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git://git.gnupg.org/gnupg.git
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gpg: Improve documentation and comments related to OpenPGP packets.
-- Signed-off-by: Neal H. Walfield <neal@g10code.com>
This commit is contained in:
Neal H. Walfield
parent
c9636a1acc
commit
b7b4a1bdd9
3 changed files with 362 additions and 66 deletions
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@ -310,6 +310,11 @@ write_fake_data (IOBUF out, gcry_mpi_t a)
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}
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/* Serialize the user id (RFC 4880, Section 5.11) or the user
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attribute UID (Section 5.12) and write it to OUT.
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CTB is the serialization's CTB. It specifies the header format and
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the packet's type. The header length must not be set. */
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static int
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do_user_id( IOBUF out, int ctb, PKT_user_id *uid )
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{
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@ -332,12 +337,31 @@ do_user_id( IOBUF out, int ctb, PKT_user_id *uid )
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}
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/* Serialize the key (RFC 4880, Section 5.5) described by PK and write
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it to OUT.
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This function serializes both primary keys and subkeys with or
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without a secret part.
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CTB is the serialization's CTB. It specifies the header format and
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the packet's type. The header length must not be set.
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PK->VERSION specifies the serialization format. A value of 0 means
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to use the default version. Currently, only version 4 packets are
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supported.
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*/
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static int
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do_key (iobuf_t out, int ctb, PKT_public_key *pk)
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{
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gpg_error_t err = 0;
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/* The length of the body is stored in the packet's header, which
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occurs before the body. Unfortunately, we don't know the length
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of the packet's body until we've written all of the data! To
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work around this, we first write the data into this temporary
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buffer, then generate the header, and finally copy the contents
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of this buffer to OUT. */
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iobuf_t a = iobuf_temp();
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int i, nskey, npkey;
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iobuf_t a = iobuf_temp(); /* Build in a self-enlarging buffer. */
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log_assert (pk->version == 0 || pk->version == 4);
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log_assert (ctb_pkttype (ctb) == PKT_PUBLIC_KEY
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@ -355,7 +379,7 @@ do_key (iobuf_t out, int ctb, PKT_public_key *pk)
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iobuf_put (a, pk->pubkey_algo );
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/* Get number of secret and public parameters. They are held in one
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array first the public ones, then the secret ones. */
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array: the public ones followed by the secret ones. */
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nskey = pubkey_get_nskey (pk->pubkey_algo);
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npkey = pubkey_get_npkey (pk->pubkey_algo);
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@ -463,7 +487,7 @@ do_key (iobuf_t out, int ctb, PKT_public_key *pk)
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writing all the other stuff, so that we know the length of
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the packet */
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write_header2 (out, ctb, iobuf_get_temp_length(a), pk->hdrbytes);
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/* And finally write it out to the real stream. */
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/* And finally write it out to the real stream. */
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err = iobuf_write_temp (out, a);
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}
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@ -471,6 +495,11 @@ do_key (iobuf_t out, int ctb, PKT_public_key *pk)
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return err;
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}
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/* Serialize the symmetric-key encrypted session key packet (RFC 4880,
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5.3) described by ENC and write it to OUT.
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CTB is the serialization's CTB. It specifies the header format and
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the packet's type. The header length must not be set. */
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static int
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do_symkey_enc( IOBUF out, int ctb, PKT_symkey_enc *enc )
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{
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@ -479,10 +508,23 @@ do_symkey_enc( IOBUF out, int ctb, PKT_symkey_enc *enc )
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log_assert (ctb_pkttype (ctb) == PKT_SYMKEY_ENC);
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/* The only acceptable version. */
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assert( enc->version == 4 );
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switch( enc->s2k.mode ) {
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case 0: case 1: case 3: break;
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default: log_bug("do_symkey_enc: s2k=%d\n", enc->s2k.mode );
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/* RFC 4880, Section 3.7. */
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switch( enc->s2k.mode )
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{
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/* Simple S2K. */
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case 0:
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/* Salted S2K. */
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case 1:
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/* Iterated and salted S2K. */
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case 3:
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/* Reasonable values. */
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break;
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default:
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log_bug("do_symkey_enc: s2k=%d\n", enc->s2k.mode );
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}
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iobuf_put( a, enc->version );
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iobuf_put( a, enc->cipher_algo );
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@ -504,6 +546,11 @@ do_symkey_enc( IOBUF out, int ctb, PKT_symkey_enc *enc )
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}
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/* Serialize the public-key encrypted session key packet (RFC 4880,
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5.1) described by ENC and write it to OUT.
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CTB is the serialization's CTB. It specifies the header format and
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the packet's type. The header length must not be set. */
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static int
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do_pubkey_enc( IOBUF out, int ctb, PKT_pubkey_enc *enc )
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{
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@ -548,6 +595,8 @@ do_pubkey_enc( IOBUF out, int ctb, PKT_pubkey_enc *enc )
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}
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/* Calculate the length of the serialized plaintext packet PT (RFC
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4480, Section 5.9). */
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static u32
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calc_plaintext( PKT_plaintext *pt )
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{
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@ -561,6 +610,15 @@ calc_plaintext( PKT_plaintext *pt )
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return pt->len? (1 + 1 + pt->namelen + 4 + pt->len) : 0;
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}
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/* Serialize the plaintext packet (RFC 4880, 5.9) described by PT and
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write it to OUT.
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The body of the message is stored in PT->BUF. The amount of data
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to write is PT->LEN. (PT->BUF should be configured to return EOF
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after this much data has been read.) If PT->LEN is 0 and CTB
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indicates that this is a new format packet, then partial block mode
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is assumed to have been enabled on OUT. On success, partial block
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mode is disabled. */
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static int
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do_plaintext( IOBUF out, int ctb, PKT_plaintext *pt )
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{
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@ -591,6 +649,13 @@ do_plaintext( IOBUF out, int ctb, PKT_plaintext *pt )
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/* Serialize the symmetrically encrypted data packet (RFC 4880,
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Section 5.7) described by ED and write it to OUT.
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Note: this only writes the packets header! The call must then
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follow up and write the initial random data and the body to OUT.
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(If you use the encryption iobuf filter (cipher_filter), then this
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is done automatically.) */
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static int
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do_encrypted( IOBUF out, int ctb, PKT_encrypted *ed )
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{
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@ -608,6 +673,14 @@ do_encrypted( IOBUF out, int ctb, PKT_encrypted *ed )
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return rc;
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}
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/* Serialize the symmetrically encrypted integrity protected data
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packet (RFC 4880, Section 5.13) described by ED and write it to
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OUT.
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Note: this only writes the packet's header! The caller must then
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follow up and write the initial random data, the body and the MDC
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packet to OUT. (If you use the encryption iobuf filter
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(cipher_filter), then this is done automatically.) */
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static int
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do_encrypted_mdc( IOBUF out, int ctb, PKT_encrypted *ed )
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{
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@ -628,6 +701,11 @@ do_encrypted_mdc( IOBUF out, int ctb, PKT_encrypted *ed )
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}
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/* Serialize the compressed packet (RFC 4880, Section 5.6) described
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by CD and write it to OUT.
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Note: this only writes the packet's header! The caller must then
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follow up and write the body to OUT. */
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static int
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do_compressed( IOBUF out, int ctb, PKT_compressed *cd )
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{
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@ -983,6 +1061,15 @@ build_attribute_subpkt(PKT_user_id *uid,byte type,
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uid->attrib_len+=idx+headerlen+buflen;
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}
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/* Turn the notation described by the string STRING into a notation.
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STRING has the form:
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- -name - Delete the notation.
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- name@domain.name=value - Normal notation
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- !name@domain.name=value - Notation with critical bit set.
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The caller must free the result using free_notation(). */
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struct notation *
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string_to_notation(const char *string,int is_utf8)
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{
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@ -1073,6 +1160,8 @@ string_to_notation(const char *string,int is_utf8)
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return NULL;
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}
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/* Return all of the notations stored in the signature SIG. The
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caller must free them using free_notation(). */
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struct notation *
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sig_to_notation(PKT_signature *sig)
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{
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@ -1081,6 +1170,15 @@ sig_to_notation(PKT_signature *sig)
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int seq=0,crit;
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struct notation *list=NULL;
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/* See RFC 4880, 5.2.3.16 for the format of notation data. In
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short, a notation has:
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- 4 bytes of flags
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- 2 byte name length (n1)
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- 2 byte value length (n2)
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- n1 bytes of name data
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- n2 bytes of value data
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*/
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while((p=enum_sig_subpkt(sig->hashed,SIGSUBPKT_NOTATION,&len,&seq,&crit)))
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{
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int n1,n2;
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@ -1092,7 +1190,9 @@ sig_to_notation(PKT_signature *sig)
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continue;
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}
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/* name length. */
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n1=(p[4]<<8)|p[5];
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/* value length. */
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n2=(p[6]<<8)|p[7];
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if(8+n1+n2!=len)
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@ -1108,12 +1208,14 @@ sig_to_notation(PKT_signature *sig)
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n->name[n1]='\0';
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if(p[0]&0x80)
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/* The value is human-readable. */
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{
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n->value=xmalloc(n2+1);
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memcpy(n->value,&p[8+n1],n2);
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n->value[n2]='\0';
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}
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else
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/* Binary data. */
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{
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n->bdat=xmalloc(n2);
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n->blen=n2;
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@ -1134,6 +1236,9 @@ sig_to_notation(PKT_signature *sig)
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return list;
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}
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/* Release the resources associated with the *list* of notations. To
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release a single notation, make sure that notation->next is
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NULL. */
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void
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free_notation(struct notation *notation)
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{
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@ -1150,6 +1255,8 @@ free_notation(struct notation *notation)
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}
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}
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/* Serialize the signature packet (RFC 4880, Section 5.2) described by
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SIG and write it to OUT. */
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static int
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do_signature( IOBUF out, int ctb, PKT_signature *sig )
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{
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@ -1217,6 +1324,8 @@ do_signature( IOBUF out, int ctb, PKT_signature *sig )
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}
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/* Serialize the one-pass signature packet (RFC 4880, Section 5.4)
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described by OPS and write it to OUT. */
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static int
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do_onepass_sig( IOBUF out, int ctb, PKT_onepass_sig *ops )
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{
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@ -1236,6 +1345,7 @@ do_onepass_sig( IOBUF out, int ctb, PKT_onepass_sig *ops )
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}
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/* Write a 16-bit quantity to OUT in big endian order. */
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static int
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write_16(IOBUF out, u16 a)
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{
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@ -1245,6 +1355,7 @@ write_16(IOBUF out, u16 a)
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return 0;
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}
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/* Write a 32-bit quantity to OUT in big endian order. */
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static int
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write_32(IOBUF out, u32 a)
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{
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@ -1308,11 +1419,26 @@ write_sign_packet_header (IOBUF out, int ctb, u32 len)
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}
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/****************
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* If HDRLEN is > 0, try to build a header of this length. We need
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* this so that we can hash packets without reading them again. If
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* len is 0, write a partial or indeterminate length header, unless
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* hdrlen is specified in which case write an actual zero length
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* (using the specified hdrlen).
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* Write a packet header to OUT.
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*
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* CTB is the ctb. It determines whether a new or old format packet
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* header should be written. The length field is adjusted, but the
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* CTB is otherwise written out as is.
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*
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* LEN is the length of the packet's body.
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*
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* If HDRLEN is set, then we don't necessarily use the most efficient
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* encoding to store LEN, but the specified length. (If this is not
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* possible, this is a bug.) In this case, LEN=0 means a 0 length
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* packet. Note: setting HDRLEN is only supported for old format
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* packets!
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*
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* If HDRLEN is not set, then the shortest encoding is used. In this
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* case, LEN=0 means the body has an indeterminate length and a
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* partial body length header (if a new format packet) or an
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* indeterminate length header (if an old format packet) is written
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* out. Further, if using partial body lengths, this enables partial
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* body length mode on OUT.
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*/
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static int
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write_header2( IOBUF out, int ctb, u32 len, int hdrlen )
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@ -1320,26 +1446,39 @@ write_header2( IOBUF out, int ctb, u32 len, int hdrlen )
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if( ctb & 0x40 )
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return write_new_header( out, ctb, len, hdrlen );
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/* An old format packet. Refer to RFC 4880, Section 4.2.1 to
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understand how lengths are encoded in this case. */
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log_assert (hdrlen == 0 || hdrlen == 2 || hdrlen == 3 || hdrlen == 5);
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if( hdrlen )
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if (hdrlen)
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/* Header length is given. */
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{
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if( hdrlen == 2 && len < 256 )
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/* 00 => 1 byte length. */
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;
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else if( hdrlen == 3 && len < 65536 )
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/* 01 => 2 byte length. If len < 256, this is not the most
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compact encoding, but it is a correct encoding. */
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ctb |= 1;
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else
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/* 10 => 4 byte length. If len < 65536, this is not the most
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compact encoding, but it is a correct encoding. */
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ctb |= 2;
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}
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else
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{
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if( !len )
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/* 11 => Indeterminate length. */
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ctb |= 3;
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else if( len < 256 )
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/* 00 => 1 byte length. */
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;
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else if( len < 65536 )
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/* 01 => 2 byte length. */
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ctb |= 1;
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else
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/* 10 => 4 byte length. */
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ctb |= 2;
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}
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@ -1368,6 +1507,20 @@ write_header2( IOBUF out, int ctb, u32 len, int hdrlen )
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}
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/* Write a new format header to OUT.
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CTB is the ctb.
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LEN is the length of the packet's body. If LEN is 0, then enables
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partial body length mode (i.e., the body is of an indeterminant
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length) on OUT. Note: this function cannot be used to generate a
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header for a zero length packet.
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HDRLEN is the length of the packet's header. If HDRLEN is 0, the
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shortest encoding is chosen based on the length of the packet's
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body. Currently, values other than 0 are not supported.
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Returns 0 on success. */
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static int
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write_new_header( IOBUF out, int ctb, u32 len, int hdrlen )
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{
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