openpam_readword.c revision 348980 
1/*-
2 * Copyright (c) 2012-2017 Dag-Erling Sm��rgrav
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. The name of the author may not be used to endorse or promote
14 *    products derived from this software without specific prior written
15 *    permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * $OpenPAM: openpam_readword.c 938 2017-04-30 21:34:42Z des $
30 */
31
32#ifdef HAVE_CONFIG_H
33# include "config.h"
34#endif
35
36#include <errno.h>
37#include <stdio.h>
38#include <stdlib.h>
39
40#include <security/pam_appl.h>
41
42#include "openpam_impl.h"
43#include "openpam_ctype.h"
44
45#define MIN_WORD_SIZE	32
46
47/*
48 * OpenPAM extension
49 *
50 * Read a word from a file, respecting shell quoting rules.
51 */
52
53char *
54openpam_readword(FILE *f, int *lineno, size_t *lenp)
55{
56	char *word;
57	size_t size, len;
58	int ch, escape, quote;
59	int serrno;
60
61	errno = 0;
62
63	/* skip initial whitespace */
64	escape = quote = 0;
65	while ((ch = getc(f)) != EOF) {
66		if (ch == '\n') {
67			/* either EOL or line continuation */
68			if (!escape)
69				break;
70			if (lineno != NULL)
71				++*lineno;
72			escape = 0;
73		} else if (escape) {
74			/* escaped something else */
75			break;
76		} else if (ch == '#') {
77			/* comment: until EOL, no continuation */
78			while ((ch = getc(f)) != EOF)
79				if (ch == '\n')
80					break;
81			break;
82		} else if (ch == '\\') {
83			escape = 1;
84		} else if (!is_ws(ch)) {
85			break;
86		}
87	}
88	if (ch == EOF)
89		return (NULL);
90	ungetc(ch, f);
91	if (ch == '\n')
92		return (NULL);
93
94	word = NULL;
95	size = len = 0;
96	while ((ch = fgetc(f)) != EOF && (!is_ws(ch) || quote || escape)) {
97		if (ch == '\\' && !escape && quote != '\'') {
98			/* escape next character */
99			escape = ch;
100		} else if ((ch == '\'' || ch == '"') && !quote && !escape) {
101			/* begin quote */
102			quote = ch;
103			/* edge case: empty quoted string */
104			if (openpam_straddch(&word, &size, &len, 0) != 0)
105				return (NULL);
106		} else if (ch == quote && !escape) {
107			/* end quote */
108			quote = 0;
109		} else if (ch == '\n' && escape) {
110			/* line continuation */
111			escape = 0;
112		} else {
113			if (escape && quote && ch != '\\' && ch != quote &&
114			    openpam_straddch(&word, &size, &len, '\\') != 0) {
115				free(word);
116				errno = ENOMEM;
117				return (NULL);
118			}
119			if (openpam_straddch(&word, &size, &len, ch) != 0) {
120				free(word);
121				errno = ENOMEM;
122				return (NULL);
123			}
124			escape = 0;
125		}
126		if (lineno != NULL && ch == '\n')
127			++*lineno;
128	}
129	if (ch == EOF && ferror(f)) {
130		serrno = errno;
131		free(word);
132		errno = serrno;
133		return (NULL);
134	}
135	if (ch == EOF && (escape || quote)) {
136		/* Missing escaped character or closing quote. */
137		openpam_log(PAM_LOG_DEBUG, "unexpected end of file");
138		free(word);
139		errno = EINVAL;
140		return (NULL);
141	}
142	ungetc(ch, f);
143	if (lenp != NULL)
144		*lenp = len;
145	return (word);
146}
147
148/**
149 * The =openpam_readword function reads the next word from a file, and
150 * returns it in a NUL-terminated buffer allocated with =!malloc.
151 *
152 * A word is a sequence of non-whitespace characters.
153 * However, whitespace characters can be included in a word if quoted or
154 * escaped according to the following rules:
155 *
156 *  - An unescaped single or double quote introduces a quoted string,
157 *    which ends when the same quote character is encountered a second
158 *    time.
159 *    The quotes themselves are stripped.
160 *
161 *  - Within a single- or double-quoted string, all whitespace characters,
162 *    including the newline character, are preserved as-is.
163 *
164 *  - Outside a quoted string, a backslash escapes the next character,
165 *    which is preserved as-is, unless that character is a newline, in
166 *    which case it is discarded and reading continues at the beginning of
167 *    the next line as if the backslash and newline had not been there.
168 *    In all cases, the backslash itself is discarded.
169 *
170 *  - Within a single-quoted string, double quotes and backslashes are
171 *    preserved as-is.
172 *
173 *  - Within a double-quoted string, a single quote is preserved as-is,
174 *    and a backslash is preserved as-is unless used to escape a double
175 *    quote.
176 *
177 * In addition, if the first non-whitespace character on the line is a
178 * hash character (#), the rest of the line is discarded.
179 * If a hash character occurs within a word, however, it is preserved
180 * as-is.
181 * A backslash at the end of a comment does cause line continuation.
182 *
183 * If =lineno is not =NULL, the integer variable it points to is
184 * incremented every time a quoted or escaped newline character is read.
185 *
186 * If =lenp is not =NULL, the length of the word (after quotes and
187 * backslashes have been removed) is stored in the variable it points to.
188 *
189 * RETURN VALUES
190 *
191 * If successful, the =openpam_readword function returns a pointer to a
192 * dynamically allocated NUL-terminated string containing the first word
193 * encountered on the line.
194 *
195 * The caller is responsible for releasing the returned buffer by passing
196 * it to =!free.
197 *
198 * If =openpam_readword reaches the end of the line or file before any
199 * characters are copied to the word, it returns =NULL.  In the former
200 * case, the newline is pushed back to the file.
201 *
202 * If =openpam_readword reaches the end of the file while a quote or
203 * backslash escape is in effect, it sets :errno to =EINVAL and returns
204 * =NULL.
205 *
206 * IMPLEMENTATION NOTES
207 *
208 * The parsing rules are intended to be equivalent to the normal POSIX
209 * shell quoting rules.
210 * Any discrepancy is a bug and should be reported to the author along
211 * with sample input that can be used to reproduce the error.
212 *
213 * >openpam_readline
214 * >openpam_readlinev
215 *
216 * AUTHOR DES
217 */
218