2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
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9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
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13 * included in all copies or substantial portions of the Software.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
25 #ifndef BR_BEARSSL_PRF_H__
26 #define BR_BEARSSL_PRF_H__
31 /** \file bearssl_prf.h
35 * The "PRF" is the pseudorandom function used internally during the
36 * SSL/TLS handshake, notably to expand negociated shared secrets into
37 * the symmetric encryption keys that will be used to process the
40 * TLS 1.0 and 1.1 define a PRF that is based on both MD5 and SHA-1. This
41 * is implemented by the `br_tls10_prf()` function.
43 * TLS 1.2 redefines the PRF, using an explicit hash function. The
44 * `br_tls12_sha256_prf()` and `br_tls12_sha384_prf()` functions apply that
45 * PRF with, respectively, SHA-256 and SHA-384. Most standard cipher suites
46 * rely on the SHA-256 based PRF, but some use SHA-384.
48 * The PRF always uses as input three parameters: a "secret" (some
49 * bytes), a "label" (ASCII string), and a "seed" (again some bytes).
50 * An arbitrary output length can be produced.
53 /** \brief PRF implementation for TLS 1.0 and 1.1.
55 * This PRF is the one specified by TLS 1.0 and 1.1. It internally uses
58 * \param dst destination buffer.
59 * \param len output length (in bytes).
60 * \param secret secret value (key) for this computation.
61 * \param secret_len length of "secret" (in bytes).
62 * \param label PRF label (zero-terminated ASCII string).
63 * \param seed seed for this computation (usually non-secret).
64 * \param seed_len length of "seed" (in bytes).
66 void br_tls10_prf(void *dst
, size_t len
,
67 const void *secret
, size_t secret_len
,
68 const char *label
, const void *seed
, size_t seed_len
);
70 /** \brief PRF implementation for TLS 1.2, with SHA-256.
72 * This PRF is the one specified by TLS 1.2, when the underlying hash
73 * function is SHA-256.
75 * \param dst destination buffer.
76 * \param len output length (in bytes).
77 * \param secret secret value (key) for this computation.
78 * \param secret_len length of "secret" (in bytes).
79 * \param label PRF label (zero-terminated ASCII string).
80 * \param seed seed for this computation (usually non-secret).
81 * \param seed_len length of "seed" (in bytes).
83 void br_tls12_sha256_prf(void *dst
, size_t len
,
84 const void *secret
, size_t secret_len
,
85 const char *label
, const void *seed
, size_t seed_len
);
87 /** \brief PRF implementation for TLS 1.2, with SHA-384.
89 * This PRF is the one specified by TLS 1.2, when the underlying hash
90 * function is SHA-384.
92 * \param dst destination buffer.
93 * \param len output length (in bytes).
94 * \param secret secret value (key) for this computation.
95 * \param secret_len length of "secret" (in bytes).
96 * \param label PRF label (zero-terminated ASCII string).
97 * \param seed seed for this computation (usually non-secret).
98 * \param seed_len length of "seed" (in bytes).
100 void br_tls12_sha384_prf(void *dst
, size_t len
,
101 const void *secret
, size_t secret_len
,
102 const char *label
, const void *seed
, size_t seed_len
);
104 /** \brief A convenient type name for a PRF implementation.
106 * \param dst destination buffer.
107 * \param len output length (in bytes).
108 * \param secret secret value (key) for this computation.
109 * \param secret_len length of "secret" (in bytes).
110 * \param label PRF label (zero-terminated ASCII string).
111 * \param seed seed for this computation (usually non-secret).
112 * \param seed_len length of "seed" (in bytes).
114 typedef void (*br_tls_prf_impl
)(void *dst
, size_t len
,
115 const void *secret
, size_t secret_len
,
116 const char *label
, const void *seed
, size_t seed_len
);