X-Git-Url: https://www.bearssl.org/gitweb//home/git/?p=BearSSL;a=blobdiff_plain;f=inc%2Fbearssl_prf.h;h=fdf608c85387d5fecf368a144e66855a63ac965d;hp=779a75b48b170540b0bbb1b2724808af8456fe63;hb=cfbc702d3d64c209784b664eeab8867b603f4d4c;hpb=3210f38e0491b39aec1ef419cb4114e9483089fb

diff --git a/inc/bearssl_prf.h b/inc/bearssl_prf.h
index 779a75b..fdf608c 100644
--- a/inc/bearssl_prf.h
+++ b/inc/bearssl_prf.h
@@ -28,39 +28,123 @@
 #include <stddef.h>
 #include <stdint.h>
 
-/*
- * The TLS PRF
- * -----------
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** \file bearssl_prf.h
+ *
+ * # The TLS PRF
+ *
+ * The "PRF" is the pseudorandom function used internally during the
+ * SSL/TLS handshake, notably to expand negotiated shared secrets into
+ * the symmetric encryption keys that will be used to process the
+ * application data.
  *
  * TLS 1.0 and 1.1 define a PRF that is based on both MD5 and SHA-1. This
- * is implemented by the br_tls10_prf() function.
+ * is implemented by the `br_tls10_prf()` function.
  *
  * TLS 1.2 redefines the PRF, using an explicit hash function. The
- * br_tls12_sha256_prf() and br_tls12_sha384_prf() functions apply that
- * PRF with, respectively, SHA-256 and SHA-384.
+ * `br_tls12_sha256_prf()` and `br_tls12_sha384_prf()` functions apply that
+ * PRF with, respectively, SHA-256 and SHA-384. Most standard cipher suites
+ * rely on the SHA-256 based PRF, but some use SHA-384.
  *
  * The PRF always uses as input three parameters: a "secret" (some
- * bytes), a "label" (ASCII string), and a "seed" (again some bytes).
- * An arbitrary output length can be produced.
+ * bytes), a "label" (ASCII string), and a "seed" (again some bytes). An
+ * arbitrary output length can be produced. The "seed" is provided as an
+ * arbitrary number of binary chunks, that gets internally concatenated.
  */
 
+/**
+ * \brief Type for a seed chunk.
+ *
+ * Each chunk may have an arbitrary length, and may be empty (no byte at
+ * all). If the chunk length is zero, then the pointer to the chunk data
+ * may be `NULL`.
+ */
+typedef struct {
+	/**
+	 * \brief Pointer to the chunk data.
+	 */
+	const void *data;
+
+	/**
+	 * \brief Chunk length (in bytes).
+	 */
+	size_t len;
+} br_tls_prf_seed_chunk;
+
+/**
+ * \brief PRF implementation for TLS 1.0 and 1.1.
+ *
+ * This PRF is the one specified by TLS 1.0 and 1.1. It internally uses
+ * MD5 and SHA-1.
+ *
+ * \param dst          destination buffer.
+ * \param len          output length (in bytes).
+ * \param secret       secret value (key) for this computation.
+ * \param secret_len   length of "secret" (in bytes).
+ * \param label        PRF label (zero-terminated ASCII string).
+ * \param seed_num     number of seed chunks.
+ * \param seed         seed chnks for this computation (usually non-secret).
+ */
 void br_tls10_prf(void *dst, size_t len,
-	const void *secret, size_t secret_len,
-	const char *label, const void *seed, size_t seed_len);
+	const void *secret, size_t secret_len, const char *label,
+	size_t seed_num, const br_tls_prf_seed_chunk *seed);
 
+/**
+ * \brief PRF implementation for TLS 1.2, with SHA-256.
+ *
+ * This PRF is the one specified by TLS 1.2, when the underlying hash
+ * function is SHA-256.
+ *
+ * \param dst          destination buffer.
+ * \param len          output length (in bytes).
+ * \param secret       secret value (key) for this computation.
+ * \param secret_len   length of "secret" (in bytes).
+ * \param label        PRF label (zero-terminated ASCII string).
+ * \param seed_num     number of seed chunks.
+ * \param seed         seed chnks for this computation (usually non-secret).
+ */
 void br_tls12_sha256_prf(void *dst, size_t len,
-	const void *secret, size_t secret_len,
-	const char *label, const void *seed, size_t seed_len);
+	const void *secret, size_t secret_len, const char *label,
+	size_t seed_num, const br_tls_prf_seed_chunk *seed);
 
+/**
+ * \brief PRF implementation for TLS 1.2, with SHA-384.
+ *
+ * This PRF is the one specified by TLS 1.2, when the underlying hash
+ * function is SHA-384.
+ *
+ * \param dst          destination buffer.
+ * \param len          output length (in bytes).
+ * \param secret       secret value (key) for this computation.
+ * \param secret_len   length of "secret" (in bytes).
+ * \param label        PRF label (zero-terminated ASCII string).
+ * \param seed_num     number of seed chunks.
+ * \param seed         seed chnks for this computation (usually non-secret).
+ */
 void br_tls12_sha384_prf(void *dst, size_t len,
-	const void *secret, size_t secret_len,
-	const char *label, const void *seed, size_t seed_len);
+	const void *secret, size_t secret_len, const char *label,
+	size_t seed_num, const br_tls_prf_seed_chunk *seed);
 
-/*
- * A convenient type name for a PRF implementation.
+/** 
+ * brief A convenient type name for a PRF implementation.
+ *
+ * \param dst          destination buffer.
+ * \param len          output length (in bytes).
+ * \param secret       secret value (key) for this computation.
+ * \param secret_len   length of "secret" (in bytes).
+ * \param label        PRF label (zero-terminated ASCII string).
+ * \param seed_num     number of seed chunks.
+ * \param seed         seed chnks for this computation (usually non-secret).
  */
 typedef void (*br_tls_prf_impl)(void *dst, size_t len,
-	const void *secret, size_t secret_len,
-	const char *label, const void *seed, size_t seed_len);
+	const void *secret, size_t secret_len, const char *label,
+	size_t seed_num, const br_tls_prf_seed_chunk *seed);
+
+#ifdef __cplusplus
+}
+#endif
 
 #endif