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gpg-interface: limit search for primary key fingerprint

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The VALIDSIG status line from GnuPG with --status-fd is documented to
have 9 required and 1 optional fields [1].  The final, and optional,
field is used to specify the fingerprint of the primary key that made
the signature in case it was made by a subkey.  However, this field is
only available for OpenPGP signatures; not for CMS/X.509.

If the VALIDSIG status line does not have the optional 10th field, the
current code will continue reading onto the next status line.  And this
is the case for non-OpenPGP signatures [1].

The consequence is that a subsequent status line may be considered as
the "primary key" for signatures that does not have an actual primary
key.

Limit the search of these 9 or 10 fields to the single line to avoid
this problem.  If the 10th field is missing, report that there is no
primary key fingerprint.

[Reference]

[1] GnuPG Details, General status codes
https://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=blob;f=doc/DETAILS;h=6ce340e8c04794add995e84308bb3091450bd28f;hb=HEAD#l483

The documentation says:

    VALIDSIG <args>

    The args are:

    - <fingerprint_in_hex>
    - <sig_creation_date>
    - <sig-timestamp>
    - <expire-timestamp>
    - <sig-version>
    - <reserved>
    - <pubkey-algo>
    - <hash-algo>
    - <sig-class>
    - [ <primary-key-fpr> ]

    This status indicates that the signature is cryptographically
    valid. [...] PRIMARY-KEY-FPR is the fingerprint of the primary key
    or identical to the first argument.

    The primary-key-fpr parameter is used for OpenPGP and not available
    for CMS signatures.  [...]

Signed-off-by: Hans Jerry Illikainen <hji@dyntopia.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Hans Jerry Illikainen
2019-11-22 20:23:12 +00:00
committed by Junio C Hamano
parent 392b862e9a
commit 67a6ea6300
2 changed files with 38 additions and 6 deletions
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24
gpg-interface.c
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@ -156,21 +156,33 @@ static void parse_gpg_output(struct signature_check *sigc)
}
/* Do we have fingerprint? */
if (sigcheck_gpg_status[i].flags & GPG_STATUS_FINGERPRINT) {
const char *limit;
char **field;
next = strchrnul(line, ' ');
replace_cstring(&sigc->fingerprint, line, next);
/* Skip interim fields */
/*
* Skip interim fields. The search is
* limited to the same line since only
* OpenPGP signatures has a field with
* the primary fingerprint.
*/
limit = strchrnul(line, '\n');
for (j = 9; j > 0; j--) {
if (!*next)
if (!*next || limit <= next)
break;
line = next + 1;
next = strchrnul(line, ' ');
}
next = strchrnul(line, '\n');
free(sigc->primary_key_fingerprint);
replace_cstring(&sigc->primary_key_fingerprint,
line, next);
field = &sigc->primary_key_fingerprint;
if (!j) {
next = strchrnul(line, '\n');
replace_cstring(field, line, next);
} else {
replace_cstring(field, NULL, NULL);
}
}
break;