| 1 |
Fix MMA (Bleichenbacher's attack on PKCS #1 v1.5 RSA padding) weakness |
| 2 |
in PKCS7 code. When RSA decryption fails use a random key for |
| 3 |
content decryption and always return the same error. |
| 4 |
diff -up openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c.pk7-mma openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c |
| 5 |
--- openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c.pk7-mma 2007-02-03 10:51:58.000000000 +0100 |
| 6 |
+++ openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c 2012-03-19 17:51:35.879037258 +0100 |
| 7 |
@@ -423,6 +423,8 @@ BIO *PKCS7_dataDecode(PKCS7 *p7, EVP_PKE |
| 8 |
int max; |
| 9 |
X509_OBJECT ret; |
| 10 |
#endif |
| 11 |
+ unsigned char *tkey = NULL; |
| 12 |
+ int tkeylen; |
| 13 |
int jj; |
| 14 |
|
| 15 |
if ((etmp=BIO_new(BIO_f_cipher())) == NULL) |
| 16 |
@@ -464,36 +466,42 @@ BIO *PKCS7_dataDecode(PKCS7 *p7, EVP_PKE |
| 17 |
|
| 18 |
if (pcert == NULL) |
| 19 |
{ |
| 20 |
+ /* Temporary storage in case EVP_PKEY_decrypt |
| 21 |
+ * overwrites output buffer on error. |
| 22 |
+ */ |
| 23 |
+ unsigned char *tmp2; |
| 24 |
+ tmp2 = OPENSSL_malloc(jj); |
| 25 |
+ if (!tmp2) |
| 26 |
+ goto err; |
| 27 |
+ jj = -1; |
| 28 |
+ /* Always attempt to decrypt all cases to avoid |
| 29 |
+ * leaking timing information about a successful |
| 30 |
+ * decrypt. |
| 31 |
+ */ |
| 32 |
for (i=0; i<sk_PKCS7_RECIP_INFO_num(rsk); i++) |
| 33 |
{ |
| 34 |
+ int tret; |
| 35 |
ri=sk_PKCS7_RECIP_INFO_value(rsk,i); |
| 36 |
- jj=EVP_PKEY_decrypt(tmp, |
| 37 |
+ tret=EVP_PKEY_decrypt(tmp2, |
| 38 |
M_ASN1_STRING_data(ri->enc_key), |
| 39 |
M_ASN1_STRING_length(ri->enc_key), |
| 40 |
pkey); |
| 41 |
- if (jj > 0) |
| 42 |
- break; |
| 43 |
+ if (tret > 0) |
| 44 |
+ { |
| 45 |
+ memcpy(tmp, tmp2, tret); |
| 46 |
+ OPENSSL_cleanse(tmp2, tret); |
| 47 |
+ jj = tret; |
| 48 |
+ } |
| 49 |
ERR_clear_error(); |
| 50 |
- ri = NULL; |
| 51 |
- } |
| 52 |
- if (ri == NULL) |
| 53 |
- { |
| 54 |
- PKCS7err(PKCS7_F_PKCS7_DATADECODE, |
| 55 |
- PKCS7_R_NO_RECIPIENT_MATCHES_KEY); |
| 56 |
- goto err; |
| 57 |
} |
| 58 |
+ OPENSSL_free(tmp2); |
| 59 |
} |
| 60 |
else |
| 61 |
{ |
| 62 |
jj=EVP_PKEY_decrypt(tmp, |
| 63 |
M_ASN1_STRING_data(ri->enc_key), |
| 64 |
M_ASN1_STRING_length(ri->enc_key), pkey); |
| 65 |
- if (jj <= 0) |
| 66 |
- { |
| 67 |
- PKCS7err(PKCS7_F_PKCS7_DATADECODE, |
| 68 |
- ERR_R_EVP_LIB); |
| 69 |
- goto err; |
| 70 |
- } |
| 71 |
+ ERR_clear_error(); |
| 72 |
} |
| 73 |
|
| 74 |
evp_ctx=NULL; |
| 75 |
@@ -502,24 +510,49 @@ BIO *PKCS7_dataDecode(PKCS7 *p7, EVP_PKE |
| 76 |
goto err; |
| 77 |
if (EVP_CIPHER_asn1_to_param(evp_ctx,enc_alg->parameter) < 0) |
| 78 |
goto err; |
| 79 |
+ /* Generate random key to counter MMA */ |
| 80 |
+ tkeylen = EVP_CIPHER_CTX_key_length(evp_ctx); |
| 81 |
+ tkey = OPENSSL_malloc(tkeylen); |
| 82 |
+ if (!tkey) |
| 83 |
+ goto err; |
| 84 |
+ if (EVP_CIPHER_CTX_rand_key(evp_ctx, tkey) <= 0) |
| 85 |
+ goto err; |
| 86 |
+ /* If we have no key use random key */ |
| 87 |
+ if (jj <= 0) |
| 88 |
+ { |
| 89 |
+ OPENSSL_free(tmp); |
| 90 |
+ jj = tkeylen; |
| 91 |
+ tmp = tkey; |
| 92 |
+ tkey = NULL; |
| 93 |
+ } |
| 94 |
|
| 95 |
- if (jj != EVP_CIPHER_CTX_key_length(evp_ctx)) { |
| 96 |
+ if (jj != tkeylen) { |
| 97 |
/* Some S/MIME clients don't use the same key |
| 98 |
* and effective key length. The key length is |
| 99 |
* determined by the size of the decrypted RSA key. |
| 100 |
*/ |
| 101 |
if(!EVP_CIPHER_CTX_set_key_length(evp_ctx, jj)) |
| 102 |
{ |
| 103 |
- PKCS7err(PKCS7_F_PKCS7_DATADECODE, |
| 104 |
- PKCS7_R_DECRYPTED_KEY_IS_WRONG_LENGTH); |
| 105 |
- goto err; |
| 106 |
+ /* As MMA defence use random key instead */ |
| 107 |
+ OPENSSL_cleanse(tmp, jj); |
| 108 |
+ OPENSSL_free(tmp); |
| 109 |
+ jj = tkeylen; |
| 110 |
+ tmp = tkey; |
| 111 |
+ tkey = NULL; |
| 112 |
} |
| 113 |
} |
| 114 |
+ ERR_clear_error(); |
| 115 |
if (EVP_CipherInit_ex(evp_ctx,NULL,NULL,tmp,NULL,0) <= 0) |
| 116 |
goto err; |
| 117 |
|
| 118 |
OPENSSL_cleanse(tmp,jj); |
| 119 |
|
| 120 |
+ if (tkey) |
| 121 |
+ { |
| 122 |
+ OPENSSL_cleanse(tkey, tkeylen); |
| 123 |
+ OPENSSL_free(tkey); |
| 124 |
+ } |
| 125 |
+ |
| 126 |
if (out == NULL) |
| 127 |
out=etmp; |
| 128 |
else |
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