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Date:: Sun Feb 6 20:15:21 2022 UTC
Message:: portable: add support for landlock landlock is a new set of linux APIs that is conceptually similar to unveil(2): the idea is to restrict what a process can do on a specified part of the filesystem. There are some differences in the behaviour: the major one being that the landlock ruleset is inherited across execve(2). This just restricts the libexec helpers by completely revoking ANY filesystem access; after all they are the biggest attack surface. got send/fetch/clone *may* end up spawning ssh(1), so at the moment is not possible to landlock the main process. From Omar Polo.
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  1 ad242220 2018-09-08 stsp /*
  2 5aa81393 2020-01-06 stsp  * Copyright (c) 2018, 2019, 2020 Stefan Sperling <stsp@openbsd.org>
  3 ad242220 2018-09-08 stsp  *
  4 ad242220 2018-09-08 stsp  * Permission to use, copy, modify, and distribute this software for any
  5 ad242220 2018-09-08 stsp  * purpose with or without fee is hereby granted, provided that the above
  6 ad242220 2018-09-08 stsp  * copyright notice and this permission notice appear in all copies.
  7 ad242220 2018-09-08 stsp  *
  8 ad242220 2018-09-08 stsp  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9 ad242220 2018-09-08 stsp  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10 ad242220 2018-09-08 stsp  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 11 ad242220 2018-09-08 stsp  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12 ad242220 2018-09-08 stsp  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 13 ad242220 2018-09-08 stsp  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 14 ad242220 2018-09-08 stsp  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15 ad242220 2018-09-08 stsp  */
 16 ad242220 2018-09-08 stsp 
 17 ad242220 2018-09-08 stsp #include <sys/types.h>
 18 ad242220 2018-09-08 stsp #include <sys/uio.h>
 19 ad242220 2018-09-08 stsp #include <sys/time.h>
 20 ad242220 2018-09-08 stsp 
 21 ad242220 2018-09-08 stsp #include <stdint.h>
 22 12ce7a6c 2019-08-12 stsp #include <limits.h>
 23 99437157 2018-11-11 stsp #include <signal.h>
 24 ad242220 2018-09-08 stsp #include <stdio.h>
 25 ad242220 2018-09-08 stsp #include <stdlib.h>
 26 ad242220 2018-09-08 stsp #include <string.h>
 27 81a12da5 2020-09-09 naddy #include <unistd.h>
 28 ad242220 2018-09-08 stsp #include <zlib.h>
 29 ad242220 2018-09-08 stsp 
 30 dd038bc6 2021-09-21 thomas.ad #include "got_compat.h"
 31 dd038bc6 2021-09-21 thomas.ad 
 32 ad242220 2018-09-08 stsp #include "got_error.h"
 33 ad242220 2018-09-08 stsp #include "got_object.h"
 34 ad242220 2018-09-08 stsp 
 35 ad242220 2018-09-08 stsp #include "got_lib_delta.h"
 36 ad242220 2018-09-08 stsp #include "got_lib_inflate.h"
 37 ad242220 2018-09-08 stsp #include "got_lib_object.h"
 38 ad242220 2018-09-08 stsp #include "got_lib_object_parse.h"
 39 ad242220 2018-09-08 stsp #include "got_lib_privsep.h"
 40 d5c81d44 2021-07-08 stsp #include "got_lib_sha1.h"
 41 ad242220 2018-09-08 stsp 
 42 99437157 2018-11-11 stsp static volatile sig_atomic_t sigint_received;
 43 99437157 2018-11-11 stsp 
 44 99437157 2018-11-11 stsp static void
 45 99437157 2018-11-11 stsp catch_sigint(int signo)
 46 99437157 2018-11-11 stsp {
 47 99437157 2018-11-11 stsp 	sigint_received = 1;
 48 99437157 2018-11-11 stsp }
 49 99437157 2018-11-11 stsp 
 50 ad242220 2018-09-08 stsp static const struct got_error *
 51 d5c81d44 2021-07-08 stsp read_commit_object(struct got_commit_object **commit, FILE *f,
 52 d5c81d44 2021-07-08 stsp     struct got_object_id *expected_id)
 53 ad242220 2018-09-08 stsp {
 54 d5c81d44 2021-07-08 stsp 	struct got_object *obj = NULL;
 55 41fa1437 2018-11-05 stsp 	const struct got_error *err = NULL;
 56 41fa1437 2018-11-05 stsp 	size_t len;
 57 41fa1437 2018-11-05 stsp 	uint8_t *p;
 58 d5c81d44 2021-07-08 stsp 	struct got_inflate_checksum csum;
 59 d5c81d44 2021-07-08 stsp 	SHA1_CTX sha1_ctx;
 60 d5c81d44 2021-07-08 stsp 	struct got_object_id id;
 61 ad242220 2018-09-08 stsp 
 62 d5c81d44 2021-07-08 stsp 	SHA1Init(&sha1_ctx);
 63 d5c81d44 2021-07-08 stsp 	memset(&csum, 0, sizeof(csum));
 64 d5c81d44 2021-07-08 stsp 	csum.output_sha1 = &sha1_ctx;
 65 d5c81d44 2021-07-08 stsp 
 66 d5c81d44 2021-07-08 stsp 	err = got_inflate_to_mem(&p, &len, NULL, &csum, f);
 67 ad242220 2018-09-08 stsp 	if (err)
 68 ad242220 2018-09-08 stsp 		return err;
 69 ad242220 2018-09-08 stsp 
 70 d5c81d44 2021-07-08 stsp 	SHA1Final(id.sha1, &sha1_ctx);
 71 d5c81d44 2021-07-08 stsp 	if (memcmp(expected_id->sha1, id.sha1, SHA1_DIGEST_LENGTH) != 0) {
 72 d5c81d44 2021-07-08 stsp 		char buf[SHA1_DIGEST_STRING_LENGTH];
 73 d5c81d44 2021-07-08 stsp 		err = got_error_fmt(GOT_ERR_OBJ_CSUM,
 74 d5c81d44 2021-07-08 stsp 		    "checksum failure for object %s",
 75 d5c81d44 2021-07-08 stsp 		    got_sha1_digest_to_str(expected_id->sha1, buf,
 76 d5c81d44 2021-07-08 stsp 		    sizeof(buf)));
 77 d5c81d44 2021-07-08 stsp 		goto done;
 78 3f7f9bd9 2020-01-06 stsp 	}
 79 1785f84a 2018-12-23 stsp 
 80 d5c81d44 2021-07-08 stsp 	err = got_object_parse_header(&obj, p, len);
 81 d5c81d44 2021-07-08 stsp 	if (err)
 82 d5c81d44 2021-07-08 stsp 		goto done;
 83 d5c81d44 2021-07-08 stsp 
 84 41fa1437 2018-11-05 stsp 	if (len < obj->hdrlen + obj->size) {
 85 41fa1437 2018-11-05 stsp 		err = got_error(GOT_ERR_BAD_OBJ_DATA);
 86 41fa1437 2018-11-05 stsp 		goto done;
 87 ad242220 2018-09-08 stsp 	}
 88 ad242220 2018-09-08 stsp 
 89 1785f84a 2018-12-23 stsp 	if (obj->type != GOT_OBJ_TYPE_COMMIT) {
 90 1785f84a 2018-12-23 stsp 		err = got_error(GOT_ERR_OBJ_TYPE);
 91 1785f84a 2018-12-23 stsp 		goto done;
 92 1785f84a 2018-12-23 stsp 	}
 93 1785f84a 2018-12-23 stsp 
 94 ad242220 2018-09-08 stsp 	/* Skip object header. */
 95 41fa1437 2018-11-05 stsp 	len -= obj->hdrlen;
 96 ad242220 2018-09-08 stsp 	err = got_object_parse_commit(commit, p + obj->hdrlen, len);
 97 41fa1437 2018-11-05 stsp done:
 98 1785f84a 2018-12-23 stsp 	free(p);
 99 d5c81d44 2021-07-08 stsp 	if (obj)
100 d5c81d44 2021-07-08 stsp 		got_object_close(obj);
101 ad242220 2018-09-08 stsp 	return err;
102 ad242220 2018-09-08 stsp }
103 ad242220 2018-09-08 stsp 
104 ad242220 2018-09-08 stsp int
105 ad242220 2018-09-08 stsp main(int argc, char *argv[])
106 ad242220 2018-09-08 stsp {
107 ad242220 2018-09-08 stsp 	const struct got_error *err = NULL;
108 ad242220 2018-09-08 stsp 	struct imsgbuf ibuf;
109 d5c81d44 2021-07-08 stsp 	size_t datalen;
110 ad242220 2018-09-08 stsp 
111 99437157 2018-11-11 stsp 	signal(SIGINT, catch_sigint);
112 99437157 2018-11-11 stsp 
113 ad242220 2018-09-08 stsp 	imsg_init(&ibuf, GOT_IMSG_FD_CHILD);
114 ad242220 2018-09-08 stsp 
115 2ff12563 2018-09-15 stsp #ifndef PROFILE
116 ad242220 2018-09-08 stsp 	/* revoke access to most system calls */
117 ad242220 2018-09-08 stsp 	if (pledge("stdio recvfd", NULL) == -1) {
118 638f9024 2019-05-13 stsp 		err = got_error_from_errno("pledge");
119 ad242220 2018-09-08 stsp 		got_privsep_send_error(&ibuf, err);
120 ad242220 2018-09-08 stsp 		return 1;
121 ad242220 2018-09-08 stsp 	}
122 97799ccd 2022-02-06 thomas 
123 97799ccd 2022-02-06 thomas 	/* revoke fs access */
124 97799ccd 2022-02-06 thomas 	if (landlock_no_fs() == -1) {
125 97799ccd 2022-02-06 thomas 		err = got_error_from_errno("landlock_no_fs");
126 97799ccd 2022-02-06 thomas 		got_privsep_send_error(&ibuf, err);
127 97799ccd 2022-02-06 thomas 		return 1;
128 97799ccd 2022-02-06 thomas 	}
129 2ff12563 2018-09-15 stsp #endif
130 ad242220 2018-09-08 stsp 
131 656b1f76 2019-05-11 jcs 	for (;;) {
132 ad242220 2018-09-08 stsp 		struct imsg imsg;
133 ad242220 2018-09-08 stsp 		FILE *f = NULL;
134 1785f84a 2018-12-23 stsp 		struct got_commit_object *commit = NULL;
135 d5c81d44 2021-07-08 stsp 		struct got_object_id expected_id;
136 99437157 2018-11-11 stsp 
137 99437157 2018-11-11 stsp 		if (sigint_received) {
138 99437157 2018-11-11 stsp 			err = got_error(GOT_ERR_CANCELLED);
139 99437157 2018-11-11 stsp 			break;
140 99437157 2018-11-11 stsp 		}
141 230a42bd 2019-05-11 jcs 
142 ad242220 2018-09-08 stsp 		err = got_privsep_recv_imsg(&imsg, &ibuf, 0);
143 ad242220 2018-09-08 stsp 		if (err) {
144 876c234b 2018-09-10 stsp 			if (err->code == GOT_ERR_PRIVSEP_PIPE)
145 ad242220 2018-09-08 stsp 				err = NULL;
146 ad242220 2018-09-08 stsp 			break;
147 ad242220 2018-09-08 stsp 		}
148 ad242220 2018-09-08 stsp 
149 ad242220 2018-09-08 stsp 		if (imsg.hdr.type == GOT_IMSG_STOP)
150 ad242220 2018-09-08 stsp 			break;
151 ad242220 2018-09-08 stsp 
152 41fa1437 2018-11-05 stsp 		if (imsg.hdr.type != GOT_IMSG_COMMIT_REQUEST) {
153 41fa1437 2018-11-05 stsp 			err = got_error(GOT_ERR_PRIVSEP_MSG);
154 41fa1437 2018-11-05 stsp 			goto done;
155 ad242220 2018-09-08 stsp 		}
156 ad242220 2018-09-08 stsp 
157 d5c81d44 2021-07-08 stsp 		datalen = imsg.hdr.len - IMSG_HEADER_SIZE;
158 d5c81d44 2021-07-08 stsp 		if (datalen != sizeof(expected_id)) {
159 d5c81d44 2021-07-08 stsp 			err = got_error(GOT_ERR_PRIVSEP_LEN);
160 d5c81d44 2021-07-08 stsp 			goto done;
161 d5c81d44 2021-07-08 stsp 		}
162 d5c81d44 2021-07-08 stsp 		memcpy(&expected_id, imsg.data, sizeof(expected_id));
163 d5c81d44 2021-07-08 stsp 
164 ad242220 2018-09-08 stsp 		if (imsg.fd == -1) {
165 ad242220 2018-09-08 stsp 			err = got_error(GOT_ERR_PRIVSEP_NO_FD);
166 ad242220 2018-09-08 stsp 			goto done;
167 ad242220 2018-09-08 stsp 		}
168 ad242220 2018-09-08 stsp 
169 ad242220 2018-09-08 stsp 		/* Always assume file offset zero. */
170 ad242220 2018-09-08 stsp 		f = fdopen(imsg.fd, "rb");
171 ad242220 2018-09-08 stsp 		if (f == NULL) {
172 638f9024 2019-05-13 stsp 			err = got_error_from_errno("fdopen");
173 ad242220 2018-09-08 stsp 			goto done;
174 ad242220 2018-09-08 stsp 		}
175 ad242220 2018-09-08 stsp 
176 d5c81d44 2021-07-08 stsp 		err = read_commit_object(&commit, f, &expected_id);
177 41fa1437 2018-11-05 stsp 		if (err)
178 41fa1437 2018-11-05 stsp 			goto done;
179 41fa1437 2018-11-05 stsp 
180 41fa1437 2018-11-05 stsp 		err = got_privsep_send_commit(&ibuf, commit);
181 fe558a04 2020-01-06 stsp 		got_object_commit_close(commit);
182 ad242220 2018-09-08 stsp done:
183 fb43ecf1 2019-02-11 stsp 		if (f) {
184 56b63ca4 2021-01-22 stsp 			if (fclose(f) == EOF && err == NULL)
185 638f9024 2019-05-13 stsp 				err = got_error_from_errno("fclose");
186 3a6ce05a 2019-02-11 stsp 		} else if (imsg.fd != -1) {
187 08578a35 2021-01-22 stsp 			if (close(imsg.fd) == -1 && err == NULL)
188 638f9024 2019-05-13 stsp 				err = got_error_from_errno("close");
189 3a6ce05a 2019-02-11 stsp 		}
190 ad242220 2018-09-08 stsp 		imsg_free(&imsg);
191 99437157 2018-11-11 stsp 		if (err)
192 ad242220 2018-09-08 stsp 			break;
193 ad242220 2018-09-08 stsp 	}
194 ad242220 2018-09-08 stsp 
195 ad242220 2018-09-08 stsp 	imsg_clear(&ibuf);
196 99437157 2018-11-11 stsp 	if (err) {
197 80d5f134 2018-11-11 stsp 		if (!sigint_received && err->code != GOT_ERR_PRIVSEP_PIPE) {
198 80d5f134 2018-11-11 stsp 			fprintf(stderr, "%s: %s\n", getprogname(), err->msg);
199 99437157 2018-11-11 stsp 			got_privsep_send_error(&ibuf, err);
200 80d5f134 2018-11-11 stsp 		}
201 99437157 2018-11-11 stsp 	}
202 08578a35 2021-01-22 stsp 	if (close(GOT_IMSG_FD_CHILD) == -1 && err == NULL)
203 638f9024 2019-05-13 stsp 		err = got_error_from_errno("close");
204 ad242220 2018-09-08 stsp 	return err ? 1 : 0;
205 ad242220 2018-09-08 stsp }