Standard preamble:
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..
.... Set up some character translations and predefined strings. \*(-- will
give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
double quote, and \*(R" will give a right double quote. \*(C+ will
give a nicer C++. Capital omega is used to do unbreakable dashes and
therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
nothing in troff, for use with C<>.
.tr \(*W- . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\}
Escape single quotes in literal strings from groff's Unicode transform.
If the F register is turned on, we'll generate index entries on stderr for
titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
entries marked with X<> in POD. Of course, you'll have to process the
output yourself in some meaningful fashion.
Avoid warning from groff about undefined register 'F'.
.. .nr rF 0 . if \nF \{ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{ . nr % 0 . nr F 2 . \} . \} .\} .rr rF
Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
Fear. Run. Save yourself. No user-serviceable parts.
. \" fudge factors for nroff and troff . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} ========================================================================
Title "PKCS7_verify 3"
way too many mistakes in technical documents.
\fBflags is an optional set of flags, which can be used to modify the verify operation.
\fIPKCS7_get0_signers() retrieves the signer's certificates from p7, it does \fBnot check their validity or whether any signatures are valid. The certs and flags parameters have the same meanings as in PKCS7_verify().
Initially some sanity checks are performed on p7. The type of p7 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 signer's certificates, first looking in the certs parameter (if it is not \s-1NULL\s0) and then looking in any certificates contained in the p7 structure itself. If any signer's certificates cannot be located the operation fails.
Each signer's 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 any chain verify fails an error code is returned.
Finally the signed content is read (and written to out is 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. Only the flag \s-1PKCS7_NOINTERN\s0 is meaningful to PKCS7_get0_signers().
If \s-1PKCS7_NOINTERN\s0 is set the certificates in the message itself are not searched when locating the signer's certificate. This means that all the signers certificates must be in the certs parameter.
If the \s-1PKCS7_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-1PKCS7_NOVERIFY\s0 is set the signer's certificates are not chain verified.
If \s-1PKCS7_NOCHAIN\s0 is set then the certificates contained in the message are not used as untrusted CAs. This means that the whole verify chain (apart from the signer's certificate) must be contained in the trusted store.
If \s-1PKCS7_NOSIGS\s0 is set then the signatures on the data are not checked.
Care should be taken when modifying the default verify behaviour, for example setting PKCS7_NOVERIFY|PKCS7_NOSIGS will totally disable all verification and any signed message 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).
\fIPKCS7_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 and need to hold all data in memory as mentioned in PKCS7_sign() also applies to PKCS7_verify().