Fix leak with ASN.1 combine.

When parsing a combined structure pass a flag to the decode routine
so on error a pointer to the parent structure is not zeroed as
this will leak any additional components in the parent.

This can leak memory in any application parsing PKCS#7 or CMS structures.

CVE-2015-3195.

Thanks to Adam Langley (Google/BoringSSL) for discovering this bug using
libFuzzer.

PR#4131

Reviewed-by: Richard Levitte <levitte@openssl.org>

diff --git a/crypto/asn1/tasn_dec.c b/crypto/asn1/tasn_dec.c
index 6e4a3252d07816470b2aee687c77d62b3c94f727..91e76981133705d5ed65501f0712c3ce0f280d35 100644 (file)
--- a/crypto/asn1/tasn_dec.c
+++ b/crypto/asn1/tasn_dec.c
@@ -178,6 +178,8 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
     int otag;
     int ret = 0;
     ASN1_VALUE **pchptr, *ptmpval;
+    int combine = aclass & ASN1_TFLG_COMBINE;
+    aclass &= ~ASN1_TFLG_COMBINE;
     if (!pval)
         return 0;
     if (aux && aux->asn1_cb)
@@ -498,7 +500,8 @@ int ASN1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
  auxerr:
     ASN1err(ASN1_F_ASN1_ITEM_EX_D2I, ASN1_R_AUX_ERROR);
  err:
-    ASN1_item_ex_free(pval, it);
+    if (combine == 0)
+        ASN1_item_ex_free(pval, it);
     if (errtt)
         ERR_add_error_data(4, "Field=", errtt->field_name,
                            ", Type=", it->sname);
@@ -687,7 +690,7 @@ static int asn1_template_noexp_d2i(ASN1_VALUE **val,
     } else {
         /* Nothing special */
         ret = ASN1_item_ex_d2i(val, &p, len, ASN1_ITEM_ptr(tt->item),
-                               -1, 0, opt, ctx);
+                               -1, tt->flags & ASN1_TFLG_COMBINE, opt, ctx);
         if (!ret) {
             ASN1err(ASN1_F_ASN1_TEMPLATE_NOEXP_D2I, ERR_R_NESTED_ASN1_ERROR);
             goto err;