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Title "CMS_verify 3"
way too many mistakes in technical documents.
.nh
\fBflags is an optional set of flags, which can be used to modify the verify operation.
\fBCMS_get0_signers() retrieves the signing certificate(s) from cms, it may only be called after a successful CMS_verify() operation.
Initially some sanity checks are performed on cms. The type of cms must be SignedData. There must be at least one signature on the data and if the content is detached indata cannot be \s-1NULL\s0.
An attempt is made to locate all the signing certificate(s), first looking in the certs parameter (if it is not \s-1NULL\s0) and then looking in any certificates contained in the cms structure itself. If any signing certificate cannot be located the operation fails.
Each signing certificate is chain verified using the smimesign purpose and the supplied trusted certificate store. Any internal certificates in the message are used as untrusted CAs. If \s-1CRL\s0 checking is enabled in store any internal CRLs are used in addition to attempting to look them up in store. If any chain verify fails an error code is returned.
Finally the signed content is read (and written to out if it is not \s-1NULL\s0) and the signature's checked.
If all signature's verify correctly then the function is successful.
Any of the following flags (ored together) can be passed in the flags parameter to change the default verify behaviour.
If \s-1CMS_NOINTERN\s0 is set the certificates in the message itself are not searched when locating the signing certificate(s). This means that all the signing certificates must be in the certs parameter.
If \s-1CMS_NOCRL\s0 is set and \s-1CRL\s0 checking is enabled in store then any CRLs in the message itself are ignored.
If the \s-1CMS_TEXT\s0 flag is set \s-1MIME\s0 headers for type text/plain are deleted from the content. If the content is not of type text/plain then an error is returned.
If \s-1CMS_NO_SIGNER_CERT_VERIFY\s0 is set the signing certificates are not verified.
If \s-1CMS_NO_ATTR_VERIFY\s0 is set the signed attributes signature is not verified.
If \s-1CMS_NO_CONTENT_VERIFY\s0 is set then the content digest is not checked.
In some cases the standard techniques for looking up and validating certificates are not appropriate: for example an application may wish to lookup certificates in a database or perform customised verification. This can be achieved by setting and verifying the signers certificates manually using the signed data utility functions.
Care should be taken when modifying the default verify behaviour, for example setting \s-1CMS_NO_CONTENT_VERIFY\s0 will totally disable all content verification and any modified content will be considered valid. This combination is however useful if one merely wishes to write the content to out and its validity is not considered important.
Chain verification should arguably be performed using the signing time rather than the current time. However, since the signing time is supplied by the signer it cannot be trusted without additional evidence (such as a trusted timestamp).
\fBCMS_get0_signers() returns all signers or \s-1NULL\s0 if an error occurred.
The error can be obtained from ERR_get_error\|(3)
The lack of single pass processing means that the signed content must all be held in memory if it is not detached.
Licensed under the OpenSSL license (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>.
Indexes created Wed Apr 22 00:22:44 UTC 2026