Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * fe-secure-common.c
4 : *
5 : * common implementation-independent SSL support code
6 : *
7 : * While fe-secure.c contains the interfaces that the rest of libpq call, this
8 : * file contains support routines that are used by the library-specific
9 : * implementations such as fe-secure-openssl.c.
10 : *
11 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
12 : * Portions Copyright (c) 1994, Regents of the University of California
13 : *
14 : * IDENTIFICATION
15 : * src/interfaces/libpq/fe-secure-common.c
16 : *
17 : *-------------------------------------------------------------------------
18 : */
19 :
20 : #include "postgres_fe.h"
21 :
22 : #include <arpa/inet.h>
23 :
24 : #include "fe-secure-common.h"
25 :
26 : #include "libpq-int.h"
27 : #include "pqexpbuffer.h"
28 :
29 : /*
30 : * Check if a wildcard certificate matches the server hostname.
31 : *
32 : * The rule for this is:
33 : * 1. We only match the '*' character as wildcard
34 : * 2. We match only wildcards at the start of the string
35 : * 3. The '*' character does *not* match '.', meaning that we match only
36 : * a single pathname component.
37 : * 4. We don't support more than one '*' in a single pattern.
38 : *
39 : * This is roughly in line with RFC2818, but contrary to what most browsers
40 : * appear to be implementing (point 3 being the difference)
41 : *
42 : * Matching is always case-insensitive, since DNS is case insensitive.
43 : */
44 : static bool
45 42 : wildcard_certificate_match(const char *pattern, const char *string)
46 : {
47 42 : int lenpat = strlen(pattern);
48 42 : int lenstr = strlen(string);
49 :
50 : /* If we don't start with a wildcard, it's not a match (rule 1 & 2) */
51 42 : if (lenpat < 3 ||
52 42 : pattern[0] != '*' ||
53 6 : pattern[1] != '.')
54 36 : return false;
55 :
56 : /* If pattern is longer than the string, we can never match */
57 6 : if (lenpat > lenstr)
58 0 : return false;
59 :
60 : /*
61 : * If string does not end in pattern (minus the wildcard), we don't match
62 : */
63 6 : if (pg_strcasecmp(pattern + 1, string + lenstr - lenpat + 1) != 0)
64 2 : return false;
65 :
66 : /*
67 : * If there is a dot left of where the pattern started to match, we don't
68 : * match (rule 3)
69 : */
70 4 : if (strchr(string, '.') < string + lenstr - lenpat)
71 2 : return false;
72 :
73 : /* String ended with pattern, and didn't have a dot before, so we match */
74 2 : return true;
75 : }
76 :
77 : /*
78 : * Check if a name from a server's certificate matches the peer's hostname.
79 : *
80 : * Returns 1 if the name matches, and 0 if it does not. On error, returns
81 : * -1, and sets the libpq error message.
82 : *
83 : * The name extracted from the certificate is returned in *store_name. The
84 : * caller is responsible for freeing it.
85 : */
86 : int
87 68 : pq_verify_peer_name_matches_certificate_name(PGconn *conn,
88 : const char *namedata, size_t namelen,
89 : char **store_name)
90 : {
91 : char *name;
92 : int result;
93 68 : char *host = conn->connhost[conn->whichhost].host;
94 :
95 68 : *store_name = NULL;
96 :
97 68 : if (!(host && host[0] != '\0'))
98 : {
99 0 : libpq_append_conn_error(conn, "host name must be specified");
100 0 : return -1;
101 : }
102 :
103 : /*
104 : * There is no guarantee the string returned from the certificate is
105 : * NULL-terminated, so make a copy that is.
106 : */
107 68 : name = malloc(namelen + 1);
108 68 : if (name == NULL)
109 : {
110 0 : libpq_append_conn_error(conn, "out of memory");
111 0 : return -1;
112 : }
113 68 : memcpy(name, namedata, namelen);
114 68 : name[namelen] = '\0';
115 :
116 : /*
117 : * Reject embedded NULLs in certificate common or alternative name to
118 : * prevent attacks like CVE-2009-4034.
119 : */
120 68 : if (namelen != strlen(name))
121 : {
122 0 : free(name);
123 0 : libpq_append_conn_error(conn, "SSL certificate's name contains embedded null");
124 0 : return -1;
125 : }
126 :
127 68 : if (pg_strcasecmp(name, host) == 0)
128 : {
129 : /* Exact name match */
130 26 : result = 1;
131 : }
132 42 : else if (wildcard_certificate_match(name, host))
133 : {
134 : /* Matched wildcard name */
135 2 : result = 1;
136 : }
137 : else
138 : {
139 40 : result = 0;
140 : }
141 :
142 68 : *store_name = name;
143 68 : return result;
144 : }
145 :
146 : /*
147 : * Check if an IP address from a server's certificate matches the peer's
148 : * hostname (which must itself be an IPv4/6 address).
149 : *
150 : * Returns 1 if the address matches, and 0 if it does not. On error, returns
151 : * -1, and sets the libpq error message.
152 : *
153 : * A string representation of the certificate's IP address is returned in
154 : * *store_name. The caller is responsible for freeing it.
155 : */
156 : int
157 48 : pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
158 : const unsigned char *ipdata,
159 : size_t iplen,
160 : char **store_name)
161 : {
162 : char *addrstr;
163 48 : int match = 0;
164 48 : char *host = conn->connhost[conn->whichhost].host;
165 : int family;
166 : char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"];
167 : char sebuf[PG_STRERROR_R_BUFLEN];
168 :
169 48 : *store_name = NULL;
170 :
171 48 : if (!(host && host[0] != '\0'))
172 : {
173 0 : libpq_append_conn_error(conn, "host name must be specified");
174 0 : return -1;
175 : }
176 :
177 : /*
178 : * The data from the certificate is in network byte order. Convert our
179 : * host string to network-ordered bytes as well, for comparison. (The host
180 : * string isn't guaranteed to actually be an IP address, so if this
181 : * conversion fails we need to consider it a mismatch rather than an
182 : * error.)
183 : */
184 48 : if (iplen == 4)
185 : {
186 : /* IPv4 */
187 : struct in_addr addr;
188 :
189 28 : family = AF_INET;
190 :
191 : /*
192 : * The use of inet_aton() is deliberate; we accept alternative IPv4
193 : * address notations that are accepted by inet_aton() but not
194 : * inet_pton() as server addresses.
195 : */
196 28 : if (inet_aton(host, &addr))
197 : {
198 12 : if (memcmp(ipdata, &addr.s_addr, iplen) == 0)
199 8 : match = 1;
200 : }
201 : }
202 :
203 : /*
204 : * If they don't have inet_pton(), skip this. Then, an IPv6 address in a
205 : * certificate will cause an error.
206 : */
207 : #ifdef HAVE_INET_PTON
208 20 : else if (iplen == 16)
209 : {
210 : /* IPv6 */
211 : struct in6_addr addr;
212 :
213 20 : family = AF_INET6;
214 :
215 20 : if (inet_pton(AF_INET6, host, &addr) == 1)
216 : {
217 12 : if (memcmp(ipdata, &addr.s6_addr, iplen) == 0)
218 10 : match = 1;
219 : }
220 : }
221 : #endif
222 : else
223 : {
224 : /*
225 : * Not IPv4 or IPv6. We could ignore the field, but leniency seems
226 : * wrong given the subject matter.
227 : */
228 0 : libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
229 : iplen);
230 0 : return -1;
231 : }
232 :
233 : /* Generate a human-readable representation of the certificate's IP. */
234 48 : addrstr = pg_inet_net_ntop(family, ipdata, 8 * iplen, tmp, sizeof(tmp));
235 48 : if (!addrstr)
236 : {
237 0 : libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
238 0 : strerror_r(errno, sebuf, sizeof(sebuf)));
239 0 : return -1;
240 : }
241 :
242 48 : *store_name = strdup(addrstr);
243 48 : return match;
244 : }
245 :
246 : /*
247 : * Verify that the server certificate matches the hostname we connected to.
248 : *
249 : * The certificate's Common Name and Subject Alternative Names are considered.
250 : */
251 : bool
252 206 : pq_verify_peer_name_matches_certificate(PGconn *conn)
253 : {
254 206 : char *host = conn->connhost[conn->whichhost].host;
255 : int rc;
256 206 : int names_examined = 0;
257 206 : char *first_name = NULL;
258 :
259 : /*
260 : * If told not to verify the peer name, don't do it. Return true
261 : * indicating that the verification was successful.
262 : */
263 206 : if (strcmp(conn->sslmode, "verify-full") != 0)
264 134 : return true;
265 :
266 : /* Check that we have a hostname to compare with. */
267 72 : if (!(host && host[0] != '\0'))
268 : {
269 0 : libpq_append_conn_error(conn, "host name must be specified for a verified SSL connection");
270 0 : return false;
271 : }
272 :
273 72 : rc = pgtls_verify_peer_name_matches_certificate_guts(conn, &names_examined, &first_name);
274 :
275 72 : if (rc == 0)
276 : {
277 : /*
278 : * No match. Include the name from the server certificate in the error
279 : * message, to aid debugging broken configurations. If there are
280 : * multiple names, only print the first one to avoid an overly long
281 : * error message.
282 : */
283 26 : if (names_examined > 1)
284 : {
285 14 : appendPQExpBuffer(&conn->errorMessage,
286 14 : libpq_ngettext("server certificate for \"%s\" (and %d other name) does not match host name \"%s\"",
287 : "server certificate for \"%s\" (and %d other names) does not match host name \"%s\"",
288 14 : names_examined - 1),
289 : first_name, names_examined - 1, host);
290 14 : appendPQExpBufferChar(&conn->errorMessage, '\n');
291 : }
292 12 : else if (names_examined == 1)
293 : {
294 10 : libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
295 : first_name, host);
296 : }
297 : else
298 : {
299 2 : libpq_append_conn_error(conn, "could not get server's host name from server certificate");
300 : }
301 : }
302 :
303 : /* clean up */
304 72 : free(first_name);
305 :
306 72 : return (rc == 1);
307 : }
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