1 /***************************************************************************
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7  *
8  * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
9  *
10  * This software is licensed as described in the file COPYING, which
11  * you should have received as part of this distribution. The terms
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15  * copies of the Software, and permit persons to whom the Software is
16  * furnished to do so, under the terms of the COPYING file.
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18  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19  * KIND, either express or implied.
20  *
21  ***************************************************************************/
22 
23 #include "curl_setup.h"
24 
25 #include "curl_gethostname.h"
26 
27 /*
28  * Curl_gethostname() is a wrapper around gethostname() which allows
29  * overriding the host name that the function would normally return.
30  * This capability is used by the test suite to verify exact matching
31  * of NTLM authentication, which exercises libcurl's MD4 and DES code
32  * as well as by the SMTP module when a hostname is not provided.
33  *
34  * For libcurl debug enabled builds host name overriding takes place
35  * when environment variable CURL_GETHOSTNAME is set, using the value
36  * held by the variable to override returned host name.
37  *
38  * Note: The function always returns the un-qualified hostname rather
39  * than being provider dependent.
40  *
41  * For libcurl shared library release builds the test suite preloads
42  * another shared library named libhostname using the LD_PRELOAD
43  * mechanism which intercepts, and might override, the gethostname()
44  * function call. In this case a given platform must support the
45  * LD_PRELOAD mechanism and additionally have environment variable
46  * CURL_GETHOSTNAME set in order to override the returned host name.
47  *
48  * For libcurl static library release builds no overriding takes place.
49  */
50 
Curl_gethostname(char * name,GETHOSTNAME_TYPE_ARG2 namelen)51 int Curl_gethostname(char *name, GETHOSTNAME_TYPE_ARG2 namelen)
52 {
53 #ifndef HAVE_GETHOSTNAME
54 
55   /* Allow compilation and return failure when unavailable */
56   (void) name;
57   (void) namelen;
58   return -1;
59 
60 #else
61   int err;
62   char *dot;
63 
64 #ifdef DEBUGBUILD
65 
66   /* Override host name when environment variable CURL_GETHOSTNAME is set */
67   const char *force_hostname = getenv("CURL_GETHOSTNAME");
68   if(force_hostname) {
69     strncpy(name, force_hostname, namelen);
70     err = 0;
71   }
72   else {
73     name[0] = '\0';
74     err = gethostname(name, namelen);
75   }
76 
77 #else /* DEBUGBUILD */
78 
79   /* The call to system's gethostname() might get intercepted by the
80      libhostname library when libcurl is built as a non-debug shared
81      library when running the test suite. */
82   name[0] = '\0';
83   err = gethostname(name, namelen);
84 
85 #endif
86 
87   name[namelen - 1] = '\0';
88 
89   if(err)
90     return err;
91 
92   /* Truncate domain, leave only machine name */
93   dot = strchr(name, '.');
94   if(dot)
95     *dot = '\0';
96 
97   return 0;
98 #endif
99 
100 }
101