More secure storage of key material.

[openssl.git] / doc / crypto / hmac.pod

diff --git a/doc/crypto/hmac.pod b/doc/crypto/hmac.pod
index f86e7d7ddf7e266bf456c70c1bb287cf80eec0ba..58a57f47bb4fe4ffeec3a93683b8a9bb12e2016f 100644 (file)
--- a/doc/crypto/hmac.pod
+++ b/doc/crypto/hmac.pod
@@ -2,8 +2,8 @@
 
 =head1 NAME
 
-HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup - HMAC message
-authentication code
+HMAC, HMAC_CTX_init, HMAC_Init, HMAC_Init_ex, HMAC_Update, HMAC_Final, HMAC_CTX_cleanup,
+HMAC_cleanup - HMAC message authentication code
 
 =head1 SYNOPSIS
 
@@ -13,11 +13,16 @@ authentication code
                int key_len, const unsigned char *d, int n,
                unsigned char *md, unsigned int *md_len);
 
- void HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
+ void HMAC_CTX_init(HMAC_CTX *ctx);
+
+ int HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
                const EVP_MD *md);
- void HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
- void HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
+ int HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len,
+                          const EVP_MD *md, ENGINE *impl);
+ int HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
+ int HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
 
+ void HMAC_CTX_cleanup(HMAC_CTX *ctx);
  void HMAC_cleanup(HMAC_CTX *ctx);
 
 =head1 DESCRIPTION
@@ -36,16 +41,32 @@ If B<md> is NULL, the digest is placed in a static array.  The size of
 the output is placed in B<md_len>, unless it is B<NULL>.
 
 B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc.
-B<key> and B<evp_md> may be B<NULL> if a key and hash function have
-been set in a previous call to HMAC_Init() for that B<HMAC_CTX>.
 
-HMAC_cleanup() erases the key and other data from the B<HMAC_CTX>.
+HMAC_CTX_init() initialises a B<HMAC_CTX> before first use. It must be
+called.
+
+HMAC_CTX_cleanup() erases the key and other data from the B<HMAC_CTX>
+and releases any associated resources. It must be called when an
+B<HMAC_CTX> is no longer required.
+
+HMAC_cleanup() is an alias for HMAC_CTX_cleanup() included for back
+compatibility with 0.9.6b, it is deprecated.
 
 The following functions may be used if the message is not completely
 stored in memory:
 
 HMAC_Init() initializes a B<HMAC_CTX> structure to use the hash
-function B<evp_md> and the key B<key> which is B<key_len> bytes long.
+function B<evp_md> and the key B<key> which is B<key_len> bytes
+long. It is deprecated and only included for backward compatibility
+with OpenSSL 0.9.6b.
+
+HMAC_Init_ex() initializes or reuses a B<HMAC_CTX> structure to use
+the function B<evp_md> and key B<key>. Either can be NULL, in which
+case the existing one will be reused. HMAC_CTX_init() must have been
+called before the first use of an B<HMAC_CTX> in this
+function. B<N.B. HMAC_Init() had this undocumented behaviour in
+previous versions of OpenSSL - failure to switch to HMAC_Init_ex() in
+programs that expect it will cause them to stop working>.
 
 HMAC_Update() can be called repeatedly with chunks of the message to
 be authenticated (B<len> bytes at B<data>).
@@ -55,10 +76,13 @@ must have space for the hash function output.
 
 =head1 RETURN VALUES
 
-HMAC() returns a pointer to the message authentication code.
+HMAC() returns a pointer to the message authentication code or NULL if
+an error occurred.
 
-HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup() do not
-return values.
+HMAC_Init_ex(), HMAC_Update() and HMAC_Final() return 1 for success or 0 if
+an error occurred.
+
+HMAC_CTX_init() and HMAC_CTX_cleanup() do not return values.
 
 =head1 CONFORMING TO
 
@@ -73,4 +97,10 @@ L<sha(3)|sha(3)>, L<evp(3)|evp(3)>
 HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup()
 are available since SSLeay 0.9.0.
 
+HMAC_CTX_init(), HMAC_Init_ex() and HMAC_CTX_cleanup() are available
+since OpenSSL 0.9.7.
+
+HMAC_Init_ex(), HMAC_Update() and HMAC_Final() did not return values in
+versions of OpenSSL before 1.0.0.
+
 =cut