newly allocated in that case. + BN_exp() raises I<a> to the I<p>-th power and places the result in I<r> (C<r=a^p>). This function is faster than repeated applications of BN_mul(). @@ -108,7 +116,10 @@ the arguments. =head1 RETURN VALUES -For all functions, 1 is returned for success, 0 on error. The return +The BN_mod_sqrt() returns the result (possibly incorrect if I<p> is +not a prime), or NULL. + +For all remaining functions, 1 is returned for success, 0 on error. The return value should always be checked (e.g., C<if (!BN_add(r,a,b)) goto err;>). The error codes can be obtained by L<ERR_get_error(3)>.