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Commitf75a959

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Refactor client-side SSL certificate checking code
Separate the parts specific to the SSL library from the general logic.The previous code structure wasopen_client_SSL()calls verify_peer_name_matches_certificate()calls verify_peer_name_matches_certificate_name()calls wildcard_certificate_match()and was completely in fe-secure-openssl.c. The new structure isopen_client_SSL() [openssl]calls pq_verify_peer_name_matches_certificate() [generic]calls pgtls_verify_peer_name_matches_certificate_guts() [openssl]calls openssl_verify_peer_name_matches_certificate_name() [openssl]calls pq_verify_peer_name_matches_certificate_name() [generic]calls wildcard_certificate_match() [generic]Move the generic functions into a new file fe-secure-common.c, so thecalls generally go fe-connect.c -> fe-secure.c -> fe-secure-${impl}.c ->fe-secure-common.c, although there is a bit of back-and-forth betweenthe last two.Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
1 parent38d485f commitf75a959

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7 files changed

+271
-187
lines changed

7 files changed

+271
-187
lines changed

‎src/interfaces/libpq/Makefile‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -52,7 +52,7 @@ OBJS += encnames.o wchar.o
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OBJS += base64.o ip.o md5.o scram-common.o saslprep.o unicode_norm.o
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5454
ifeq ($(with_openssl),yes)
55-
OBJS += fe-secure-openssl.o sha2_openssl.o
55+
OBJS += fe-secure-openssl.ofe-secure-common.osha2_openssl.o
5656
else
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OBJS += sha2.o
5858
endif
Lines changed: 204 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,204 @@
1+
/*-------------------------------------------------------------------------
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*
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* fe-secure-common.c
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*
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* common implementation-independent SSL support code
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*
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* While fe-secure.c contains the interfaces that the rest of libpq call, this
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* file contains support routines that are used by the library-specific
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* implementations such as fe-secure-openssl.c.
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*
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* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/interfaces/libpq/fe-secure-common.c
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*
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*-------------------------------------------------------------------------
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*/
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#include"postgres_fe.h"
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#include"fe-secure-common.h"
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#include"libpq-int.h"
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#include"pqexpbuffer.h"
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/*
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* Check if a wildcard certificate matches the server hostname.
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*
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* The rule for this is:
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*1. We only match the '*' character as wildcard
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*2. We match only wildcards at the start of the string
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*3. The '*' character does *not* match '.', meaning that we match only
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* a single pathname component.
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*4. We don't support more than one '*' in a single pattern.
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*
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* This is roughly in line with RFC2818, but contrary to what most browsers
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* appear to be implementing (point 3 being the difference)
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*
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* Matching is always case-insensitive, since DNS is case insensitive.
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*/
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staticbool
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wildcard_certificate_match(constchar*pattern,constchar*string)
44+
{
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intlenpat=strlen(pattern);
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intlenstr=strlen(string);
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/* If we don't start with a wildcard, it's not a match (rule 1 & 2) */
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if (lenpat<3||
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pattern[0]!='*'||
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pattern[1]!='.')
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return false;
53+
54+
/* If pattern is longer than the string, we can never match */
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if (lenpat>lenstr)
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return false;
57+
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/*
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* If string does not end in pattern (minus the wildcard), we don't match
60+
*/
61+
if (pg_strcasecmp(pattern+1,string+lenstr-lenpat+1)!=0)
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return false;
63+
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/*
65+
* If there is a dot left of where the pattern started to match, we don't
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* match (rule 3)
67+
*/
68+
if (strchr(string,'.')<string+lenstr-lenpat)
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return false;
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/* String ended with pattern, and didn't have a dot before, so we match */
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return true;
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}
74+
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/*
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* Check if a name from a server's certificate matches the peer's hostname.
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*
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* Returns 1 if the name matches, and 0 if it does not. On error, returns
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* -1, and sets the libpq error message.
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*
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* The name extracted from the certificate is returned in *store_name. The
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* caller is responsible for freeing it.
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*/
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int
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pq_verify_peer_name_matches_certificate_name(PGconn*conn,
86+
constchar*namedata,size_tnamelen,
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char**store_name)
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{
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char*name;
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intresult;
91+
char*host=PQhost(conn);
92+
93+
*store_name=NULL;
94+
95+
/*
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* There is no guarantee the string returned from the certificate is
97+
* NULL-terminated, so make a copy that is.
98+
*/
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name=malloc(namelen+1);
100+
if (name==NULL)
101+
{
102+
printfPQExpBuffer(&conn->errorMessage,
103+
libpq_gettext("out of memory\n"));
104+
return-1;
105+
}
106+
memcpy(name,namedata,namelen);
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name[namelen]='\0';
108+
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/*
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* Reject embedded NULLs in certificate common or alternative name to
111+
* prevent attacks like CVE-2009-4034.
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*/
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if (namelen!=strlen(name))
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{
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free(name);
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printfPQExpBuffer(&conn->errorMessage,
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libpq_gettext("SSL certificate's name contains embedded null\n"));
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return-1;
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}
120+
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if (pg_strcasecmp(name,host)==0)
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{
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/* Exact name match */
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result=1;
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}
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elseif (wildcard_certificate_match(name,host))
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{
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/* Matched wildcard name */
129+
result=1;
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}
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else
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{
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result=0;
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}
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*store_name=name;
137+
returnresult;
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}
139+
140+
/*
141+
* Verify that the server certificate matches the hostname we connected to.
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*
143+
* The certificate's Common Name and Subject Alternative Names are considered.
144+
*/
145+
bool
146+
pq_verify_peer_name_matches_certificate(PGconn*conn)
147+
{
148+
char*host=PQhost(conn);
149+
intrc;
150+
intnames_examined=0;
151+
char*first_name=NULL;
152+
153+
/*
154+
* If told not to verify the peer name, don't do it. Return true
155+
* indicating that the verification was successful.
156+
*/
157+
if (strcmp(conn->sslmode,"verify-full")!=0)
158+
return true;
159+
160+
/* Check that we have a hostname to compare with. */
161+
if (!(host&&host[0]!='\0'))
162+
{
163+
printfPQExpBuffer(&conn->errorMessage,
164+
libpq_gettext("host name must be specified for a verified SSL connection\n"));
165+
return false;
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}
167+
168+
rc=pgtls_verify_peer_name_matches_certificate_guts(conn,&names_examined,&first_name);
169+
170+
if (rc==0)
171+
{
172+
/*
173+
* No match. Include the name from the server certificate in the error
174+
* message, to aid debugging broken configurations. If there are
175+
* multiple names, only print the first one to avoid an overly long
176+
* error message.
177+
*/
178+
if (names_examined>1)
179+
{
180+
printfPQExpBuffer(&conn->errorMessage,
181+
libpq_ngettext("server certificate for \"%s\" (and %d other name) does not match host name \"%s\"\n",
182+
"server certificate for \"%s\" (and %d other names) does not match host name \"%s\"\n",
183+
names_examined-1),
184+
first_name,names_examined-1,host);
185+
}
186+
elseif (names_examined==1)
187+
{
188+
printfPQExpBuffer(&conn->errorMessage,
189+
libpq_gettext("server certificate for \"%s\" does not match host name \"%s\"\n"),
190+
first_name,host);
191+
}
192+
else
193+
{
194+
printfPQExpBuffer(&conn->errorMessage,
195+
libpq_gettext("could not get server's host name from server certificate\n"));
196+
}
197+
}
198+
199+
/* clean up */
200+
if (first_name)
201+
free(first_name);
202+
203+
return (rc==1);
204+
}
Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,26 @@
1+
/*-------------------------------------------------------------------------
2+
*
3+
* fe-secure-common.h
4+
*
5+
* common implementation-independent SSL support code
6+
*
7+
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
8+
* Portions Copyright (c) 1994, Regents of the University of California
9+
*
10+
* IDENTIFICATION
11+
* src/interfaces/libpq/fe-secure-common.h
12+
*
13+
*-------------------------------------------------------------------------
14+
*/
15+
16+
#ifndefFE_SECURE_COMMON_H
17+
#defineFE_SECURE_COMMON_H
18+
19+
#include"libpq-fe.h"
20+
21+
externintpq_verify_peer_name_matches_certificate_name(PGconn*conn,
22+
constchar*namedata,size_tnamelen,
23+
char**store_name);
24+
externboolpq_verify_peer_name_matches_certificate(PGconn*conn);
25+
26+
#endif/* FE_SECURE_COMMON_H */

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