1 /*-
2 * Copyright (c) 2012-2017 Dag-Erling Smørgrav
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
30 #ifdef HAVE_CONFIG_H
31 # include "config.h"
32 #endif
33
34 #include <errno.h>
35 #include <stdio.h>
36 #include <stdlib.h>
37
38 #include <security/pam_appl.h>
39
40 #include "openpam_impl.h"
41 #include "openpam_ctype.h"
42
43 #define MIN_WORD_SIZE 32
44
45 /*
46 * OpenPAM extension
47 *
48 * Read a word from a file, respecting shell quoting rules.
49 */
50
51 char *
openpam_readword(FILE * f,int * lineno,size_t * lenp)52 openpam_readword(FILE *f, int *lineno, size_t *lenp)
53 {
54 char *word;
55 size_t size, len;
56 int ch, escape, quote;
57 int serrno;
58
59 errno = 0;
60
61 /* skip initial whitespace */
62 escape = quote = 0;
63 while ((ch = getc(f)) != EOF) {
64 if (ch == '\n') {
65 /* either EOL or line continuation */
66 if (!escape)
67 break;
68 if (lineno != NULL)
69 ++*lineno;
70 escape = 0;
71 } else if (escape) {
72 /* escaped something else */
73 break;
74 } else if (ch == '#') {
75 /* comment: until EOL, no continuation */
76 while ((ch = getc(f)) != EOF)
77 if (ch == '\n')
78 break;
79 break;
80 } else if (ch == '\\') {
81 escape = 1;
82 } else if (!is_ws(ch)) {
83 break;
84 }
85 }
86 if (ch == EOF)
87 return (NULL);
88 ungetc(ch, f);
89 if (ch == '\n')
90 return (NULL);
91
92 word = NULL;
93 size = len = 0;
94 while ((ch = fgetc(f)) != EOF && (!is_ws(ch) || quote || escape)) {
95 if (ch == '\\' && !escape && quote != '\'') {
96 /* escape next character */
97 escape = ch;
98 } else if ((ch == '\'' || ch == '"') && !quote && !escape) {
99 /* begin quote */
100 quote = ch;
101 /* edge case: empty quoted string */
102 if (openpam_straddch(&word, &size, &len, 0) != 0)
103 return (NULL);
104 } else if (ch == quote && !escape) {
105 /* end quote */
106 quote = 0;
107 } else if (ch == '\n' && escape) {
108 /* line continuation */
109 escape = 0;
110 } else {
111 if (escape && quote && ch != '\\' && ch != quote &&
112 openpam_straddch(&word, &size, &len, '\\') != 0) {
113 free(word);
114 errno = ENOMEM;
115 return (NULL);
116 }
117 if (openpam_straddch(&word, &size, &len, ch) != 0) {
118 free(word);
119 errno = ENOMEM;
120 return (NULL);
121 }
122 escape = 0;
123 }
124 if (lineno != NULL && ch == '\n')
125 ++*lineno;
126 }
127 if (ch == EOF && ferror(f)) {
128 serrno = errno;
129 free(word);
130 errno = serrno;
131 return (NULL);
132 }
133 if (ch == EOF && (escape || quote)) {
134 /* Missing escaped character or closing quote. */
135 free(word);
136 errno = EINVAL;
137 return (NULL);
138 }
139 ungetc(ch, f);
140 if (lenp != NULL)
141 *lenp = len;
142 return (word);
143 }
144
145 /**
146 * The =openpam_readword function reads the next word from a file, and
147 * returns it in a NUL-terminated buffer allocated with =!malloc.
148 *
149 * A word is a sequence of non-whitespace characters.
150 * However, whitespace characters can be included in a word if quoted or
151 * escaped according to the following rules:
152 *
153 * - An unescaped single or double quote introduces a quoted string,
154 * which ends when the same quote character is encountered a second
155 * time.
156 * The quotes themselves are stripped.
157 *
158 * - Within a single- or double-quoted string, all whitespace characters,
159 * including the newline character, are preserved as-is.
160 *
161 * - Outside a quoted string, a backslash escapes the next character,
162 * which is preserved as-is, unless that character is a newline, in
163 * which case it is discarded and reading continues at the beginning of
164 * the next line as if the backslash and newline had not been there.
165 * In all cases, the backslash itself is discarded.
166 *
167 * - Within a single-quoted string, double quotes and backslashes are
168 * preserved as-is.
169 *
170 * - Within a double-quoted string, a single quote is preserved as-is,
171 * and a backslash is preserved as-is unless used to escape a double
172 * quote.
173 *
174 * In addition, if the first non-whitespace character on the line is a
175 * hash character (#), the rest of the line is discarded.
176 * If a hash character occurs within a word, however, it is preserved
177 * as-is.
178 * A backslash at the end of a comment does cause line continuation.
179 *
180 * If =lineno is not =NULL, the integer variable it points to is
181 * incremented every time a quoted or escaped newline character is read.
182 *
183 * If =lenp is not =NULL, the length of the word (after quotes and
184 * backslashes have been removed) is stored in the variable it points to.
185 *
186 * RETURN VALUES
187 *
188 * If successful, the =openpam_readword function returns a pointer to a
189 * dynamically allocated NUL-terminated string containing the first word
190 * encountered on the line.
191 *
192 * The caller is responsible for releasing the returned buffer by passing
193 * it to =!free.
194 *
195 * If =openpam_readword reaches the end of the line or file before any
196 * characters are copied to the word, it returns =NULL. In the former
197 * case, the newline is pushed back to the file.
198 *
199 * If =openpam_readword reaches the end of the file while a quote or
200 * backslash escape is in effect, it sets :errno to =EINVAL and returns
201 * =NULL.
202 *
203 * IMPLEMENTATION NOTES
204 *
205 * The parsing rules are intended to be equivalent to the normal POSIX
206 * shell quoting rules.
207 * Any discrepancy is a bug and should be reported to the author along
208 * with sample input that can be used to reproduce the error.
209 *
210 * >openpam_readline
211 * >openpam_readlinev
212 *
213 * AUTHOR DES
214 */
215