298 lines
12 KiB
Groff
298 lines
12 KiB
Groff
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.\" ========================================================================
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.\"
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.IX Title "EVP_DIGESTVERIFYINIT 3"
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.TH EVP_DIGESTVERIFYINIT 3 "2020-03-02" "3.0.0-dev" "OpenSSL"
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.if n .ad l
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.nh
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.SH "NAME"
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EVP_DigestVerifyInit_ex, EVP_DigestVerifyInit, EVP_DigestVerifyUpdate,
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EVP_DigestVerifyFinal, EVP_DigestVerify \- EVP signature verification functions
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/evp.h>
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\&
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\& int EVP_DigestVerifyInit_ex(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
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\& const char *mdname, const char *props,
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\& EVP_PKEY *pkey, EVP_SIGNATURE *signature);
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\& int EVP_DigestVerifyInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
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\& const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
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\& int EVP_DigestVerifyUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
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\& int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, const unsigned char *sig,
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\& size_t siglen);
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\& int EVP_DigestVerify(EVP_MD_CTX *ctx, const unsigned char *sigret,
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\& size_t siglen, const unsigned char *tbs, size_t tbslen);
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.Ve
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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The \s-1EVP\s0 signature routines are a high level interface to digital signatures.
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Input data is digested first before the signature verification takes place.
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.PP
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\&\fIEVP_DigestVerifyInit_ex()\fR sets up verification context \fBctx\fR to use a digest
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with the name \fBmdname\fR and public key \fBpkey\fR. The signature algorithm
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\&\fBsignature\fR will be used for the actual signature verification which must be
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compatible with the public key. The name of the digest to be used is passed to
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the provider of the signature algorithm in use. How that provider interprets the
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digest name is provider specific. The provider may implement that digest
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directly itself or it may (optionally) choose to fetch it (which could result in
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a digest from a different provider being selected). If the provider supports
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fetching the digest then it may use the \fBprops\fR argument for the properties to
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be used during the fetch.
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.PP
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The \fBsignature\fR parameter may be \s-1NULL\s0 in which case a suitable signature
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algorithm implementation will be implicitly fetched based on the type of key in
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use. See \fIprovider\fR\|(7) for further information about providers and fetching
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algorithms.
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.PP
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The OpenSSL default and legacy providers support fetching digests and can fetch
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those digests from any available provider. The OpenSSL fips provider also
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supports fetching digests but will only fetch digests that are themselves
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implemented inside the fips provider.
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.PP
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\&\fBctx\fR must be created with \fIEVP_MD_CTX_new()\fR before calling this function. If
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\&\fBpctx\fR is not \s-1NULL\s0, the \s-1EVP_PKEY_CTX\s0 of the verification operation will be
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written to \fB*pctx\fR: this can be used to set alternative verification options.
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Note that any existing value in \fB*pctx\fR is overwritten. The \s-1EVP_PKEY_CTX\s0 value
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returned must not be freed directly by the application if \fBctx\fR is not assigned
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an \s-1EVP_PKEY_CTX\s0 value before being passed to \fIEVP_DigestVerifyInit_ex()\fR (which
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means the \s-1EVP_PKEY_CTX\s0 is created inside \fIEVP_DigestVerifyInit_ex()\fR and it will
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be freed automatically when the \s-1EVP_MD_CTX\s0 is freed).
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.PP
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No \fB\s-1EVP_PKEY_CTX\s0\fR will be created by \fIEVP_DigestSignInit_ex()\fR if the passed
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\&\fBctx\fR has already been assigned one via \fIEVP_MD_CTX_set_pkey_ctx\fR\|(3). See also
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\&\s-1\fISM2\s0\fR\|(7).
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.PP
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Not all digests can be used for all key types. The following combinations apply.
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.IP "\s-1DSA\s0" 4
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.IX Item "DSA"
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Supports \s-1SHA1\s0, \s-1SHA224\s0, \s-1SHA256\s0, \s-1SHA384\s0 and \s-1SHA512\s0
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.IP "\s-1ECDSA\s0" 4
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.IX Item "ECDSA"
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Supports \s-1SHA1\s0, \s-1SHA224\s0, \s-1SHA256\s0, \s-1SHA384\s0, \s-1SHA512\s0 and \s-1SM3\s0
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.IP "\s-1RSA\s0 with no padding" 4
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.IX Item "RSA with no padding"
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Supports no digests (the digest \fBtype\fR must be \s-1NULL\s0)
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.IP "\s-1RSA\s0 with X931 padding" 4
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.IX Item "RSA with X931 padding"
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Supports \s-1SHA1\s0, \s-1SHA256\s0, \s-1SHA384\s0 and \s-1SHA512\s0
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.IP "All other \s-1RSA\s0 padding types" 4
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.IX Item "All other RSA padding types"
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Support \s-1SHA1\s0, \s-1SHA224\s0, \s-1SHA256\s0, \s-1SHA384\s0, \s-1SHA512\s0, \s-1MD5\s0, \s-1MD5_SHA1\s0, \s-1MD2\s0, \s-1MD4\s0, \s-1MDC2\s0,
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\&\s-1SHA3\-224\s0, \s-1SHA3\-256\s0, \s-1SHA3\-384\s0, \s-1SHA3\-512\s0
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.IP "Ed25519 and Ed448" 4
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.IX Item "Ed25519 and Ed448"
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Support no digests (the digest \fBtype\fR must be \s-1NULL\s0)
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.IP "\s-1HMAC\s0" 4
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.IX Item "HMAC"
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Supports any digest
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.IP "\s-1CMAC\s0, Poly1305 and SipHash" 4
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.IX Item "CMAC, Poly1305 and SipHash"
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Will ignore any digest provided.
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.PP
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If RSA-PSS is used and restrictions apply then the digest must match.
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.PP
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\&\fIEVP_DigestVerifyInit()\fR works in the same way as \fIEVP_DigestVerifyInit_ex()\fR except
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that the \fBmdname\fR parameter will be inferred from the supplied digest \fBtype\fR,
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and \fBprops\fR will be \s-1NULL\s0. Where supplied the \s-1ENGINE\s0 \fBe\fR will be used for the
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signature verification and digest algorithm implementations. \fBe\fR may be \s-1NULL\s0.
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.PP
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\&\fIEVP_DigestVerifyUpdate()\fR hashes \fBcnt\fR bytes of data at \fBd\fR into the
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verification context \fBctx\fR. This function can be called several times on the
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same \fBctx\fR to include additional data.
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.PP
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\&\fIEVP_DigestVerifyFinal()\fR verifies the data in \fBctx\fR against the signature in
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\&\fBsig\fR of length \fBsiglen\fR.
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.PP
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\&\fIEVP_DigestVerify()\fR verifies \fBtbslen\fR bytes at \fBtbs\fR against the signature
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in \fBsig\fR of length \fBsiglen\fR.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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\&\fIEVP_DigestVerifyInit()\fR and \fIEVP_DigestVerifyUpdate()\fR return 1 for success and 0
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for failure.
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.PP
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\&\fIEVP_DigestVerifyFinal()\fR and \fIEVP_DigestVerify()\fR return 1 for success; any other
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value indicates failure. A return value of zero indicates that the signature
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did not verify successfully (that is, \fBtbs\fR did not match the original data or
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the signature had an invalid form), while other values indicate a more serious
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error (and sometimes also indicate an invalid signature form).
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.PP
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The error codes can be obtained from \fIERR_get_error\fR\|(3).
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.SH "NOTES"
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.IX Header "NOTES"
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The \fB\s-1EVP\s0\fR interface to digital signatures 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 algorithm used and much more flexible.
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.PP
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\&\fIEVP_DigestVerify()\fR is a one shot operation which verifies a single block of
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data in one function. For algorithms that support streaming it is equivalent
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to calling \fIEVP_DigestVerifyUpdate()\fR and \fIEVP_DigestVerifyFinal()\fR. For
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algorithms which do not support streaming (e.g. PureEdDSA) it is the only way
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to verify data.
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.PP
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In previous versions of OpenSSL there was a link between message digest types
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and public key algorithms. This meant that \*(L"clone\*(R" digests such as \fIEVP_dss1()\fR
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needed to be used to sign using \s-1SHA1\s0 and \s-1DSA\s0. This is no longer necessary and
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the use of clone digest is now discouraged.
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.PP
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For some key types and parameters the random number generator must be seeded.
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If the automatic seeding or reseeding of the OpenSSL \s-1CSPRNG\s0 fails due to
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external circumstances (see \s-1\fIRAND\s0\fR\|(7)), the operation will fail.
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.PP
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The call to \fIEVP_DigestVerifyFinal()\fR internally finalizes a copy of the digest
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context. This means that \fIEVP_VerifyUpdate()\fR and \fIEVP_VerifyFinal()\fR can
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be called later to digest and verify additional data.
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.PP
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Since only a copy of the digest context is ever finalized, the context must
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be cleaned up after use by calling \fIEVP_MD_CTX_free()\fR or a memory leak
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will occur.
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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\&\fIEVP_DigestSignInit\fR\|(3),
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\&\fIEVP_DigestInit\fR\|(3),
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\&\fIevp\fR\|(7), \s-1\fIHMAC\s0\fR\|(3), \s-1\fIMD2\s0\fR\|(3),
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\&\s-1\fIMD5\s0\fR\|(3), \s-1\fIMDC2\s0\fR\|(3), \s-1\fIRIPEMD160\s0\fR\|(3),
|
||
|
|
\&\s-1\fISHA1\s0\fR\|(3), \fIopenssl\-dgst\fR\|(1),
|
||
|
|
\&\s-1\fIRAND\s0\fR\|(7)
|
||
|
|
.SH "HISTORY"
|
||
|
|
.IX Header "HISTORY"
|
||
|
|
\&\fIEVP_DigestVerifyInit()\fR, \fIEVP_DigestVerifyUpdate()\fR and \fIEVP_DigestVerifyFinal()\fR
|
||
|
|
were added in OpenSSL 1.0.0.
|
||
|
|
.PP
|
||
|
|
\&\fIEVP_DigestVerifyInit_ex()\fR was added in OpenSSL 3.0.
|
||
|
|
.PP
|
||
|
|
\&\fIEVP_DigestVerifyUpdate()\fR was converted from a macro to a function in OpenSSL
|
||
|
|
3.0.
|
||
|
|
.SH "COPYRIGHT"
|
||
|
|
.IX Header "COPYRIGHT"
|
||
|
|
Copyright 2006\-2018 The OpenSSL Project Authors. All Rights Reserved.
|
||
|
|
.PP
|
||
|
|
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use
|
||
|
|
this file except in compliance with the License. You can obtain a copy
|
||
|
|
in the file \s-1LICENSE\s0 in the source distribution or at
|
||
|
|
<https://www.openssl.org/source/license.html>.
|