Fix i2d_X509_AUX and update docs

When *pp is NULL, don't write garbage, return an unexpected pointer
or leak memory on error.

Reviewed-by: Dr. Stephen Henson <steve@openssl.org>

diff --git a/crypto/asn1/x_x509.c b/crypto/asn1/x_x509.c
index e31e1e750d9db0325074763d888773e3a5a541ee..aada4a8413f2eb51a648f6fd108b7c8b878328e8 100644 (file)
--- a/crypto/asn1/x_x509.c
+++ b/crypto/asn1/x_x509.c
@@ -199,12 +199,26 @@ X509 *d2i_X509_AUX(X509 **a, const unsigned char **pp, long length)
     return NULL;
 }
 
-int i2d_X509_AUX(X509 *a, unsigned char **pp)
+/*
+ * Serialize trusted certificate to *pp or just return the required buffer
+ * length if pp == NULL.  We ultimately want to avoid modifying *pp in the
+ * error path, but that depends on similar hygiene in lower-level functions.
+ * Here we avoid compounding the problem.
+ */
+static int i2d_x509_aux_internal(X509 *a, unsigned char **pp)
 {
     int length, tmplen;
     unsigned char *start = pp != NULL ? *pp : NULL;
+
+    OPENSSL_assert(pp == NULL || *pp != NULL);
+
+    /*
+     * This might perturb *pp on error, but fixing that belongs in i2d_X509()
+     * not here.  It should be that if a == NULL length is zero, but we check
+     * both just in case.
+     */
     length = i2d_X509(a, pp);
-    if (length < 0 || a == NULL)
+    if (length <= 0 || a == NULL)
         return length;
 
     tmplen = i2d_X509_CERT_AUX(a->aux, pp);
@@ -218,6 +232,42 @@ int i2d_X509_AUX(X509 *a, unsigned char **pp)
     return length;
 }
 
+/*
+ * Serialize trusted certificate to *pp, or just return the required buffer
+ * length if pp == NULL.
+ *
+ * When pp is not NULL, but *pp == NULL, we allocate the buffer, but since
+ * we're writing two ASN.1 objects back to back, we can't have i2d_X509() do
+ * the allocation, nor can we allow i2d_X509_CERT_AUX() to increment the
+ * allocated buffer.
+ */
+int i2d_X509_AUX(X509 *a, unsigned char **pp)
+{
+    int length;
+    unsigned char *tmp;
+
+    /* Buffer provided by caller */
+    if (pp == NULL || *pp != NULL)
+        return i2d_x509_aux_internal(a, pp);
+
+    /* Obtain the combined length */
+    if ((length = i2d_x509_aux_internal(a, NULL)) <= 0)
+        return length;
+
+    /* Allocate requisite combined storage */
+    *pp = tmp = OPENSSL_malloc(length);
+    if (tmp == NULL)
+        return -1; /* Push error onto error stack? */
+
+    /* Encode, but keep *pp at the originally malloced pointer */
+    length = i2d_x509_aux_internal(a, &tmp);
+    if (length <= 0) {
+        OPENSSL_free(*pp);
+        *pp = NULL;
+    }
+    return length;
+}
+
 int i2d_re_X509_tbs(X509 *x, unsigned char **pp)
 {
     x->cert_info->enc.modified = 1;

diff --git a/doc/crypto/d2i_X509.pod b/doc/crypto/d2i_X509.pod
index 5b7c16fd0316bc260cd416f18e9ce1db2ff5ea88..2743bc73e70ef578c49a0d2d8dddd45e3bf45e2f 100644 (file)
--- a/doc/crypto/d2i_X509.pod
+++ b/doc/crypto/d2i_X509.pod
@@ -9,8 +9,10 @@ i2d_X509_fp - X509 encode and decode functions
 
  #include <openssl/x509.h>
 
- X509 *d2i_X509(X509 **px, const unsigned char **in, int len);
+ X509 *d2i_X509(X509 **px, const unsigned char **in, long len);
+ X509 *d2i_X509_AUX(X509 **px, const unsigned char **in, long len);
  int i2d_X509(X509 *x, unsigned char **out);
+ int i2d_X509_AUX(X509 *x, unsigned char **out);
 
  X509 *d2i_X509_bio(BIO *bp, X509 **x);
  X509 *d2i_X509_fp(FILE *fp, X509 **x);
@@ -37,6 +39,11 @@ below, and the discussion in the RETURN VALUES section).
 If the call is successful B<*in> is incremented to the byte following the
 parsed data.
 
+d2i_X509_AUX() is similar to d2i_X509() but the input is expected to consist of
+an X509 certificate followed by auxiliary trust information.
+This is used by the PEM routines to read "TRUSTED CERTIFICATE" objects.
+This function should not be called on untrusted input.
+
 i2d_X509() encodes the structure pointed to by B<x> into DER format.
 If B<out> is not B<NULL> is writes the DER encoded data to the buffer
 at B<*out>, and increments it to point after the data just written.
@@ -48,6 +55,11 @@ 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_X509_AUX() is similar to i2d_X509(), but the encoded output contains both
+the certificate and any auxiliary trust information.
+This is used by the PEM routines to write "TRUSTED CERTIFICATE" objects.
+Note, this is a non-standard OpenSSL-specific data format.
+
 d2i_X509_bio() is similar to d2i_X509() except it attempts
 to parse data from BIO B<bp>.