Is philosophy about proof? Depends on what you mean by philosophy. Like most complex endeavors, science comes to mind, definitions are not entirely beyond controversy. Some would call this metaphilosopy which is discussion over the nature of what constitutes 'philosophy'. Ironically, not everyone even sees metaphilosophy and metaphysics as a part of or meaningful to philosophy. The WP article on philosophy quotes Ryle:
Many philosophers have expressed doubts over the value of metaphilosophy.2 Among them is Gilbert Ryle: "preoccupation with questions about methods tends to distract us from prosecuting the methods themselves. We run as a rule, worse, not better if we think a lot about our feet. So let us ... not speak of it all but just do it."3
The question of what constitutes 'proof' would be part of epistemology and could be considered a meta-epistemological question, but certainly, this neologism would have been rejected by Ryle given his participation in ordinary language philosophy. One can avoid the normative question, 'what should philosophy be' and take a look at 'what philosophy is'.
Gilbert Ryle, in the broadly defined analytic philosophical tradition rejected what some consider Metaphysical Speculation which can be understood simply as a rejection on the overreliance of rational methods and an under reliance on empirical ones. To put it in another way, some philosophers aspire to grand, sweeping theories of everything where all has it's reasonable position to all else, and other philosophers see this as a pipe dream. Some of the logical empiricists and positivists went so far as to reject all metaphysics entirely. Men like Hempel, Mach, and others attempted to eliminate and minimize metaphysics from knowledge entirely. Ordinary language philosophers were skeptical of Metaphysics with a capital 'M'.
How does this relate to proof and philosophy? Well, in ordinary language, proof is that which makes our knowledge certain. It is a concept that defines the relationship between belief and knowledge, whatever that may be. And if there's one consistency of philosophy, it's the constant demonstration by philosophy that certainly is elusive. In fact, The Encyclopedia of Philosophy, the Internet Encyclopedia of Philosophy, and the Stanford Encyclopedia of Philosophy all have no entry for 'proof'. This might seem odd given how proof is used so frequently in discourse such as logic, mathematics, argumentation, and law. Burden of proof is a very well known term, for instance.
And yet, 'proof' has since the beginning of philosophy been undermined by skepticism. And since Quine and Duhem have been around, skepticism has been bolstered by the underdetermination of scientific theory, which has taken what logical positivists held as a certain path to truth and fact, and riddled it with doubt. Most philosophers of the analytic tradition hold to some form of fallibilism, which seems to trace its roots back to the Agrippan Trilemma.
There are still theologians, who start off with the certainty of God's existence and try to impute certainty to proof, and there are still Metaphysicians who chase a grand theory of everything and claim that certain principles are beyond doubt, but they are not part of the Anglo-American analytical tradition which fully has embraced the power of doubt.
Now, proof does have use in some limited contexts in philosophy like logical proofs, legal theoretical ontological questions like "what constitutes evidence", and in mathematics where there's an entire branch called proof theory. But most analytic philosophers agree that Gettier's problems has thrown a wrench in creating any universally acceptable notion of proof or justification in a broad sense.
So, philosophy isn't so much about proof of things, as it is about in some broad sense explaining them. Of course, what constitutes an explanation is also quite the sticky wicket.