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-rw-r--r--src/data-identify.c247
1 files changed, 247 insertions, 0 deletions
diff --git a/src/data-identify.c b/src/data-identify.c
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+++ b/src/data-identify.c
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+/* data-identify.c - Try to identify the data
+ Copyright (C) 2013 g10 Code GmbH
+
+ This file is part of GPGME.
+
+ GPGME 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.
+
+ GPGME 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 program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "gpgme.h"
+#include "data.h"
+#include "util.h"
+#include "parsetlv.h"
+
+/* The size of the sample data we take for detection. */
+#define SAMPLE_SIZE 2048
+
+
+
+/* Note that DATA may be binary but a final nul is required so that
+ string operations will find a terminator.
+
+ Returns: GPGME_DATA_TYPE_xxxx */
+static gpgme_data_type_t
+basic_detection (const char *data, size_t datalen)
+{
+ tlvinfo_t ti;
+ const char *s;
+ size_t n;
+ int maybe_p12 = 0;
+
+ if (datalen < 24) /* Object is probably too short for detection. */
+ return GPGME_DATA_TYPE_UNKNOWN;
+
+ /* This is a common example of a CMS object - it is obvious that we
+ only need to read a few bytes to get to the OID:
+ 30 82 0B 59 06 09 2A 86 48 86 F7 0D 01 07 02 A0 82 0B 4A 30 82 0B 46 02
+ ----------- ++++++++++++++++++++++++++++++++
+ SEQUENCE OID (signedData)
+ (2 byte len)
+
+ A PKCS#12 message is:
+
+ 30 82 08 59 02 01 03 30 82 08 1F 06 09 2A 86 48 86 F7 0D 01 07 01 A0 82
+ ----------- ++++++++ ----------- ++++++++++++++++++++++++++++++++
+ SEQUENCE INTEGER SEQUENCE OID (data)
+
+ A X.509 certificate is:
+
+ 30 82 05 B8 30 82 04 A0 A0 03 02 01 02 02 07 15 46 A0 BF 30 07 39 30 0D
+ ----------- +++++++++++ ----- ++++++++ --------------------------
+ SEQUENCE SEQUENCE [0] INTEGER INTEGER SEQU
+ (tbs) (version) (s/n) (Algo)
+
+ Thus we need to read at least 22 bytes, we add 2 bytes to cope with
+ length headers stored with 4 bytes.
+ */
+
+
+ s = data;
+ n = datalen;
+
+ if (parse_tlv (&s, &n, &ti))
+ goto try_pgp; /* Not properly BER encoded. */
+ if (!(ti.cls == ASN1_CLASS_UNIVERSAL && ti.tag == ASN1_TAG_SEQUENCE
+ && ti.is_cons))
+ goto try_pgp; /* A CMS object always starts with a sequence. */
+
+ if (parse_tlv (&s, &n, &ti))
+ goto try_pgp; /* Not properly BER encoded. */
+ if (ti.cls == ASN1_CLASS_UNIVERSAL && ti.tag == ASN1_TAG_SEQUENCE
+ && ti.is_cons && n >= ti.length)
+ {
+ if (parse_tlv (&s, &n, &ti))
+ goto try_pgp;
+ if (!(ti.cls == ASN1_CLASS_CONTEXT && ti.tag == 0
+ && ti.is_cons && ti.length == 3 && n >= ti.length))
+ goto try_pgp;
+
+ if (parse_tlv (&s, &n, &ti))
+ goto try_pgp;
+ if (!(ti.cls == ASN1_CLASS_UNIVERSAL && ti.tag == ASN1_TAG_INTEGER
+ && !ti.is_cons && ti.length == 1 && n && (*s == 1 || *s == 2)))
+ goto try_pgp;
+ s++;
+ n--;
+ if (!(ti.cls == ASN1_CLASS_UNIVERSAL && ti.tag == ASN1_TAG_INTEGER
+ && !ti.is_cons))
+ goto try_pgp;
+ /* Because the now following S/N may be larger than the sample
+ data we have, we stop parsing here and don't check for the
+ algorithm ID. */
+ return GPGME_DATA_TYPE_X509_CERT;
+ }
+ if (ti.cls == ASN1_CLASS_UNIVERSAL && ti.tag == ASN1_TAG_INTEGER
+ && !ti.is_cons && ti.length == 1 && n && *s == 3)
+ {
+ maybe_p12 = 1;
+ s++;
+ n--;
+ if (parse_tlv (&s, &n, &ti))
+ goto try_pgp;
+ if (!(ti.cls == ASN1_CLASS_UNIVERSAL && ti.tag == ASN1_TAG_SEQUENCE
+ && ti.is_cons))
+ goto try_pgp;
+ if (parse_tlv (&s, &n, &ti))
+ goto try_pgp;
+ }
+ if (ti.cls == ASN1_CLASS_UNIVERSAL && ti.tag == ASN1_TAG_OBJECT_ID
+ && !ti.is_cons && ti.length && n >= ti.length)
+ {
+ if (ti.length == 9)
+ {
+ if (!memcmp (s, "\x2A\x86\x48\x86\xF7\x0D\x01\x07\x01", 9))
+ {
+ /* Data. */
+ return (maybe_p12 ? GPGME_DATA_TYPE_PKCS12
+ /* */ : GPGME_DATA_TYPE_CMS_OTHER);
+ }
+ if (!memcmp (s, "\x2A\x86\x48\x86\xF7\x0D\x01\x07\x02", 9))
+ {
+ /* Signed Data. */
+ return (maybe_p12 ? GPGME_DATA_TYPE_PKCS12
+ /* */ : GPGME_DATA_TYPE_CMS_SIGNED);
+ }
+ if (!memcmp (s, "\x2A\x86\x48\x86\xF7\x0D\x01\x07\x03", 9))
+ return GPGME_DATA_TYPE_CMS_ENCRYPTED; /* Enveloped Data. */
+ if (!memcmp (s, "\x2A\x86\x48\x86\xF7\x0D\x01\x07\x05", 9))
+ return GPGME_DATA_TYPE_CMS_OTHER; /* Digested Data. */
+ if (!memcmp (s, "\x2A\x86\x48\x86\xF7\x0D\x01\x07\x06", 9))
+ return GPGME_DATA_TYPE_CMS_OTHER; /* Encrypted Data. */
+ }
+ else if (ti.length == 11)
+ {
+ if (!memcmp (s, "\x2A\x86\x48\x86\xF7\x0D\x01\x09\x10\x01\x02", 11))
+ return GPGME_DATA_TYPE_CMS_OTHER; /* Auth Data. */
+ }
+ }
+
+
+ try_pgp:
+ /* Check whether this might be a non-armored PGP message. We need
+ to do this before checking for armor lines, so that we don't get
+ fooled by armored messages inside a signed binary PGP message. */
+ if ((data[0] & 0x80))
+ {
+ /* That might be a binary PGP message. At least it is not plain
+ ASCII. Of course this might be certain lead-in text of
+ armored CMS messages. However, I am not sure whether this is
+ at all defined and in any case it is uncommon. Thus we don't
+ do any further plausibility checks but stupidly assume no CMS
+ armored data will follow. */
+ return GPGME_DATA_TYPE_UNKNOWN;
+ }
+
+ /* Now check whether there are armor lines. */
+ for (s = data; s && *s; s = (*s=='\n')?(s+1):((s=strchr (s,'\n'))?(s+1):s))
+ {
+ if (!strncmp (s, "-----BEGIN ", 11))
+ {
+ if (!strncmp (s+11, "SIGNED ", 7))
+ return GPGME_DATA_TYPE_CMS_SIGNED;
+ if (!strncmp (s+11, "ENCRYPTED ", 10))
+ return GPGME_DATA_TYPE_CMS_ENCRYPTED;
+ if (!strncmp (s+11, "PGP ", 4))
+ {
+ if (!strncmp (s+15, "SIGNATURE", 9))
+ return GPGME_DATA_TYPE_PGP_SIGNED;
+ if (!strncmp (s+15, "SIGNED MESSAGE", 14))
+ return GPGME_DATA_TYPE_PGP_SIGNED;
+ if (!strncmp (s+15, "PUBLIC KEY BLOCK", 16))
+ return GPGME_DATA_TYPE_PGP_KEY;
+ if (!strncmp (s+15, "PRIVATE KEY BLOCK", 17))
+ return GPGME_DATA_TYPE_PGP_KEY;
+ if (!strncmp (s+15, "SECRET KEY BLOCK", 16))
+ return GPGME_DATA_TYPE_PGP_KEY;
+ if (!strncmp (s+15, "ARMORED FILE", 12))
+ return GPGME_DATA_TYPE_UNKNOWN;
+ return GPGME_DATA_TYPE_PGP_OTHER; /* PGP MESSAGE */
+ }
+ if (!strncmp (s+11, "CERTIFICATE", 11))
+ return GPGME_DATA_TYPE_X509_CERT;
+ if (!strncmp (s+11, "PKCS12", 6))
+ return GPGME_DATA_TYPE_PKCS12;
+ return GPGME_DATA_TYPE_CMS_OTHER; /* Not PGP, thus we assume CMS. */
+ }
+ }
+
+ return GPGME_DATA_TYPE_UNKNOWN;
+}
+
+
+/* Try to detect the type of the data. Note that this function works
+ only on seekable data objects. The function tries to reset the
+ file pointer but there is no guarantee that it will work.
+
+ FIXME: We may want to add internal buffering so that this function
+ can be implemented for allmost all kind of data objects.
+ */
+gpgme_data_type_t
+gpgme_data_identify (gpgme_data_t dh, int reserved)
+{
+ gpgme_data_type_t result;
+ char *sample;
+ int n;
+ gpgme_off_t off;
+
+ /* Check whether we can seek the data object. */
+ off = gpgme_data_seek (dh, 0, SEEK_CUR);
+ if (off == (gpgme_off_t)(-1))
+ return GPGME_DATA_TYPE_INVALID;
+
+ /* Allocate a buffer and read the data. */
+ sample = malloc (SAMPLE_SIZE);
+ if (!sample)
+ return GPGME_DATA_TYPE_INVALID; /* Ooops. */
+ n = gpgme_data_read (dh, sample, SAMPLE_SIZE - 1);
+ if (n < 0)
+ {
+ free (sample);
+ return GPGME_DATA_TYPE_INVALID; /* Ooops. */
+ }
+ sample[n] = 0; /* (Required for our string functions.) */
+
+ result = basic_detection (sample, n);
+ free (sample);
+ gpgme_data_seek (dh, off, SEEK_SET);
+
+ return result;
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-05-01 11:13:34 +0000