df75c2bfcd
While stereotyped repetitions are frowned upon in literature, they serve a useful purpose in manual pages, because it is easier for the user to find certain information if it is always presented in the same way. For that reason, this commit harmonizes the varying formulations in the HISTORY section about which functions, flags, etc. were added in which OpenSSL version. It also attempts to make the pod files more grep friendly by avoiding to insert line breaks between the symbol names and the corresponding version number in which they were introduced (wherever possible). Some punctuation and typographical errors were fixed on the way. Reviewed-by: Tim Hudson <tjh@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7854)
391 lines
12 KiB
Text
391 lines
12 KiB
Text
=pod
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=head1 NAME
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EVP_MD_CTX_new, EVP_MD_CTX_reset, EVP_MD_CTX_free, EVP_MD_CTX_copy_ex,
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EVP_MD_CTX_ctrl, EVP_MD_CTX_set_flags, EVP_MD_CTX_clear_flags,
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EVP_MD_CTX_test_flags, EVP_DigestInit_ex, EVP_DigestInit, EVP_DigestUpdate,
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EVP_DigestFinal_ex, EVP_DigestFinalXOF, EVP_DigestFinal,
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EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size,
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EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size,
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EVP_MD_CTX_block_size, EVP_MD_CTX_type, EVP_MD_CTX_md_data,
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EVP_md_null,
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EVP_get_digestbyname, EVP_get_digestbynid,
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EVP_get_digestbyobj,
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EVP_MD_CTX_set_pkey_ctx - EVP digest routines
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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EVP_MD_CTX *EVP_MD_CTX_new(void);
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int EVP_MD_CTX_reset(EVP_MD_CTX *ctx);
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void EVP_MD_CTX_free(EVP_MD_CTX *ctx);
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void EVP_MD_CTX_ctrl(EVP_MD_CTX *ctx, int cmd, int p1, void* p2);
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void EVP_MD_CTX_set_flags(EVP_MD_CTX *ctx, int flags);
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void EVP_MD_CTX_clear_flags(EVP_MD_CTX *ctx, int flags);
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int EVP_MD_CTX_test_flags(const EVP_MD_CTX *ctx, int flags);
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int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
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int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
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int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s);
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int EVP_DigestFinalXOF(EVP_MD_CTX *ctx, unsigned char *md, size_t len);
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int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out, const EVP_MD_CTX *in);
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int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
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int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s);
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int EVP_MD_CTX_copy(EVP_MD_CTX *out, EVP_MD_CTX *in);
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int EVP_MD_type(const EVP_MD *md);
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int EVP_MD_pkey_type(const EVP_MD *md);
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int EVP_MD_size(const EVP_MD *md);
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int EVP_MD_block_size(const EVP_MD *md);
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const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx);
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int EVP_MD_CTX_size(const EVP_MD *ctx);
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int EVP_MD_CTX_block_size(const EVP_MD *ctx);
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int EVP_MD_CTX_type(const EVP_MD *ctx);
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void *EVP_MD_CTX_md_data(const EVP_MD_CTX *ctx);
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const EVP_MD *EVP_md_null(void);
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const EVP_MD *EVP_get_digestbyname(const char *name);
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const EVP_MD *EVP_get_digestbynid(int type);
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const EVP_MD *EVP_get_digestbyobj(const ASN1_OBJECT *o);
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void EVP_MD_CTX_set_pkey_ctx(EVP_MD_CTX *ctx, EVP_PKEY_CTX *pctx);
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=head1 DESCRIPTION
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The EVP digest routines are a high level interface to message digests,
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and should be used instead of the cipher-specific functions.
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=over 4
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=item EVP_MD_CTX_new()
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Allocates and returns a digest context.
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=item EVP_MD_CTX_reset()
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Resets the digest context B<ctx>. This can be used to reuse an already
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existing context.
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=item EVP_MD_CTX_free()
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Cleans up digest context B<ctx> and frees up the space allocated to it.
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=item EVP_MD_CTX_ctrl()
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Performs digest-specific control actions on context B<ctx>.
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=item EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags(), EVP_MD_CTX_test_flags()
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Sets, clears and tests B<ctx> flags. See L</FLAGS> below for more information.
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=item EVP_DigestInit_ex()
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Sets up digest context B<ctx> to use a digest B<type> from ENGINE B<impl>.
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B<type> will typically be supplied by a function such as EVP_sha1(). If
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B<impl> is NULL then the default implementation of digest B<type> is used.
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=item EVP_DigestUpdate()
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Hashes B<cnt> bytes of data at B<d> into the digest context B<ctx>. This
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function can be called several times on the same B<ctx> to hash additional
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data.
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=item EVP_DigestFinal_ex()
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Retrieves the digest value from B<ctx> and places it in B<md>. If the B<s>
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parameter is not NULL then the number of bytes of data written (i.e. the
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length of the digest) will be written to the integer at B<s>, at most
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B<EVP_MAX_MD_SIZE> bytes will be written. After calling EVP_DigestFinal_ex()
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no additional calls to EVP_DigestUpdate() can be made, but
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EVP_DigestInit_ex() can be called to initialize a new digest operation.
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=item EVP_DigestFinalXOF()
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Interfaces to extendable-output functions, XOFs, such as SHAKE128 and SHAKE256.
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It retrieves the digest value from B<ctx> and places it in B<len>-sized <B>md.
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After calling this function no additional calls to EVP_DigestUpdate() can be
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made, but EVP_DigestInit_ex() can be called to initialize a new operation.
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=item EVP_MD_CTX_copy_ex()
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Can be used to copy the message digest state from B<in> to B<out>. This is
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useful if large amounts of data are to be hashed which only differ in the last
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few bytes.
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=item EVP_DigestInit()
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Behaves in the same way as EVP_DigestInit_ex() except it always uses the
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default digest implementation.
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=item EVP_DigestFinal()
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Similar to EVP_DigestFinal_ex() except the digest context B<ctx> is
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automatically cleaned up.
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=item EVP_MD_CTX_copy()
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Similar to EVP_MD_CTX_copy_ex() except the destination B<out> does not have to
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be initialized.
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=item EVP_MD_size(),
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EVP_MD_CTX_size()
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Return the size of the message digest when passed an B<EVP_MD> or an
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B<EVP_MD_CTX> structure, i.e. the size of the hash.
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=item EVP_MD_block_size(),
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EVP_MD_CTX_block_size()
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Return the block size of the message digest when passed an B<EVP_MD> or an
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B<EVP_MD_CTX> structure.
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=item EVP_MD_type(),
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EVP_MD_CTX_type()
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Return the NID of the OBJECT IDENTIFIER representing the given message digest
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when passed an B<EVP_MD> structure. For example, C<EVP_MD_type(EVP_sha1())>
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returns B<NID_sha1>. This function is normally used when setting ASN1 OIDs.
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=item EVP_MD_CTX_md_data()
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Return the digest method private data for the passed B<EVP_MD_CTX>.
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The space is allocated by OpenSSL and has the size originally set with
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EVP_MD_meth_set_app_datasize().
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=item EVP_MD_CTX_md()
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Returns the B<EVP_MD> structure corresponding to the passed B<EVP_MD_CTX>.
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=item EVP_MD_pkey_type()
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Returns the NID of the public key signing algorithm associated with this
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digest. For example EVP_sha1() is associated with RSA so this will return
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B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms are no
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longer linked this function is only retained for compatibility reasons.
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=item EVP_md_null()
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A "null" message digest that does nothing: i.e. the hash it returns is of zero
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length.
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=item EVP_get_digestbyname(),
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EVP_get_digestbynid(),
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EVP_get_digestbyobj()
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Returns an B<EVP_MD> structure when passed a digest name, a digest B<NID> or an
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B<ASN1_OBJECT> structure respectively.
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=item EVP_MD_CTX_set_pkey_ctx()
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Assigns an B<EVP_PKEY_CTX> to B<EVP_MD_CTX>. This is usually used to provide
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a customzied B<EVP_PKEY_CTX> to L<EVP_DigestSignInit(3)> or
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L<EVP_DigestVerifyInit(3)>. The B<pctx> passed to this function should be freed
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by the caller. A NULL B<pctx> pointer is also allowed to clear the B<EVP_PKEY_CTX>
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assigned to B<ctx>. In such case, freeing the cleared B<EVP_PKEY_CTX> or not
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depends on how the B<EVP_PKEY_CTX> is created.
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=back
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=head1 FLAGS
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EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags() and EVP_MD_CTX_test_flags()
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can be used the manipulate and test these B<EVP_MD_CTX> flags:
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=over 4
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=item EVP_MD_CTX_FLAG_ONESHOT
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This flag instructs the digest to optimize for one update only, if possible.
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=for comment EVP_MD_CTX_FLAG_CLEANED is internal, don't mention it
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=for comment EVP_MD_CTX_FLAG_REUSE is internal, don't mention it
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=for comment We currently avoid documenting flags that are only bit holder:
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EVP_MD_CTX_FLAG_NON_FIPS_ALLOW, EVP_MD_CTX_FLAGS_PAD_*
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=item EVP_MD_CTX_FLAG_NO_INIT
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This flag instructs EVP_DigestInit() and similar not to initialise the
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implementation specific data.
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=item EVP_MD_CTX_FLAG_FINALISE
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Some functions such as EVP_DigestSign only finalise copies of internal
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contexts so additional data can be included after the finalisation call.
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This is inefficient if this functionality is not required, and can be
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disabled with this flag.
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=back
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=head1 RETURN VALUES
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=over 4
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=item EVP_DigestInit_ex(),
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EVP_DigestUpdate(),
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EVP_DigestFinal_ex()
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Returns 1 for
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success and 0 for failure.
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=item EVP_MD_CTX_ctrl()
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Returns 1 if successful or 0 for failure.
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=item EVP_MD_CTX_copy_ex()
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Returns 1 if successful or 0 for failure.
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=item EVP_MD_type(),
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EVP_MD_pkey_type(),
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EVP_MD_type()
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Returns the NID of the corresponding OBJECT IDENTIFIER or NID_undef if none
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exists.
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=item EVP_MD_size(),
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EVP_MD_block_size(),
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EVP_MD_CTX_size(),
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EVP_MD_CTX_block_size()
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Returns the digest or block size in bytes.
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=item EVP_md_null()
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Returns a pointer to the B<EVP_MD> structure of the "null" message digest.
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=item EVP_get_digestbyname(),
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EVP_get_digestbynid(),
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EVP_get_digestbyobj()
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Returns either an B<EVP_MD> structure or NULL if an error occurs.
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=item EVP_MD_CTX_set_pkey_ctx()
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This function has no return value.
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=back
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=head1 NOTES
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The B<EVP> interface to message digests should almost always be used in
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preference to the low level interfaces. This is because the code then becomes
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transparent to the digest used and much more flexible.
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New applications should use the SHA-2 (such as L<EVP_sha256(3)>) or the SHA-3
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digest algorithms (such as L<EVP_sha3_512(3)>). The other digest algorithms
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are still in common use.
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For most applications the B<impl> parameter to EVP_DigestInit_ex() will be
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set to NULL to use the default digest implementation.
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The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are
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obsolete but are retained to maintain compatibility with existing code. New
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applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and
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EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context
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instead of initializing and cleaning it up on each call and allow non default
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implementations of digests to be specified.
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If digest contexts are not cleaned up after use,
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memory leaks will occur.
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EVP_MD_CTX_size(), EVP_MD_CTX_block_size(), EVP_MD_CTX_type(),
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EVP_get_digestbynid() and EVP_get_digestbyobj() are defined as
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macros.
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EVP_MD_CTX_ctrl() sends commands to message digests for additional configuration
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or control.
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=head1 EXAMPLE
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This example digests the data "Test Message\n" and "Hello World\n", using the
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digest name passed on the command line.
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#include <stdio.h>
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#include <string.h>
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#include <openssl/evp.h>
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int main(int argc, char *argv[])
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{
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EVP_MD_CTX *mdctx;
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const EVP_MD *md;
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char mess1[] = "Test Message\n";
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char mess2[] = "Hello World\n";
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unsigned char md_value[EVP_MAX_MD_SIZE];
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unsigned int md_len, i;
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if (argv[1] == NULL) {
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printf("Usage: mdtest digestname\n");
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exit(1);
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}
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md = EVP_get_digestbyname(argv[1]);
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if (md == NULL) {
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printf("Unknown message digest %s\n", argv[1]);
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exit(1);
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}
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mdctx = EVP_MD_CTX_new();
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EVP_DigestInit_ex(mdctx, md, NULL);
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EVP_DigestUpdate(mdctx, mess1, strlen(mess1));
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EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
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EVP_DigestFinal_ex(mdctx, md_value, &md_len);
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EVP_MD_CTX_free(mdctx);
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printf("Digest is: ");
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for (i = 0; i < md_len; i++)
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printf("%02x", md_value[i]);
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printf("\n");
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exit(0);
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}
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=head1 SEE ALSO
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L<dgst(1)>,
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L<evp(7)>
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The full list of digest algorithms are provided below.
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L<EVP_blake2b512(3)>,
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L<EVP_md2(3)>,
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L<EVP_md4(3)>,
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L<EVP_md5(3)>,
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L<EVP_mdc2(3)>,
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L<EVP_ripemd160(3)>,
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L<EVP_sha1(3)>,
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L<EVP_sha224(3)>,
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L<EVP_sha3_224(3)>,
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L<EVP_sm3(3)>,
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L<EVP_whirlpool(3)>
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=head1 HISTORY
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The EVP_MD_CTX_create() and EVP_MD_CTX_destroy() functions were renamed to
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EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.0, respectively.
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The link between digests and signing algorithms was fixed in OpenSSL 1.0 and
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later, so now EVP_sha1() can be used with RSA and DSA.
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The EVP_dss1() function was removed in OpenSSL 1.1.0.
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The EVP_MD_CTX_set_pkey_ctx() function was added in 1.1.1.
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=head1 COPYRIGHT
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Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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