#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
projects / BearSSL / blobdiff