2006-09-28 19:59:16 +00:00
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Dr S N Henson of the OpenSSL core team and Open Network Security
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recently developed an ASN1 test suite for NISCC (www.niscc.gov.uk). When
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the test suite was run against OpenSSL two denial of service
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vulnerabilities were discovered.
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Certain types of public key can take disproportionate amounts of time
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to process. This could be used by an attacker in a denial of service attack.
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CVE-2006-2940
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Any code which uses OpenSSL to parse ASN1 data from untrusted sources is
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affected. This includes SSL servers which enable client authentication,
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and S/MIME applications.
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diff -u -r1.37.2.2 dh.h
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--- crypto/dh/dh.h 9 Jan 2006 16:05:22 -0000 1.37.2.2
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+++ crypto/dh/dh.h 15 Sep 2006 13:59:47 -0000
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@@ -73,6 +73,8 @@
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#include <openssl/bn.h>
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#endif
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+#define OPENSSL_DH_MAX_MODULUS_BITS 10000
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+
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#define DH_FLAG_CACHE_MONT_P 0x01
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#define DH_FLAG_NO_EXP_CONSTTIME 0x02 /* new with 0.9.7h; the built-in DH
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* implementation now uses constant time
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@@ -221,6 +223,7 @@
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/* Reason codes. */
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#define DH_R_BAD_GENERATOR 101
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#define DH_R_INVALID_PUBKEY 102
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+#define DH_R_MODULUS_TOO_LARGE 103
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#define DH_R_NO_PRIVATE_VALUE 100
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#ifdef __cplusplus
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diff -u -r1.11.2.2 dh_err.c
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--- crypto/dh/dh_err.c 9 Jan 2006 16:05:22 -0000 1.11.2.2
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+++ crypto/dh/dh_err.c 15 Sep 2006 13:59:47 -0000
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@@ -84,6 +84,7 @@
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{
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{ERR_REASON(DH_R_BAD_GENERATOR) ,"bad generator"},
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{ERR_REASON(DH_R_INVALID_PUBKEY) ,"invalid public key"},
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+{ERR_REASON(DH_R_MODULUS_TOO_LARGE) ,"modulus too large"},
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{ERR_REASON(DH_R_NO_PRIVATE_VALUE) ,"no private value"},
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{0,NULL}
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};
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diff -u -r1.24.2.3 dh_key.c
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--- crypto/dh/dh_key.c 13 Mar 2006 23:12:06 -0000 1.24.2.3
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+++ crypto/dh/dh_key.c 15 Sep 2006 13:59:47 -0000
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@@ -179,6 +179,12 @@
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int ret= -1;
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int check_result;
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+ if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS)
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+ {
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+ DHerr(DH_F_COMPUTE_KEY,DH_R_MODULUS_TOO_LARGE);
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2006-10-02 08:37:59 +00:00
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+ return -1;
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2006-09-28 19:59:16 +00:00
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+ }
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+
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ctx = BN_CTX_new();
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if (ctx == NULL) goto err;
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BN_CTX_start(ctx);
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diff -u -r1.39 dsa.h
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--- crypto/dsa/dsa.h 16 May 2005 01:43:30 -0000 1.39
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+++ crypto/dsa/dsa.h 15 Sep 2006 13:59:47 -0000
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@@ -84,6 +84,8 @@
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#endif
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#endif
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+#define OPENSSL_DSA_MAX_MODULUS_BITS 10000
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+
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#define DSA_FLAG_CACHE_MONT_P 0x01
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#define DSA_FLAG_NO_EXP_CONSTTIME 0x02 /* new with 0.9.7h; the built-in DSA
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* implementation now uses constant time
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@@ -270,8 +272,10 @@
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#define DSA_F_SIG_CB 114
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/* Reason codes. */
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+#define DSA_R_BAD_Q_VALUE 102
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#define DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE 100
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#define DSA_R_MISSING_PARAMETERS 101
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+#define DSA_R_MODULUS_TOO_LARGE 103
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#ifdef __cplusplus
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}
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diff -u -r1.13 dsa_err.c
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--- crypto/dsa/dsa_err.c 12 Apr 2005 16:15:12 -0000 1.13
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+++ crypto/dsa/dsa_err.c 15 Sep 2006 13:59:47 -0000
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@@ -89,8 +89,10 @@
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static ERR_STRING_DATA DSA_str_reasons[]=
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{
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+{ERR_REASON(DSA_R_BAD_Q_VALUE) ,"bad q value"},
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{ERR_REASON(DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE),"data too large for key size"},
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{ERR_REASON(DSA_R_MISSING_PARAMETERS) ,"missing parameters"},
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+{ERR_REASON(DSA_R_MODULUS_TOO_LARGE) ,"modulus too large"},
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{0,NULL}
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};
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diff -u -r1.24.2.1 dsa_ossl.c
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--- crypto/dsa/dsa_ossl.c 26 May 2005 04:40:57 -0000 1.24.2.1
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+++ crypto/dsa/dsa_ossl.c 15 Sep 2006 13:59:47 -0000
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@@ -304,6 +304,18 @@
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return -1;
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}
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+ if (BN_num_bits(dsa->q) != 160)
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+ {
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+ DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
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+ return -1;
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+ }
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+
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+ if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
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+ {
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+ DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
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+ return -1;
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+ }
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+
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BN_init(&u1);
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BN_init(&u2);
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BN_init(&t1);
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diff -u -r1.55.2.6 rsa.h
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--- crypto/rsa/rsa.h 6 Sep 2006 06:43:25 -0000 1.55.2.6
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+++ crypto/rsa/rsa.h 15 Sep 2006 13:59:48 -0000
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@@ -159,6 +159,11 @@
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BN_BLINDING *mt_blinding;
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};
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+#define OPENSSL_RSA_MAX_MODULUS_BITS 16384
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+
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+#define OPENSSL_RSA_SMALL_MODULUS_BITS 3072
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+#define OPENSSL_RSA_MAX_PUBEXP_BITS 64 /* exponent limit enforced for "small" modulus only */
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+
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#define RSA_3 0x3L
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#define RSA_F4 0x10001L
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@@ -407,6 +412,7 @@
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#define RSA_R_IQMP_NOT_INVERSE_OF_Q 126
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#define RSA_R_KEY_SIZE_TOO_SMALL 120
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#define RSA_R_LAST_OCTET_INVALID 134
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+#define RSA_R_MODULUS_TOO_LARGE 105
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#define RSA_R_NO_PUBLIC_EXPONENT 140
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#define RSA_R_NULL_BEFORE_BLOCK_MISSING 113
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#define RSA_R_N_DOES_NOT_EQUAL_P_Q 127
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diff -u -r1.46.2.6 rsa_eay.c
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--- crypto/rsa/rsa_eay.c 6 Sep 2006 06:43:25 -0000 1.46.2.6
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+++ crypto/rsa/rsa_eay.c 15 Sep 2006 13:59:48 -0000
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@@ -168,6 +168,28 @@
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unsigned char *buf=NULL;
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BN_CTX *ctx=NULL;
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+ if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS)
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+ {
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+ RSAerr(RSA_F_RSA_EAY_PUBLIC_ENCRYPT, RSA_R_MODULUS_TOO_LARGE);
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+ return -1;
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+ }
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+
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+ if (BN_ucmp(rsa->n, rsa->e) <= 0)
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+ {
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+ RSAerr(RSA_F_RSA_EAY_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
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+ return -1;
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+ }
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+
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+ /* for large moduli, enforce exponent limit */
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+ if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS)
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+ {
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+ if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS)
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+ {
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+ RSAerr(RSA_F_RSA_EAY_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
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+ return -1;
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+ }
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+ }
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+
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if ((ctx=BN_CTX_new()) == NULL) goto err;
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BN_CTX_start(ctx);
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f = BN_CTX_get(ctx);
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@@ -597,6 +619,28 @@
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unsigned char *buf=NULL;
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BN_CTX *ctx=NULL;
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+ if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS)
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+ {
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+ RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT, RSA_R_MODULUS_TOO_LARGE);
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+ return -1;
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+ }
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+
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+ if (BN_ucmp(rsa->n, rsa->e) <= 0)
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+ {
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+ RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
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+ return -1;
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+ }
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+
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+ /* for large moduli, enforce exponent limit */
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+ if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS)
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+ {
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+ if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS)
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+ {
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+ RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
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+ return -1;
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+ }
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+ }
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+
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if((ctx = BN_CTX_new()) == NULL) goto err;
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BN_CTX_start(ctx);
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f = BN_CTX_get(ctx);
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diff -u -r1.17.2.5 rsa_err.c
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--- crypto/rsa/rsa_err.c 6 Sep 2006 06:43:26 -0000 1.17.2.5
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+++ crypto/rsa/rsa_err.c 15 Sep 2006 13:59:48 -0000
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@@ -137,6 +137,7 @@
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{ERR_REASON(RSA_R_IQMP_NOT_INVERSE_OF_Q) ,"iqmp not inverse of q"},
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{ERR_REASON(RSA_R_KEY_SIZE_TOO_SMALL) ,"key size too small"},
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{ERR_REASON(RSA_R_LAST_OCTET_INVALID) ,"last octet invalid"},
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+{ERR_REASON(RSA_R_MODULUS_TOO_LARGE) ,"modulus too large"},
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{ERR_REASON(RSA_R_NO_PUBLIC_EXPONENT) ,"no public exponent"},
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{ERR_REASON(RSA_R_NULL_BEFORE_BLOCK_MISSING),"null before block missing"},
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{ERR_REASON(RSA_R_N_DOES_NOT_EQUAL_P_Q) ,"n does not equal p q"},
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