Fix faulty free

On error, i2o_SCT_signature() and i2o_SCT() free a pointer that may
have wandered off from the start of the allocated block (not currently
true for i2o_SCT_signature(), but has that potential as the code may
change.  To avoid this, save away the start of the allocated block and
free that instead.

Thanks to Guido Vranken for reporting this issue.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2323)

diff --git a/crypto/ct/ct_oct.c b/crypto/ct/ct_oct.c
index d3edd39f5d9dc124a68c1b15490f59444dad82cc..0dd691c0f711d4907c7751591940ffba75222f2c 100644 (file)
--- a/crypto/ct/ct_oct.c
+++ b/crypto/ct/ct_oct.c
@@ -153,7 +153,7 @@ err:
 int i2o_SCT_signature(const SCT *sct, unsigned char **out)
 {
     size_t len;
-    unsigned char *p = NULL;
+    unsigned char *p = NULL, *pstart = NULL;
 
     if (!SCT_signature_is_complete(sct)) {
         CTerr(CT_F_I2O_SCT_SIGNATURE, CT_R_SCT_INVALID_SIGNATURE);
@@ -177,7 +177,7 @@ int i2o_SCT_signature(const SCT *sct, unsigned char **out)
             p = *out;
             *out += len;
         } else {
-            p = OPENSSL_malloc(len);
+            pstart = p = OPENSSL_malloc(len);
             if (p == NULL) {
                 CTerr(CT_F_I2O_SCT_SIGNATURE, ERR_R_MALLOC_FAILURE);
                 goto err;
@@ -193,14 +193,14 @@ int i2o_SCT_signature(const SCT *sct, unsigned char **out)
 
     return len;
 err:
-    OPENSSL_free(p);
+    OPENSSL_free(pstart);
     return -1;
 }
 
 int i2o_SCT(const SCT *sct, unsigned char **out)
 {
     size_t len;
-    unsigned char *p = NULL;
+    unsigned char *p = NULL, *pstart = NULL;
 
     if (!SCT_is_complete(sct)) {
         CTerr(CT_F_I2O_SCT, CT_R_SCT_NOT_SET);
@@ -224,7 +224,7 @@ int i2o_SCT(const SCT *sct, unsigned char **out)
         p = *out;
         *out += len;
     } else {
-        p = OPENSSL_malloc(len);
+        pstart = p = OPENSSL_malloc(len);
         if (p == NULL) {
             CTerr(CT_F_I2O_SCT, ERR_R_MALLOC_FAILURE);
             goto err;
@@ -250,7 +250,7 @@ int i2o_SCT(const SCT *sct, unsigned char **out)
 
     return len;
 err:
-    OPENSSL_free(p);
+    OPENSSL_free(pstart);
     return -1;
 }