wiretap: Add a reader for files in the PEM-like format specified by RFC 7468

Change-Id: I8109025120d01c915f3a9d5550aa9272ec83893a
Reviewed-on: https://code.wireshark.org/review/27334
Petri-Dish: Stig Bjørlykke <stig@bjorlykke.org>
Reviewed-by: Stig Bjørlykke <stig@bjorlykke.org>

7 files changed, 242 insertions, 2 deletions

diff --git a/epan/dissectors/packet-ber.c b/epan/dissectors/packet-ber.c
index 9f7d358510..03842543a6 100644
--- a/epan/dissectors/packet-ber.c
+++ b/epan/dissectors/packet-ber.c
@@ -4233,7 +4233,7 @@ dissect_ber(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
 
     col_set_str(pinfo->cinfo, COL_PROTOCOL, "BER");
 
-    col_set_str(pinfo->cinfo, COL_DEF_SRC, "BER encoded file");
+    col_set_str(pinfo->cinfo, COL_DEF_SRC, "BER encoded value");
 
     if (!decode_as_syntax) {
 
diff --git a/file.c b/file.c
index de1f65af1b..c9b9878f81 100644
--- a/file.c
+++ b/file.c
@@ -318,7 +318,8 @@ cf_open(capture_file *cf, const char *fname, unsigned int type, gboolean is_temp
   packet_list_queue_draw();
   cf_callback_invoke(cf_cb_file_opened, cf);
 
-  if (cf->cd_t == WTAP_FILE_TYPE_SUBTYPE_BER) {
+  if ((cf->cd_t == WTAP_FILE_TYPE_SUBTYPE_BER)
+      || (cf->cd_t == WTAP_FILE_TYPE_SUBTYPE_PEM)) {
     /* tell the BER dissector the file name */
     ber_set_filename(cf->filename);
   }
diff --git a/wiretap/CMakeLists.txt b/wiretap/CMakeLists.txt
index 35c404155c..3bfc5870b1 100644
--- a/wiretap/CMakeLists.txt
+++ b/wiretap/CMakeLists.txt
@@ -68,6 +68,7 @@ set(WIRETAP_NONGENERATED_FILES
 	pcapng.c
 	peekclassic.c
 	peektagged.c
+	pem.c
 	pppdump.c
 	radcom.c
 	snoop.c
diff --git a/wiretap/file_access.c b/wiretap/file_access.c
index 0c054c4670..2e501dfeef 100644
--- a/wiretap/file_access.c
+++ b/wiretap/file_access.c
@@ -73,6 +73,7 @@
 #include "nettrace_3gpp_32_423.h"
 #include "mplog.h"
 #include "dpa400.h"
+#include "pem.h"
 
 /*
  * Add an extension, and all compressed versions thereof, to a GSList
@@ -353,6 +354,7 @@ static const struct open_info open_info_base[] = {
 	{ "MIME Files Format",                      OPEN_INFO_MAGIC,     mime_file_open,           NULL,       NULL, NULL },
 	{ "Micropross mplog",                       OPEN_INFO_MAGIC,     mplog_open,               "mplog",    NULL, NULL },
 	{ "Unigraf DPA-400 capture",                OPEN_INFO_MAGIC,     dpa400_open,              "bin",      NULL, NULL },
+	{ "ASN.1 (PEM-like encoding)",              OPEN_INFO_MAGIC,     pem_open,                 "pem;crt",  NULL, NULL },
 	{ "Novell LANalyzer",                       OPEN_INFO_HEURISTIC, lanalyzer_open,           "tr1",      NULL, NULL },
 	/*
 	 * PacketLogger must come before MPEG, because its files
@@ -1610,6 +1612,11 @@ static const struct file_type_subtype_info dump_open_table_base[] = {
 	/* WTAP_FILE_TYPE_SUBTYPE_DPA400 */
 	{ "Unigraf DisplayPort AUX channel monitor output parser", "dpa400", "bin", NULL,
 	  FALSE, FALSE, 0,
+	  NULL, NULL, NULL },
+
+	/* WTAP_FILE_TYPE_SUBTYPE_PEM */
+	{ "ASN.1 (PEM-like encoding)", "pem", NULL, NULL,
+	  FALSE, FALSE, 0,
 	  NULL, NULL, NULL }
 };
 
diff --git a/wiretap/pem.c b/wiretap/pem.c
new file mode 100644
index 0000000000..dd1502795b
--- /dev/null
+++ b/wiretap/pem.c
@@ -0,0 +1,203 @@
+/* pem.c
+ *
+ * Implements loading of files in the format specified by RFC 7468.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "config.h"
+
+#include "pem.h"
+
+#include "file_wrappers.h"
+#include "wtap-int.h"
+
+#include <wsutil/buffer.h>
+
+#include <glib.h>
+
+#include <string.h>
+
+/* 128 bytes should be enough to contain any line. Strictly speaking, 64 is
+   enough, but we provide some leeway to accomodate nonconformant producers and
+   trailing whitespace. The 2 extra bytes are for the trailing newline and NUL
+   terminator. */
+#define MAX_LINE_LENGTH (128 + 2)
+
+/* based on the `label` production in RFC 7468 */
+#define RE_LABEL "([!-,.-~]([-\\s]?[!-,.-~])*)?"
+
+struct pem_priv {
+    GRegex *re_blank_line;
+    GRegex *re_pre_eb;
+    GRegex *re_post_eb;
+};
+
+static char *read_complete_text_line(char line[MAX_LINE_LENGTH], FILE_T fh, int *err, gchar **err_info)
+{
+    char *line_end;
+
+    if (!(line_end = file_getsp(line, MAX_LINE_LENGTH, fh))) {
+        *err = file_error(fh, err_info);
+        return NULL;
+    }
+
+    if (strlen(line) != (size_t)(line_end - line)) {
+        *err = WTAP_ERR_BAD_FILE;
+        *err_info = g_strdup("unexpected NUL inside a line");
+        return NULL;
+    }
+
+    if (line_end[-1] != '\n' && !file_eof(fh)) {
+        *err = WTAP_ERR_BAD_FILE;
+        *err_info = g_strdup("overlong line");
+        return NULL;
+    }
+
+    return line_end;
+}
+
+static gboolean pem_read_value(wtap *wth, FILE_T fh, wtap_rec *rec,
+                               Buffer *buf, int *err, gchar **err_info)
+{
+    struct pem_priv *priv = (struct pem_priv *)wth->priv;
+
+    char line[MAX_LINE_LENGTH];
+
+    // skip blank lines
+    do {
+        if (!read_complete_text_line(line, fh, err, err_info)) return FALSE;
+    } while (g_regex_match(priv->re_blank_line, line, (GRegexMatchFlags)0, NULL));
+
+    if (!g_regex_match(priv->re_pre_eb, line, (GRegexMatchFlags)0, NULL)) {
+        *err = WTAP_ERR_BAD_FILE;
+        *err_info = g_strdup("invalid pre-encapsulation boundary");
+        return FALSE;
+    }
+
+    gint base64_state = 0;
+    guint base64_save = 0;
+
+    ws_buffer_clean(buf);
+
+    for (; ; ) {
+        char *line_end = read_complete_text_line(line, fh, err, err_info);
+        if (!line_end) {
+            if (*err == 0) {
+                *err = WTAP_ERR_BAD_FILE;
+                *err_info = g_strdup("missing post-encapsulation boundary");
+            }
+            return FALSE;
+        }
+
+        if (g_regex_match(priv->re_post_eb, line, (GRegexMatchFlags)0, NULL))
+            break;
+
+        guchar decoded[(sizeof(line) / 4) * 3 + 3];
+        guint32 decoded_size = (guint32) g_base64_decode_step(
+            line, line_end - line, decoded, &base64_state, &base64_save);
+
+        if ((guint32)ws_buffer_length(buf) > G_MAXUINT32 - decoded_size) {
+            // we can't set the packet length if this happens
+            *err = WTAP_ERR_BAD_FILE;
+            *err_info = g_strdup("encoded value too large");
+            return FALSE;
+        }
+
+        ws_buffer_append(buf, decoded, decoded_size);
+    }
+
+    rec->rec_type = REC_TYPE_PACKET;
+    rec->presence_flags = 0;
+    rec->rec_header.packet_header.len =
+        rec->rec_header.packet_header.caplen =
+        (guint32)ws_buffer_length(buf);
+
+    return TRUE;
+}
+
+static gboolean pem_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
+{
+    *data_offset = file_tell(wth->fh);
+
+    return pem_read_value(wth, wth->fh, &wth->rec, wth->rec_data, err, err_info);
+}
+
+static gboolean pem_seek_read(wtap *wth, gint64 seek_off, wtap_rec *rec,
+                              Buffer *buf, int *err, gchar **err_info)
+{
+    if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
+        return FALSE;
+
+    return pem_read_value(wth, wth->random_fh, rec, buf, err, err_info);
+}
+
+static void pem_close(wtap *wth)
+{
+    struct pem_priv *priv = (struct pem_priv *)wth->priv;
+
+    g_regex_unref(priv->re_pre_eb);
+    g_regex_unref(priv->re_post_eb);
+}
+
+wtap_open_return_val pem_open(wtap *wth, int *err, gchar **err_info)
+{
+    static const char expected_magic[] = "-----BEGIN ";
+    char actual_magic[sizeof(expected_magic) - 1];
+
+    if (!wtap_read_bytes(wth->fh, &actual_magic, sizeof(actual_magic), err, err_info)) {
+        if (*err == WTAP_ERR_SHORT_READ)
+            return WTAP_OPEN_NOT_MINE;
+        return WTAP_OPEN_ERROR;
+    }
+
+    if (memcmp(expected_magic, actual_magic, sizeof(actual_magic)) != 0)
+        return WTAP_OPEN_NOT_MINE;
+
+    if (file_seek(wth->fh, 0, SEEK_SET, err) == -1)
+        return WTAP_OPEN_ERROR;
+
+    wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_PEM;
+    wth->file_encap = WTAP_ENCAP_BER;
+
+    wth->snapshot_length = 0;
+    wth->file_tsprec = WTAP_TSPREC_SEC;
+
+    struct pem_priv *priv = g_new0(struct pem_priv, 1);
+
+    priv->re_blank_line = g_regex_new("^\\s*$", G_REGEX_RAW, (GRegexMatchFlags)0, NULL);
+
+    priv->re_pre_eb = g_regex_new("^-----BEGIN " RE_LABEL "-----\\s*$",
+        (GRegexCompileFlags)(G_REGEX_RAW | G_REGEX_NO_AUTO_CAPTURE),
+        (GRegexMatchFlags)0, NULL);
+    priv->re_post_eb = g_regex_new("^-----END " RE_LABEL "-----\\s*$",
+        (GRegexCompileFlags)(G_REGEX_RAW | G_REGEX_NO_AUTO_CAPTURE),
+        (GRegexMatchFlags)0, NULL);
+
+    wth->priv = priv;
+
+    wth->subtype_read = pem_read;
+    wth->subtype_seek_read = pem_seek_read;
+    wth->subtype_close = pem_close;
+
+    if (!priv->re_blank_line || !priv->re_pre_eb || !priv->re_post_eb) {
+        *err = WTAP_ERR_INTERNAL;
+        *err_info = g_strdup("failed to initialize reader");
+        return WTAP_OPEN_ERROR;
+    }
+
+    return WTAP_OPEN_MINE;
+}
+
+/*
+ * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
+ *
+ * Local Variables:
+ * c-basic-offset: 4
+ * tab-width: 8
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * vi: set shiftwidth=4 tabstop=8 expandtab:
+ * :indentSize=4:tabSize=8:noTabs=true:
+ */
diff --git a/wiretap/pem.h b/wiretap/pem.h
new file mode 100644
index 0000000000..5a6cff58ba
--- /dev/null
+++ b/wiretap/pem.h
@@ -0,0 +1,27 @@
+/* pem.h
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef __PEM_H__
+#define __PEM_H__
+
+#include <glib.h>
+#include "wtap.h"
+
+wtap_open_return_val pem_open(wtap *wth, int *err, gchar **err_info);
+
+#endif
+
+/*
+* Editor modelines  -  http://www.wireshark.org/tools/modelines.html
+*
+* Local Variables:
+* c-basic-offset: 4
+* tab-width: 8
+* indent-tabs-mode: nil
+* End:
+*
+* vi: set shiftwidth=4 tabstop=8 expandtab:
+* :indentSize=4:tabSize=8:noTabs=true:
+*/
diff --git a/wiretap/wtap.h b/wiretap/wtap.h
index d0cc052507..8f3c235990 100644
--- a/wiretap/wtap.h
+++ b/wiretap/wtap.h
@@ -373,6 +373,7 @@ extern "C" {
 #define WTAP_FILE_TYPE_SUBTYPE_NETTRACE_3GPP_32_423          79
 #define WTAP_FILE_TYPE_SUBTYPE_MPLOG                         80
 #define WTAP_FILE_TYPE_SUBTYPE_DPA400                        81
+#define WTAP_FILE_TYPE_SUBTYPE_PEM                           82
 
 #define WTAP_NUM_FILE_TYPES_SUBTYPES  wtap_get_num_file_types_subtypes()