sha256: add helper than hashes a buffer *and* its size

We use this pattern all the time in order to thward extension attacks,
add a helper to make it shorter.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/fundamental/sha256.h b/src/fundamental/sha256.h
index 7c29c785cb..4805cc553a 100644
--- a/src/fundamental/sha256.h
+++ b/src/fundamental/sha256.h
@@ -28,6 +28,11 @@ void sha256_init_ctx(struct sha256_ctx *ctx);
 uint8_t *sha256_finish_ctx(struct sha256_ctx *ctx, uint8_t resbuf[static SHA256_DIGEST_SIZE]);
 void sha256_process_bytes(const void *buffer, size_t len, struct sha256_ctx *ctx);
 
+static inline void sha256_process_bytes_and_size(const void *buffer, size_t len, struct sha256_ctx *ctx) {
+        sha256_process_bytes(&len, sizeof(len), ctx);
+        sha256_process_bytes(buffer, len, ctx);
+}
+
 uint8_t* sha256_direct(const void *buffer, size_t sz, uint8_t result[static SHA256_DIGEST_SIZE]);
 
 #define SHA256_DIRECT(buffer, sz) sha256_direct(buffer, sz, (uint8_t[SHA256_DIGEST_SIZE]) {})