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Improve documentation of TLS-1.2 PRF and PSK-to-MS KDF

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This commit is contained in:
Hanno Becker 2018-11-16 16:05:13 +00:00
parent 6b123fbc39
commit 2255a360a6
1 changed files with 21 additions and 14 deletions
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35
include/psa/crypto.h
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@ -1201,6 +1201,16 @@ typedef uint32_t psa_algorithm_t;
#define PSA_ALG_TLS12_PRF_BASE ((psa_algorithm_t)0x30000200)
/** Macro to build a TLS-1.2 PRF algorithm.
*
* TLS 1.2 uses a custom pseudorandom function (PRF) for key schedule,
* specified in Section 5 of RFC 5246. It is based on HMAC and can be
* used with either SHA-256 or SHA-384.
*
* For the application to TLS-1.2, the salt and label arguments passed
* to psa_key_derivation() are what's called 'seed' and 'label' in RFC 5246,
* respectively. For example, for TLS key expansion, the salt is the
* concatenation of ServerHello.Random + ClientHello.Random,
* while the label is "key expansion".
*
* For example, `PSA_ALG_TLS12_PRF(PSA_ALG_SHA256)` represents the
* TLS 1.2 PRF using HMAC-SHA-256.
@ -1216,10 +1226,6 @@ typedef uint32_t psa_algorithm_t;
(PSA_ALG_TLS12_PRF_BASE | ((hash_alg) & PSA_ALG_HASH_MASK))
/** Whether the specified algorithm is a TLS-1.2 PRF algorithm.
*
* TLS 1.2 uses a custom pseudorandom function (PRF) for key schedule,
* specified in Section 5 of RFC 5246. It is based on HMAC and can be
* used with either SHA-256 or SHA-384.
*
* \param alg An algorithm identifier (value of type #psa_algorithm_t).
*
@ -1234,6 +1240,17 @@ typedef uint32_t psa_algorithm_t;
#define PSA_ALG_TLS12_PSK_TO_MS_BASE ((psa_algorithm_t)0x30000300)
/** Macro to build a TLS-1.2 PSK-to-MasterSecret algorithm.
*
* In a pure-PSK handshake in TLS 1.2, the master secret is derived
* from the PreSharedKey (PSK) through the application of padding
* (RFC 4279, Section 2) and the TLS-1.2 PRF (RFC 5246, Section 5).
* The latter is based on HMAC and can be used with either SHA-256
* or SHA-384.
*
* For the application to TLS-1.2, the salt passed to psa_key_derivation()
* (and forwarded to the TLS-1.2 PRF) is the concatenation of the
* ClientHello.Random + ServerHello.Random, while the label is "master secret"
* or "extended master secret".
*
* For example, `PSA_ALG_TLS12_PSK_TO_MS(PSA_ALG_SHA256)` represents the
* TLS-1.2 PSK to MasterSecret derivation PRF using HMAC-SHA-256.
@ -1249,16 +1266,6 @@ typedef uint32_t psa_algorithm_t;
(PSA_ALG_TLS12_PSK_TO_MS_BASE | ((hash_alg) & PSA_ALG_HASH_MASK))
/** Whether the specified algorithm is a TLS-1.2 PSK to MS algorithm.
*
* In a pure-PSK handshake in TLS 1.2, the master secret is derived
* from the PreSharedKey (PSK) through the application of padding and
* the TLS-1.2 PRF (see below). The latter is based on HMAC and can
* be used with either SHA-256 or SHA-384.
*
* For the application to TLS-1.2, the salt passed to psa_key_derivation()
* (and forwarded to the TLS-1.2 PRF) is the concatenation of the
* ClientHello.Random + ServerHello.Random, while the label is "master secret".
* See RFC 5246, Section 8.1, Computing the Master Secret.
*
* \param alg An algorithm identifier (value of type #psa_algorithm_t).
*