Avoid PKCS #1 v1.5 signature attack discovered by Daniel Bleichenbacher

(CVE-2006-4339)

Submitted by: Ben Laurie, Google Security Team
Reviewed by: bmoeller, mjc, shenson

4 files changed, 28 insertions, 0 deletions

diff --git a/crypto/rsa/rsa.h b/crypto/rsa/rsa.h
index 31f3792a4c..c8b6a814a0 100644
--- a/crypto/rsa/rsa.h
+++ b/crypto/rsa/rsa.h
@@ -457,6 +457,7 @@ void ERR_load_RSA_strings(void);
 #define RSA_R_N_DOES_NOT_EQUAL_P_Q			 127
 #define RSA_R_OAEP_DECODING_ERROR			 121
 #define RSA_R_PADDING_CHECK_FAILED			 114
+#define RSA_R_PKCS1_PADDING_TOO_SHORT			 105
 #define RSA_R_P_NOT_PRIME				 128
 #define RSA_R_Q_NOT_PRIME				 129
 #define RSA_R_RSA_OPERATIONS_NOT_SUPPORTED		 130
diff --git a/crypto/rsa/rsa_eay.c b/crypto/rsa/rsa_eay.c
index c6ceaee6e7..863a45a975 100644
--- a/crypto/rsa/rsa_eay.c
+++ b/crypto/rsa/rsa_eay.c
@@ -640,6 +640,15 @@ static int RSA_eay_public_decrypt(int flen, const unsigned char *from,
 		{
 	case RSA_PKCS1_PADDING:
 		r=RSA_padding_check_PKCS1_type_1(to,num,buf,i,num);
+		/* Generally signatures should be at least 2/3 padding, though
+		   this isn't possible for really short keys and some standard
+		   signature schemes, so don't check if the unpadded data is
+		   small. */
+		if(r > 42 && 3*8*r >= BN_num_bits(rsa->n))
+			{
+			RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT, RSA_R_PKCS1_PADDING_TOO_SHORT);
+			goto err;
+			}
 		break;
 	case RSA_X931_PADDING:
 		r=RSA_padding_check_X931(to,num,buf,i,num);
diff --git a/crypto/rsa/rsa_err.c b/crypto/rsa/rsa_err.c
index 163b143a73..1a7f8b7719 100644
--- a/crypto/rsa/rsa_err.c
+++ b/crypto/rsa/rsa_err.c
@@ -160,6 +160,7 @@ static ERR_STRING_DATA RSA_str_reasons[]=
 {ERR_REASON(RSA_R_N_DOES_NOT_EQUAL_P_Q)  ,"n does not equal p q"},
 {ERR_REASON(RSA_R_OAEP_DECODING_ERROR)   ,"oaep decoding error"},
 {ERR_REASON(RSA_R_PADDING_CHECK_FAILED)  ,"padding check failed"},
+{ERR_REASON(RSA_R_PKCS1_PADDING_TOO_SHORT),"pkcs1 padding too short"},
 {ERR_REASON(RSA_R_P_NOT_PRIME)           ,"p not prime"},
 {ERR_REASON(RSA_R_Q_NOT_PRIME)           ,"q not prime"},
 {ERR_REASON(RSA_R_RSA_OPERATIONS_NOT_SUPPORTED),"rsa operations not supported"},
diff --git a/crypto/rsa/rsa_sign.c b/crypto/rsa/rsa_sign.c
index e5a015d1a6..e1b1714210 100644
--- a/crypto/rsa/rsa_sign.c
+++ b/crypto/rsa/rsa_sign.c
@@ -193,6 +193,23 @@ int int_rsa_verify(int dtype, const unsigned char *m,
 		sig=d2i_X509_SIG(NULL,&p,(long)i);
 
 		if (sig == NULL) goto err;
+
+		/* Excess data can be used to create forgeries */
+		if(p != s+i)
+			{
+			RSAerr(RSA_F_RSA_VERIFY,RSA_R_BAD_SIGNATURE);
+			goto err;
+			}
+
+		/* Parameters to the signature algorithm can also be used to
+		   create forgeries */
+		if(sig->algor->parameter
+		   && ASN1_TYPE_get(sig->algor->parameter) != V_ASN1_NULL)
+			{
+			RSAerr(RSA_F_RSA_VERIFY,RSA_R_BAD_SIGNATURE);
+			goto err;
+			}
+
 		sigtype=OBJ_obj2nid(sig->algor->algorithm);