diff --git a/libgcrypt-1.9.3-CVE-2021-33560.patch b/libgcrypt-1.9.3-CVE-2021-33560.patch new file mode 100644 index 0000000..2161840 --- /dev/null +++ b/libgcrypt-1.9.3-CVE-2021-33560.patch @@ -0,0 +1,100 @@ +commit 3462280f2e23e16adf3ed5176e0f2413d8861320 +Author: NIIBE Yutaka +Date: Fri May 21 11:15:07 2021 +0900 + + cipher: Fix ElGamal encryption for other implementations. + + * cipher/elgamal.c (gen_k): Remove support of smaller K. + (do_encrypt): Never use smaller K. + (sign): Folllow the change of gen_k. + + -- + + Cherry-pick master commit of: + 632d80ef30e13de6926d503aa697f92b5dbfbc5e + + This change basically reverts encryption changes in two commits: + + 74386120dad6b3da62db37f7044267c8ef34689b + 78531373a342aeb847950f404343a05e36022065 + + Use of smaller K for ephemeral key in ElGamal encryption is only good, + when we can guarantee that recipient's key is generated by our + implementation (or compatible). + + For detail, please see: + + Luca De Feo, Bertram Poettering, Alessandro Sorniotti, + "On the (in)security of ElGamal in OpenPGP"; + in the proceedings of CCS'2021. + + CVE-id: CVE-2021-33560 + GnuPG-bug-id: 5328 + Suggested-by: Luca De Feo, Bertram Poettering, Alessandro Sorniotti + Signed-off-by: NIIBE Yutaka + +diff --git a/cipher/elgamal.c b/cipher/elgamal.c +index 9835122f..eead4502 100644 +--- a/cipher/elgamal.c ++++ b/cipher/elgamal.c +@@ -66,7 +66,7 @@ static const char *elg_names[] = + + + static int test_keys (ELG_secret_key *sk, unsigned int nbits, int nodie); +-static gcry_mpi_t gen_k (gcry_mpi_t p, int small_k); ++static gcry_mpi_t gen_k (gcry_mpi_t p); + static gcry_err_code_t generate (ELG_secret_key *sk, unsigned nbits, + gcry_mpi_t **factors); + static int check_secret_key (ELG_secret_key *sk); +@@ -189,11 +189,10 @@ test_keys ( ELG_secret_key *sk, unsigned int nbits, int nodie ) + + /**************** + * Generate a random secret exponent k from prime p, so that k is +- * relatively prime to p-1. With SMALL_K set, k will be selected for +- * better encryption performance - this must never be used signing! ++ * relatively prime to p-1. + */ + static gcry_mpi_t +-gen_k( gcry_mpi_t p, int small_k ) ++gen_k( gcry_mpi_t p ) + { + gcry_mpi_t k = mpi_alloc_secure( 0 ); + gcry_mpi_t temp = mpi_alloc( mpi_get_nlimbs(p) ); +@@ -202,18 +201,7 @@ gen_k( gcry_mpi_t p, int small_k ) + unsigned int nbits, nbytes; + char *rndbuf = NULL; + +- if (small_k) +- { +- /* Using a k much lesser than p is sufficient for encryption and +- * it greatly improves the encryption performance. We use +- * Wiener's table and add a large safety margin. */ +- nbits = wiener_map( orig_nbits ) * 3 / 2; +- if( nbits >= orig_nbits ) +- BUG(); +- } +- else +- nbits = orig_nbits; +- ++ nbits = orig_nbits; + + nbytes = (nbits+7)/8; + if( DBG_CIPHER ) +@@ -492,7 +480,7 @@ do_encrypt(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_public_key *pkey ) + * error code. + */ + +- k = gen_k( pkey->p, 1 ); ++ k = gen_k( pkey->p ); + mpi_powm (a, pkey->g, k, pkey->p); + + /* b = (y^k * input) mod p +@@ -608,7 +596,7 @@ sign(gcry_mpi_t a, gcry_mpi_t b, gcry_mpi_t input, ELG_secret_key *skey ) + * + */ + mpi_sub_ui(p_1, p_1, 1); +- k = gen_k( skey->p, 0 /* no small K ! */ ); ++ k = gen_k( skey->p ); + mpi_powm( a, skey->g, k, skey->p ); + mpi_mul(t, skey->x, a ); + mpi_subm(t, input, t, p_1 ); diff --git a/libgcrypt.spec b/libgcrypt.spec index ca19c19..2eb80a0 100644 --- a/libgcrypt.spec +++ b/libgcrypt.spec @@ -48,6 +48,8 @@ Patch27: libgcrypt-1.8.3-md-fips-enforce.patch Patch28: libgcrypt-1.8.5-intel-cet.patch # FIPS module is redefined a little bit (implicit by kernel FIPS mode) Patch30: libgcrypt-1.8.5-fips-module.patch +# Fix for CVE-2021-33560 +Patch31: libgcrypt-1.9.3-CVE-2021-33560.patch %global gcrylibdir %{_libdir} %global gcrysoname libgcrypt.so.20 @@ -97,6 +99,7 @@ applications using libgcrypt. %patch27 -p1 -b .fips-enforce %patch28 -p1 -b .intel-cet %patch30 -p1 -b .fips-module +%patch31 -p1 -b .CVE-2021-33560 cp %{SOURCE4} cipher/ cp %{SOURCE5} %{SOURCE6} %{SOURCE8} tests/