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.\"
.IX Title "Crypt::ASN1 3"
.TH Crypt::ASN1 3 2026-05-12 "perl v5.42.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
Crypt::ASN1 \- DER ASN.1 parser and encoder based on libtomcrypt
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\&  use Crypt::ASN1 qw(asn1_decode_der asn1_encode_der asn1_to_string);
\&
\&  # \-\-\- decode \-\-\-
\&  my $tree = asn1_decode_der($der_bytes);
\&  my $tree = asn1_decode_der($der_bytes, { int => \*(Aqhex\*(Aq, bin => \*(Aqhex\*(Aq });
\&
\&  # \-\-\- inspect \-\-\-
\&  print asn1_to_string($tree);
\&
\&  # \-\-\- encode a decoded tree \-\-\-
\&  my $der2 = asn1_encode_der($tree);
\&
\&  # \-\-\- build from scratch \-\-\-
\&  my $der = asn1_encode_der([{
\&    type  => \*(AqSEQUENCE\*(Aq,
\&    value => [
\&      { type => \*(AqINTEGER\*(Aq,      value => \*(Aq42\*(Aq },
\&      { type => \*(AqBOOLEAN\*(Aq,      value => 1 },
\&      { type => \*(AqOID\*(Aq,          value => \*(Aq1.2.840.113549.1.1.11\*(Aq },
\&      { type => \*(AqUTF8_STRING\*(Aq,  value => \*(Aqhello\*(Aq },
\&      { type => \*(AqOCTET_STRING\*(Aq, value => "\ex00\ex01\ex02" },
\&      { type => \*(AqBIT_STRING\*(Aq,   value => "\ex03\ex02\ex01", bits => 20 },
\&      { type => \*(AqNULL\*(Aq },
\&      { type => \*(AqUTCTIME\*(Aq,      value => \*(Aq2025\-06\-15T12:00:00Z\*(Aq },
\&      { type => \*(AqCUSTOM\*(Aq, class => \*(AqCONTEXT_SPECIFIC\*(Aq,
\&        constructed => 1, tag => 0,
\&        value => [{ type => \*(AqINTEGER\*(Aq, value => \*(Aq2\*(Aq }] },
\&    ],
\&  }]);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fISince: CryptX\-0.089\fR
.PP
Parses DER\-encoded ASN.1 data into a Perl data structure without requiring
any schema, and encodes Perl data structures back to DER.
Uses libtomcrypt\*(Aqs \f(CW\*(C`der_decode_sequence_flexi\*(C'\fR for decoding.
.PP
Both the decoder output and the encoder input use the same \fBnode hash\fR
structure described below.  When given a tree produced by the decoder, the
encoder does its best to produce the same ASN.1 that was originally parsed,
regardless of what decode options were used.
.SH EXPORT
.IX Header "EXPORT"
Nothing is exported by default.
.PP
You can export selected functions:
.PP
.Vb 1
\&  use Crypt::ASN1 qw(asn1_decode_der asn1_encode_der);
.Ve
.PP
Or all of them at once:
.PP
.Vb 1
\&  use Crypt::ASN1 \*(Aq:all\*(Aq;
.Ve
.SH "NODE HASH STRUCTURE"
.IX Header "NODE HASH STRUCTURE"
Both the decoder and encoder operate on the same data structure: an \fBarrayref
of node hashrefs\fR.  Each hashref represents one ASN.1 TLV (Tag\-Length\-Value)
element.
.SS "Common keys"
.IX Subsection "Common keys"
Every node has three keys:
.ie n .IP """type"" (string, required)" 4
.el .IP "\f(CWtype\fR (string, required)" 4
.IX Item "type (string, required)"
The ASN.1 type name.  Built\-in values include:
.Sp
.Vb 5
\&  BOOLEAN  INTEGER  NULL  OID
\&  OCTET_STRING  BIT_STRING  UTF8_STRING
\&  PRINTABLE_STRING  IA5_STRING  TELETEX_STRING
\&  UTCTIME  GENERALIZEDTIME
\&  SEQUENCE  SET  CUSTOM
.Ve
.Sp
The list above is not exhaustive for decoded input.  If the decoder encounters
an ASN.1 tag that does not map to one of the built\-in type names above, it is
returned as \f(CW\*(C`CUSTOM\*(C'\fR with the appropriate \f(CW\*(C`class\*(C'\fR, \f(CW\*(C`constructed\*(C'\fR, and
\&\f(CW\*(C`tag\*(C'\fR fields.  This includes unsupported universal tags such as
\&\f(CW\*(C`ENUMERATED\*(C'\fR, which decode as \f(CW\*(C`CUSTOM\*(C'\fR with \f(CW\*(C`class => "UNIVERSAL"\*(C'\fR.
.ie n .IP """value"" (varies, required for most types)" 4
.el .IP "\f(CWvalue\fR (varies, required for most types)" 4
.IX Item "value (varies, required for most types)"
The decoded value.  Its Perl type depends on \f(CW\*(C`type\*(C'\fR and sometimes on the
\&\f(CW\*(C`format\*(C'\fR key \-\- see "Per\-type details" below.
.ie n .IP """format"" (string, decoder sets it, encoder reads it)" 4
.el .IP "\f(CWformat\fR (string, decoder sets it, encoder reads it)" 4
.IX Item "format (string, decoder sets it, encoder reads it)"
Tells the encoder how the \f(CW\*(C`value\*(C'\fR is represented so it can convert it back
to DER.  Set automatically by the decoder; when building nodes from scratch
you may omit it \-\- the encoder then assumes the default representation for
each type.
.SS "Per\-type details"
.IX Subsection "Per-type details"
Each subsection below documents one \f(CW\*(C`type\*(C'\fR.  For types where the \f(CW\*(C`value\*(C'\fR
representation depends on the decode option used, a \fBformat table\fR lists
every \f(CW\*(C`format\*(C'\fR/\f(CW\*(C`value\*(C'\fR combination.  \fBThe encoder accepts every
combination shown\fR \-\- it reads \f(CW\*(C`format\*(C'\fR and converts \f(CW\*(C`value\*(C'\fR back to DER
automatically.
.PP
\fIBOOLEAN\fR
.IX Subsection "BOOLEAN"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is \f(CW1\fR (true) or \f(CW0\fR (false).  \f(CW\*(C`format\*(C'\fR is always \f(CW"bool"\fR.
.PP
.Vb 1
\&  { type => "BOOLEAN", format => "bool", value => 1 }
.Ve
.PP
\fIINTEGER\fR
.IX Subsection "INTEGER"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is an arbitrary\-precision signed integer.  \f(CW\*(C`format\*(C'\fR describes the
representation:
.PP
.Vb 5
\&  format    value                        decode option     example
\&  \-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
\&  decimal   decimal string               (default)         "255"
\&  hex       lowercase hex string         int => \*(Aqhex\*(Aq      "ff"
\&  bytes     big\-endian binary string     int => \*(Aqbytes\*(Aq    "\exff"
.Ve
.PP
All three forms are accepted by the encoder.  When \f(CW\*(C`format\*(C'\fR is absent the
encoder treats \f(CW\*(C`value\*(C'\fR as a decimal string (a Perl integer is fine too).
.PP
Negative integers: \f(CW\*(C`decimal\*(C'\fR and \f(CW\*(C`hex\*(C'\fR carry a leading \f(CW\*(C`\-\*(C'\fR (e.g. \f(CW"\-5"\fR).
\&\f(CW\*(C`bytes\*(C'\fR stores the unsigned magnitude only and is intended for naturally
unsigned values such as RSA moduli.  When decoding with \f(CW\*(C`int => \*(Aqbytes\*(Aq\*(C'\fR,
negative ASN.1 INTEGER values are rejected.
.PP
\fINULL\fR
.IX Subsection "NULL"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is always \f(CW\*(C`undef\*(C'\fR.  \f(CW\*(C`format\*(C'\fR is always \f(CW"null"\fR.  The encoder
ignores \f(CW\*(C`value\*(C'\fR.
.PP
.Vb 1
\&  { type => "NULL", format => "null", value => undef }
.Ve
.PP
\fIOID\fR
.IX Subsection "OID"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR, and optionally \f(CW\*(C`name\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is a dotted\-decimal OID string (at least two arcs).  \f(CW\*(C`format\*(C'\fR is
always \f(CW"oid"\fR.
.PP
.Vb 1
\&  { type => "OID", format => "oid", value => "1.2.840.113549.1.1.11" }
.Ve
.PP
As a convenience, the encoder accepts textual arcs with leading zeros and
lets DER encoding canonicalize them.  For example, \f(CW"2.000.1"\fR encodes and
decodes back as \f(CW"2.0.1"\fR.
.PP
\&\fBOptional key\fR: \f(CW\*(C`name\*(C'\fR \-\- present only when the \f(CW\*(C`oidmap\*(C'\fR decode option
is supplied and the OID is found in the map.  Ignored by the encoder.
.PP
.Vb 1
\&  { ..., name => "sha256WithRSAEncryption" }   # when oidmap matches
.Ve
.PP
\fIOCTET_STRING\fR
.IX Subsection "OCTET_STRING"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is binary data.  \f(CW\*(C`format\*(C'\fR describes the representation:
.PP
.Vb 5
\&  format    value                        decode option      example
\&  \-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-
\&  bytes     raw binary string            (default)          "\ex04\ex01"
\&  hex       lowercase hex string         bin => \*(Aqhex\*(Aq       "0401"
\&  base64    Base64\-encoded string        bin => \*(Aqbase64\*(Aq    "BAE="
.Ve
.PP
All three forms are accepted by the encoder.  When \f(CW\*(C`format\*(C'\fR is absent the
encoder treats \f(CW\*(C`value\*(C'\fR as raw bytes.
.PP
\fIBIT_STRING\fR
.IX Subsection "BIT_STRING"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR, \f(CW\*(C`bits\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is the packed bit data (MSB\-first).  \f(CW\*(C`format\*(C'\fR follows the same
rules as \f(CW\*(C`OCTET_STRING\*(C'\fR (\f(CW"bytes"\fR, \f(CW"hex"\fR, or \f(CW"base64"\fR).  All three
forms are accepted by the encoder.
.PP
\&\f(CW\*(C`bits\*(C'\fR is the exact number of significant bits.  The quantity
\&\f(CW\*(C`8 * byte_length(value) \- bits\*(C'\fR gives the number of unused trailing
bits in the last byte.
.PP
When \f(CW\*(C`format\*(C'\fR is absent the encoder treats \f(CW\*(C`value\*(C'\fR as raw bytes.  When
\&\f(CW\*(C`bits\*(C'\fR is absent it defaults to \f(CW\*(C`8 * length(value)\*(C'\fR (no unused bits).
.PP
.Vb 3
\&  # default format (raw bytes, 25 significant bits)
\&  { type => "BIT_STRING", format => "bytes",
\&    value => "\ex03\ex02\ex01\ex00", bits => 25 }
\&
\&  # hex format
\&  { type => "BIT_STRING", format => "hex",
\&    value => "03020100", bits => 25 }
.Ve
.PP
\fIUTF8_STRING\fR
.IX Subsection "UTF8_STRING"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is a Perl Unicode string (\f(CW\*(C`utf8\*(C'\fR flag on).  \f(CW\*(C`format\*(C'\fR is always
\&\f(CW"utf8"\fR.
.PP
.Vb 1
\&  { type => "UTF8_STRING", format => "utf8", value => "caf\ex{e9}" }
.Ve
.PP
\fIPRINTABLE_STRING, IA5_STRING, TELETEX_STRING\fR
.IX Subsection "PRINTABLE_STRING, IA5_STRING, TELETEX_STRING"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is a byte string.  \f(CW\*(C`format\*(C'\fR is always \f(CW"string"\fR for all three.
.PP
.Vb 3
\&  { type => "PRINTABLE_STRING", format => "string", value => "abc" }
\&  { type => "IA5_STRING",       format => "string", value => "ia5" }
\&  { type => "TELETEX_STRING",   format => "string", value => "tele" }
.Ve
.PP
\fIUTCTIME\fR
.IX Subsection "UTCTIME"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is a timestamp.  \f(CW\*(C`format\*(C'\fR describes the representation:
.PP
.Vb 4
\&  format    value                          decode option    example
\&  \-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
\&  rfc3339   RFC 3339 string                (default)        "2024\-01\-15T10:30:00Z"
\&  epoch     Unix timestamp (integer)       dt => \*(Aqepoch\*(Aq    1705314600
.Ve
.PP
Both forms are accepted by the encoder.  When \f(CW\*(C`format\*(C'\fR is absent, the
encoder auto\-detects: an all\-digit value is treated as epoch, a value
matching \f(CW\*(C`YYYY\-\*(C'\fR is treated as RFC 3339.
.PP
For \f(CW\*(C`UTCTIME\*(C'\fR, encoder input must fall within the UTCTime year window
\&\f(CW1950..2049\fR; values outside that range are rejected.  Fractional seconds
are also rejected for \f(CW\*(C`UTCTIME\*(C'\fR.
.PP
Time validation in the encoder is currently \fBsyntactic\fR, not full calendar
validation.  The encoder checks the accepted input shape and ASN.1\-specific
constraints above, but it does not verify that every RFC 3339\-looking date
and time is semantically valid.
.PP
The decoder expands the 2\-digit UTCTime year using the RFC 5280 window
(YY >= 50 → 19YY, else 20YY).  Timezone offsets are preserved
(e.g. \f(CW"2024\-01\-15T10:30:00+05:30"\fR).
.PP
\fIGENERALIZEDTIME\fR
.IX Subsection "GENERALIZEDTIME"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
Same \f(CW\*(C`format\*(C'\fR rules as \f(CW\*(C`UTCTIME\*(C'\fR; both forms are accepted by the encoder.
Fractional seconds are preserved (e.g. \f(CW"2024\-01\-15T10:30:00.125Z"\fR).
Validation is likewise syntactic only; semantically invalid calendar values
that match the accepted timestamp syntax are not currently rejected.
.PP
\fISEQUENCE\fR
.IX Subsection "SEQUENCE"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
\&\f(CW\*(C`value\*(C'\fR is an arrayref of child node hashrefs (in order).  \f(CW\*(C`format\*(C'\fR is
always \f(CW"array"\fR.
.PP
.Vb 1
\&  { type => "SEQUENCE", format => "array", value => [ ...children... ] }
.Ve
.PP
\fISET\fR
.IX Subsection "SET"
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR.
.PP
Same structure as \f(CW\*(C`SEQUENCE\*(C'\fR.  \f(CW\*(C`format\*(C'\fR is always \f(CW"array"\fR.  Both
ASN.1 SET and SET OF are represented as \f(CW\*(C`type => "SET"\*(C'\fR (they share
the same DER tag \f(CW0x31\fR).
.PP
\fICUSTOM\fR
.IX Subsection "CUSTOM"
.PP
Represents any tag that does not map to one of the built\-in type names above.
This is commonly used for context\-specific implicit/explicit tags (\f(CW\*(C`[0]\*(C'\fR,
\&\f(CW\*(C`[1]\*(C'\fR, ...) found in X.509 certificates and other ASN.1 schemas, but it can
also be emitted by the decoder for unsupported universal tags.
.PP
\&\fBKeys\fR: \f(CW\*(C`type\*(C'\fR, \f(CW\*(C`format\*(C'\fR, \f(CW\*(C`value\*(C'\fR, \f(CW\*(C`class\*(C'\fR, \f(CW\*(C`constructed\*(C'\fR, \f(CW\*(C`tag\*(C'\fR.
.ie n .IP """class"" (string) \-\- ""CONTEXT_SPECIFIC"", ""APPLICATION"", ""UNIVERSAL"", or ""PRIVATE""" 4
.el .IP "\f(CWclass\fR (string) \-\- \f(CW""CONTEXT_SPECIFIC""\fR, \f(CW""APPLICATION""\fR, \f(CW""UNIVERSAL""\fR, or \f(CW""PRIVATE""\fR" 4
.IX Item "class (string) -- ""CONTEXT_SPECIFIC"", ""APPLICATION"", ""UNIVERSAL"", or ""PRIVATE"""
.PD 0
.ie n .IP """constructed"" (integer) \-\- 1 if constructed, 0 if primitive" 4
.el .IP "\f(CWconstructed\fR (integer) \-\- \f(CW1\fR if constructed, \f(CW0\fR if primitive" 4
.IX Item "constructed (integer) -- 1 if constructed, 0 if primitive"
.ie n .IP """tag"" (integer) \-\- the tag number (e.g. 0 for ""[0]"")" 4
.el .IP "\f(CWtag\fR (integer) \-\- the tag number (e.g. \f(CW0\fR for \f(CW[0]\fR)" 4
.IX Item "tag (integer) -- the tag number (e.g. 0 for [0])"
.PD
Must be a non\-negative integer within the range supported by the current
encoder build.
.PP
\&\fBConstructed\fR (\f(CW\*(C`constructed => 1\*(C'\fR): \f(CW\*(C`value\*(C'\fR is an arrayref of child
nodes.  \f(CW\*(C`format\*(C'\fR is \f(CW"array"\fR.
.PP
.Vb 3
\&  { type => "CUSTOM", format => "array",
\&    class => "CONTEXT_SPECIFIC", constructed => 1, tag => 0,
\&    value => [ { type => "INTEGER", ... } ] }
.Ve
.PP
\&\fBPrimitive\fR (\f(CW\*(C`constructed => 0\*(C'\fR): \f(CW\*(C`value\*(C'\fR is raw data.  \f(CW\*(C`format\*(C'\fR
follows the same rules as \f(CW\*(C`OCTET_STRING\*(C'\fR (\f(CW"bytes"\fR, \f(CW"hex"\fR, or
\&\f(CW"base64"\fR depending on the \f(CW\*(C`bin\*(C'\fR decode option).  All three forms are
accepted by the encoder.  Primitive \f(CW\*(C`CUSTOM\*(C'\fR values must not be references.
.PP
.Vb 4
\&  # default format
\&  { type => "CUSTOM", format => "bytes",
\&    class => "CONTEXT_SPECIFIC", constructed => 0, tag => 1,
\&    value => "\exAA\exBB" }
\&
\&  # hex format (bin => \*(Aqhex\*(Aq)
\&  { type => "CUSTOM", format => "hex",
\&    class => "CONTEXT_SPECIFIC", constructed => 0, tag => 1,
\&    value => "aabb" }
.Ve
.SS "Re\-encoding Decoded Trees"
.IX Subsection "Re-encoding Decoded Trees"
The encoder reads \f(CW\*(C`format\*(C'\fR and converts \f(CW\*(C`value\*(C'\fR back to DER before
encoding.  When given a tree returned by \f(CW\*(C`asn1_decode_der\*(C'\fR, it does its best
to produce the same ASN.1 that was originally parsed, regardless of the
decode options used:
.PP
.Vb 2
\&  my $tree = asn1_decode_der($der, { int=>\*(Aqhex\*(Aq, bin=>\*(Aqbase64\*(Aq, dt=>\*(Aqepoch\*(Aq });
\&  my $der2 = asn1_encode_der($tree);
.Ve
.SS "Building nodes from scratch"
.IX Subsection "Building nodes from scratch"
When constructing nodes by hand you need \f(CW\*(C`type\*(C'\fR and \f(CW\*(C`value\*(C'\fR (plus the
extra keys noted above for \f(CW\*(C`CUSTOM\*(C'\fR and \f(CW\*(C`BIT_STRING\*(C'\fR).  You may omit
\&\f(CW\*(C`format\*(C'\fR; the encoder assumes:
.PP
.Vb 8
\&  Type              default value interpretation
\&  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-  \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-
\&  INTEGER           decimal string or Perl integer
\&  OCTET_STRING      raw bytes
\&  BIT_STRING        raw packed bytes, bits = length(value) * 8
\&  UTCTIME           RFC 3339 string (or all\-digit epoch)
\&  GENERALIZEDTIME   RFC 3339 string (or all\-digit epoch)
\&  CUSTOM primitive  raw bytes
.Ve
.PP
You may also supply \f(CW\*(C`format\*(C'\fR explicitly if you prefer to work with hex
or base64 representations:
.PP
.Vb 3
\&  # these two produce identical DER
\&  { type => "OCTET_STRING", value => "\ex04\ex01" }
\&  { type => "OCTET_STRING", format => "hex", value => "0401" }
.Ve
.SH FUNCTIONS
.IX Header "FUNCTIONS"
.SS asn1_decode_der
.IX Subsection "asn1_decode_der"
.Vb 2
\&  my $tree = asn1_decode_der($der_bytes);
\&  my $tree = asn1_decode_der($der_bytes, \e%opts);
.Ve
.PP
Parses \f(CW$der_bytes\fR and returns an arrayref of top\-level node hashrefs.
Croaks on parse error.
.PP
The optional \f(CW%opts\fR hashref controls value formatting:
.ie n .IP """int => \*(Aqhex\*(Aq | \*(Aqbytes\*(Aq""" 4
.el .IP "\f(CWint => \*(Aqhex\*(Aq | \*(Aqbytes\*(Aq\fR" 4
.IX Item "int => 'hex' | 'bytes'"
How to represent \f(CW\*(C`INTEGER\*(C'\fR values.  Default is a decimal string
(\f(CW\*(C`format=>"decimal"\*(C'\fR).
\&\f(CW\*(Aqhex\*(Aq\fR gives a lowercase hex string (\f(CW\*(C`format=>"hex"\*(C'\fR).
\&\f(CW\*(Aqbytes\*(Aq\fR gives a raw big\-endian binary string (\f(CW\*(C`format=>"bytes"\*(C'\fR) for
non\-negative INTEGER values only; decoding croaks if the DER INTEGER is
negative.
.ie n .IP """bin => \*(Aqhex\*(Aq | \*(Aqbase64\*(Aq""" 4
.el .IP "\f(CWbin => \*(Aqhex\*(Aq | \*(Aqbase64\*(Aq\fR" 4
.IX Item "bin => 'hex' | 'base64'"
How to represent \f(CW\*(C`OCTET_STRING\*(C'\fR, \f(CW\*(C`BIT_STRING\*(C'\fR, and primitive \f(CW\*(C`CUSTOM\*(C'\fR
values.  Default is raw binary bytes (\f(CW\*(C`format=>"bytes"\*(C'\fR).
\&\f(CW\*(Aqhex\*(Aq\fR gives a lowercase hex string (\f(CW\*(C`format=>"hex"\*(C'\fR).
\&\f(CW\*(Aqbase64\*(Aq\fR gives a Base64\-encoded string (\f(CW\*(C`format=>"base64"\*(C'\fR).
.ie n .IP """dt => \*(Aqepoch\*(Aq""" 4
.el .IP "\f(CWdt => \*(Aqepoch\*(Aq\fR" 4
.IX Item "dt => 'epoch'"
How to represent \f(CW\*(C`UTCTIME\*(C'\fR and \f(CW\*(C`GENERALIZEDTIME\*(C'\fR values.  Default is an
RFC 3339 string (\f(CW\*(C`format=>"rfc3339"\*(C'\fR).
\&\f(CW\*(Aqepoch\*(Aq\fR gives a Unix timestamp integer (\f(CW\*(C`format=>"epoch"\*(C'\fR).
This works reliably only on Perls with 64\-bit integers; on 32\-bit integer
Perls, large timestamps may overflow or lose precision.
.ie n .IP """oidmap => \e%map""" 4
.el .IP "\f(CWoidmap => \e%map\fR" 4
.IX Item "oidmap => %map"
A hashref mapping dotted OID strings to friendly names.  When a decoded
\&\f(CW\*(C`OID\*(C'\fR node\*(Aqs value exists as a key in \f(CW%map\fR, the node gets an additional
\&\f(CW\*(C`name\*(C'\fR key with the mapped value.  Does not affect encoding.
.SS asn1_decode_pem
.IX Subsection "asn1_decode_pem"
.Vb 2
\&  my $tree = asn1_decode_pem($pem_string);
\&  my $tree = asn1_decode_pem($pem_string, \e%opts);
.Ve
.PP
Decodes the PEM envelope first (via "pem_to_der" in Crypt::Misc), then parses
the resulting DER bytes.  Accepts the same \f(CW%opts\fR as \f(CW\*(C`asn1_decode_der\*(C'\fR.
.SS asn1_decode_der_file
.IX Subsection "asn1_decode_der_file"
.Vb 2
\&  my $tree = asn1_decode_der_file($filename);
\&  my $tree = asn1_decode_der_file($filename, \e%opts);
.Ve
.PP
Reads \f(CW$filename\fR as raw binary and parses it as DER.
.SS asn1_decode_pem_file
.IX Subsection "asn1_decode_pem_file"
.Vb 2
\&  my $tree = asn1_decode_pem_file($filename);
\&  my $tree = asn1_decode_pem_file($filename, \e%opts);
.Ve
.PP
Reads \f(CW$filename\fR, decodes the PEM envelope, then parses the DER bytes.
.SS asn1_encode_der
.IX Subsection "asn1_encode_der"
.Vb 1
\&  my $der_bytes = asn1_encode_der($tree);
.Ve
.PP
Encodes \f(CW$tree\fR (an arrayref of node hashrefs) to DER bytes.  The input
may be a tree previously returned by \f(CW\*(C`asn1_decode_der\*(C'\fR or one
built from scratch.  Croaks on invalid input.
.PP
The encoder normalizes every node before encoding: it reads \f(CW\*(C`format\*(C'\fR (if
present) to determine how to interpret \f(CW\*(C`value\*(C'\fR, converts it to the canonical
DER form, and encodes it.
.PP
The current low\-level encoder supports element content lengths up to
\&\f(CW0xffffffff\fR bytes; larger values are rejected.
.SS asn1_encode_pem
.IX Subsection "asn1_encode_pem"
.Vb 1
\&  my $pem_string = asn1_encode_pem($tree, $header);
.Ve
.PP
Encodes \f(CW$tree\fR to DER, then wraps in a PEM envelope with the given
\&\f(CW$header\fR (e.g. \f(CW"CERTIFICATE"\fR, \f(CW"RSA PRIVATE KEY"\fR).  Defaults to
\&\f(CW"DATA"\fR if \f(CW$header\fR is omitted.
.SS asn1_encode_der_file
.IX Subsection "asn1_encode_der_file"
.Vb 1
\&  asn1_encode_der_file($tree, $filename);
.Ve
.PP
Encodes \f(CW$tree\fR to DER and writes it to \f(CW$filename\fR.
.SS asn1_encode_pem_file
.IX Subsection "asn1_encode_pem_file"
.Vb 1
\&  asn1_encode_pem_file($tree, $header, $filename);
.Ve
.PP
Encodes \f(CW$tree\fR to PEM and writes it to \f(CW$filename\fR.
.SS asn1_to_string
.IX Subsection "asn1_to_string"
.Vb 1
\&  my $text = asn1_to_string($tree);
.Ve
.PP
Returns a human\-readable text representation of \f(CW$tree\fR (an arrayref of
node hashrefs as returned by any \f(CW\*(C`asn1_decode_*\*(C'\fR function).  Useful for
debugging and inspection, similar to \f(CW\*(C`openssl asn1parse\*(C'\fR output.
.PP
.Vb 1
\&  print asn1_to_string(asn1_decode_pem_file("cert.pem"));
.Ve
.PP
produces output like:
.PP
.Vb 10
\&  SEQUENCE (3 elem)
\&    SEQUENCE (8 elem)
\&      context_specific [0] cons (1 elem)
\&        INTEGER:2
\&      INTEGER:17923815188543234454
\&      SEQUENCE (2 elem)
\&        OBJECT:1.2.840.113549.1.1.11
\&        NULL:
\&      ...
\&    BIT STRING:3082010a0282010100c242299a49420c21dcf9b957afcdc49... (2160 bit)
.Ve
.PP
Binary values (\f(CW\*(C`OCTET_STRING\*(C'\fR, \f(CW\*(C`BIT_STRING\*(C'\fR, primitive \f(CW\*(C`CUSTOM\*(C'\fR) are
shown as lowercase hex, truncated to 64 characters with \f(CW\*(C`...\*(C'\fR for longer
values.  \f(CW\*(C`BIT_STRING\*(C'\fR additionally shows the bit count in parentheses.
\&\f(CW\*(C`OID\*(C'\fR nodes that have a \f(CW\*(C`name\*(C'\fR key (via \f(CW\*(C`oidmap\*(C'\fR) show the name in
parentheses after the dotted value.
.PP
The function handles trees decoded with any combination of decode options
(\f(CW\*(C`int\*(C'\fR, \f(CW\*(C`bin\*(C'\fR, \f(CW\*(C`dt\*(C'\fR).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
CryptX, Crypt::Misc