v1/v2 Create/Parse PROXY protocol headers

Author: kosmas-valianos

.gitignore

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+*.o
+libs/libproxyprotocol.so
+tests/test_libproxyprotocol

COPYING

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COPYING.LESSER

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+#
+# libproxyprotocol is an ANSI C library to parse and create PROXY protocol v1 and v2 headers
+# Copyright (C) 2022  Kosmas Valianos (kosmas.valianos@gmail.com)
+#
+# The libproxyprotocol 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 3 of the License, or
+# (at your option) any later version.
+#
+# The libproxyprotocol 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 program.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+CFLAGS := -Wall -Wextra -Wshadow -ansi -fshort-enums -fpic
+
+all: build
+
+build: libs_dir libs/libproxyprotocol.so
+
+libs_dir:
+	mkdir -p libs
+
+libs/libproxyprotocol.so: src/proxy_protocol.o
+	$(CC) -shared -o $@ $+
+
+src/%.o: %.c src/proxy_protocol.h
+	$(CC) ${CFLAGS} -c -o $@ $<
+
+tests: tests/test_libproxyprotocol
+	LD_LIBRARY_PATH=libs/ $<
+
+tests/test_libproxyprotocol: tests/test.o libs/libproxyprotocol.so
+	$(CC) -Llibs/ ${CFLAGS} -o $@ $< -lproxyprotocol
+
+clean:
+	$(RM) src/*.o libs/libproxyprotocol.so
+	$(RM) tests/*.o tests/test_libproxyprotocol

Makefile

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+# libproxyprotocol
+An ANSI C library to parse and create [PROXY protocol](https://www.haproxy.org/download/2.6/doc/proxy-protocol.txt) v1 and v2 headers
+>The PROXY protocol provides a convenient way to safely transport connection information such as a client's address across multiple layers of NAT or TCP proxies. It is designed to require little changes to existing components and to limit the performance impact caused by the processing of the transported information.
+
+## Installation
+The library should be compilable to any platform as it is written in ANSI C. It comes with a Makefile which can create the shared library `libproxyprotocol.so` which can then be linked to your application. Special care has been taken to make it work with Windows as well. In that case you have to compile it to a DLL yourself. In case of windows remember that you have to link with the `ws2_32.lib`. An example of this is shown in tests.
+
+## API
+### Parsing
+To parse a PROXY protocol header you need to use `pp_parse()` with the following parameters:
+* `uint8_t *pkt`: Pointer to a buffer with the data to parse. Normally it will be the buffer used to peek data from a socket.
+* `uint32_t pktlen`: Data's length. Normally it will be the return value of a `recv(MSG_PEEK)`.
+* `pp_info_t *proxy_info`: Pointer to a `pp_info_t` variable which will be used to save all the extracted information of the PROXY protocol header including the TLVs
+* `return value: int32_t`: The length of the PROXY protocol header in case of success or a negative integer in case of error. You can use `pp_strerror()` to get a descriptive error message. In case the data dont't match any of the v1/v2 signatures `0` is returned.
+
+You shall not pass your `pp_info_t` variable to `pp_parse()` again without first clearing it with `pp_info_clear()` (see below)
+
+To extract TLVs' values it is strongly suggested that you use `pp_info_get_tlv_value()` with the following parameters:
+* `pp_info_t *pp_info`: The `pp_info_t` used in the `pp_parse()`
+* `uint8_t type`: The type of the TLV you are looking for as per the specification e.g. PP2_TYPE_AWS, PP2_TYPE_AZURE etc.
+* `uint8_t subtype`: The subtype of the TLV you are looking for (in case it is needed or just a value <= 0 to be ignored) as per the specification e.g. PP2_SUBTYPE_AWS_VPCE_ID, PP2_SUBTYPE_AZURE_PRIVATEENDPOINT_LINKID
+* `uint16_t *value_len_out`: The length of the value so that applications can copy and use the value properly
+* `return value: uint8_t *`: Pointer to the value. In case the value is a string e.g. PP2_TYPE_AWS-PP2_SUBTYPE_AWS_VPCE_ID thenthe buffer is NULL terminated so that it can be used directly for string operations like `strcmp()` etc. **Do not manipulate these data in any way, rather make copies of them if you need to modify them.**
+
+To clear a `pp_info_t` structure you **MUST** use  `pp_info_clear()` with the following parameter:
+* `pp_info_t *pp_info`: A pointer to the `pp_info_t` used in `pp_parse()`
+
+It basically clears the saved TLVs structure. For v1 it is not really needed as there are not any TLVs but to be safe always use it! A PROXY protocol sender might change from v1 to v2 so better to have your application prepared.
+
+### Creating
+To create a PROXY protocol header you need to use `pp_create_hdr()` with the following parameters:
+* `uint8_t version`: `1` or `2` depending on the PROXY protocol version you want to use.
+* `uint8_t fam`: Transport and address family. The values match exactly the specification:
+  * v2 
+    * `'\x00'` : UNSPEC
+    * `'\x11'` : TCP over IPv4
+    * `'\x12'` : UDP over IPv4
+    * `'\x21'` : TCP over IPv6
+    * `'\x22'` : UDP over IPv6
+    * `'\x31'` : UNIX stream
+    * `'\x32'` : UNIX datagram
+  * v1
+    * `AF_INET`
+    * `AF_INET6`
+* `pp_info_t *pp_info` : Pointer to a filled `pp_info_t` structure. Note that at the moment tlvs from the `tlv_array_t tlv_array` inside it will not be included in the header. This functionality will be added with the next release.
+* `uint32_t *pp_hdr_len`: Output parameter where the length of the the PROXY protocol header will be stored.
+* `uint32_t *error`: Outpur parameter where its value will be set to a negative integer in case of error or `ERR_NULL` in case of success. You can use `pp_strerror()` to get a descriptive error message
+* `return value: uint8_t *`: Pointer to a dynamically allocated buffer where the PROXY protocol header exists. Shall be freed with `free()`
+
+## Example
+See `examples/client_server.c`
+
+## Limitations
+* Creating v2 PROXY protocol headers with TLVs is not yet supported. Will be added in the next release 1.0.0
+* Parsing `PP2_TYPE_SSL` TLV of the v2 PROXY protocol header is not yet supported. TLVs of this type will not be saved in the `pp_info_t` structure. Will be added in the next release 1.0.0
+* The library is not heavily tested. Much more test coverage will be added in the next release 1.0.0

README.md

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+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+
+#include "../src/proxy_protocol.h"
+
+int main()
+{
+    // Create a v1 PROXY protocol header
+    pp_info_t pp_info_in = {
+        .src_addr = "172.22.32.1",
+        .dst_addr = "172.22.33.1",
+        .src_port = 4040,
+        .dst_port = 443
+    };
+    uint32_t pp1_hdr_len;
+    uint32_t error;
+    uint8_t *pp1_hdr = pp_create_hdr(1, AF_INET, &pp_info_in, &pp1_hdr_len, &error);
+    if (!pp1_hdr)
+    {
+        fprintf(stderr, "pp_create_hdr() failed: %s", pp_strerror(error));
+        free(pp1_hdr);
+        return EXIT_FAILURE;
+    }
+
+    // Parse
+    pp_info_t pp_info_out;
+    int32_t rc = pp_parse_hdr(pp1_hdr, pp1_hdr_len, &pp_info_out);
+    free(pp1_hdr);
+    if (rc == 0)
+    {
+        printf("Not a PROXY protocol header\n");
+    }
+    else if (rc < 0)
+    {
+        fprintf(stderr, "pp_parse_hdr() failed: %s", pp_strerror(rc));
+        pp_info_clear(&pp_info_out);
+        return EXIT_FAILURE;
+    }
+    else
+    {
+        printf("%d bytes PROXY protocol header: %s %s %hu %hu\n",
+            rc,
+            pp_info_out.src_addr, pp_info_out.dst_addr,
+            pp_info_out.src_port, pp_info_out.dst_port);
+    }
+    pp_info_clear(&pp_info_out);
+
+    // Parse
+    uint8_t pp2_hdr_vpce[] = {
+            0x0d, 0x0a, 0x0d, 0x0a, /* Start of v2 signature */
+            0x00, 0x0d, 0x0a, 0x51,
+            0x55, 0x49, 0x54, 0x0a, /* End of v2 signature */
+            0x21, 0x11, 0x00, 0x40, /* ver_cmd, fam and len */
+            0xc0, 0xa8, 0x0a, 0x64, /* Source IP */
+            0xc0, 0xa8, 0x0b, 0x5a, /* Destination IP */
+            0xa5, 0x5c, 0x1f, 0x90, /* Source port, Destination port */
+            0x03, 0x00, 0x04, 0xe5, /* CRC32C TLV start */
+            0x18, 0x86, 0xf8, 0xea, /* CRC32C TLV end, AWS VPCE ID TLV start */
+            0x00, 0x17, 0x01, 0x76,
+            0x70, 0x63, 0x65, 0x2d,
+            0x32, 0x33, 0x64, 0x38,
+            0x65, 0x7a, 0x6a, 0x6b,
+            0x33, 0x38, 0x62, 0x63,
+            0x68, 0x69, 0x6c, 0x6d,
+            0x34, 0x04, 0x00, 0x10, /* AWS VPCE ID TLV end, NOOP TLV start */
+            0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, /* NOOP TLV end */
+    };
+
+    rc = pp_parse_hdr(pp2_hdr_vpce, sizeof(pp2_hdr_vpce), &pp_info_out);
+    if (rc == 0)
+    {
+        printf("Not a PROXY protocol header\n");
+    }
+    else if (rc < 0)
+    {
+        fprintf(stderr, "pp_parse_hdr() failed: %s", pp_strerror(rc));
+        pp_info_clear(&pp_info_out);
+        return EXIT_FAILURE;
+    }
+    else
+    {
+        uint16_t tlv_value_len;
+        char *vpc_id = pp_info_get_tlv_value(&pp_info_out, PP2_TYPE_AWS, PP2_SUBTYPE_AWS_VPCE_ID, &tlv_value_len);
+        printf("%d bytes PROXY protocol header:  AWS VPC ID: %s. %s %s %hu %hu\n",
+            rc, vpc_id,
+            pp_info_out.src_addr, pp_info_out.dst_addr,
+            pp_info_out.src_port, pp_info_out.dst_port);
+    }
+    pp_info_clear(&pp_info_out);
+
+    return EXIT_SUCCESS;
+}