feat: first commit

.gitignore

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+config.h
+**/*.swp
+**/*~
+**/*.o
+**/*.core
+sis

LICENSE

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+Copyright (c) 2024, Lorenzo Torres
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+3. Neither the name of the <organization> nor the
+   names of its contributors may be used to endorse or promote products
+   derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ''AS IS'' AND ANY
+EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Makefile

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+# sis - simple imap server
+# See LICENSE file for copyright and license details.
+
+include config.mk
+
+SRC = sis.c imap.c
+HDR = config.def.h
+OBJ = ${SRC:.c=.o}
+
+all: options sis
+
+options:
+	@echo sis build options:
+	@echo "CFLAGS   = ${CFLAGS}"
+	@echo "LDFLAGS  = ${LDFLAGS}"
+	@echo "CC       = ${CC}"
+
+.c.o:
+	${CC} -c ${CFLAGS} $<
+
+${OBJ}: config.h config.mk
+
+config.h:
+	cp config.def.h $@
+
+sis: ${OBJ}
+	${CC} -o $@ ${OBJ} ${LDFLAGS}
+
+clean:
+	rm -f sis ${OBJ} sis-${VERSION}.tar.gz
+
+dist: clean
+	mkdir -p sis-${VERSION}
+	cp -R LICENSE Makefile README config.mk\
+		sis.1 ${HDR} ${SRC} sis-${VERSION}
+	tar -cf sis-${VERSION}.tar sis-${VERSION}
+	gzip sis-${VERSION}.tar
+	rm -rf sis-${VERSION}
+
+install: all
+	mkdir -p ${DESTDIR}${PREFIX}/bin
+	cp -f sis ${DESTDIR}${PREFIX}/bin
+	chmod 755 ${DESTDIR}${PREFIX}/bin/sis
+	mkdir -p ${DESTDIR}${MANPREFIX}/man1
+	sed "s/VERSION/${VERSION}/g" < sis.1 > ${DESTDIR}${MANPREFIX}/man1/sis.1
+	chmod 644 ${DESTDIR}${MANPREFIX}/man1/sis.1
+
+uninstall:
+	rm -f ${DESTDIR}${PREFIX}/bin/dwm\
+		${DESTDIR}${MANPREFIX}/man1/dwm.1
+
+.PHONY: all options clean dist install uninstall

README

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+sis - simple imap server
+============================
+sis is an IMAP server, following the unix philosophy,
+trying to be as small as possible while providing
+a reliable service.
+
+
+Requirements
+------------
+In order to build sis you need... a computer
+
+
+Installation
+------------
+Edit config.mk to match your local setup (sis is installed into
+the /usr/local namespace by default).
+
+Afterwards enter the following command to build and install sis (if
+necessary as root):
+
+    make clean install
+
+
+Running sis
+-----------
+By default, sis runs in daemon mode, if you want to avoid detaching use the -d option
+    sis -d
+
+
+Configuration
+-------------
+The configuration of sis is done by creating a custom config.h
+and (re)compiling the source code.

config.def.h

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+/* See LICENSE file for copyright and license details. */
+
+/* network */
+#define IMAP_PORT       143
+#define IMAPS_PORT      993
+/*-
+ * Maximum number of connected clients,
+ * NOTE: each one of these is a currently
+ * connected client! Unless your server
+ * has to manage a lot of accounts you
+ * should be good with the default value.
+ */
+#define MAX_CLIENTS     30
+/*-
+ * Maximum size for the command buffer.
+ * IMAP sends plain text commands, so
+ * the default value can receive up to
+ * 8000 characters long commands.
+ * It should be enough but feel free to
+ * modify this.
+ */
+#define CMD_MAX_SIZE    8000

config.mk

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+# sis version
+VERSION = 0.1
+
+# Customize below to fit your system
+
+# paths
+PREFIX = /usr
+MANPREFIX = ${PREFIX}/share/man
+
+# OpenBSD (uncomment)
+#MANPREFIX = ${PREFIX}/man
+
+# includes and libs
+INCS = -I.
+LIBS =
+# flags
+CPPFLAGS = -DVERSION=\"${VERSION}\" 
+CFLAGS   = -g -std=c99 -pedantic -Wall -O0 ${INCS} ${CPPFLAGS}
+#CFLAGS   = -std=c99 -pedantic -Wall -Wno-deprecated-declarations -Os ${INCS} ${CPPFLAGS}
+LDFLAGS  = ${LIBS}
+
+# Solaris
+#CFLAGS = -fast ${INCS} -DVERSION=\"${VERSION}\"
+#LDFLAGS = ${LIBS}
+
+# compiler and linker
+CC = cc

imap.c

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+/*-
+ * Copyright (c) 2024, Lorenzo Torres
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the <organization> nor the
+ *    names of its contributors may be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/select.h>
+#include <syslog.h>
+#include <errno.h>
+#include <config.h>
+#include <imap.h>
+
+uint8_t imap_init(uint8_t daemon, imap_t *instance)
+{
+    imap_t imap;
+
+    /* Create a new socket using IPv4 protocol */
+    if ((imap.socket = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
+        perror("socker");
+        return 1;
+    }
+
+    bzero(&imap.addr, sizeof(struct sockaddr_in));
+
+    imap.addr.sin_family = AF_INET;
+    /* From config.h */
+    imap.addr.sin_port = htons(IMAP_PORT);
+    
+    if (INADDR_ANY) {
+        imap.addr.sin_addr.s_addr = htonl(INADDR_ANY);
+    }
+
+    /* Bind the socket to the specified address */
+    if ((bind(imap.socket, (struct sockaddr *)&imap.addr, sizeof(imap.addr)) < 0)) {
+        perror("bind");
+        return 2;
+    }
+
+    /* If daemon mode is activated, detach */
+    if (daemon) {
+        switch (fork()) {
+            case -1:
+                perror("fork");
+                return 3;
+                break;
+            default:
+                close(imap.socket);
+                free(instance);
+                exit(0);
+                break;
+            case 0:
+                break;
+        }
+    }
+
+    memcpy(instance, &imap, sizeof(imap));
+
+    return 0;
+}
+
+int imap_get_max_fd(client_list *list, int master)
+{
+    int max_fd = 0;
+    client_list *node = list;
+
+    while (node != NULL) {
+        if (max_fd < node->socket) {
+            max_fd = node->socket;
+        }
+
+        node = node->next;
+    }
+
+    return max_fd > master ? max_fd : master;
+}
+
+client_list *imap_add_client(client_list *list, int sock)
+{
+    client_list *node = (client_list *) malloc(sizeof(client_list));
+    node->socket = sock;
+    node->next = list;
+    node->prev = NULL;
+    if (list != NULL) {
+        list->prev = node;
+    }
+
+    return node; 
+}
+
+client_list *imap_remove_client(client_list *list, client_list *node)
+{
+    if (node->next != NULL) {
+        node->next->prev = node->prev;
+    }
+
+    if (node->prev != NULL) {
+        node->prev->next = node->next;
+    }
+
+    close(node->socket);
+
+    if (node == list) {
+        return NULL;
+    }
+
+    return list;
+}
+
+client_list *imap_remove_sock(client_list *list, int sock)
+{
+    client_list *node = list;
+
+    while (node != NULL && node->socket != sock) {
+        node = node->next;
+    }
+
+    if (node != NULL) {
+        imap_remove_client(list, node);
+    }
+
+    return node;
+}
+
+void imap_start(imap_t *instance)
+{
+    int activity, max_fd, connection;
+    size_t bytes_read;
+    char buf[CMD_MAX_SIZE];
+    /* List of all the file descriptors (sockets) being used. */
+    fd_set fds;
+    instance->clients = NULL;
+    client_list *node = instance->clients;
+    client_list *tmp = instance->clients;
+
+    listen(instance->socket, BACKLOG);
+    syslog(LOG_INFO, "Listening on %d.", IMAP_PORT);
+
+    for (;;) {
+        FD_ZERO(&fds);
+        FD_SET(instance->socket, &fds);
+        node = instance->clients;
+
+        while (node != NULL) {
+            FD_SET(node->socket, &fds);
+            node = node->next;
+        }
+
+        max_fd = imap_get_max_fd(instance->clients, instance->socket);
+        activity = select(max_fd + 1, &fds, NULL, NULL, NULL);
+
+        if ((activity < 0) && (errno!=EINTR)) {
+            perror("select");
+        }
+
+        /* New connection. */
+        if (FD_ISSET(instance->socket, &fds)) {
+            if ((connection = accept(instance->socket, NULL, NULL)) < 0) {
+                perror("accept");
+                syslog(LOG_ERR, "Connection failed.");
+                imap_close(instance);
+                exit(EXIT_FAILURE);
+            }
+
+            instance->clients = imap_add_client(instance->clients, connection);
+            syslog(LOG_INFO, "Connection enstablished.");
+            FD_SET(connection, &fds);
+        }
+
+        node = instance->clients;
+        tmp = node;
+        while (node != NULL) {
+            connection = node->socket;
+            tmp = node->next;
+            
+            if (FD_ISSET(connection, &fds)) {
+                /* Error occured. */
+                if ((bytes_read = read(connection, buf, CMD_MAX_SIZE)) < 0) {
+                    perror("recv");
+                    instance->clients = imap_remove_client(instance->clients, node);
+                    free(node);
+                    FD_CLR(connection, &fds);
+                    syslog(LOG_ERR, "Failed to receive data.");
+                /* Somebody disconnected */
+                }  else if (bytes_read == 0) {
+                    instance->clients = imap_remove_client(instance->clients, node);
+                    free(node);
+                    FD_CLR(connection, &fds);
+                    syslog(LOG_INFO, "Connection closed.");
+                } else {
+                    buf[bytes_read] = '\0';
+                }
+            }
+
+            node = tmp;
+        }
+    }
+}
+
+void imap_close(imap_t *instance)
+{
+    client_list *node = instance->clients;
+    client_list *tmp = node;
+    while (node != NULL) {
+        close(node->socket);
+        tmp = node->next;
+        free(node);
+        node = tmp;
+    }
+
+    close(instance->socket);
+    free(instance);
+}

imap.h

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+/*-
+ * Copyright (c) 2024, Lorenzo Torres
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the <organization> nor the
+ *    names of its contributors may be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef IMAP_H
+#define IMAP_H
+
+#include <stdint.h>
+#include <stddef.h>
+#include <netinet/in.h>
+
+#define BACKLOG 4
+
+typedef struct _client_list {
+    int32_t socket;
+    struct _client_list *next;
+    struct _client_list *prev;
+} client_list;
+
+
+typedef struct imap {
+    int32_t socket;
+    client_list *clients;
+    struct sockaddr_in addr;
+} imap_t;
+
+/* Create a new imap_t instance and initialize the server. */
+uint8_t imap_init(uint8_t daemon, imap_t *instance);
+/* Start the IMAP server. */
+void imap_start(imap_t *instance);
+/* Close all connections and free the allocated memory. */
+void imap_close(imap_t *instance);
+/* Add client to client list */
+client_list *imap_add_client(client_list *list, int sock);
+/* Close connection with client */
+client_list *imap_remove_client(client_list *list, client_list *node);
+client_list *imap_remove_sock(client_list *list, int sock);
+/* Get the higher file descriptor in the client list */
+int imap_get_max_fd(client_list *list, int master);
+
+#endif /* ifndef IMAP_H */

sis.c

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+/*-
+ * Copyright (c) 2024, Lorenzo Torres
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the <organization> nor the
+ *    names of its contributors may be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <signal.h>
+#include <syslog.h>
+#include <imap.h>
+
+static imap_t *instance;
+
+void int_handler(int sig)
+{
+    if (instance != NULL) {
+        imap_close(instance);
+    }
+}
+
+int main(void)
+{
+    signal(SIGINT, int_handler);
+
+    openlog("sis", LOG_PID, LOG_MAIL);
+    syslog(LOG_INFO, "Starting sis %s.", VERSION);
+
+    int status = 0;
+    instance = (imap_t *) malloc(sizeof(imap_t));    
+
+    if ((status = imap_init(0, instance)) != 0) {
+        perror("imap_init");
+        goto ret;
+    }
+
+    imap_start(instance);
+
+ret:
+    if (instance != NULL) {
+        imap_close(instance);
+    }
+
+    closelog();
+    return status;
+}