static int internal_verify(X509_STORE_CTX *ctx)
	{
	int ok=0,n;
	X509 *xs,*xi;
	EVP_PKEY *pkey=NULL;
	int (*cb)(int xok,X509_STORE_CTX *xctx);
	cb=ctx->verify_cb;
	n=sk_X509_num(ctx->chain);
	ctx->error_depth=n-1;
	n--;
	xi=sk_X509_value(ctx->chain,n);
	if (ctx->check_issued(ctx, xi, xi))
		xs=xi;
	else
		{
		if (ctx->param->flags & X509_V_FLAG_PARTIAL_CHAIN && n == 0)
			{
			xs = xi;
			goto check_cert;
			}
		if (n <= 0)
			{
			ctx->error=X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE;
			ctx->current_cert=xi;
			ok=cb(0,ctx);
			goto end;
			}
		else
			{
			n--;
			ctx->error_depth=n;
			xs=sk_X509_value(ctx->chain,n);
			}
		}
	while (n >= 0)
		{
		ctx->error_depth=n;
		if (!xs->valid && (xs != xi || (ctx->param->flags & X509_V_FLAG_CHECK_SS_SIGNATURE)))
			{
			if ((pkey=X509_get_pubkey(xi)) == NULL)
				{
				ctx->error=X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY;
				ctx->current_cert=xi;
				ok=(*cb)(0,ctx);
				if (!ok) goto end;
				}
			else if (X509_verify(xs,pkey) <= 0)
				{
				ctx->error=X509_V_ERR_CERT_SIGNATURE_FAILURE;
				ctx->current_cert=xs;
				ok=(*cb)(0,ctx);
				if (!ok)
					{
					EVP_PKEY_free(pkey);
					goto end;
					}
				}
			EVP_PKEY_free(pkey);
			pkey=NULL;
			}
		xs->valid = 1;
		check_cert:
		ok = check_cert_time(ctx, xs);
		if (!ok)
			goto end;
		ctx->current_issuer=xi;
		ctx->current_cert=xs;
		ok=(*cb)(1,ctx);
		if (!ok) goto end;
		n--;
		if (n >= 0)
			{
			xi=xs;
			xs=sk_X509_value(ctx->chain,n);
			}
		}
	ok=1;
end:
	return ok;
	}
['static int internal_verify(X509_STORE_CTX *ctx)\n\t{\n\tint ok=0,n;\n\tX509 *xs,*xi;\n\tEVP_PKEY *pkey=NULL;\n\tint (*cb)(int xok,X509_STORE_CTX *xctx);\n\tcb=ctx->verify_cb;\n\tn=sk_X509_num(ctx->chain);\n\tctx->error_depth=n-1;\n\tn--;\n\txi=sk_X509_value(ctx->chain,n);\n\tif (ctx->check_issued(ctx, xi, xi))\n\t\txs=xi;\n\telse\n\t\t{\n\t\tif (ctx->param->flags & X509_V_FLAG_PARTIAL_CHAIN && n == 0)\n\t\t\t{\n\t\t\txs = xi;\n\t\t\tgoto check_cert;\n\t\t\t}\n\t\tif (n <= 0)\n\t\t\t{\n\t\t\tctx->error=X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE;\n\t\t\tctx->current_cert=xi;\n\t\t\tok=cb(0,ctx);\n\t\t\tgoto end;\n\t\t\t}\n\t\telse\n\t\t\t{\n\t\t\tn--;\n\t\t\tctx->error_depth=n;\n\t\t\txs=sk_X509_value(ctx->chain,n);\n\t\t\t}\n\t\t}\n\twhile (n >= 0)\n\t\t{\n\t\tctx->error_depth=n;\n\t\tif (!xs->valid && (xs != xi || (ctx->param->flags & X509_V_FLAG_CHECK_SS_SIGNATURE)))\n\t\t\t{\n\t\t\tif ((pkey=X509_get_pubkey(xi)) == NULL)\n\t\t\t\t{\n\t\t\t\tctx->error=X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY;\n\t\t\t\tctx->current_cert=xi;\n\t\t\t\tok=(*cb)(0,ctx);\n\t\t\t\tif (!ok) goto end;\n\t\t\t\t}\n\t\t\telse if (X509_verify(xs,pkey) <= 0)\n\t\t\t\t{\n\t\t\t\tctx->error=X509_V_ERR_CERT_SIGNATURE_FAILURE;\n\t\t\t\tctx->current_cert=xs;\n\t\t\t\tok=(*cb)(0,ctx);\n\t\t\t\tif (!ok)\n\t\t\t\t\t{\n\t\t\t\t\tEVP_PKEY_free(pkey);\n\t\t\t\t\tgoto end;\n\t\t\t\t\t}\n\t\t\t\t}\n\t\t\tEVP_PKEY_free(pkey);\n\t\t\tpkey=NULL;\n\t\t\t}\n\t\txs->valid = 1;\n\t\tcheck_cert:\n\t\tok = check_cert_time(ctx, xs);\n\t\tif (!ok)\n\t\t\tgoto end;\n\t\tctx->current_issuer=xi;\n\t\tctx->current_cert=xs;\n\t\tok=(*cb)(1,ctx);\n\t\tif (!ok) goto end;\n\t\tn--;\n\t\tif (n >= 0)\n\t\t\t{\n\t\t\txi=xs;\n\t\t\txs=sk_X509_value(ctx->chain,n);\n\t\t\t}\n\t\t}\n\tok=1;\nend:\n\treturn ok;\n\t}', 'int sk_num(const _STACK *st)\n{\n\tif(st == NULL) return -1;\n\treturn st->num;\n}', 'void *sk_value(const _STACK *st, int i)\n{\n\tif(!st || (i < 0) || (i >= st->num)) return NULL;\n\treturn st->data[i];\n}']