Document i2c_ASN1_INTEGER(3).

While it was probably a mistake that steve@ made some i2c_*() and c2i_*()
functions public back in 2000 and while we would like to delete them from
the API, it may not be possible to delete this particular function because
in contrast to the others (which are already marked as intentionally
undocumented), this one is used by various real-world software, so for now,
explain what it does, just in case people find it in existing code.

While here, use the familiar term "byte" that we generally use
throughout all our manual pages, even though the ASN.1 standard
uses the term "octet" instead, which is more precise only in theory.

1 files changed, 46 insertions, 7 deletions

diff --git a/src/lib/libcrypto/man/d2i_ASN1_OCTET_STRING.3 b/src/lib/libcrypto/man/d2i_ASN1_OCTET_STRING.3
index b6c62106b7..faccbe6ad9 100644
--- a/src/lib/libcrypto/man/d2i_ASN1_OCTET_STRING.3
+++ b/src/lib/libcrypto/man/d2i_ASN1_OCTET_STRING.3
@@ -1,4 +1,4 @@
-.\"     $OpenBSD: d2i_ASN1_OCTET_STRING.3,v 1.15 2021/12/14 20:14:22 schwarze Exp $
+.\"     $OpenBSD: d2i_ASN1_OCTET_STRING.3,v 1.16 2021/12/15 15:29:23 schwarze Exp $
 .\"
 .\" Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: December 14 2021 $
+.Dd $Mdocdate: December 15 2021 $
 .Dt D2I_ASN1_OCTET_STRING 3
 .Os
 .Sh NAME
@@ -24,6 +24,7 @@
 .Nm i2d_ASN1_BIT_STRING ,
 .Nm d2i_ASN1_INTEGER ,
 .Nm i2d_ASN1_INTEGER ,
+.Nm i2c_ASN1_INTEGER ,
 .Nm d2i_ASN1_UINTEGER ,
 .Nm d2i_ASN1_ENUMERATED ,
 .Nm i2d_ASN1_ENUMERATED ,
@@ -94,6 +95,11 @@
 .Fa "ASN1_INTEGER *val_in"
 .Fa "unsigned char **der_out"
 .Fc
+.Ft int
+.Fo i2c_ASN1_INTEGER
+.Fa "ASN1_INTEGER *val_in"
+.Fa "unsigned char **der_out"
+.Fc
 .Ft ASN1_INTEGER *
 .Fo d2i_ASN1_UINTEGER
 .Fa "ASN1_INTEGER **val_out"
@@ -273,10 +279,9 @@ objects.
 For details about the semantics, examples, caveats, and bugs, see
 .Xr ASN1_item_d2i 3 .
 .Pp
-The format consists of one identifier octet,
-one or more length octets,
-and one or more content octets.
-The identifier octets and corresponding ASN.1 types are as follows:
+The format consists of one identifier byte, one or more length bytes,
+and one or more content bytes.
+The identifier bytes and corresponding ASN.1 types are as follows:
 .Bl -column ASN1_GENERALIZEDTIME identifier
 .It Em OpenSSL type Ta Em identifier Ta Em ASN.1 type
 .It Ta
@@ -296,6 +301,27 @@ The identifier octets and corresponding ASN.1 types are as follows:
 .It Vt ASN1_UTCTIME         Ta 0x17 Ta UTCTime
 .El
 .Pp
+.Fn i2c_ASN1_INTEGER
+writes only the content bytes of
+.Fa val_in
+to
+.Pf * Fa der_out
+and advances
+.Pf * Fa der_out
+to the byte after the last one written.
+The identifier and content length bytes are not written.
+It is the responsibility of the caller to make sure that the buffer
+pointed to by
+.Pf * Fa der_out
+is long enough, such that no buffer overflow can occur.
+This function does not support automatic memory allocation.
+If
+.Fa der_out
+is a
+.Dv NULL
+pointer, the function only calculates the number of content bytes
+that would be written, without writing them anywhere.
+.Pp
 .Fn d2i_DIRECTORYSTRING
 and
 .Fn i2d_DIRECTORYSTRING
@@ -320,7 +346,7 @@ and
 .Fn i2d_DIRECTORYSTRING
 that also accept IA5String, NumericString, BIT STRING, and SEQUENCE
 ASN.1 values as well as ASN.1 values with unknown identifier
-octets (0x07, 0x08, 0x09, 0x0b, 0x0d, 0x0e, 0x0f, 0x1d, and 0x1f).
+bytes (0x07, 0x08, 0x09, 0x0b, 0x0d, 0x0e, 0x0f, 0x1d, and 0x1f).
 Even though the standard requires the use of
 .Vt DirectoryString
 in the relative distinguished names described in
@@ -392,6 +418,15 @@ The
 .Fn i2d_*
 encoding functions return the number of bytes successfully encoded
 or a negative value if an error occurs.
+.Pp
+.Fn i2c_ASN1_INTEGER
+returns the number of content bytes that were or would be written or 0 if
+.Fa val_in
+is a
+.Dv NULL
+pointer or if its
+.Xr ASN1_STRING_length 3
+is negative.
 .Sh SEE ALSO
 .Xr ASN1_item_d2i 3 ,
 .Xr ASN1_STRING_new 3
@@ -449,6 +484,10 @@ first appeared in OpenSSL 0.9.3.
 These functions have been available since
 .Ox 2.6 .
 .Pp
+.Fn i2c_ASN1_INTEGER
+first appeared in OpenSSL 0.9.6 and has been available since
+.Ox 2.9 .
+.Pp
 .Fn d2i_ASN1_UNIVERSALSTRING ,
 .Fn i2d_ASN1_UNIVERSALSTRING ,
 .Fn d2i_ASN1_GENERALSTRING ,