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Add cryptographically signed update support (#5213)

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Using a pluggable architecture, allow updates delivered via the Update
class to be verified as signed by a certificate.  By using plugins, avoid
pulling either axTLS or BearSSL into normal builds.

A signature is appended to a binary image, followed by the size of the
signature as a 32-bit int.  The updater takes a verification function
and checks this signature using whatever method it chooses, and if it
fails the update is not applied.

A SHA256 hash class is presently implemented for the signing hash (since
MD5 is a busted algorithm).

A BearSSLPublicKey based verifier is implemented for RSA keys.  The
application only needs the Public Key, while to sign you can use
OpenSSL and your private key (which should never leave your control
or be deployed on any endpoints).

An example using automatic signing is included.

Update the docs to show the signing steps and how to use it in the
automatic and manual modes.

Also remove one debugging line from the signing tool.

Saves ~600 bytes when in debug mode by moving strings to PMEM

Windows can't run the signing script, nor does it normally have OpenSSL
installed.  When trying to build an automatically signed binary, warn
and don't run the python.
This commit is contained in:
Earle F. Philhower, III
2018-12-02 19:57:47 -08:00
committed by GitHub
parent e5d50a6e4b
commit d8acfffdb0
11 changed files with 532 additions and 27 deletions
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26
cores/esp8266/Updater.h
View File

@ -17,6 +17,7 @@
#define UPDATE_ERROR_NEW_FLASH_CONFIG (9)
#define UPDATE_ERROR_MAGIC_BYTE (10)
#define UPDATE_ERROR_BOOTSTRAP (11)
#define UPDATE_ERROR_SIGN (12)
#define U_FLASH 0
#define U_SPIFFS 100
@ -28,9 +29,30 @@
#endif
#endif
// Abstract class to implement whatever signing hash desired
class UpdaterHashClass {
public:
virtual void begin() = 0;
virtual void add(const void *data, uint32_t len) = 0;
virtual void end() = 0;
virtual int len() = 0;
virtual const void *hash() = 0;
};
// Abstract class to implement a signature verifier
class UpdaterVerifyClass {
public:
virtual uint32_t length() = 0; // How many bytes of signature are expected
virtual bool verify(UpdaterHashClass *hash, const void *signature, uint32_t signatureLen) = 0; // Verify, return "true" on success
};
class UpdaterClass {
public:
UpdaterClass();
/* Optionally add a cryptographic signature verification hash and method */
void installSignature(UpdaterHashClass *hash, UpdaterVerifyClass *verify) { _hash = hash; _verify = verify; }
/*
Call this to check the space needed for the update
Will return false if there is not enough space
@ -165,6 +187,10 @@ class UpdaterClass {
int _ledPin;
uint8_t _ledOn;
// Optional signed binary verification
UpdaterHashClass *_hash;
UpdaterVerifyClass *_verify;
};
extern UpdaterClass Update;