Isolated Execution Environments (IEEs), such as ARM TrustZone and Intel SGX, offer the possibility to execute sensitive code in isolation from other malicious programs, running on the same machine, or a potentially corrupted OS. A key feature of IEEs is the ability to produce reports binding cryptographically a message to the program that produced it, typically ensuring that this message is the result of the given program running on an IEE. We present a symbolic model for specifying and verifying applications that make use of such features. For this we introduce the S(ell)APIC process calculus, that allows to reason about reports issued at given locations. We also provide tool support, extending the SAPIC/TAMARIN toolchain and demonstrate the applicability of our framework on several examples implementing secure outsourced computation (SOC), a secure licensing protocol and a one-time password protocol that all rely on such IEEs.