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wellsi |
1.1 |
Fix MMA (Bleichenbacher's attack on PKCS #1 v1.5 RSA padding) weakness |
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in PKCS7 code. When RSA decryption fails use a random key for |
| 3 |
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content decryption and always return the same error. |
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diff -up openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c.pk7-mma openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c |
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--- openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c.pk7-mma 2007-02-03 10:51:58.000000000 +0100 |
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+++ openssl-fips-0.9.8e/crypto/pkcs7/pk7_doit.c 2012-03-19 17:51:35.879037258 +0100 |
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@@ -423,6 +423,8 @@ BIO *PKCS7_dataDecode(PKCS7 *p7, EVP_PKE |
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int max; |
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X509_OBJECT ret; |
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#endif |
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+ unsigned char *tkey = NULL; |
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+ int tkeylen; |
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int jj; |
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if ((etmp=BIO_new(BIO_f_cipher())) == NULL) |
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@@ -464,36 +466,42 @@ BIO *PKCS7_dataDecode(PKCS7 *p7, EVP_PKE |
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if (pcert == NULL) |
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{ |
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+ /* Temporary storage in case EVP_PKEY_decrypt |
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+ * overwrites output buffer on error. |
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+ */ |
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+ unsigned char *tmp2; |
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+ tmp2 = OPENSSL_malloc(jj); |
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+ if (!tmp2) |
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+ goto err; |
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+ jj = -1; |
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+ /* Always attempt to decrypt all cases to avoid |
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+ * leaking timing information about a successful |
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+ * decrypt. |
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+ */ |
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for (i=0; i<sk_PKCS7_RECIP_INFO_num(rsk); i++) |
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{ |
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+ int tret; |
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ri=sk_PKCS7_RECIP_INFO_value(rsk,i); |
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- jj=EVP_PKEY_decrypt(tmp, |
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+ tret=EVP_PKEY_decrypt(tmp2, |
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M_ASN1_STRING_data(ri->enc_key), |
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M_ASN1_STRING_length(ri->enc_key), |
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pkey); |
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- if (jj > 0) |
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- break; |
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+ if (tret > 0) |
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+ { |
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+ memcpy(tmp, tmp2, tret); |
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+ OPENSSL_cleanse(tmp2, tret); |
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+ jj = tret; |
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+ } |
| 49 |
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ERR_clear_error(); |
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- ri = NULL; |
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- } |
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- if (ri == NULL) |
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- { |
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- PKCS7err(PKCS7_F_PKCS7_DATADECODE, |
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- PKCS7_R_NO_RECIPIENT_MATCHES_KEY); |
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- goto err; |
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} |
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+ OPENSSL_free(tmp2); |
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} |
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else |
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{ |
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jj=EVP_PKEY_decrypt(tmp, |
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M_ASN1_STRING_data(ri->enc_key), |
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M_ASN1_STRING_length(ri->enc_key), pkey); |
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- if (jj <= 0) |
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- { |
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- PKCS7err(PKCS7_F_PKCS7_DATADECODE, |
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- ERR_R_EVP_LIB); |
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- goto err; |
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- } |
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+ ERR_clear_error(); |
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} |
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evp_ctx=NULL; |
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@@ -502,24 +510,49 @@ BIO *PKCS7_dataDecode(PKCS7 *p7, EVP_PKE |
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goto err; |
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if (EVP_CIPHER_asn1_to_param(evp_ctx,enc_alg->parameter) < 0) |
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goto err; |
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+ /* Generate random key to counter MMA */ |
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+ tkeylen = EVP_CIPHER_CTX_key_length(evp_ctx); |
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+ tkey = OPENSSL_malloc(tkeylen); |
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+ if (!tkey) |
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+ goto err; |
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+ if (EVP_CIPHER_CTX_rand_key(evp_ctx, tkey) <= 0) |
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+ goto err; |
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+ /* If we have no key use random key */ |
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+ if (jj <= 0) |
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+ { |
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+ OPENSSL_free(tmp); |
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+ jj = tkeylen; |
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+ tmp = tkey; |
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+ tkey = NULL; |
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+ } |
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- if (jj != EVP_CIPHER_CTX_key_length(evp_ctx)) { |
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+ if (jj != tkeylen) { |
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/* Some S/MIME clients don't use the same key |
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* and effective key length. The key length is |
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* determined by the size of the decrypted RSA key. |
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*/ |
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if(!EVP_CIPHER_CTX_set_key_length(evp_ctx, jj)) |
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{ |
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- PKCS7err(PKCS7_F_PKCS7_DATADECODE, |
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- PKCS7_R_DECRYPTED_KEY_IS_WRONG_LENGTH); |
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- goto err; |
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+ /* As MMA defence use random key instead */ |
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+ OPENSSL_cleanse(tmp, jj); |
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+ OPENSSL_free(tmp); |
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+ jj = tkeylen; |
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+ tmp = tkey; |
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+ tkey = NULL; |
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} |
| 113 |
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} |
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+ ERR_clear_error(); |
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if (EVP_CipherInit_ex(evp_ctx,NULL,NULL,tmp,NULL,0) <= 0) |
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goto err; |
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| 118 |
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OPENSSL_cleanse(tmp,jj); |
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| 120 |
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+ if (tkey) |
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+ { |
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+ OPENSSL_cleanse(tkey, tkeylen); |
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+ OPENSSL_free(tkey); |
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+ } |
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+ |
| 126 |
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if (out == NULL) |
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out=etmp; |
| 128 |
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else |
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