Ensure EVP_EncodeUpdate handles an output length that is too long

With the EVP_EncodeUpdate function it is the caller's responsibility to
determine how big the output buffer should be. The function writes the
amount actually used to |*outl|. However this could go negative with a
sufficiently large value for |inl|. We add a check for this error
condition.

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

crypto/evp/encode.c

@@ -57,6 +57,7 @@
  */
 
 #include <stdio.h>
+#include <limits.h>
 #include "cryptlib.h"
 #include <openssl/evp.h>
 
@@ -151,7 +152,7 @@ void EVP_EncodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl,
                       const unsigned char *in, int inl)
 {
     int i, j;
-    unsigned int total = 0;
+    size_t total = 0;
 
     *outl = 0;
     if (inl <= 0)
@@ -174,7 +175,7 @@ void EVP_EncodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl,
         *out = '\0';
         total = j + 1;
     }
-    while (inl >= ctx->length) {
+    while (inl >= ctx->length && total <= INT_MAX) {
         j = EVP_EncodeBlock(out, in, ctx->length);
         in += ctx->length;
         inl -= ctx->length;
@@ -183,6 +184,11 @@ void EVP_EncodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl,
         *out = '\0';
         total += j + 1;
     }
+    if (total > INT_MAX) {
+        /* Too much output data! */
+        *outl = 0;
+        return;
+    }
     if (inl != 0)
         memcpy(&(ctx->enc_data[0]), in, inl);
     ctx->num = inl;