match.c revision 65668 
1/*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 *                    All rights reserved
5 * Simple pattern matching, with '*' and '?' as wildcards.
6 *
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose.  Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 */
13
14#include "includes.h"
15RCSID("$OpenBSD: match.c,v 1.9 2000/09/07 20:27:52 deraadt Exp $");
16
17#include "ssh.h"
18
19/*
20 * Returns true if the given string matches the pattern (which may contain ?
21 * and * as wildcards), and zero if it does not match.
22 */
23
24int
25match_pattern(const char *s, const char *pattern)
26{
27	for (;;) {
28		/* If at end of pattern, accept if also at end of string. */
29		if (!*pattern)
30			return !*s;
31
32		if (*pattern == '*') {
33			/* Skip the asterisk. */
34			pattern++;
35
36			/* If at end of pattern, accept immediately. */
37			if (!*pattern)
38				return 1;
39
40			/* If next character in pattern is known, optimize. */
41			if (*pattern != '?' && *pattern != '*') {
42				/*
43				 * Look instances of the next character in
44				 * pattern, and try to match starting from
45				 * those.
46				 */
47				for (; *s; s++)
48					if (*s == *pattern &&
49					    match_pattern(s + 1, pattern + 1))
50						return 1;
51				/* Failed. */
52				return 0;
53			}
54			/*
55			 * Move ahead one character at a time and try to
56			 * match at each position.
57			 */
58			for (; *s; s++)
59				if (match_pattern(s, pattern))
60					return 1;
61			/* Failed. */
62			return 0;
63		}
64		/*
65		 * There must be at least one more character in the string.
66		 * If we are at the end, fail.
67		 */
68		if (!*s)
69			return 0;
70
71		/* Check if the next character of the string is acceptable. */
72		if (*pattern != '?' && *pattern != *s)
73			return 0;
74
75		/* Move to the next character, both in string and in pattern. */
76		s++;
77		pattern++;
78	}
79	/* NOTREACHED */
80}
81
82/*
83 * Tries to match the host name (which must be in all lowercase) against the
84 * comma-separated sequence of subpatterns (each possibly preceded by ! to
85 * indicate negation).  Returns -1 if negation matches, 1 if there is
86 * a positive match, 0 if there is no match at all.
87 */
88
89int
90match_hostname(const char *host, const char *pattern, unsigned int len)
91{
92	char sub[1024];
93	int negated;
94	int got_positive;
95	unsigned int i, subi;
96
97	got_positive = 0;
98	for (i = 0; i < len;) {
99		/* Check if the subpattern is negated. */
100		if (pattern[i] == '!') {
101			negated = 1;
102			i++;
103		} else
104			negated = 0;
105
106		/*
107		 * Extract the subpattern up to a comma or end.  Convert the
108		 * subpattern to lowercase.
109		 */
110		for (subi = 0;
111		     i < len && subi < sizeof(sub) - 1 && pattern[i] != ',';
112		     subi++, i++)
113			sub[subi] = isupper(pattern[i]) ? tolower(pattern[i]) : pattern[i];
114		/* If subpattern too long, return failure (no match). */
115		if (subi >= sizeof(sub) - 1)
116			return 0;
117
118		/* If the subpattern was terminated by a comma, skip the comma. */
119		if (i < len && pattern[i] == ',')
120			i++;
121
122		/* Null-terminate the subpattern. */
123		sub[subi] = '\0';
124
125		/* Try to match the subpattern against the host name. */
126		if (match_pattern(host, sub)) {
127			if (negated)
128				return -1;		/* Negative */
129			else
130				got_positive = 1;	/* Positive */
131		}
132	}
133
134	/*
135	 * Return success if got a positive match.  If there was a negative
136	 * match, we have already returned -1 and never get here.
137	 */
138	return got_positive;
139}
140