1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
|
package java.security;
class SecurityUtil
{
static class Implementation
{
Object engine;
Provider provider;
Implementation(
Object engine,
Provider provider)
{
this.engine = engine;
this.provider = provider;
}
Object getEngine()
{
return engine;
}
Provider getProvider()
{
return provider;
}
}
/**
* see if we can find an algorithm (or its alias and what it represents) in
* the property table for the given provider.
*
* @return null if no algorithm found, an Implementation if it is.
*/
static private Implementation getImplementation(
String baseName,
String algorithm,
Provider prov)
{
String alias;
while ((alias = prov.getProperty("Alg.Alias." + baseName + "." + algorithm)) != null)
{
algorithm = alias;
}
String className = prov.getProperty(baseName + "." + algorithm);
if (className != null)
{
try
{
return new Implementation(Class.forName(className).newInstance(), prov);
}
catch (ClassNotFoundException e)
{
throw new IllegalStateException(
"algorithm " + algorithm + " in provider " + prov.getName() + " but no class found!");
}
catch (Exception e)
{
throw new IllegalStateException(
"algorithm " + algorithm + " in provider " + prov.getName() + " but class inaccessible!");
}
}
return null;
}
/**
* return an implementation for a given algorithm/provider.
* If the provider is null, we grab the first avalaible who has the required algorithm.
*
* @return null if no algorithm found, an Implementation if it is.
* @exception NoSuchProviderException if a provider is specified and not found.
*/
static Implementation getImplementation(
String baseName,
String algorithm,
String provider)
throws NoSuchProviderException
{
if (provider == null)
{
Provider[] prov = Security.getProviders();
//
// search every provider looking for the algorithm we want.
//
for (int i = 0; i != prov.length; i++)
{
Implementation imp = getImplementation(baseName, algorithm, prov[i]);
if (imp != null)
{
return imp;
}
}
}
else
{
Provider prov = Security.getProvider(provider);
if (prov == null)
{
throw new NoSuchProviderException("Provider " + provider + " not found");
}
return getImplementation(baseName, algorithm, prov);
}
return null;
}
}
|
