GMime
What is GMime?
GMime is a C/C++ library which may be used for the creation and parsing of messages using the Multipurpose Internet Mail Extension (MIME) as defined by numerous IETF specifications.
GMime features an extremely robust high-performance parser designed to be able to preserve byte-for-byte information allowing developers to re-seralize the parsed messages back to a stream exactly as the parser found them. It also features integrated GnuPG and S/MIME v3.2 support.
Built on top of GObject (the object system used by the GNOME desktop), many developers should find its API design and memory management very familiar.
History
As a developer and user of Electronic Mail clients, I had come to realize that the vast majority of E-Mail client (and server) software had less-than-satisfactory MIME implementations. More often than not these E-Mail clients created broken MIME messages and/or would incorrectly try to parse a MIME message thus subtracting from the full benefits that MIME was meant to provide. GMime is meant to address this issue by following the MIME specification as closely as possible while also providing programmers with an extremely easy to use high-level application programming interface (API).
License Information
The GMime library is Copyright (C) 2000-2022 Jeffrey Stedfast and is licensed under the LGPL v2.1
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
Getting the Source Code
You can download official public release tarballs of GMime at https://download.gnome.org/sources/gmime/ or ftp://ftp.gnome.org/pub/GNOME/sources/gmime/.
If you would like to contribute to the GMime project, it is recommended that you grab the source code from the official GitHub repository at http://github.com/jstedfast/gmime. Cloning this repository can be done using the following command:
git clone https://github.com/jstedfast/gmime.git
Requirements
For proper compilation and functionality of GMime, the following packages are REQUIRED:
-
Glib version >= 2.58.0
Glib provides a number of portability-enhancing functions and types. Glib is included in most GMime-supported operating system distributions. Glib sources may be obtained from: ftp://ftp.gtk.org/pub/glib
The following packages are RECOMMENDED:
-
Libidn2 >= 2.0.0
Libidn2 provides APIs needed for encoding and decoding Internationalized Domain Names. Libidn2 sources may be obtained from: https://www.gnu.org/software/libidn/#downloading
-
GPGME >= 1.8.0 (will build with 1.6.0, but will be missing some functionality)
GPGME (GnuPG Made Easy) provides high-level crypto APIs needed for encryption, decryption, signing and signature verification for both OpenPGP and S/MIME. GPGME sources may be obtained from: https://www.gnupg.org/download/index.html#gpgme
Using GMime
Parsing Messages
One of the more common operations that GMime is meant for is parsing email messages from arbitrary streams.
To do this, you will need to use a GMimeParser
:
/* load a GMimeMessage from a stream */
GMimeMessage *message;
GMimeStream *stream;
GMimeParser *parser;
stream = g_mime_stream_fs_open ("message.eml", O_RDONLY, 0644, NULL);
parser = g_mime_parser_new_with_stream (stream);
/* Note: we can unref the stream now since the GMimeParser has a reference to it... */
g_object_unref (stream);
message = g_mime_parser_construct_message (parser, NULL);
/* unref the parser since we no longer need it */
g_object_unref (parser);
If you are planning to parse messages from an mbox stream, you can do something like this:
GMimeMessage *message;
GMimeStream *stream;
GMimeParser *parser;
gint64 offset;
char *marker;
stream = g_mime_stream_fs_open ("Inbox.mbox", O_RDONLY, 0644, NULL);
parser = g_mime_parser_new_with_stream (stream);
/* tell the parser to scan mbox-style "From " markers */
g_mime_parser_set_format (parser, GMIME_FORMAT_MBOX);
/* Note: we can unref the stream now since the GMimeParser has a reference to it... */
g_object_unref (stream);
while (!g_mime_parser_eos (parser)) {
/* load the next message from the mbox */
if ((message = g_mime_parser_construct_message (parser, NULL)) != NULL)
g_object_unref (message);
/* get information about the mbox "From " marker... */
offset = g_mime_parser_get_mbox_marker_offset (parser);
marker = g_mime_parser_get_mbox_marker (parser);
}
g_object_unref (parser);
Getting the Body of a Message
A common misunderstanding about email is that there is a well-defined message body and then a list of attachments. This is not really the case. The reality is that MIME is a tree structure of content, much like a file system.
Luckily, MIME does define a set of general rules for how mail clients should interpret this tree
structure of MIME parts. The Content-Disposition
header is meant to provide hints to the receiving
client as to which parts are meant to be displayed as part of the message body and which are meant
to be interpreted as attachments.
The Content-Disposition
header will generally have one of two values: inline
or attachment
.
The meaning of these value should be fairly obvious. If the value is attachment
, then the content
of said MIME part is meant to be presented as a file attachment separate from the core message.
However, if the value is inline
, then the content of that MIME part is meant to be displayed inline
within the mail client's rendering of the core message body. If the Content-Disposition
header does
not exist, then it should be treated as if the value were inline
.
Technically, every part that lacks a Content-Disposition
header or that is marked as inline
, then,
is part of the core message body.
There's a bit more to it than that, though.
Modern MIME messages will often contain a multipart/alternative
MIME container which will generally contain
a text/plain
and text/html
version of the text that the sender wrote. The text/html
version is typically
formatted much closer to what the sender saw in his or her WYSIWYG editor than the text/plain
version.
The reason for sending the message text in both formats is that not all mail clients are capable of displaying HTML.
The receiving client should only display one of the alternative views contained within the multipart/alternative
container. Since alternative views are listed in order of least faithful to most faithful with what the sender
saw in his or her WYSIWYG editor, the receiving client should walk over the list of alternative views starting
at the end and working backwards until it finds a part that it is capable of displaying.
Example:
multipart/alternative
text/plain
text/html
As seen in the example above, the text/html
part is listed last because it is the most faithful to
what the sender saw in his or her WYSIWYG editor when writing the message.
To make matters even more complicated, sometimes modern mail clients will use a multipart/related
MIME container instead of a simple text/html
part in order to embed images and other content
within the HTML.
Example:
multipart/alternative
text/plain
multipart/related
text/html
image/jpeg
video/mp4
image/png
In the example above, one of the alternative views is a multipart/related
container which contains
an HTML version of the message body that references the sibling video and images.
Now that you have a rough idea of how a message is structured and how to interpret various MIME entities, the next step is learning how to traverse the MIME tree using GMime.
Traversing a GMimeMessage
The top-level MIME entity of the message will generally either be a GMimePart
or a GMimeMultipart
.
As an example, if you wanted to rip out all of the attachments of a message, your code might look something like this:
GMimePartIter *iter = g_mime_part_iter_new (message);
GPtrArray *attachments = g_ptr_array_new ();
GPtrArray *multiparts = g_ptr_array_new ();
/* collect our list of attachments and their parent multiparts */
while (g_mime_part_iter_next (iter)) {
GMimeObject *current = g_mime_part_iter_get_current (iter);
GMimeObject *parent = g_mime_part_iter_get_parent (iter);
if (GMIME_IS_MULTIPART (parent) && GMIME_IS_PART (current)) {
GMimePart *part = (GMimePart *) current;
if (g_mime_part_is_attachment (part)) {
/* keep track of each attachment's parent multipart */
g_ptr_array_add (multiparts, parent);
g_ptr_array_add (attachments, part);
}
}
}
/* now remove each attachment its parent multipart... */
for (int i = 0; i < attachments->len; i++) {
GMimeMultipart *multipart = (GMimeMultipart *) multiparts->pdata[i];
GMimeObject *attachment = (GMimeObject *) attachments->pdata[i];
g_mime_multipart_remove (multipart, attachment);
}
Creating a Simple Message
Creating MIME messages using GMime is really trivial.
GMimeMessage *message;
GMimeTextPart *body;
message = g_mime_message_new (TRUE);
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_FROM, "Joey", "joey@friends.com");
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_TO, "Alice", "alice@wonderland.com");
g_mime_message_set_subject (message, "How you doin?", NULL);
body = g_mime_text_part_new_with_subtype ("plain");
g_mime_text_part_set_text (body, "Hey Alice,\n\n"
"What are you up to this weekend? Monica is throwing one of her parties on\n"
"Saturday and I was hoping you could make it.\n\n"
"Will you be my +1?\n\n"
"-- Joey\n");
g_mime_message_set_mime_part (message, (GMimeObject *) body);
g_object_unref (body);
Creating a Message with Attachments
Attachments are just like any other GMimePart
, the only difference is that they typically have
a Content-Disposition
header with a value of "attachment" instead of "inline" or no
Content-Disposition
header at all.
Typically, when a mail client adds attachments to a message, it will create a multipart/mixed
part and add the text body part and all of the file attachments to the multipart/mixed
.
Here's how you can do that with GMime:
GMimeMultipart *multipart;
GMimeDataWrapper *content;
GMimeMessage *message;
GMimePart *attachment;
GMimeTextPart *body;
GMimeStream *stream;
message = g_mime_message_new (TRUE);
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_FROM, "Joey", "joey@friends.com");
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_TO, "Alice", "alice@wonderland.com");
g_mime_message_set_subject (message, "How you doin?", NULL);
/* create our message text, just like before... */
body = g_mime_text_part_new_with_subtype ("plain");
g_mime_text_part_set_text (body, "Hey Alice,\n\n"
"What are you up to this weekend? Monica is throwing one of her parties on\n"
"Saturday and I was hoping you could make it.\n\n"
"Will you be my +1?\n\n"
"-- Joey\n");
/* create an image attachment for the file located at path */
attachment = g_mime_part_new_with_type ("image", "gif");
g_mime_part_set_filename (attachment, basename (path));
/* create the content for the image attachment */
stream = g_mime_stream_fs_open (path, O_RDONLY, 0644, NULL);
content = g_mime_data_wrapper_new_with_stream (stream, GMIME_CONTENT_ENCODING_DEFAULT);
g_object_unref (stream);
/* set the content of the attachment */
g_mime_part_set_content (attachment, content);
g_object_unref (content);
/* set the Content-Transfer-Encoding to base64 */
g_mime_part_set_content_encoding (attachment, GMIME_CONTENT_ENCODING_BASE64);
/* now create the multipart/mixed container to hold the message text and the image attachment */
multipart = g_mime_multipart_new_with_subtype ("mixed");
/* add the text body first */
g_mime_multipart_add (multipart, (GMimeObject *) body);
g_object_unref (body);
/* now add the attachment(s) */
g_mime_multipart_add (multipart, (GMimeObject *) attachment);
g_object_unref (attachment);
/* set the multipart/mixed as the message body */
g_mime_message_set_mime_part (message, (GMimeObject *) multipart);
g_object_unref (multipart);
Of course, that is just a simple example. A lot of modern mail clients such as Outlook or Thunderbird will
send out both a text/html
and a text/plain
version of the message text. To do this, you'd create a
GMimeTextPart
for the text/plain
part and another GMimeTextPart
for the text/html
part and then add
them to a multipart/alternative
like so:
GMimeMultipart *mixed, *alternative;
GMimeTextPart *plain, *html;
GMimePart *attachment;
/* see above for how to create each of these... */
attachment = CreateAttachment ();
plain = CreateTextPlainPart ();
html = CreateTextHtmlPart ();
/* Note: it is important that the text/html part is added second, because it is the
* most expressive version and (probably) the most faithful to the sender's WYSIWYG
* editor. */
alternative = g_mime_multipart_new_with_subtype ("alternative");
g_mime_multipart_add (alternative, (GMimeObject *) plain);
g_object_unref (plain);
g_mime_multipart_add (alternative, (GMimeObject *) html);
g_object_unref (html);
/* now create the multipart/mixed container to hold the multipart/alternative
* and the image attachment */
mixed = g_mime_multipart_new_with_subtype ("mixed");
g_mime_multipart_add (mixed, (GMimeObject *) alternative);
g_object_unref (alternative);
g_mime_multipart_add (mixed, (GMimeObject *) attachment);
g_object_unref (attachment);
/* now set the multipart/mixed as the message body */
g_mime_message_set_mime_part (message, (GMimeObject *) mixed);
g_object_unref (mixed);
Encrypting Messages with S/MIME
S/MIME uses an application/pkcs7-mime
MIME part to encapsulate encrypted content (as well as other things).
GMimeApplicationPkcs7Mime *encrypted;
GMimeMessage *message;
GError *err = NULL;
GMimeObject *body;
GPtrArray *rcpts;
message = g_mime_message_new (TRUE);
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_FROM, "Joey", "joey@friends.com");
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_TO, "Alice", "alice@wonderland.com");
g_mime_message_set_subject (message, "How you doin?", NULL);
/* create our message body (perhaps a multipart/mixed with the message text and some
* image attachments, for example) */
body = CreateMessageBody ();
/* create a list of key ids to encrypt to */
rcpts = g_ptr_array_new ();
g_ptr_array_add (rcpts, "alice@wonderland.com"); // or use her fingerprint
/* now to encrypt our message body */
if (!(encrypted = g_mime_application_pkcs7_mime_encrypt (body, GMIME_ENCRYPT_NONE, rcpts, &err))) {
fprintf (stderr, "encrypt failed: %s\n", err->message);
g_object_unref (body);
g_error_free (err);
return;
}
g_object_unref (body);
g_mime_message_set_mime_part (message, encrypted);
g_object_unref (encrypted);
Decrypting S/MIME Messages
As mentioned earlier, S/MIME uses an application/pkcs7-mime
part with an "smime-type" parameter with a value of
"enveloped-data" to encapsulate the encrypted content.
The first thing you must do is find the GMimeApplicationPkcs7Mime
part (see the section on traversing MIME parts).
if (GMIME_IS_APPLICATION_PKCS7_MIME (entity)) {
GMimeApplicationPkcs7Mime *pkcs7 = (GMimeApplicationPkcs7Mime *) entity;
GMimeSecureMimeType smime_type;
GError *err = NULL;
smime_type = g_mime_application_pkcs7_mime_get_smime_type (pkcs7_mime);
if (smime_type == GMIME_SECURE_MIME_TYPE_ENVELOPED_DATA)
return g_mime_application_pkcs7_mime_decrypt (pkcs7, 0, NULL, NULL, &err);
}
Encrypting Messages with PGP/MIME
Unlike S/MIME, PGP/MIME uses multipart/encrypted
to encapsulate its encrypted data.
GMimeMultipartEncrypted *encrypted;
GMimeCryptoContext *ctx;
GMimeMessage *message;
GError *err = NULL;
GMimeObject *body;
GPtrArray *rcpts;
message = g_mime_message_new (TRUE);
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_FROM, "Joey", "joey@friends.com");
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_TO, "Alice", "alice@wonderland.com");
g_mime_message_set_subject (message, "How you doin?", NULL);
/* create our message body (perhaps a multipart/mixed with the message text and some
* image attachments, for example) */
body = CreateMessageBody ();
/* create a list of key ids to encrypt to */
rcpts = g_ptr_array_new ();
g_ptr_array_add (rcpts, "alice@wonderland.com"); // or use her fingerprint
/* now to encrypt our message body */
ctx = g_mime_gpg_context_new ();
encrypted = g_mime_multipart_encrypted_encrypt (ctx, body, FALSE, NULL, GMIME_ENCRYPT_NONE, rcpts, &err);
g_ptr_array_free (rcpts, TRUE);
g_object_unref (body);
g_object_unref (ctx);
if (encrypted == NULL) {
fprintf (stderr, "encrypt failed: %s\n", err->message);
g_error_free (err);
return;
}
g_mime_message_set_mime_part (message, (GMimeObject *) encrypted);
g_object_unref (encrypted);
Decrypting PGP/MIME Messages
As mentioned earlier, PGP/MIME uses a multipart/encrypted
part to encapsulate the encrypted content.
A multipart/encrypted
contains exactly 2 parts: the first GMimeObject
is the version information while the
second GMimeObject
is the actual encrypted content and will typically be an application/octet-stream
.
The first thing you must do is find the GMimeMultipartEncrypted
part (see the section on traversing MIME parts).
if (GMIME_IS_MULTIPART_ENCRYPTED (entity)) {
GMimeMultipartEncrypted *encrypted = (GMimeMultipartEncrypted *) entity;
GMimeDecryptResult *result = NULL;
GError *err = NULL;
return g_mime_multipart_encrypted_decrypt (encrypted, GMIME_DECRYPT_NONE, NULL, &result, &err);
}
Digitally Signing Messages with S/MIME or PGP/MIME
Both S/MIME and PGP/MIME use a multipart/signed
to contain the signed content and the detached signature data.
Here's how you might digitally sign a message using S/MIME:
GMimeApplicationPkcs7Mime *pkcs7;
GMimeMessage *message;
GError *err = NULL;
GMimeObject *body;
message = g_mime_message_new (TRUE);
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_FROM, "Joey", "joey@friends.com");
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_TO, "Alice", "alice@wonderland.com");
g_mime_message_set_subject (message, "How you doin?", NULL);
/* create our message body (perhaps a multipart/mixed with the message text and some
* image attachments, for example) */
body = CreateMessageBody ();
/* now to sign our message body */
if (!(pkcs7 = g_mime_application_pkcs7_mime_sign (body, "joey@friends.com", &err))) {
fprintf (stderr, "sign failed: %s\n", err->message);
g_object_unref (body);
g_error_free (err);
return;
}
g_object_unref (body);
g_mime_message_set_mime_part (message, (GMimeObject *) pkcs7);
g_object_unref (pkcs7);
S/MIME also gives you the option of using a multipart/signed
method of signing a message.
GMimeMultipartSigned *ms;
GMimeCryptoContext *ctx;
GMimeMessage *message;
GError *err = NULL;
GMimeObject *body;
message = g_mime_message_new (TRUE);
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_FROM, "Joey", "joey@friends.com");
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_TO, "Alice", "alice@wonderland.com");
g_mime_message_set_subject (message, "How you doin?", NULL);
/* create our message body (perhaps a multipart/mixed with the message text and some
* image attachments, for example) */
body = CreateMessageBody ();
/* create our crypto context - needed because multipart/signed works for both S/MIME and PGP/MIME */
ctx = g_mime_pkcs7_context_new ();
/* now to sign our message body */
if (!(ms = g_mime_multipart_signed_sign (ctx, body, "joey@friends.com", &err))) {
fprintf (stderr, "sign failed: %s\n", err->message);
g_object_unref (body);
g_object_unref (ctx);
g_error_free (err);
return;
}
g_object_unref (body);
g_object_unref (ctx);
g_mime_message_set_mime_part (message, (GMimeObject *) ms);
g_object_unref (ms);
If you'd prefer to use PGP instead of S/MIME, things work almost exactly the same except that you
would use the GMimeGpgContext
.
GMimeMultipartSigned *ms;
GMimeCryptoContext *ctx;
GMimeMessage *message;
GError *err = NULL;
GMimeObject *body;
message = g_mime_message_new (TRUE);
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_FROM, "Joey", "joey@friends.com");
g_mime_message_add_mailbox (message, GMIME_ADDRESS_TYPE_TO, "Alice", "alice@wonderland.com");
g_mime_message_set_subject (message, "How you doin?", NULL);
/* create our message body (perhaps a multipart/mixed with the message text and some
* image attachments, for example) */
body = CreateMessageBody ();
/* create our crypto context - needed because multipart/signed works for both S/MIME and PGP/MIME */
ctx = g_mime_gpg_context_new ();
/* now to sign our message body */
if (!(ms = g_mime_multipart_signed_sign (ctx, body, "joey@friends.com", &err))) {
fprintf (stderr, "sign failed: %s\n", err->message);
g_object_unref (body);
g_object_unref (ctx);
g_error_free (err);
return;
}
g_object_unref (body);
g_object_unref (ctx);
g_mime_message_set_mime_part (message, (GMimeObject *) ms);
g_object_unref (ms);
Verifying S/MIME and PGP/MIME Digital Signatures
As mentioned earlier, both S/MIME and PGP/MIME typically use a multipart/signed
part to contain the
signed content and the detached signature data.
A multipart/signed
contains exactly 2 parts: the first GMimeObject
is the signed content while the second
GMimeObject
is the detached signature and, by default, will either be a GMimeApplicationPgpSignature
part
or a GMimeApplicationPkcs7Signature
part (depending on whether the sending client signed using OpenPGP or
S/MIME).
Because the multipart/signed
part may have been signed by multiple signers, the
g_mime_multipart_signed_verify()
function returns a GMimeSignatureList
which contains a list of
digital signatures (one for each signer) that each contain their own metadata describing who that
signer is and what the status of their signature is.
if (GMIME_IS_MULTIPART_SIGNED (entity)) {
GMimeMultipartSigned *ms = (GMimeMultipartSigned *) entity;
GMimeSignatureList *signatures;
GError *err = NULL;
int i, count;
if (!(signatures = g_mime_multipart_signed_verify (ms, GMIME_VERIFY_ENABLE_KEYSERVER_LOOKUPS, &err))) {
fprintf (stderr, "verify failed: %s\n", err->message);
g_error_free (err);
return;
}
fputs ("\nSignatures:\n", stdout);
count = g_mime_signature_list_length (signatures);
for (i = 0; i < count; i++) {
GMimeSignature *sig = g_mime_signature_list_get_signature (signatures, i);
GMimeSignatureStatus status = g_mime_signature_get_status (sig);
GMimeCertificate *cert = g_mime_signature_get_certificate (sig);
time_t created = g_mime_signature_get_created (sig);
time_t expires = g_mime_signature_get_expires (sig);
fprintf (stdout, "\tName: %s\n", g_mime_certificate_get_name (cert));
fprintf (stdout, "\tKeyId: %s\n", g_mime_certificate_get_key_id (cert));
fprintf (stdout, "\tFingerprint: %s\n", g_mime_certificate_get_fingerprint (cert));
fprintf (stdout, "\tTrust: ");
switch (g_mime_certificate_get_trust (cert)) {
case GMIME_TRUST_UNKNOWN: fputs ("Unknown\n", stdout); break;
case GMIME_TRUST_NEVER: fputs ("Never\n", stdout); break;
case GMIME_TRUST_UNDEFINED: fputs ("Undefined\n", stdout); break;
case GMIME_TRUST_MARGINAL: fputs ("Marginal\n", stdout); break;
case GMIME_TRUST_FULL: fputs ("Full\n", stdout); break;
case GMIME_TRUST_ULTIMATE: fputs ("Ultimate\n", stdout); break;
}
fprintf (stdout, "\tStatus: ");
if (status & GMIME_SIGNATURE_STATUS_RED)
fputs ("BAD\n", stdout);
else if (status & GMIME_SIGNATURE_STATUS_GREEN)
fputs ("GOOD\n", stdout);
else if (status & GMIME_SIGNATURE_STATUS_VALID)
fputs ("VALID\n", stdout);
else
fputs ("UNKNOWN\n", stdout);
fprintf (stdout, "\tSignature made on %s", ctime (&created));
if (expires != (time_t) 0)
fprintf (stdout, "\tSignature expires on %s", ctime (&expires));
else
fprintf (stdout, "\tSignature never expires\n");
fprintf (stdout, "\tErrors: ");
if (status & GMIME_SIGNATURE_STATUS_KEY_REVOKED)
fputs ("Key Revoked, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_KEY_EXPIRED)
fputs ("Key Expired, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_SIG_EXPIRED)
fputs ("Sig Expired, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_KEY_MISSING)
fputs ("Key Missing, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_CRL_MISSING)
fputs ("CRL Missing, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_CRL_TOO_OLD)
fputs ("CRL Too Old, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_BAD_POLICY)
fputs ("Bad Policy, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_SYS_ERROR)
fputs ("System Error, ", stdout);
if (status & GMIME_SIGNATURE_STATUS_TOFU_CONFLICT)
fputs ("Tofu Conflict", stdout);
if ((status & GMIME_SIGNATURE_STATUS_ERROR_MASK) == 0)
fputs ("None", stdout);
fputs ("\n\n", stdout);
}
g_object_unref (signatures);
}
It should be noted, however, that while most S/MIME clients will use the preferred multipart/signed
approach, it is possible that you may encounter an application/pkcs7-mime
part with an "smime-type"
parameter set to "signed-data". Luckily, GMime can handle this format as well:
if (GMIME_IS_APPLICATION_PKCS7_MIME (entity)) {
GMimeApplicationPkcs7Mime *pkcs7 = (GMimeApplicationPkcs7Mime *) entity;
GMimeSecureMimeType smime_type;
smime_type = g_mime_application_pkcs7_mime_get_smime_type (pkcs7);
if (smime_type == GMIME_SECURE_MIME_TYPE_SIGNED_DATA) {
/* extract the original content and get a list of signatures */
GMimeSignatureList *signatures;
GMimeObject *extracted;
GError *err = NULL;
int i, count;
/* Note: if you are rendering the message, you'll want to render the
* extracted mime part rather than the application/pkcs7-mime part. */
if (!(signatures = g_mime_application_pkcs7_mime_verify (pkcs7, GMIME_VERIFY_NONE, &extracted, &err))) {
fprintf (stderr, "verify failed: %s\n", err->message);
g_error_free (err);
return;
}
count = g_mime_signature_list_length (signatures);
for (i = 0; i < count; i++) {
GMimeSignature *sig = g_mime_signature_list_get_signature (signatures, i);
/* ... */
}
g_object_unref (signatures);
}
}
Understanding Memory Management in GMime
-
Functions that return
const char *
return a pointer to a string stored on theGObject
that will be released when the object itself is finalized and therefore should never be fed tog_free()
by the caller. -
Functions that return
char *
are left up to the caller tog_free()
when the caller is done with them.
For functions throughout the GMime API that return an object reference:
- If the function that returned the object allocated the object, then you need to unref it, otherwise you don't.
For example, the stream
in the following code would need to be unreffed (using g_object_unref()
) because it was
freshly allocated by the function:
GMimeStream *stream = g_mime_stream_mem_new ();
The next example shows a function that returns a reference to an existing GMimeStream
object that is stored on
(and therefor managed by) the GMimeDataWrapper
object:
GMimeStream *stream = g_mime_data_wrapper_get_stream (wrapper);
In the above example, the stream
should not be unreffed because the stream
object's memory is managed by the
wrapper
object. In other words, when the wrapper
object is freed, the stream
will be freed as well.
Where many developers get confused is when they create a new object and then add it to another object.
For example:
GMimeStream *stream = g_mime_stream_mem_new ();
GMimeDataWrapper *wrapper = g_mime_data_wrapper_new_with_stream (stream, GMIME_CONTENT_ENCODING_DEFAULT);
g_object_unref (stream);
Even in this situation, it is necessary to unref the allocated object because all GMime functions that add an object to another object will ref that object themselves.
In other words, in the above example, the GMimeStream
is being added to the GMimeDataWrapper
. The
GMimeDataWrapper
calls g_object_ref()
on the stream
which means that the stream
object now has
a ref count of 2.
When g_object_unref()
is called on the stream after adding it to the GMimeDataWrapper
, the ref count drops
down to 1.
And when the wrapper
object is eventually finalized after calling g_object_unref()
on it, the ref count
on the stream
object will be reduced to 0 as well, thereby freeing the stream
object.
Documentation
This is the README file for GMime. Additional documentation related to development using GMime has been included within the source release of GMime.
Description | |
---|---|
docs/reference/ | Contains SGML and HTML versions of the GMime reference manual |
docs/tutorial/ | Contains SGML and HTML versions of the GMime tutorial |
AUTHORS | List of primary authors (source code developers) |
COPYING | The GNU Lesser General Public License, version 2 |
INSTALL | In-depth installation instructions |
TODO | Description of planned GMime development |
PORTING | Guide for developers porting their application from an older version of GMime |
You can find online developer documentation at https://developer-old.gnome.org/gmime/stable/
Mailing Lists
For discussion of GMime development (either of GMime itself or using GMime in your own application), you may find the GMime-Devel mailing-list helpful. To subscribe, please see http://mail.gnome.org/mailman/listinfo/gmime-devel-list
Bindings
Other developers have been working to make GMime available to programmers in other languages. The current list of known bindings are:
Language | Location |
---|---|
Go | https://github.com/sendgrid/go-gmime |
Perl | http://search.cpan.org/dist/MIME-Fast |
C# | https://github.com/jstedfast/MimeKit |
Reporting Bugs
Bugs may be reported to the GMime development team by creating a new issue.
Reporting Security Issues
Security issues should be reported to jestedfa@microsoft.com.
Using a Subject along the lines of "GMime security issue" would be helpful in helping to spot the email message.