i2d_ASN1_OBJECT(): allocate memory if the user didn't provide a buffer

Since 0.9.7, all i2d_ functions were documented to allocate an output
buffer if the user didn't provide one, under these conditions (from
the 1.0.2 documentation):

    For OpenSSL 0.9.7 and later if B<*out> is B<NULL> memory will be
    allocated for a buffer and the encoded data written to it. In this
    case B<*out> is not incremented and it points to the start of the
    data just written.

i2d_ASN1_OBJECT was found not to do this, and would crash if a NULL
output buffer was provided.

Fixes openssl#6914

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from openssl#6918)

(cherry picked from commit cba024d)

Author: levitte

crypto/asn1/a_object.c

@@ -19,7 +19,7 @@
 
 int i2d_ASN1_OBJECT(const ASN1_OBJECT *a, unsigned char **pp)
 {
-    unsigned char *p;
+    unsigned char *p, *allocated = NULL;
     int objsize;
 
     if ((a == NULL) || (a->data == NULL))
@@ -29,13 +29,24 @@ int i2d_ASN1_OBJECT(const ASN1_OBJECT *a, unsigned char **pp)
     if (pp == NULL || objsize == -1)
         return objsize;
 
-    p = *pp;
+    if (*pp == NULL) {
+        if ((p = allocated = OPENSSL_malloc(objsize)) == NULL) {
+            ASN1err(ASN1_F_I2D_ASN1_OBJECT, ERR_R_MALLOC_FAILURE);
+            return 0;
+        }
+    } else {
+        p = *pp;
+    }
+
     ASN1_put_object(&p, 0, a->length, V_ASN1_OBJECT, V_ASN1_UNIVERSAL);
     memcpy(p, a->data, a->length);
-    p += a->length;
 
-    *pp = p;
-    return (objsize);
+    /*
+     * If a new buffer was allocated, just return it back.
+     * If not, return the incremented buffer pointer.
+     */
+    *pp = allocated != NULL ? allocated : p + a->length;
+    return objsize;
 }
 
 int a2d_ASN1_OBJECT(unsigned char *out, int olen, const char *buf, int num)

crypto/asn1/asn1_err.c

@@ -95,6 +95,7 @@ static ERR_STRING_DATA ASN1_str_functs[] = {
     {ERR_FUNC(ASN1_F_DO_BUF), "do_buf"},
     {ERR_FUNC(ASN1_F_DO_TCREATE), "do_tcreate"},
     {ERR_FUNC(ASN1_F_I2D_ASN1_BIO_STREAM), "i2d_ASN1_bio_stream"},
+    {ERR_FUNC(ASN1_F_I2D_ASN1_OBJECT), "i2d_ASN1_OBJECT"},
     {ERR_FUNC(ASN1_F_I2D_DSA_PUBKEY), "i2d_DSA_PUBKEY"},
     {ERR_FUNC(ASN1_F_I2D_EC_PUBKEY), "i2d_EC_PUBKEY"},
     {ERR_FUNC(ASN1_F_I2D_PRIVATEKEY), "i2d_PrivateKey"},

include/openssl/asn1.h

@@ -956,6 +956,7 @@ int ERR_load_ASN1_strings(void);
 # define ASN1_F_DO_BUF                                    142
 # define ASN1_F_DO_TCREATE                                222
 # define ASN1_F_I2D_ASN1_BIO_STREAM                       211
+# define ASN1_F_I2D_ASN1_OBJECT                           143
 # define ASN1_F_I2D_DSA_PUBKEY                            161
 # define ASN1_F_I2D_EC_PUBKEY                             181
 # define ASN1_F_I2D_PRIVATEKEY                            163