From bf3d6c0c9b58e6a78fa3ac0a60d68ef4fc0aa215 Mon Sep 17 00:00:00 2001
From: Ben Laurie <ben@openssl.org>
Date: Sun, 21 Aug 2005 16:00:17 +0000
Subject: [PATCH] Make D-H safer, include well-known primes.

---
 CHANGES                |  8 +++++++-
 crypto/asn1/asn1.h     |  1 +
 crypto/asn1/asn1_err.c |  1 +
 crypto/bn/Makefile     |  4 ++--
 crypto/bn/bn.h         | 12 ++++++++++++
 crypto/dh/dh.h         |  6 ++++++
 crypto/dh/dh_check.c   | 22 ++++++++++++++++++++++
 crypto/dh/dh_err.c     |  1 +
 crypto/dh/dh_key.c     |  7 +++++++
 9 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/CHANGES b/CHANGES
index c58c811f40..a695a4dc63 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2,7 +2,7 @@
  OpenSSL CHANGES
  _______________
 
- Changes between 0.9.8 and 0.9.9  [xx XXX xxxx]
+ Changes between 0.9.8a and 0.9.9  [xx XXX xxxx]
 
   *) Support for PKCS#1 RSAPublicKey format on rsa utility command line.
      [Steve Henson]
@@ -27,6 +27,12 @@
 
  Changes between 0.9.8 and 0.9.8a  [XX xxx XXXX]
 
+  *) Avoid small subgroup attacks in Diffie-Hellman.
+     [Nick Mathewson and Ben Laurie]
+
+  *) Add functions for well-known primes.
+     [Nick Mathewson]
+
   *) Extended Windows CE support.
      [Satoshi Nakamura and Andy Polyakov]
  
diff --git a/crypto/asn1/asn1.h b/crypto/asn1/asn1.h
index e0e474f2c8..680f92891e 100644
--- a/crypto/asn1/asn1.h
+++ b/crypto/asn1/asn1.h
@@ -1040,6 +1040,7 @@ void ERR_load_ASN1_strings(void);
 #define ASN1_F_ASN1_MBSTRING_NCOPY			 122
 #define ASN1_F_ASN1_OBJECT_NEW				 123
 #define ASN1_F_ASN1_PACK_STRING				 124
+#define ASN1_F_ASN1_PCTX_NEW				 205
 #define ASN1_F_ASN1_PKCS5_PBE_SET			 125
 #define ASN1_F_ASN1_SEQ_PACK				 126
 #define ASN1_F_ASN1_SEQ_UNPACK				 127
diff --git a/crypto/asn1/asn1_err.c b/crypto/asn1/asn1_err.c
index b9df21c5fe..bef2519e65 100644
--- a/crypto/asn1/asn1_err.c
+++ b/crypto/asn1/asn1_err.c
@@ -111,6 +111,7 @@ static ERR_STRING_DATA ASN1_str_functs[]=
 {ERR_FUNC(ASN1_F_ASN1_MBSTRING_NCOPY),	"ASN1_mbstring_ncopy"},
 {ERR_FUNC(ASN1_F_ASN1_OBJECT_NEW),	"ASN1_OBJECT_new"},
 {ERR_FUNC(ASN1_F_ASN1_PACK_STRING),	"ASN1_pack_string"},
+{ERR_FUNC(ASN1_F_ASN1_PCTX_NEW),	"ASN1_PCTX_NEW"},
 {ERR_FUNC(ASN1_F_ASN1_PKCS5_PBE_SET),	"ASN1_PKCS5_PBE_SET"},
 {ERR_FUNC(ASN1_F_ASN1_SEQ_PACK),	"ASN1_seq_pack"},
 {ERR_FUNC(ASN1_F_ASN1_SEQ_UNPACK),	"ASN1_seq_unpack"},
diff --git a/crypto/bn/Makefile b/crypto/bn/Makefile
index 4afb6a393c..ab9c494913 100644
--- a/crypto/bn/Makefile
+++ b/crypto/bn/Makefile
@@ -28,13 +28,13 @@ LIBSRC=	bn_add.c bn_div.c bn_exp.c bn_lib.c bn_ctx.c bn_mul.c bn_mod.c \
 	bn_print.c bn_rand.c bn_shift.c bn_word.c bn_blind.c \
 	bn_kron.c bn_sqrt.c bn_gcd.c bn_prime.c bn_err.c bn_sqr.c bn_asm.c \
 	bn_recp.c bn_mont.c bn_mpi.c bn_exp2.c bn_gf2m.c bn_nist.c \
-	bn_depr.c
+	bn_depr.c bn_const.c
 
 LIBOBJ=	bn_add.o bn_div.o bn_exp.o bn_lib.o bn_ctx.o bn_mul.o bn_mod.o \
 	bn_print.o bn_rand.o bn_shift.o bn_word.o bn_blind.o \
 	bn_kron.o bn_sqrt.o bn_gcd.o bn_prime.o bn_err.o bn_sqr.o $(BN_ASM) \
 	bn_recp.o bn_mont.o bn_mpi.o bn_exp2.o bn_gf2m.o bn_nist.o \
-	bn_depr.o
+	bn_depr.o bn_const.o
 
 SRC= $(LIBSRC)
 
diff --git a/crypto/bn/bn.h b/crypto/bn/bn.h
index 670584ad74..b990ff2b5d 100644
--- a/crypto/bn/bn.h
+++ b/crypto/bn/bn.h
@@ -732,6 +732,18 @@ BN_ULONG bn_div_words(BN_ULONG h, BN_ULONG l, BN_ULONG d);
 BN_ULONG bn_add_words(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int num);
 BN_ULONG bn_sub_words(BN_ULONG *rp, const BN_ULONG *ap, const BN_ULONG *bp,int num);
 
+/* Primes from RFC 2409 */
+int get_rfc2409_prime_768(BIGNUM **bn);
+int get_rfc2409_prime_1024(BIGNUM **bn);
+
+/* Primes from RFC 3526 */
+int get_rfc3526_prime_1536(BIGNUM **bn);
+int get_rfc3526_prime_2048(BIGNUM **bn);
+int get_rfc3526_prime_3072(BIGNUM **bn);
+int get_rfc3526_prime_4096(BIGNUM **bn);
+int get_rfc3526_prime_6144(BIGNUM **bn);
+int get_rfc3526_prime_8192(BIGNUM **bn);
+
 int BN_bntest_rand(BIGNUM *rnd, int bits, int top,int bottom);
 
 /* BEGIN ERROR CODES */
diff --git a/crypto/dh/dh.h b/crypto/dh/dh.h
index d1559fd4f8..7871882e35 100644
--- a/crypto/dh/dh.h
+++ b/crypto/dh/dh.h
@@ -145,6 +145,10 @@ struct dh_st
 #define DH_UNABLE_TO_CHECK_GENERATOR	0x04
 #define DH_NOT_SUITABLE_GENERATOR	0x08
 
+/* DH_check_pub_key error codes */
+#define DH_CHECK_PUBKEY_TOO_SMALL	0x01
+#define DH_CHECK_PUBKEY_TOO_LARGE	0x02
+
 /* primes p where (p-1)/2 is prime too are called "safe"; we define
    this for backward compatibility: */
 #define DH_CHECK_P_NOT_STRONG_PRIME	DH_CHECK_P_NOT_SAFE_PRIME
@@ -183,6 +187,7 @@ DH *	DH_generate_parameters(int prime_len,int generator,
 int	DH_generate_parameters_ex(DH *dh, int prime_len,int generator, BN_GENCB *cb);
 
 int	DH_check(const DH *dh,int *codes);
+int	DH_check_pub_key(const DH *dh,const BIGNUM *pub_key, int *codes);
 int	DH_generate_key(DH *dh);
 int	DH_compute_key(unsigned char *key,const BIGNUM *pub_key,DH *dh);
 DH *	d2i_DHparams(DH **a,const unsigned char **pp, long length);
@@ -216,6 +221,7 @@ void ERR_load_DH_strings(void);
 /* Reason codes. */
 #define DH_R_BAD_GENERATOR				 101
 #define DH_R_NO_PRIVATE_VALUE				 100
+#define DH_R_INVALID_PUBKEY				 102
 
 #ifdef  __cplusplus
 }
diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
index bfc9c3ad76..10217c83dc 100644
--- a/crypto/dh/dh_check.c
+++ b/crypto/dh/dh_check.c
@@ -118,3 +118,25 @@ err:
 	if (q != NULL) BN_free(q);
 	return(ok);
 	}
+
+int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
+	{
+	int ok=0;
+	BIGNUM *q=NULL;
+
+	*ret=0;
+	q=BN_new();
+	if (q == NULL) goto err;
+	BN_set_word(q,1);
+	if (BN_cmp(pub_key,q)<=0)
+		*ret|=DH_CHECK_PUBKEY_TOO_SMALL;
+	BN_copy(q,dh->p);
+	BN_sub_word(q,1);
+	if (BN_cmp(pub_key,q)>=0)
+		*ret|=DH_CHECK_PUBKEY_TOO_LARGE;
+
+	ok = 1;
+err:
+	if (q != NULL) BN_free(q);
+	return(ok);
+	}
diff --git a/crypto/dh/dh_err.c b/crypto/dh/dh_err.c
index edce2c7036..ea67fb71a0 100644
--- a/crypto/dh/dh_err.c
+++ b/crypto/dh/dh_err.c
@@ -84,6 +84,7 @@ static ERR_STRING_DATA DH_str_reasons[]=
 	{
 {ERR_REASON(DH_R_BAD_GENERATOR)          ,"bad generator"},
 {ERR_REASON(DH_R_NO_PRIVATE_VALUE)       ,"no private value"},
+{ERR_REASON(DH_R_INVALID_PUBKEY)         ,"invalid public key"},
 {0,NULL}
 	};
 
diff --git a/crypto/dh/dh_key.c b/crypto/dh/dh_key.c
index 39eefe387e..cc17c8851b 100644
--- a/crypto/dh/dh_key.c
+++ b/crypto/dh/dh_key.c
@@ -177,6 +177,7 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 	BN_MONT_CTX *mont=NULL;
 	BIGNUM *tmp;
 	int ret= -1;
+        int check_result;
 
 	ctx = BN_CTX_new();
 	if (ctx == NULL) goto err;
@@ -202,6 +203,12 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 			goto err;
 		}
 
+        if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result)
+		{
+		DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY);
+		goto err;
+		}
+
 	if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
 		{
 		DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB);
-- 
2.25.1